Merge lp:~djlauk/epics-appdev/ca-protocol into lp:~epics-documenters/epics-appdev/3.16

[Daniel J. Lauk]

Converted the CA protocol documentation from Cosylab to AsciiDoc.
Generating the HTML documentation requires asciidoc and dia.
Please double check the Makefile.

[lp:~djlauk/epics-appdev/ca-protocol]

57. By Daniel J. Lauk on 2014-09-29

Makefile fix by Michael Davidsaver

58. By Daniel J. Lauk on 2014-09-29

Patch from Michael Davidsaver: Add license, move rev. history, add core-talk email address

[mdavidsaver (mdavidsaver)]

What is the status of this? It seems ready to merge to me.

review: Approve

[Andrew Johnson (anj)]

I haven't looked at it properly yet but I am working on 3.15 AppDevGuide updates right now and will merge it and publish the output once I've finished them.

[Andrew Johnson (anj)]

Merging.

I reorganized the Makefile somewhat so it now installs into a different directory to the source, so I can install the result onto our webserver by rsyncing a whole directory. The version of asciidoc that I have on my RHEL6.6 system doesn't support the html5 backend; my default backend generates xhtml11 which looks much better than the original html backend. The generated output is now online at http://www.aps.anl.gov/epics/base/R3-15/1-docs/CAproto/index.html in case anyone wants to take a look.

It would be nice to be able to use the a2x toolchain wrapper script to generate a PDF file as well, but I get errors when I run that, implying that the source text isn't quite suitable yet for the Docbook processing steps which that invokes.

review: Approve

=== modified file '.bzrignore'
--- .bzrignore	2010-11-15 18:04:26 +0000
+++ .bzrignore	2014-09-29 14:22:53 +0000
@@ -1,3 +1,5 @@
 pdf/
 AppDevGuide*
 *.backup
+ca_protocol/index.html
+ca_protocol/*.png

=== modified file 'Makefile'
--- Makefile	2013-10-14 18:38:30 +0000
+++ Makefile	2014-09-29 14:22:53 +0000
@@ -1,9 +1,11 @@
 # requires:
 # latex2html and pdflatex
+# asciidoc, dia
 
 TEXD=tex
 PDFD=pdf
 EPSD=eps
+CADIAD=ca_protocol/dia
 
 PDFS = \
 $(PDFD)/overview_1.pdf \
@@ -47,6 +49,13 @@
 $(TEXD)/registry.tex \
 $(TEXD)/databaseStructures.tex
 
+DIAS = \
+$(CADIAD)/virtual-circuit.dia \
+$(CADIAD)/connection-states.dia \
+$(CADIAD)/repeater.dia \
+
+GENPNG = $(DIAS:$(CADIAD)/%.dia=ca_protocol/%.png)
+
 # Options for latex2html:
 L2H_OPTS += -split +1
 L2H_OPTS += -link 2
@@ -59,7 +68,7 @@
 all: pdf html
 
 pdf: AppDevGuide.pdf
-html: AppDevGuide
+html: AppDevGuide ca_protocol/index.html
 
 AppDevGuide.pdf: AppDevGuide.tex $(TEXS) $(PDFS)
 	pdflatex $(basename $@)
@@ -74,9 +83,17 @@
 	mkdir -p $(PDFD)
 	epstopdf $< -o=$@
 
+ca_protocol/%.png: $(CADIAD)/%.dia
+	dia -t png -e $@ $<
+
+ca_protocol/index.html: ca_protocol/ca_protocol.txt $(GENPNG)
+	asciidoc -n -b html5 -o $@ $<
+
 clean: cleanidx
 	rm -rf AppDevGuide
 	rm -rf pdf
+	rm -f ca_protocol/index.html
+	rm -f $(GENPNG)
 
 cleanidx:
 	rm -f *.idx *.ind *.ilg *.log *.out *.pdf *.toc *.aux

=== added directory 'ca_protocol'
=== added file 'ca_protocol/ca_protocol.txt'
--- ca_protocol/ca_protocol.txt	1970-01-01 00:00:00 +0000
+++ ca_protocol/ca_protocol.txt	2014-09-29 14:22:53 +0000
@@ -0,0 +1,2610 @@
+Channel Access Protocol Specification
+=====================================
+:Email:     [e-mail]
+:Date:      2014-08-27
+:Revision:  1.4.1
+
+
+[[license]]
+== License
+
+This document is distributed under the terms of the
+http://www.gnu.org/licenses/old-licenses/fdl-1.2.html[GNU Free Documentation License, version 1.2].
+
+[[document-history]]
+== Document History
+
+[options="header"]
+|====================
+|Revision|Date|Author|Section|Modification
+|1.0|2003-12-12|mailto:[e-mail][Klemen Žagar]|all|Created.
+|1.1|2004-01-08|mailto:[e-mail][Aleš Pucelj]|all|Finalized structure.
+| |2004-01-10|mailto:[e-mail][Matej Šekoranja]|all|Review.
+|1.2|2004-04-19|mailto:[e-mail][Aleš Pucelj]|all|Draft completed.
+|1.3|2004-05-31|mailto:[e-mail][Aleš Pucelj]|all|Matej's comments considered (after Channel Access for Java implementation).
+| |2004-06-01|mailto:[e-mail][Matej Šekoranja]|all|Review.
+| |2004-08-12|mailto:[e-mail][Klemen Žagar]|all|Released
+|1.4|2008-02-07|mailto:[e-mail][Matej Šekoranja]|all|Description of `CA_PROTO_READ` and `CA_PROTO_READ_SYNC` added.
+| |2008-02-07|mailto:[e-mail][Klemen Žagar]|all|Released
+|1.4.1|2014-08-27|mailto:[e-mail][Daniel J. Lauk]|all|Transformed to link:http://asciidoc.org/[AsciiDoc] format. Recreated graphics.
+|====================
+
+== Introduction
+
+This document is a specification of the EPICS Channel Access (CA) protocol.
+Structure of messages exchanged between communicating nodes is defined, as well as semantics of the exchange.
+The documentation is focused on version 4.11 of the CA protocol, which comes with EPICS 3.14, and later versions. 
+
+=== Implementation Requirements
+
+The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
+"SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL" in this document are to be
+interpreted as described in link:http://www.ietf.org/rfc/rfc2119.txt[RFC 2119:
+Key words for use in RFCs to Indicate Requirement Levels]<<references,[3]>>.
+
+An implementation is not compliant if it fails to satisfy one or more of the
+MUST or REQUIRED level requirements for the protocols it implements.
+An implementation that satisfies all the MUST or REQUIRED level and all the
+SHOULD level requirements for its protocols is said to be "unconditionally
+compliant"; one that satisfies all the MUST level requirements but not all the
+SHOULD level requirements for its protocols is said to be "conditionally
+compliant."
+
+This document is based on the original CA protocol implementation that
+accompanies EPICS. Wherever the MAY, OPTIONAL or RECOMMENDED is specified, it
+implies that experience has shown such behaviour to improve either
+performance, portability or memory consumption.
+
+A protocol implementation that is not unconditionally compliant MUST NOT be
+used in any production environment or used with EPICS databases controlling
+physical devices.
+
+
+=== Basic Concepts
+
+
+==== Process Variables
+
+A Process Variable (PV) is representation of a single value within an EPICS
+host.
+
+
+==== Channels
+
+A channel is created whenever a PV is connected using CA.
+
+From implementation point of view, a channel is a connection, established over
+virtual circuit, between server and client through which a single PV is
+accessed. Both the client and the server will provide a way of uniquely
+identifying channels. These identifiers are explained in section
+<<message-identifiers,Message Identifiers>>.
+
+
+==== Monitors
+
+A monitor is created on a channel as a means of registering for asynchronous
+change notifications. CA protocol defines the subscription mechanism through
+which clients register for notifications. These changes will then be provided
+through monitor object or callback, depending on implementation and
+environment. Monitors may be filtered to receive only a subset of events,
+such as value or alarm changes. Several different monitors may be created for
+each channel.
+
+
+==== Channel Access Client Library
+
+A client library implements channel access protocol and exposes it through a
+programmer-friendly API. How the protocol and its mechanisms are implemented
+in the library depends on the programming language and no specific
+requirements are made with respect to this.
+
+
+==== Repeater
+
+Repeater is a standalone process that allows several clients on one machine to
+share a predefined UDP port for recieving broadcast messages. Broadcast
+messages are sent without prior knowledge of which port the CA clients and
+hosts are listening at, so predefined port numbers are used. Since most
+network stack implementations do not allow multiple clients to listen on the
+same port, repeater is installed to listen on a single port, used for
+broadcast notifications. Repeater will fan-out unmodified incoming datagram
+messages to all the clients on the same host, that have previously registered
+with the repeater.
+
+Typically, a client library will attempt to register with the repeater during
+startup. If repeater cannot be found or is not available, the library will
+attempt to spawn a new repeater process. Repeater and client communicate using
+a minimal set of messages over UDP.
+
+
+==== Server Beacons
+
+Server beacons are simple protocol messages that allow servers to broadcast
+their availability. These messages are sent out periodically to announce their
+presence. Additionally, these beacons are used to restore virtual circuits
+that have lost connections.
+
+
+==== Virtual Circuit
+
+Channel Access protocol is designed to minimize resources used on both client
+and server. Virtual circuits minimize number of TCP connections used between
+clients and servers. Each client will have exactly one active and open TCP
+connection to an individual server, regardless of how many channels it
+accesses over it. This helps to ensure that servers do not get overwhelmed by
+too many connections.
+
+The life-cycle of a virtual circuit is defined in section
+<<virtual-circuit-operation,Virtual Circuit Operation>>.
+
+
+==== Message Buffering
+
+When sending packets over network, channel access allows huge savings to be
+made by grouping individual messages in a single TCP packet. This is performed
+by maintaining per virtual circuit buffers that collect all outgoing messages.
+These buffers are flushed upon application's explicit request. This mechanism
+is independent of the TCP/IP stack, which maintains its own send queue and
+defines a maximum frame size. Messages sent over virtual circuit may be larger
+than this and will not always be aligned on frame boundary. Implementation
+should also be aware that messages received may not yet be available entirely
+or will be split over several TCP frames.
+
+
+==== Version compatibility
+
+Certain aspects of Channel Access protocol have changed between releases.
+In this document, Channel Access versions are identified using `CA_VXYY`,
+where X represents single-digit major version number and YY represents a
+single- or double-digit minor version number. Stating that a feature is
+available in `CA_VXYY` implies that any client supporting version XYY must
+support the feature. Implementation must be backward compatible with all
+versions up to and including its declared supported minor version number.
+
+.Channel Access version number
+====================
+`CA_V43`, denotes version 4.3 (major version 4, minor version 3).
+====================
+
+Currently, all protocol definitions are assumed to have major version 4.
+Minor version ranges from 1 through 11.
+
+
+==== Exceptions
+
+This document uses the concept of exceptions to refer to the mechanism of
+reporting errors that occur during command request execution. An exception
+defines reporting of error condition on the server. This can occur either due
+to client problem or due to some unexpected condition on the server (such as
+running out of resources). Exceptions are reported either within the command's
+response or using a specialized message. Actual form and method (response or
+asynchronously received message) depends on circumstances where the exception
+occurs. Individual commands and messages determine which method is used.
+
+
+=== Overall Operation
+
+This section is intended as a quick overview of channel access functionality
+and behaviour. For more information, please refer to
+link:http://www.aps.anl.gov/epics/base/R3-14/5-docs/CAref.html[Channel Access
+Reference Manual]<<references,[1]>>.
+
+The goal of channel access (CA) is to provide remote access to records and
+fields managed by <<glossary,IOC>>, including search and discovery of hosts
+and minimal flow contol. Protocol itself is designed to provide minimal
+overhead and maximize network throughput for transfer of large number of small
+data packets. Additionaly, implementation overhead of the protocol can be kept
+very small, to allow operation with limited resources.
+
+All commands and events in CA are encapsulated in predefined messages, which
+can be sent in one of three forms:
+
+* As a *beacon*, which requires no confirmation. Used for host discovery and
+  keep-alive notification.
+* As a *request/response pair*. Most commands use this method.
+* As a *subscriber notification*, where the client registers with the host and
+  receives updates. Event notification uses this method to report value
+  changes.
+
+Communication between server and client is performed by sending command
+messages over UDP and TCP. Client will use UDP to search for hosts and PVs,
+server will use them to notify its startup and shutdown. Once client requests
+a specific <<glossary,PV>> (by specifying its name), UDP message will be
+broadcast to either a subnet or a list of predefined addresses, and the server
+which hosts requested PV will respond.
+
+Data exchange between client and server is performed over TCP. After locating
+the PV, the client will establish a TCP connection to the server. If more that
+one PV is found to be on the same server, client will use existing TCP
+connection. Reusable TCP connection between client and server is called
+<<glossary,Virtual circuit>>.
+
+Once a virtual circuit is established or already available, channels can be
+created to PVs.
+
+Let's assume the following setup of PVs and hosts:
+
+* PV "A" is located on host IOC1.
+* PV "B" is located on host IOC2.
+* PV "C" does not exist on either host.
+* PV "D" is located both hosts, IOC1 and IOC2.
+
+A typical scenario would be similar to this:
+
+. User application starts and initializes channel access client library.
+  During initialization, client library might spawn a new repeater process or
+  register with an existing one. If successful, the library is ready to start
+  using the channel access.
+. Application will start searching for PVs named "A", "B", "C" and "D".
+  Client will send UDP search packets with "A", "B", "C" and "D" PV names,
+  and wait for an application-specified amount of time.
+  To which network hosts (broadcast or specific IP) these packets are actually
+  sent depends on configuration of the client.
+. All hosts that receive this message will check their database and if they
+  know about any of these PV names, they will respond using UDP search
+  response message. Thus, IOC1 will respond with "A" and "D", whereas IOC2
+  will respond with "B" and "D".
+. For each search packet sent, the client will wait for a predefined amount of
+  time or until response is received.
+. In this case (assuming no packet loss in the network), the client will
+  establish a virtual circuit (TCP connection) to IOC1 and IOC2. PV "C" will
+  be assumed to be unavailable at this point and will be ignored.
+  Since "D" is located on both hosts, client will be unable to distinguish
+  between them. First response received will be considered to be proper answer
+  and any additional responses will be considered erroneous and reported to
+  user.
+. Once virtual circuits are established, client can access values of "A", "B"
+  and "D". From now on, all messages for either of the PVs will be sent via a
+  corresponding virtual circuit.
+. If virtual circuit looses TCP connection or the host disconnects, client
+  will notify application appropriately. Client will also listen for server
+  beacon messages (sent whenever IOC host starts), to be able to restore any
+  lost connections. Beacons are also used to detect when a host stops
+  responding.
+. Once the application is done using the channel access library, it will
+  gracefully close any open connections.
+
+
+== Data Types
+
+This section defines all primitive data types employed by the CA, as well as
+their C/C++ equivalents. These data types are referred to in the subsequent
+sections.
+
+[options="header"]
+|====================
+|Type Name|C/C++|Description
+|`BYTE`|`char`|Signed 8-bit integer.
+|`UBYTE`|`unsigned char`|Unsigned 8-bit integer.
+|`INT16`|`short`|Signed 16-bit integer.
+|`UINT16`|`unsigned short`|Unsigned 16-bit integer.
+|`INT32`|`int`|Signed 32-bit integer.
+|`UINT32`|`unsigned int`|Unsigned 32-bit integer.
+|`FLOAT`|`float`|IEEE 32-bit float.
+|`DOUBLE`|`double`|IEEE 64-bit float.
+|`STRING[n]`|`char[]`|Array of `UBYTE`s. If `[n]` is specified, it indicates maximum allowed number of characters in this string including (if neccessary) termination character.
+|`TIMESTAMP`|None|Timestamp represented with two `UINT32` values. First is number of seconds since 0000 Jan 1, 1990. Second is number of nanoseconds within second
+|====================
+
+All values are transmitted over the network in big-endian (network) order.
+For example: `UINT32` 3145 (`0x00000C49`) would be sent over the network
+represented as `00 00 0C 49`.
+
+
+== Messages
+
+
+=== Message Structure
+
+All channel access messages are composed of a *header*, followed by the
+*payload*.
+
+Header is always present. Its structure is fixed, and contains predefined
+fields. At the very least, this will be command ID and payload size.
+Other header fields may carry command-specific meaning. If a field is not used
+within a certain message, its value must be 0 (`0x00`).
+
+Payload is a sequence of bytes, which are command and version dependent.
+Implementation is required to provide proper payload with respect to
+individual command specification.
+
+Total size of an individual message is limited. With CA versions older than
+`CA_V49`, the maximum message size is limited to 16384 (`0x4000`) bytes.
+Out of these, header has a fixed size of 16 (`0x10`) bytes, with the payload
+having a maximum size of 16368 (`0x3ff0`) bytes.
+
+Versions `CA_V49` and higher may use the *extended message form*, which allows
+for larger payloads. The extended message form is indicated by the header
+fields `Payload Size` and `Data Count` being set to `0xffff` and 0,
+respectively. Real payload size and data count are then given as `UINT32` type
+values immediately following the header. Maximum message size is limited by
+32-bit unsigned integer representation, 4294967295 (`0xffffffff`).
+Maximum payload size is limited to 4294967255 (`0xffffffe7`).
+
+Extended message form should only be used if payload size actualy exceeds the
+pre-`CA_V49` message size limit of 16368 bytes.
+
+
+==== Header
+
+.Standard Message Header
+[options="header"]
+|====================
+|0|1|2|3|4|5|6|7
+2+|Command 2+|Payload size 2+|Data type 2+|Data count
+4+|Parameter 1 4+|Parameter 2
+|====================
+
+.Extended Message Header
+[options="header"]
+|====================
+|0|1|2|3|4|5|6|7
+2+|Command 2+|`0xFFFF` 2+|Data type 2+|`0x0000`
+4+|Parameter 1 4+|Parameter 2
+4+|Payload size 4+|Data count
+|====================
+
+Names of header fields are based on their most common use. Certain messages
+will use individual fields for purposes other than those described here. These
+variations are documented for each message individually. All of values in
+header are unsigned integers.
+
+The common header present in all messages is structured as follows:
+
+[options="header"]
+|====================
+|Parameter|Type|Description
+|Command|`UINT16`|Identifier of the command this message requests. The meaning of other header fields and the payload depends on the command.
+|Payload Size|`UINT16`|Size of the payload (in bytes). Must not exceed `0x4000`. Value of `0xFFFF` indicates extended message.
+|Data Type|`UINT16`|Identifier of the data type carried in the payload. Data types are defined in section <<payload-data-types,Payload Data Types>>.
+|Data Count|`UINT16`|Number of elements in the payload.
+|Parameter 1|`UINT32`|Command dependent parameter.
+|Parameter 2|`UINT32`|Command dependent parameter.
+|====================
+
+The extended message header (`CA_V49` and newer) has the following structure:
+
+[options="header"]
+|====================
+|Parameter|Type|Description
+|Command|`UINT16`|Identifier of the command this message requests. The meaning of other header fields and the payload depends on the command.
+|`0xFFFF`|`UINT16`|Extended message marker.
+|Data Type|`UINT16`|Identifier of the data type carried in the payload. Data types are defined in section <<payload-data-types,Payload Data Types>>.
+|`0x0000`|`UINT16`|Extended message marker.
+|Parameter 1|`UINT32`|Command dependent parameter.
+|Parameter 2|`UINT32`|Command dependent parameter.
+|Payload Size|`UINT32`|Size of the payload (in bytes).
+|Data Count|`UINT32`|Number of elements in the payload.
+|====================
+
+
+==== Payload
+
+The structure of the payload depends on the type of the message. The size of
+the payload matches the `Payload Size` header field.
+
+[NOTE]
+If the payload size is not a multiple of 8, zero-padding must be performed to
+achieve 8-byte alignment.
+
+
+=== Message Identifiers
+
+Some fields in messages serve as identifiers, which must be properly handled
+by the implementation. These fields serve as identification tokens in
+asynchronous communication and must be unique within the context of the client
+library. Recommended scheme for allocating these values is to create them
+sequentially starting at 0. All IDs are represented with `UINT32`.
+
+Overflow must be anticipated! Although it is unlikely that an application will
+need more than 2^32^ different channel IDs, such an overflow can occur with
+the IOID identifier (see below).
+
+
+[[cid-client-id]]
+==== CID - Client ID
+
+CID identifies individual channel within client library context. When a
+message requires the CID, this value must be passed. CID for a given channel
+may not change within the lifetime of the channel.
+
+Recommended way of allocating CIDs is sequential 0-based indexing.
+First client library channel reference that is created has value of 0,
+second 1, etc. Duplicate CIDs within a single active instance of client
+library are not allowed.
+
+CID value is passed to the server when the channel is actually connected.
+
+Overflow should be potentially handled, since an application with expected
+long lifetime and frequent channel allocation and destruction might increase
+the index frequently. The best way to handle it is to ignore the problem until
+the first overflow. When that occurs, old CIDs should be no longer relevant,
+and CID value can be restarted from 0, but excluding any already used values.
+
+
+[[sid-server-id]]
+==== SID - Server ID
+
+Performs the same function as CID, but is provided by the server when the
+channel is connected. SID of channel will never change, unless the channel
+represented by particular SID is removed from the server during runtime.
+In that case, the channel will be no longer available.
+
+To handle overflows, the same method could be used as for the Client Channel
+ID.
+
+
+[[subscription-id]]
+==== Subscription ID
+
+When a subscription is created on a channel (monitor), a unique subscription
+ID must be provided. Client library will use this ID to identify different
+subscriptions on the same channel. This value will allow the client library to
+dispatch monitors appropriately.
+
+Any subscription ID is only valid during the subscription's lifespan. After
+that, IDs may be reused.
+
+
+==== IOID
+
+Unique ID is given to all read and write messages sent by the client library.
+
+ID passed with the request will be returned in the matching response.
+
+Properly handling the wrapping of identifiers is vital to IOID, since an
+individual ID is used each time a request is made.
+
+
+== Commands (TCP and UDP)
+
+The following commands are sent as either UDP datagrams or TCP messages.
+Some of the messages are also used within the context of a Virtual Circuit.
+
+
+[[ca-proto-version]]
+=== `CA_PROTO_VERSION`
+
+[horizontal]
+Command::
+    `CA_PROTO_VERSION`
+ID::
+    0 (`0x00`)
+Description::
+    Exchanges client and server protocol versions and desired circuit
+    priority. This is the first message sent when a new TCP (Virtual Circuit)
+    connection is established. Must be sent before any other exchange between
+    client, server and repeater. The communication is not strictly request
+    response, but will be perceived as such by the implementation.
+    When a new TCP connection is established by the client, `CA_PROTO_VERSION`
+    is sent. Likewise, the server will accept the connection and send the
+    response form back. Sent over UDP or TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|0|Command identifier for `CA_PROTO_VERSION`.
+|Payload size|0|Must be 0.
+|Priority|Desired priority|Virtual circuit priority.
+|Version|Version number|Minor protocol version number. Only used when sent over TCP.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+.Compatibility
+[options="header"]
+|====================
+|Version|Comment
+|>= `CA_V411`|Server will send response immediately after establishing a virtual circuit.
+|< `CA_V411`|Message does not include minor version number (it is always 0) and is interpreted as an echo command that carries no data. Version exchange is performed immediately after <<ca-proto-create-chan,`CA_PROTO_CREATE_CHAN`>>.
+|====================
+
+.Comments
+* Priority indicates the server's dispatch scheduling priority which might be
+  implemented by a circuit dedicated thread's scheduling priority in a
+  preemptive scheduled OS.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|0|Command identifier for `CA_PROTO_VERSION`.
+|Reserved|0|Must be 0.
+|Priority|0|Must be 0.
+|Version|Version number|Minor protocol version number. Only used when sent over TCP.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+.Compatibility
+[options="header"]
+|====================
+|Version|Comment
+|>= `CA_V411`|Server will not respond to request, but send response immediately after establishing a virtual circuit.
+|< `CA_V411`|Message does not include minor version number (it is always 0).
+|====================
+
+
+[[ca-proto-search]]
+=== `CA_PROTO_SEARCH`
+
+[horizontal]
+Command::
+    `CA_PROTO_SEARCH`
+ID::
+    6 (`0x06`)
+Description::
+    Searches for a given channel name. Sent over UDP or TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|6|Command identifier for `CA_PROTO_SEARCH`.
+|Payload Size|>= 0|Padded size of channel name.
+|Reply|Reply Flag|<<search-reply-flag,Search Reply Flag>>, indicating whether failed search response should be returned.
+|Version|Version Number|Client minor protocol version number.
+|CID|Channel CID|Client allocated CID.
+|CID|Channel CID|Client allocated CID.
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|Channel name|`STRING`||Name of channel to search for.
+|====================
+
+.Comments
+* Sent as a UDP datagram.
+* It is illegal to specify `DO_REPLY` flag whenever the message is sending as
+  UDP datagram, regardless of whether broadcast or multicast is used.
+* CID will be allocated by the client before this message is sent.
+* CID field value is duplicated.
+* Reply flag will be generally `DONT_REPLY` when searching using broadcast and
+  `DO_REPLY` when searching using unicast. When `DO_REPLY` is set, server will
+  send a <<ca-proto-not-found,`CA_PROTO_NOT_FOUND`>> message indicating it
+  does not have the requested channel.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|6|Command identifier for `CA_PROTO_SEARCH`.
+|Payload Size|8|Payload size is constant.
+|Data Type|Port number|TCP Port number of server that responded.
+|Data Count|0|Must be 0.
+|SID|`0xffffffff`|Temporary <<sid-server-id,SID>>.
+|CID|Same as request|Channel <<cid-client-id,CID>>.
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|Server protocol version|`UINT16`||Server protocol version.
+|====================
+
+.Comments
+* Received as UDP datagram.
+* Client channel ID field value (CID) is copied from the request.
+* Port number of the server indicates on which port the server that replied
+  listens to. This is used in case more than one server share the same IP.
+* Server-assigned channel ID will have value of `0xffffffff`, since the SID is
+  not known at this time. Real value will be returned when channel is actually
+  created using `CA_CREATE_CHAN`.
+* In `CA_V411` the server's IP address is optionally returned in the CID field
+  of the header allowing a CA server to act as a directory service.
+  If not, then the CID field is set to `0xffffffff`.
+* The port number included in the header is the *TCP* port of the server.
+  Two servers on the same host can share a UDP port number, but not a TCP port
+  number. Therefore, the port the client needs to connect to in that situation
+  may not be the same as expected if this field in the response is not used.
+
+
+[[ca-proto-not-found]]
+=== `CA_PROTO_NOT_FOUND`
+
+[horizontal]
+Command::
+    `CA_PROTO_NOT_FOUND`
+ID::
+    14 (`0x0E`)
+Description::
+    Indicates that a channel with requested name does not exist.
+    Sent in response to <<ca-proto-search,`CA_PROTO_SEARCH`>>, but only when
+    its `DO_REPLY` flag was set. Sent over UDP.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|14|Command identifier for `CA_PROTO_NOT_FOUND`.
+|Reserved|0|Must be 0.
+|Reply Flag|`DO_REPLY`|Same reply flag as in request: always `DO_REPLY`.
+|Version|Same as request|Client minor protocol version number.
+|CID|Same as request|CID of the channel.
+|CID|Same as request|CID of the channel.
+|====================
+
+.Comments
+* Contents of the header are copied from the request.
+* CID fields are diplicated.
+* Original request payload is not returned with the response.
+
+
+[[ca-proto-echo]]
+=== `CA_PROTO_ECHO`
+
+[horizontal]
+Command::
+    `CA_PROTO_ECHO`
+ID::
+    23 (`0x17`)
+Description::
+    Connection verify used by `CA_V43`. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|23|Command identifier for `CA_PROTO_ECHO`.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|23|Command identifier for `CA_PROTO_ECHO`.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+
+== Commands (UDP)
+
+The following commands are sent as UDP datagrams.
+
+
+[[ca-proto-rsrv-is-up]]
+=== `CA_PROTO_RSRV_IS_UP`
+
+[horizontal]
+Command::
+    `CA_PROTO_RSRV_IS_UP`
+ID::
+    13 (`0x0D`)
+Description::
+    Beacon sent by a server when it becomes available. Beacons are also sent
+    out periodically to announce the server is still alive. Another function
+    of beacons is to allow detection of changes in network topology.
+    Sent over UDP.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|13|Command identifier for `CA_PROTO_RSRV_IS_UP`.
+|Reserved|0|Must be 0.
+|Server port|>= 0|TCP Port the server is listening on.
+|Reserved|0|Must be 0.
+|BeaconID|Sequential integers|Sequential Beacon ID.
+|Address|0 or IP|May contain IP address of the server.
+|====================
+
+.Comments
+* IP field may contain IP of the server. If IP is not present (field Address
+  value is 0), then IP may be substituted by the receiver of the packet
+  (usually repeater) if it is capable of identifying where this packet came
+  from. Any non-zero address must be interpreted as server's IP address.
+* BeaconIDs are useful in detecting network topology changes. In certain
+  cases, same packet may be routed using two different routes, causing
+  problems with datagrams. If multiple beacons are received from the same
+  server with same BeaconID, multiple routes are the cause.
+* If a server is restarted, it will most likely start sending BeaconID values
+  from beggining (0). Such situation must be anticipated.
+
+
+[[ca-repeater-confirm]]
+=== `CA_REPEATER_CONFIRM`
+
+[horizontal]
+Command::
+    `CA_REPEATER_CONFIRM`
+ID::
+    17 (`0x11`)
+Description::
+    Confirms successful client registration with repeater. Sent over UDP.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|17|Command identifier for `CA_REPEATER_CONFIRM`.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Repeater address|IP address|Address with which the registration succeeded.
+|====================
+
+.Comments
+* Since repeater can bind to different local address, its IP is reported in
+  Repeater address. This address will be either `0.0.0.0` or `127.0.0.1`.
+
+
+[[ca-repeater-register]]
+=== `CA_REPEATER_REGISTER`
+
+[horizontal]
+Command::
+    `CA_REPEATER_REGISTER`
+ID::
+    24 (`0x18`)
+Description::
+    Requests registration with the repeater. Repeater will confirm successful
+    registration using `CA_REPEATER_CONFIRM`. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_REPEATER_REGISTER`|Command identifier
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Client IP address|IP address|IP address on which the client is listening
+|====================
+
+
+== Commands (TCP)
+
+The following commands are used within the context of Virtual Circuit and are
+sent using TCP.
+
+
+[[ca-proto-event-add]]
+=== `CA_PROTO_EVENT_ADD`
+
+[horizontal]
+Command::
+    `CA_PROTO_EVENT_ADD`
+ID::
+    1 (`0x01`)
+Description::
+    Creates a subscription on a channel, allowing the client to be notified of
+    changes in value. A request will produce at least one response.
+    Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|1|Command identifier for `CA_PROTO_EVENT_ADD`
+|Payload Size|16|Payload size is constant
+|Data Type||Desired DBR type of the return value.
+|Data Count|>= 0|Desired number of elements
+|SID|SID of the channel.|SID of the channel on which to register this subscription. See <<sid-server-id,SID - Server ID>>.
+|SubscriptionID|Client provided Subscription ID|Subscription ID identifying this subscription.See <<subscription-id,Subscription ID>>.
+|====================
+
+Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|Low val|`FLOAT32`|0.0|Low value
+|High val|`FLOAT32`|0.0|High value
+|To val|`FLOAT32`|0.0|To value
+|Mask|`UINT16`|Monitor mask|<<monitor-mask,Mask>> indicating which events to report
+|====================
+
+.Comments
+* All payload fields except Mask are initialized to 0 and are present only for
+  backward compatibility.
+* Successful subscription will result in an immediate response with the
+  current value. Additional responses will be sent as the change occurs based
+  on the Mask parameter.
+* Mask defines a filter on which events will be sent.
+* A subscription should be destroyed when no longer needed to reduce load on
+  server. See <<ca-proto-event-cancel,`CA_PROTO_EVENT_CANCEL`>>.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|1|Command identifier for `CA_PROTO_EVENT_ADD`
+|Payload Size|>= 0|Size of the response.
+|Data Type|same as request|Payload data type.
+|Data Count|same as request|Payload data count.
+|Status code|One of ECA codes|<<return-codes,Status code>> (`ECA_NORMAL` on success).
+|SubscriptionID|same as request|Subscription ID
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|Values|DBR||Value stored as DBR type specified in Data Type field. See <<payload-data-types,Payload Data Types>>.
+|====================
+
+.Comments
+* Response data type and count match that of the request.
+* To confirm successful subscription, first response will be sent immediately.
+  Additional responses will be sent as the change occurs based on mask
+  parameters.
+
+
+[[ca-proto-event-cancel]]
+=== `CA_PROTO_EVENT_CANCEL`
+
+[horizontal]
+Command::
+    `CA_PROTO_EVENT_CANCEL`
+ID::
+    2 (`0x02`)
+Description::
+    Clears event subscription. This message will stop event updates for
+    specified channel. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|2|Command identifier for `CA_PROTO_EVENT_CANCEL`.
+|Payload Size|0|Must be 0.
+|Data Type||Same value as in corresponding <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>>.
+|Data Count|>= 0|Same value as in corresponding <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>>.
+|SID|SID of channel|Same value as in corresponding <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>>.
+|SubscriptionID|Subscription ID|Same value as in corresponding <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>>.
+|====================
+
+.Comments
+* Both SID and SubscriptionID are used to identify which subscription on which
+  monitor to destroy.
+* Actual data type and count values are not important, but should be the same
+  as used with corresponding <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>>.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|1|Command identifier for `CA_PROTO_EVENT_ADD`.
+|Payload Size|0|Must be 0.
+|Data Type|Same as request.|Same value as `CA_PROTO_EVENT_ADD` request.
+|Data Count|0|Must be 0.
+|SID|Same as request.|Same value as `CA_PROTO_EVENT_ADD` request.
+|SubscriptionID|Same as request.|Same value as `CA_PROTO_EVENT_ADD` request.
+|====================
+
+.Comments
+* Notice that the response has <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>>
+  command identifier!
+* Regardless of data type and count, this response has no payload.
+
+
+[[ca-proto-read]]
+=== `CA_PROTO_READ`
+
+[horizontal]
+Command::
+    `CA_PROTO_READ`
+ID::
+    3 (`0x03`)
+Description::
+
+Read value of a channel. Sent over TCP.
+
+*Deprecated since protocol version 3.13.*
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|3|Command identifier for `CA_PROTO_READ_NOTIFY`.
+|Payload Size|0|Must be 0.
+|Data Type|DBR type|Desired type of the return value.
+|Data Count|>= 0|Desired number of elements to read.
+|SID|Channel SID|SID of the channel to read.
+|IOID|Client provided IOID|IOID of this operation.
+|====================
+
+.Comments
+* Channel from which to read is identified using SID.
+* Response will contain the same IOID as the request, making it possible to
+  distinguish multiple responses.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|3|Command identifier for `CA_PROTO_READ_NOTIFY`.
+|Payload size|Size of payload|Size of DBR formatted data in payload.
+|Data type|DBR type|Payload format.
+|Data count|>= 0|Payload element count.
+|SID|Same as request|SID of the channel.
+|IOID|Same as request|IOID of this operation.
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|DBR formatted data|DBR|DBR formatted data|Value stored as DBR type specified in Data type field. Data count specifies number of elements of DBR value field.
+|====================
+
+
+[[ca-proto-write]]
+=== `CA_PROTO_WRITE`
+
+[horizontal]
+Command::
+    `CA_PROTO_WRITE`
+ID::
+    4 (`0x04`)
+Description::
+    Writes new channel value. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_WRITE`|Command identifier
+|Payload size|Size of DBR formatted payload|Size of padded payload
+|Data type|DBR type|Format of payload
+|Data count|`ELEMENT_COUNT`|Number of elements in payload
+|SID|SID provided by server|Server channel ID
+|IOID|Client provided IOID|Request ID
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|DBR formatted data|DBR|DBR formatted data|Value stored as DBR type specified in Data type field. Data count specifies number of elements of DBR value field.
+|====================
+
+.Comments
+* There is no response to this command.
+
+
+[[ca-proto-snapshot]]
+=== `CA_PROTO_SNAPSHOT`
+
+[horizontal]
+Command::
+    `CA_PROTO_SNAPSHOT`
+ID::
+    5 (`0x05`)
+Description::
+    Obsolete.
+
+
+[[ca-proto-build]]
+=== `CA_PROTO_BUILD`
+
+[horizontal]
+Command::
+    `CA_PROTO_BUILD`
+ID::
+    7 (`0x07`)
+Description::
+    Obsolete.
+
+
+[[ca-proto-events-off]]
+=== `CA_PROTO_EVENTS_OFF`
+
+[horizontal]
+Command::
+    `CA_PROTO_EVENTS_OFF`
+ID::
+    8 (`0x08`)
+Description::
+    Disables a server from sending any subscription updates over this virtual
+    circuit. Sent over TCP. This mechanism is used by clients with slow CPU to
+    prevent congestion when they are unable to handle all updates received.
+    Effective automated handling of flow control is beyond the scope of this
+    document.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|8|Command identifier for `CA_PROTO_EVENTS_OFF`
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+.Comments
+* This request will disable sending of subscription updates on the server to
+  which it is sent.
+* Command applies to a single virtual circuit, so having multiple priority
+  virtual circuit connections to the server would only affect the one on which
+  the message is sent.
+* No response will be sent for this request.
+
+
+[[ca-proto-events-on]]
+=== `CA_PROTO_EVENTS_ON`
+
+[horizontal]
+Command::
+    `CA_PROTO_EVENTS_ON`
+ID::
+    9 (`0x09`)
+Description::
+    Enables the server to resume sending subscription updates for this virtual
+    circuit. Sent over TCP. This mechanism is used by clients with slow CPU to
+    prevent congestion when they are unable to handle all updates received.
+    Effective automated handling of flow control is beyond the scope of this
+    document.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|9|Command identifier for `CA_PROTO_EVENTS_ON`
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+.Comments
+* This request will enable sending of subscription updates on the server to
+  which it is sent.
+* Command applies to a single virtual circuit, so having multiple priority
+  virtual circuit connections to the server would only affect the one on which
+  the message is sent.
+* No response will be sent for this request.
+
+
+[[ca-proto-read-sync]]
+=== `CA_PROTO_READ_SYNC`
+
+[horizontal]
+Command::
+    `CA_PROTO_READ_SYNC`
+ID::
+    10 (`0x0A`)
+Description::
+    *Deprecated since protocol version 3.13.*
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|10|Command identifier for `CA_PROTO_READ_SYNC`.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+
+[[ca-proto-error]]
+=== `CA_PROTO_ERROR`
+
+[horizontal]
+Command::
+    `CA_PROTO_ERROR`
+ID::
+    11 (`0x0B`)
+Description::
+    Sends error message and code. This message is only sent from server to
+    client in response to any request that fails and does not include error
+    code in response. This applies to all asynchronous commands. Error message
+    will contain a copy of original request and textual description of the
+    error. Sent over UDP.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|11|Command identifier for `CA_PROTO_ERROR`
+|Payload Size||Size of the request header that triggered the error plus size of the error message.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|CID|Channel CID|<<cid-client-id,CID>> of the channel for which request failed.
+|Status Code|One of ECA codes|<<return-codes,Error status code>>.
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|Original Request|Message Header||Header of the request that caused the error.
+|Error Message|`STRING`||A null-terminated string conveying the error message.
+|====================
+
+.Comments
+* Complete exception report is returned. This includes error message code, CID
+  of channel on which the request failed, original request and string
+  description of the message.
+* CID value depends on original request and may not actually identify a
+  channel.
+* First part of payload is original request header with the same structure as
+  sent. Any payload that was part of this request is not included.
+  Textual error message starts immediately after the header.
+
+
+[[ca-proto-clear-channel]]
+=== `CA_PROTO_CLEAR_CHANNEL`
+
+[horizontal]
+Command::
+    `CA_PROTO_CLEAR_CHANNEL`
+ID::
+    12 (`0x0C`)
+Description::
+    Clears a channel. This command will cause server to release the associated
+    channel resources and no longer accept any requests for this SID/CID.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|12|Command identifier of `CA_PROTO_CLEAR_COMMAND`
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|SID|SID of the channel|SID of channel to clear.
+|CID|CID of the channel|CID of channel to clear.
+|====================
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|12|Command identifier of `CA_PROTO_CLEAR_COMMAND`
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|SID|Same as request|SID of cleared channel.
+|CID|Same as request|CID of cleared channel.
+|====================
+
+.Comments
+* Server responds immediately and only then releases channel resources.
+* Once a channel with a given SID has been cleared, any request sent with this
+  SID will fail.
+* Sent over TCP.
+
+
+[[ca-proto-read-notify]]
+=== `CA_PROTO_READ_NOTIFY`
+
+[horizontal]
+Command::
+    `CA_PROTO_READ_NOTIFY`
+ID::
+    15 (`0x0F`)
+Description::
+    Read value of a channel. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|15|Command identifier for `CA_PROTO_READ_NOTIFY`.
+|Payload Size|0|Must be 0.
+|Data Type|DBR type|Desired type of the return value.
+|Data Count|>= 0|Desired number of elements to read.
+|SID|Channel SID|SID of the channel to read.
+|IOID|Client provided IOID|IOID of this operation.
+|====================
+
+.Comments
+* Channel from which to read is identified using SID.
+* Response will contain the same IOID as the request, making it possible to
+  distinguish multiple responses.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|15|Command identifier for `CA_PROTO_READ_NOTIFY`.
+|Payload size|Size of payload|Size of DBR formatted data in payload.
+|Data type|DBR type|Payload format.
+|Data count|>= 0|Payload element count.
+|SID|Same as request|SID of the channel.
+|IOID|Same as request|IOID of this operation.
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|DBR formatted data|DBR|DBR formatted data|Value stored as DBR type specified in Data type field. Data count specifies number of elements of DBR value field.
+|====================
+
+
+[[ca-proto-read-build]]
+=== `CA_PROTO_READ_BUILD`
+
+[horizontal]
+Command::
+    `CA_PROTO_READ_BUILD`
+ID::
+    16 (`0x10`)
+Description::
+    Obsolete
+
+
+==== Request
+
+
+[[ca-proto-create-chan]]
+=== `CA_PROTO_CREATE_CHAN`
+
+[horizontal]
+Command::
+    `CA_PROTO_CREATE_CHAN`
+ID::
+    18 (`0x12`)
+Description::
+    Requests creation of channel. Server will allocate required resources and
+    return initialized SID. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|18|Command identifier for `CA_PROTO_CREATE_CHAN`
+|Payload size|Size of payload|Padded length of channel name.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|CID|Channel CID|CID of the channel to create.
+|Client version|Version number|Client minor protocol version.
+|====================
+
+.Payload
+|[options="header"]
+|====================
+|Name|Type|Value|Description
+|Channel name|`STRING`||Name of channel to create.
+|====================
+
+.Comments
+* CID sent should be the same as used with `CA_PROTO_SEARCH`.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_CREATE_CHAN`|
+|Payload size|0|Must be 0
+|Data type|DBR type|Native channel data type
+|Data count|>= 0|Native channel data count
+|CID|Same as request|Channel client ID
+|SID|SID provided by server|Channel server ID
+|====================
+
+.Comments
+* SID will be associated with CID on the server and will be reused sending
+  certain commands that require it as a parameter.
+* SID will be valid until the channel is cleared using `CA_PROTO_CLEAR` or
+  server destroys the PV the channel references.
+
+
+[[ca-proto-write-notify]]
+=== `CA_PROTO_WRITE_NOTIFY`
+
+[horizontal]
+Command::
+    `CA_PROTO_WRITE_NOTIFY`
+ID::
+    19 (`0x13`)
+Description::
+    Writes new channel value. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_WRITE_NOTIFY`|Command identifier
+|Payload size|Size of DBR formatted payload|Size of padded payload
+|Data type|DBR type|Format of payload
+|Data count|`ELEMENT_COUNT`|Number of elements in payload
+|SID|SID provided by server|Server channel ID
+|IOID|Client provided IOID|Request ID
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|DBR formatted data|DBR|DBR formatted data|Value stored as DBR type specified in Data type field. Data count specifies number of elements of DBR value field.
+|====================
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_WRITE_NOTIFY`|Command identifier
+|Payload size|0|Must be 0
+|Data type|Same as request|Format of data written
+|Data count|Same as request|Number of elements written
+|Status|Status code|Status of write success
+|IOID|Same as request|Request ID
+|====================
+
+
+[[ca-proto-client-name]]
+=== `CA_PROTO_CLIENT_NAME`
+
+[horizontal]
+Command::
+    `CA_PROTO_CLIENT_NAME`
+ID::
+    20 (`0x14`)
+Description::
+    Sends local username to virtual circuit peer. This name identifies the
+    user and affects access rights.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_CLIENT_NAME`|Command identifier
+|Payload size|>=0|Length of string in payload
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|User name|`STRING`||0-terminated username string
+|====================
+
+.Comments
+* This is a one-way message and will not receive response.
+* String in payload must be 0 padded to a length that is multiple of 8.
+* Sent over TCP.
+
+
+[[ca-proto-host-name]]
+=== `CA_PROTO_HOST_NAME`
+
+[horizontal]
+Command::
+    `CA_PROTO_HOST_NAME`
+ID::
+    21 (`0x15`)
+Description::
+    Sends local host name to virtual circuit peer. This name will affect
+    access rights. Sent over TCP.
+
+
+==== Request
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|21|Command identifier for `CA_PROTO_HOST_NAME`.
+|Payload size|Size of payload|Length of host name string.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|====================
+
+.Payload
+[options="header"]
+|====================
+|Name|Type|Value|Description
+|Host name|`STRING`||Client host name.
+|====================
+
+.Comments
+* This is one-way message and will receive no response.
+
+
+[[ca-proto-access-rights]]
+=== `CA_PROTO_ACCESS_RIGHTS`
+
+[horizontal]
+Command::
+    `CA_PROTO_ACCESS_RIGHTS`
+ID::
+    22 (`0x16`)
+Description::
+    Notifies of access rights for a channel. This value is determined based on
+    host and client name and may change during runtime. Client cannot change
+    access rights nor can it explicitly query its value, so last received
+    value must be stored.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|22|Command identifier for `CA_PROTO_ACCESS_RIGHTS`.
+|Payload size|0|Must be 0.
+|Reserved|0|Must be 0.
+|Reserved|0|Must be 0.
+|CID|Channel CID|Channel affected by change.
+|Access Rights|Access Rights|<<access-rights,Access rights>> for given channel.
+|====================
+
+.Comments
+* Access Rights affect `CA_PROTO_READ_NOTIFY`, `CA_PROTO_WRITE_NOTIFY` and
+  `CA_PROTO_WRITE`.
+* `CA_PROTO_ACCESS_RIGHTS` will be sent immediately after a channel is created
+  using `CA_PROTO_CREATE_CHAN`. If they change during runtime, this message
+  sent to report new value.
+* Changes are only sent to currently connected channels, since it requires
+  valid CID.
+* Sent over TCP.
+
+
+[[ca-proto-signal]]
+=== `CA_PROTO_SIGNAL`
+
+[horizontal]
+Command::
+    `CA_PROTO_SIGNAL`
+ID::
+    25 (`0x19`)
+Description::
+    Obsolete.
+
+
+[[ca-proto-create-ch-fail]]
+=== `CA_PROTO_CREATE_CH_FAIL`
+
+[horizontal]
+Command::
+    `CA_PROTO_CREATE_CH_FAIL`
+ID::
+    26 (`0x1A`)
+Description::
+    Reports that channel creation failed. This response is sent to when
+    channel creation in `CA_PROTO_CREATE_CHAN` fails.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_CREATE_CH_FAIL`|Command identifier
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|CID|Same as request|Client channel ID
+|Reserved|0|Must be 0
+|====================
+
+.Comments
+* Sent over TCP.
+
+
+[[ca-proto-server-disconn]]
+=== `CA_PROTO_SERVER_DISCONN`
+
+[horizontal]
+Command::
+    `CA_PROTO_SERVER_DISCONN`
+ID::
+    27 (`0x1B`)
+Description::
+    Notifies the client that server has disconnected the channel. This may be
+    since the channel has been destroyed on server. Sent over TCP.
+
+
+==== Response
+
+.Header
+[options="header"]
+|====================
+|Field|Value|Description
+|Command|`CA_PROTO_SERVER_DISCONN`|Command identifier
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|Reserved|0|Must be 0
+|CID|CID provided by client|CID that was provided during `CA_PROTO_CREATE_CHAN`
+|Reserved|0|Must be 0
+|====================
+
+
+[[payload-data-types]]
+== Payload Data Types
+
+Channel access defines special structures to transferring data. Main reason is
+efficiency, since in many cases more than one value can be transferred. These
+types are organized in typed hierarchies with loose inheritance. There are
+seven basic data types: `DBR_STRING`, `DBR_SHORT`, `DBR_INT`, `DBR_FLOAT`,
+`DBR_ENUM`, `DBR_CHAR`, `DBR_LONG` and `DBR_DOUBLE`. Each of these types can
+be represented as an array, if the corresponding field in header indicates
+that.
+
+Additional to basic data types, structured types allow access to more than one
+value within the same record. These structures are status (STS), time stamp
+(TIME), graphic (GR) and control (CTRL). All these structures contain value as
+the last field.
+
+Status structure adds alarm severity. Time stamp structures extends the status
+structure by adding time stamp of the value. Graphic extends status structure
+by providing alarm limits, units and precision. Control structure extends
+graphic by adding control limits.
+
+Following is the list of all structures as transmitted over network.
+
+
+=== `DBR_STS_STRING`
+
+[horizontal]
+Type::
+    `DBR_STS_STRING`
+ID::
+    7 (`0x07`)
+Description::
+    `DBR_STS` structure for `STRING` type.
+
+
+=== `DBR_STS_SHORT`
+
+[horizontal]
+Type::
+    `DBR_STS_SHORT`
+ID::
+    8 (`0x08`)
+Description::
+    `DBR_STS` structure for `UINT16` type. May be referred to as
+    `DBR_STS_INT`.
+
+
+=== `DBR_STS_FLOAT`
+
+[horizontal]
+Type::
+    `DBR_STS_FLOAT`
+ID::
+    9 (`0x09`)
+Description::
+    `DBR_STS` structure for `FLOAT` type.
+
+
+=== `DBR_STS_ENUM`
+
+[horizontal]
+Type::
+    `DBR_STS_ENUM`
+ID::
+    10 (`0x0A`)
+Description::
+    `DBR_STS` structure for `ENUM` type.
+
+
+=== `DBR_STS_CHAR`
+
+[horizontal]
+Type::
+    `DBR_STS_CHAR`
+ID::
+    11 (`0x0B`)
+Description::
+    `DBR_STS` structure for `CHAR` type.
+
+
+=== `DBR_STS_LONG`
+
+[horizontal]
+Type::
+    `DBR_STS_LONG`
+ID::
+    12 (`0x0C`)
+Description::
+    `DBR_STS` structure for `LONG` type.
+
+
+=== `DBR_STS_DOUBLE`
+
+[horizontal]
+Type::
+    `DBR_STS_DOUBLE`
+ID::
+    13 (`0x0D`)
+Description::
+    `DBR_STS` structure for `LONG` type.
+
+
+=== `DBR_TIME_STRING`
+
+[horizontal]
+Type::
+    `DBR_TIME_STRING`
+ID::
+    14 (`0x0E`)
+Description::
+    `DBR_TIME` structure for `STRING` type.
+
+
+=== `DBR_TIME_SHORT`
+
+[horizontal]
+Type::
+    `DBR_TIME_SHORT`
+ID::
+    15 (`0x0F`)
+Description::
+    `DBR_TIME` structure for `UINT16` type. May be referred to as
+    `DBR_TIME_INT`.
+
+
+=== `DBR_TIME_FLOAT`
+
+[horizontal]
+Type::
+    `DBR_TIME_FLOAT`
+ID::
+    16 (`0x10`)
+Description::
+    `DBR_TIME` structure for `FLOAT` type.
+
+
+=== `DBR_TIME_ENUM`
+
+[horizontal]
+Type::
+    `DBR_TIME_ENUM`
+ID::
+    17 (`0x11`)
+Description::
+    `DBR_TIME` structure for `ENUM` type.
+
+
+=== `DBR_TIME_CHAR`
+
+[horizontal]
+Type::
+    `DBR_TIME_CHAR`
+ID::
+    18 (`0x12`)
+Description::
+    `DBR_TIME` structure for `CHAR` type.
+
+
+=== `DBR_TIME_LONG`
+
+[horizontal]
+Type::
+    `DBR_TIME_LONG`
+ID::
+    19 (`0x13`)
+Description::
+    `DBR_TIME` structure for `LONG` type.
+
+
+=== `DBR_TIME_DOUBLE`
+
+[horizontal]
+Type::
+    `DBR_TIME_DOUBLE`
+ID::
+    20 (`0x14`)
+Description::
+    `DBR_TIME` structure for `DOUBLE` type.
+
+
+=== `DBR_GR_STRING`
+
+[horizontal]
+Type::
+    `DBR_GR_STRING`
+ID::
+    21 (`0x15`)
+Description::
+    `DBR_GR` structure for `STRING` type.
+
+
+=== `DBR_GR_SHORT`
+
+[horizontal]
+Type::
+    `DBR_GR_SHORT`
+ID::
+    22 (`0x16`)
+Description::
+    `DBR_GR` structure for `SHORT` type.
+
+
+=== `DBR_GR_INT`
+
+[horizontal]
+Type::
+    `DBR_GR_INT`
+ID::
+    22 (`0x16`)
+Description::
+    `DBR_GR` structure for `INT` type.
+
+
+=== `DBR_GR_FLOAT`
+
+[horizontal]
+Type::
+    `DBR_GR_FLOAT`
+ID::
+    23 (`0x17`)
+Description::
+    `DBR_GR` structure for `FLOAT` type.
+
+
+=== `DBR_GR_ENUM`
+
+[horizontal]
+Type::
+    `DBR_GR_ENUM`
+ID::
+    24 (`0x18`)
+Description::
+    `DBR_GR` structure for `ENUM` type.
+
+
+=== `DBR_GR_CHAR`
+
+[horizontal]
+Type::
+    `DBR_GR_CHAR`
+ID::
+    25 (`0x19`)
+Description::
+    `DBR_GR` structure for `CHAR` type (`UINT8` representation).
+
+
+=== `DBR_GR_LONG`
+
+[horizontal]
+Type::
+    `DBR_GR_LONG`
+ID::
+    26 (`0x1A`)
+Description::
+    `DBR_GR` structure for `LONG` type (`INT32` representation).
+
+
+=== `DBR_GR_DOUBLE`
+
+[horizontal]
+Type::
+    `DBR_GR_DOUBLE`
+ID::
+    27 (`0x1B`)
+Description::
+    `DBR_GR` structure for `DOUBLE` type.
+
+
+=== `DBR_CTRL_STRING`
+
+[horizontal]
+Type::
+    `DBR_CTRL_STRING`
+ID::
+    28 (`0x1C`)
+Description::
+    `DBR_CTRL` structure for `STRING` type.
+
+
+=== `DBR_CTRL_SHORT`
+
+[horizontal]
+Type::
+    `DBR_CTRL_SHORT`
+ID::
+    29 (`0x1D`)
+Description::
+    `DBR_CTRL` structure for `SHORT` type.
+
+
+=== `DBR_CTRL_INT`
+
+[horizontal]
+Type::
+    `DBR_CTRL_INT`
+ID::
+    29 (`0x1D`)
+Description::
+    `DBR_CTRL` structure for `INT16` type.
+
+
+=== `DBR_CTRL_FLOAT`
+
+[horizontal]
+Type::
+    `DBR_CTRL_FLOAT`
+ID::
+    30 (`0x1E`)
+Description::
+    `DBR_CTRL` structure for `FLOAT` type.
+
+
+=== `DBR_CTRL_ENUM`
+
+[horizontal]
+Type::
+    `DBR_CTRL_ENUM`
+ID::
+    31 (`0x1F`)
+Description::
+    `DBR_CTRL` structure for `ENUM` type.
+
+
+=== `DBR_CTRL_CHAR`
+
+[horizontal]
+Type::
+    `DBR_CTRL_CHAR`
+ID::
+    32 (`0x20`)
+Description::
+    `DBR_CTRL` structure for `CHAR` type (`UINT8` representation).
+
+
+=== `DBR_CTRL_LONG`
+
+[horizontal]
+Type::
+    `DBR_CTRL_LONG`
+ID::
+    33 (`0x21`)
+Description::
+    `DBR_CTRL` structure for `INT32` type.
+
+
+=== `DBR_CTRL_DOUBLE`
+
+[horizontal]
+Type::
+    `DBR_CTRL_DOUBLE`
+ID::
+    34 (`0x22`)
+Description::
+    `DBR_CTRL` structure for `DOUBLE` type.
+
+
+== Constants
+
+
+=== Port numbers
+
+Although there is no requirement as to which port numbers are used by either
+servers or clients, there are some standard values which must be used as
+defaults, unless overriden by application.
+
+Port numbers are dependant on protocol versions and are calculated using the
+folowing definitions:
+
+`CA_PORT_BASE` = 5056
+
+`CA_SERVER_PORT` = `CA_PORT_BASE` + `MAJOR_PROTOCOL_VERSION` * 2
+
+`CA_REPEATER_PORT` = `CA_PORT_BASE` + `MAJOR_PROTOCOL_VERSION` * 2 + 1
+
+Based on protocol version described in this document (4.11), port numbers used
+are `CA_SERVER_PORT` = 5064 and `CA_REPEATER_PORT` = 5065.
+
+Since registration of port numbers with link:https://iana.org[IANA] and in the
+interest of compatibility, the version numbers are unlikely to change.
+Therefore, the port numbers described here (5064 and 5065) may be considered
+final.
+
+
+=== Representation of constants
+
+This section lists various constants, their types and values used by protocol.
+
+Some constants can be combined using logical OR operation. Example: Monitor
+mask of `DBE_VALUE` and `DBE_ALARM` are combined using `(DBE_VALUE or
+DBE_ALARM)` resulting in `(1 or 4 == 5)`.
+
+To query the whether certain value is present in such combined value, and
+operation is used. Example: to query whether `DBE_ALARM` of monitor mask is
+set, `(DBE_VALUE and MASK > 0)` will return 0 if `DBE_VALUE` is not present,
+otherwise `DBE_ALARM` is present.
+
+
+[[monitor-mask]]
+=== Monitor Mask
+
+Indicates which changes to the value should be reported back to client
+library. Different values can be combined using logical OR operation.
+
+*Type:* not defined, depends on the field it is in (usually `UINT16`)
+
+* `DBE_VALUE` - value 1 (`0x01`) - Value change events are reported. Value
+  changes take into consideration a dead band within which the value changes
+  are not reported.
+* `DBE_LOG` - value 2 (`0x02`) - Log events are reported. Similiar to
+  `DBR_VALUE`, `DBE_LOG` defines a different dead band value that determines
+  frequency of updates.
+* `DBE_ALARM` - value 4 (`0x04`) - Alarm events are reported whenever alarm
+  value of the channel changes.
+
+
+[[search-reply-flag]]
+=== Search Reply Flag
+
+Indicates whether server should reply to failed search messages. If a server
+does not know about channel name, it has the option of replying to request or
+ignoring it. Usually, servers contacted through address list will receive
+request for reply.
+
+*Type:* not defined, depends on the field it is in (usually `UINT16`).
+
+* `DO_REPLY` - value 10 (`0x0a`) - Server should reply to failed search
+  requests.
+* `DONT_REPLY` - value 5 (`0x05`) - Server should ignore failed requests.
+
+
+[[access-rights]]
+=== Access Rights
+
+Defines access rights for a given channel. Accss rights are defined as
+logicaly ORred value of allowed access.
+
+*Type:* not defined, depends on the field it is in (usually `UINT16`).
+
+* `CA_PROTO_ACCESS_RIGHT_READ` - value 1 (`0x01`) - Read access is allowed
+* `CA_PROTO_ACCESS_RIGHT_WRITE` - value 2 (`0x02`) - Write access is allowed.
+
+As a reference, the following values are valid.
+
+* 0 - No access
+* 1 - Read access only
+* 2 - Write access only
+* 3 - Read and write access
+
+
+== Example message
+
+This example shows construction of messages. For details of individual
+structures, see message and data type reference (`CA_PROTO_READ_NOTIFY` and
+`DBR_GR_INT16`).
+
+A client will send `CA_PROTO_READ_NOTIFY` message with the following contents.
+
+* Data type: `DBR_GR_INT16`
+* Element count: 5
+* Server ID: 22 (obtained during channel creation)
+* Sequence ID: 56 (each read or write request increases value by one)
+
+The messsage would be represented as follows:
+
+----
+00 0F (command) 00 00 (payload size) 00 16 (data type) 00 05 (element count)
+00 00 00 16 (server ID) 00 00 00 38 (sequence ID)
+----
+
+Server would respond with success and return requested value with individual
+`DBR_GR_INT16` fields having the following values.
+
+* Status: `ECA_NORMAL`
+* Severity: `NO_ALARM` (0)
+
+----
+00 0f (command) 00 20 (payload size) 00 16 (data type) 00 05 (element count)
+00 00 00 16 (server ID) 00 00 00 38 (sequence ID)
+00 05  00 02  43 6f 75 6e 74 73 00 00  00 0a  00 00
+00 08  00 06  00 04  00 02  00 00  00 00  00 00 00 00
+    8      6      4      2      0      0      0     0
+----
+
+[[virtual-circuit-operation]]
+== Virtual Circuit Operation
+
+image:virtual-circuit.png[Virtual Circuit Schematic]
+
+
+=== Establishing virtual circuit
+
+Virtual circuit is a TCP connection between a client and a server. Each
+virtual circuit has an associated priority, which can be used by server to
+prioritize requests depending on current load. An independent circuit for
+each priority level selected by the client might be used because it allows
+for preemptive prioritized dispatch scheduling in the server when the OS
+supports that, and also allows specifying the networks scheduling priority
+when the router and or LAN support that. Regardless of how many channels are
+handled by either client or server, each client-server pair will be connected
+with exactly one TCP connection for each priority level. This level is
+specified when creating a virtual circuit.
+
+When establishing a virtual circuit, a simple handshake will be performed.
+Client will open a TCP connection to the server. After that, it sends
+<<ca-proto-version,`CA_PROTO_VERSION`>>,
+<<ca-proto-client-name,`CA_PROTO_CLIENT_NAME`>> and
+<<ca-proto-host-name,`CA_PROTO_HOST_NAME`>> messages.
+If server accepts all the supplied parameters and the client and host are
+permitted to connect, the server will respond with
+<<ca-proto-version,`CA_PROTO_VERSION`>>.
+After that, client may start sending requests.
+
+Virtual circuit will remain active as long as there is at least one channel
+active. If the TCP connection is lost, all channels using this circuit must be
+notified.
+
+
+=== Basic mode of operation
+
+In most basic role, the client will send requests to the server and await one
+or more responses, or in some special cases, no response will be expected.
+For each type of request, one of three events will occur:
+
+* Matching response will be received
+* Error response will be received by client indicating either user or client error
+* The client will receive no response, and one was expected.
+* Network failure occurs
+
+When a matching response is received, the operation has completed
+successfully. Any result returned will report any applicable return
+information. Client library will then notify the client about completion.
+
+If a request fails and server could handle this failure,
+<<ca-proto-error,`CA_PROTO_ERROR`>> response will be received or error code is
+received in response, depending on the request sent. This response contains
+original request header, error code and text description of error.
+
+Although servers are designed to always return a response, in some cases this
+will not occur. An unlikely case is that a server has failed or stopped
+responding. A more common case is broadcast search, where no replies are sent
+to search messages. The later case is designed to not overload the network by
+sending failure notifications. This however does not allow client library to
+determine, whether a search has failed, or the server load is simply too high
+and the response will arrive later. In this case, client library may assume
+that search yielded no results and notify on search failure. Regardless of
+this, should any such response arrive late, the client must be notified.
+
+In case of network failure, two situations should be anticipated. One is TCP
+connection loss for a virtual circuit. Virtual circuit has mechanisms for
+dealing with such case and should attempt to restore the connection itself.
+Repeater has no such mechanisms, since it depends on reliability of UDP
+protocol. There will be in most cases no way for repeater to determine,
+whether the packets sent actually arrive at destination. Repeater can however
+verify the clients registered with it, by attempting to bind to their port.
+If binding succeeds, the client no longer exists. Alternate way is using
+connected UDP sockets and checking ICMP destination unreachable error.
+
+
+=== Detecting virtual circuit unresponsiveness
+
+During virtual circuit life-time, the circuit may become unresponsive.
+Since this is tightly related to network availability and server load,
+determining actual cause for unresponsiveness is difficult. Basic criteria on
+which unresponsiveness should be determined are:
+
+* No beacon received from server in expected time period
+* No response received from server for a predetermined ammount of time
+  (usually 30 seconds)
+* Server does not immediatelly respond to <<ca-proto-echo,`CA_PROTO_ECHO`>>
+
+Behaviour of virtual circuit implementation under such conditions is
+undefined. Experience has shown however, that virtual circuit should not be
+disconnected when it becomes unresponsive, since this negatively impacts
+network performance under load.
+
+
+=== Channel life-cycle
+
+image:connection-states.png[Connection States]
+
+A channel discussed here is based on two levels. One is channel as seen from
+client application, the other is channel implementation in client library.
+This difference will be pointed out where applicable.
+
+When a channel is created by client application, it is initialized in
+_NEVER_CONN_ state. This indicates that channel is currently being connected
+for the first time. If connection process fails, channel moves into _FAILED_
+state and is not usable. Connection proccess within the client library will
+attempt to connect the channel repeatedly. Intervals between consecutive
+attempts should be increased, before finally giving up and determining the
+channel cannot be connected and signaling _FAILED_ state. A total number of
+attempts can be on the order of 100.
+
+When connection is established, the channel will signal to client with
+_CONN_UP_ event and changing its state to connected.
+
+Should the virtual circuit connection be lost, _CONN_DOWN_ event will change
+channel state to disconnected. Whenever virtual circuit is reconnected, the
+channel state is restored to connected. Note that reconnection process follows
+the same rules as initial process. It is also possible, that the PV will move
+between the servers, but client application should not be aware of such
+internal changes to channel.
+
+Once client application is done using the channel, it will be closed and its
+state moved changed to _CLOSED_. After that, this channel can no longer be
+used.
+
+Detailed description of channel operations is outlined below.
+
+
+=== Connecting a Channel
+
+Connection of a channel is a two phase process. First, server that hosts
+channel with a given name must be located. Second, client and server must both
+register a connection.
+
+Before connection, client library allocates CID identifier that will be used
+to reference new channel. Next it sends <<ca-proto-search,`CA_PROTO_SEARCH`>>
+with channel name request via broadcast and/or to address list. Each server
+that receives such message checks to see if it knows about this name. If it
+does, response to <<ca-proto-search,`CA_PROTO_SEARCH`>> is sent back to
+client. If not, the server checks if reply field of request is `DO_REPLY` and
+responds with <<ca-proto-not-found,`CA_PROTO_NOT_FOUND`>>, otherwise does
+nothing.
+
+Client library may receive more than one response. In this case, first
+response should be used and others rejected. The cause of multiple responses
+is same PV hosted on multiple different hosts. Client or server has no method
+of knowing which PV is 'right'. Multiple responses should be reported by the
+client to the application or user.
+
+After extracting server address and port, client library checks to see if this
+server is already known and connected via virtual circuit. If not, virtual
+circuit is established. Any requests sent through this channel will use this
+circuit.
+
+For this it sends <<ca-proto-create-chan,`CA_PROTO_CREATE_CHAN`>> request with
+channels CID and channel name. Server will respond with
+<<ca-proto-create-chan,`CA_PROTO_CREATE_CHAN`>> response which will provide
+channel type, data count and server identifier SID. In case the channel could
+not be created, error message will be returned.
+
+Having initialized both CID and SID and registered the channel with the
+server, this channel is ready for use. Client library should store these
+values for further use.
+
+
+=== Read and Write operations
+
+Read and write operations require the channel to be properly initialized and
+connected and its virtual circuit to be active. These operations use
+<<ca-proto-read-notify,`CA_PROTO_READ_NOTIFY`>> and
+<<ca-proto-write-notify,`CA_PROTO_WRITE_NOTIFY`>> messages.
+
+To read a value from a channel client library will create a
+<<ca-proto-read-notify,`CA_PROTO_READ_NOTIFY`>> request. This request will
+contain desired data type and data count parameters which may differ from
+channels native type as obtained during connect. Additionally, IOID is stored
+in request to provide unique identification. Channel that is used will be
+identified by SID that was obtained during channel creation. No payload is
+sent with request.
+
+After server processes the message reponse is either valid
+<<ca-proto-read-notify,`CA_PROTO_READ_NOTIFY`>> response or
+<<ca-proto-error,`CA_PROTO_ERROR`>> to indicate error. In case of success,
+response contains same field values as request, but has additional payload.
+This payload is formatted as requested data type with desired number of
+elements.
+
+Write operation is performed identically with payload roles reversed. Here the
+request will contain payload with DBR formatted value to write and response
+will have no payload.
+
+
+=== Subscriptions and Monitors
+
+Client creates monitors by registering a subscription on a channel. This
+causes server to notify subscribers of value changes.
+
+Subscriptions are created by first allocating unique Subscription ID. This
+identifier is used to uniquely identify various subscriptions. Next,
+<<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>> request is created using SID and
+Subscription ID. Data type and data count indicate desired value format in
+response. Additional information is provided in payload as specified in
+<<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>> reference.
+
+First <<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>> response is received
+immediately to confirm successful subscription. If error occurs,
+<<ca-proto-error,`CA_PROTO_ERROR`>> response is received.
+
+Responses arrive asynchronously until client cancels the subscription using
+<<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>> response and payload containing
+DBR formatted value. If server is shutdown during this time, events will no
+longer arrive, but the subscription will not be cancelled. Once the server is
+restarted, client library will reestablish the subscription silently without
+notifying client application.
+
+Subscription is cancelled by sending
+<<ca-proto-event-cancel,`CA_PROTO_EVENT_CANCEL`>> request with relevant
+parameters identical to those in original
+<<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>> request that created the
+subscription. Successful cancelation is confirmed by
+<<ca-proto-event-add,`CA_PROTO_EVENT_ADD`>> response without payload.
+
+Cancelling the subscription while the server is down should be handled by
+cancelling the subscription locally and not reestablishing it once the server
+is up again.
+
+
+=== Connection events
+
+If a virtual circuit is disconnected (server goes down or stops sending
+beacons), any connected channels that use this circuit should be notified.
+There is no direct way to reconnect the channel from client side, but this
+will be done by the library. Once the circuit is reestablished, client
+application is notified of status change for all channels. Even if a channel
+is reported to be disconnect as a result of virtual circuit failure, the
+channel is not closed. The only way a channel connection is actually closed
+is by explicitly closing it using
+<<ca-proto-clear-channel,`CA_PROTO_CLEAR_CHANNEL`>> thereby invalidating its
+resources.
+
+
+=== Closing the channel
+
+Channel is closed by sending
+<<ca-proto-clear-channel,`CA_PROTO_CLEAR_CHANNEL`>> request.
+Regardless of whether response confirmes closing or reports an error, CID and
+SID associated with the channel are no longer valid. Any resources still
+available to the client application are considered invalid. A channel that was
+cleared may no longer be reconnected.
+
+
+== Repeater Operation
+
+image:repeater.png[Repeater Schematic]
+
+
+=== Role
+
+Simple demonstration of repeater operation. A repeater will be used both on
+client and server side to forward incoming UDP requests to multiple clients
+and/or server on same host. Each host or client will then respond on its own.
+
+Since role of the repeater is related to host, not the client, its
+implementation must be independent from individual client instance or process.
+Repeater must not stop operation until all clients depending on it registered
+with it have shut down.
+
+
+=== Startup
+
+Each client must check for presence of repeater on startup, before any access
+to EPICS hosts is made. This check is made by attempting to bind to
+`CA_REPEATER_PORT`. If binding fails, the client may assume the repeater is
+already running and may attempt to register. This is done by sending
+`CA_REPEATER_REGISTER` datagram to `CA_REPEATER_PORT`. If repeater is already
+active, it will respond with `CA_REPEATER_CONFIRM` datagram back to client,
+otherwise the client can assume, the repeater is invalid, the process bound to
+the port is not even a repeater or that some unknown error occured. In this
+case, client will spawn new repeater and attempt registration again. Attempt
+to detect the repeater and register should be made several times with some
+reasonable delay to avoid any transient unresponsiveness that might occur.
+
+After the client has received registration confirmation from the repeater, it
+should keep listening for messages from the repeater. Any broadcasts sent by
+servers will be received by the repeater and forwarded to registered clients.
+
+
+=== Client detection
+
+The repeater tests to see if its clients exist by periodically attempting to
+bind to their ports. If unsuccessful when attempting to bind to the client's
+port, then the repeater concludes that the client no longer exists.
+A technique using connected UDP sockets and ICMP destination unreachable can
+also used. If a client is determined to no longer be present then the repeater
+un-registers that client and no longer sends messages to it.
+
+
+=== Operation
+
+Each message, the repeater receives, must be forwarded to local clients, to 
+the address provided during registration. No assumption should be made about 
+existence or state of clients.
+
+
+=== Shutdown
+
+Repeater should not shutdown on its own, if it does, there should be no active 
+clients registered with it.
+
+
+== Server Beacons
+
+Each EPICS server will send beacons periodically to report it is still active. 
+Beacon messages will contain server's IP and port, as well as sequential 
+beacon ID. Beacons will be broadcast and sent to servers address list.
+
+When a server becomes active, it will immediately start sending beacons with 
+an increasing delay. Time between beacons will start at 0.02 seconds. After 
+each beacon is sent, this time is doubled. Maximum delay between beacons will 
+be limited by server specified parameter, but is commonly 15 seconds.
+
+If a beacon is not received within expexted time, virtual circuits connected 
+to this server should be notified and virtual circuit must handle this 
+situation.
+
+
+[[return-codes]]
+== Return Codes
+
+This section covers return codes and exceptions that can occur during CA 
+command processing. In general, exceptions will be used to report various 
+events to the application. Return codes are predefined values for conditions 
+that can occur, where as exceptions are actually reported. Apart from 
+exceptions that occur on server or due to network transport, additional error 
+conditions may be reported on the client side as local exceptions.
+
+Implementation is required to handle all return codes. Local exceptions should 
+be thrown whenever implied, but only if such exception is reasonable within 
+the scope of implementation. Certain local exceptions that deal with state 
+dependent exception must always be provided.
+
+*Naming convention:* All return codes defined within the scope of CA are 
+listed with all capitals, with underscore character (`_`) replacing spaces. 
+Additionally, all exception names are prefixed with string `ECA_`.
+
+Return codes are represented as `UINT16`. First 3 least signifficant bits 
+indicate severity, remaining 13 bits are return code ID.
+
+Return codes are communicated in the protocol by the `CA_PROTO_READ_NOTIFY`, 
+`CA_PROTO_WRITE_NOTIFY`, monitor subscription responses, and the 
+`CA_PROTO_ERROR` responses.
+
+[options="header"]
+|====================
+|Code|Severity|ID|Value|Description
+|`ECA_NORMAL`|`CA_K_SUCCESS`|0|0|Normal successful completion"
+|`ECA_MAXIOC`|`CA_K_ERROR`|1|1|Maximum simultaneous IOC connections exceeded
+|`ECA_UKNHOST`|`CA_K_ERROR`|2|2|Unknown internet host
+|`ECA_UKNSERV`|`CA_K_ERROR`|3|3|Unknown internet service
+|`ECA_SOCK`|`CA_K_ERROR`|4|4|Unable to allocate a new socket
+|`ECA_CONN`|`CA_K_WARNING`|5|5|Unable to connect to internet host or service
+|`ECA_ALLOCMEM`|`CA_K_WARNING`|6|6|Unable to allocate additional dynamic memory
+|`ECA_UKNCHAN`|`CA_K_WARNING`|7|7|Unknown IO channel
+|`ECA_UKNFIELD`|`CA_K_WARNING`|8|8|Record field specified inappropriate for channel specified
+|`ECA_TOLARGE`|`CA_K_WARNING`|9|9|The requested data transfer is greater than available memory or `EPICS_CA_MAX_ARRAY_BYTES`
+|`ECA_TIMEOUT`|`CA_K_WARNING`|10|10|User specified timeout on IO operation expired
+|`ECA_NOSUPPORT`|`CA_K_WARNING`|11|11|Sorry, that feature is planned but not supported at this time
+|`ECA_STRTOBIG`|`CA_K_WARNING`|12|12|The supplied string is unusually large
+|`ECA_DISCONNCHID`|`CA_K_ERROR`|13|13|The request was ignored because the specified channel is disconnected
+|`ECA_BADTYPE`|`CA_K_ERROR`|14|14|The data type specifed is invalid
+|`ECA_CHIDNOTFND`|`CA_K_INFO`|15|15|Remote Channel not found
+|`ECA_CHIDRETRY`|`CA_K_INFO`|16|16|Unable to locate all user specified channels
+|`ECA_INTERNAL`|`CA_K_FATAL`|17|17|Channel Access Internal Failure
+|`ECA_DBLCLFAIL`|`CA_K_WARNING`|18|18|The requested local DB operation failed
+|`ECA_GETFAIL`|`CA_K_WARNING`|19|19|Channel read request failed
+|`ECA_PUTFAIL`|`CA_K_WARNING`|20|20|Channel write request failed
+|`ECA_ADDFAIL`|`CA_K_WARNING`|21|21|Channel subscription request failed
+|`ECA_BADCOUNT`|`CA_K_WARNING`|22|22|Invalid element count requested
+|`ECA_BADSTR`|`CA_K_ERROR`|23|23|Invalid string
+|`ECA_DISCONN`|`CA_K_WARNING`|24|24|Virtual circuit disconnect
+|`ECA_DBLCHNL`|`CA_K_WARNING`|25|25|Identical process variable name on multiple servers
+|`ECA_EVDISALLOW`|`CA_K_ERROR`|26|26|Request inappropriate within subscription (monitor) update callback
+|`ECA_BUILDGET`|`CA_K_WARNING`|27|27|Database value get for that channel failed during channel search
+|`ECA_NEEDSFP`|`CA_K_WARNING`|28|28|Unable to initialize without the vxWorks `VX_FP_TASK` task option set
+|`ECA_OVEVFAIL`|`CA_K_WARNING`|29|29|Event queue overflow has prevented first pass event after event add
+|`ECA_BADMONID`|`CA_K_ERROR`|30|30|Bad event subscription (monitor) identifier
+|`ECA_NEWADDR`|`CA_K_WARNING`|31|31|Remote channel has new network address
+|`ECA_NEWCONN`|`CA_K_INFO`|32|32|New or resumed network connection
+|`ECA_NOCACTX`|`CA_K_WARNING`|33|33|Specified task isnt a member of a CA context
+|`ECA_DEFUNCT`|`CA_K_FATAL`|34|34|Attempt to use defunct CA feature failed
+|`ECA_EMPTYSTR`|`CA_K_WARNING`|35|35|The supplied string is empty
+|`ECA_NOREPEATER`|`CA_K_WARNING`|36|36|Unable to spawn the CA repeater thread- auto reconnect will fail
+|`ECA_NOCHANMSG`|`CA_K_WARNING`|37|37|No channel id match for search reply- search reply ignored
+|`ECA_DLCKREST`|`CA_K_WARNING`|38|38|Reseting dead connection- will try to reconnect
+|`ECA_SERVBEHIND`|`CA_K_WARNING`|39|39|Server (IOC) has fallen behind or is not responding- still waiting
+|`ECA_NOCAST`|`CA_K_WARNING`|40|40|No internet interface with broadcast available
+|`ECA_BADMASK`|`CA_K_ERROR`|41|41|Invalid event selection mask
+|`ECA_IODONE`|`CA_K_INFO`|42|42|IO operations have completed
+|`ECA_IOINPROGRESS`|`CA_K_INFO`|43|43|IO operations are in progress
+|`ECA_BADSYNCGRP`|`CA_K_ERROR`|44|44|Invalid synchronous group identifier
+|`ECA_PUTCBINPROG`|`CA_K_ERROR`|45|45|Put callback timed out
+|`ECA_NORDACCESS`|`CA_K_WARNING`|46|46|Read access denied
+|`ECA_NOWTACCESS`|`CA_K_WARNING`|47|47|Write access denied
+|`ECA_ANACHRONISM`|`CA_K_ERROR`|48|48|Requested feature is no longer supported
+|`ECA_NOSEARCHADDR`|`CA_K_WARNING`|49|49|Empty PV search address list
+|`ECA_NOCONVERT`|`CA_K_WARNING`|50|50|No reasonable data conversion between client and server types
+|`ECA_BADCHID`|`CA_K_ERROR`|51|51|Invalid channel identifier
+|`ECA_BADFUNCPTR`|`CA_K_ERROR`|52|52|Invalid function pointer
+|`ECA_ISATTACHED`|`CA_K_WARNING`|53|53|Thread is already attached to a client context
+|`ECA_UNAVAILINSERV`|`CA_K_WARNING`|54|54|Not supported by attached service
+|`ECA_CHANDESTROY`|`CA_K_WARNING`|55|55|User destroyed channel
+|`ECA_BADPRIORITY`|`CA_K_ERROR`|56|56|Invalid channel priority
+|`ECA_NOTTHREADED`|`CA_K_ERROR`|57|57|Preemptive callback not enabled - additional threads may not join context
+|`ECA_16KARRAYCLIENT`|`CA_K_WARNING`|58|58|Client's protocol revision does not support transfers exceeding 16k bytes
+|`ECA_CONNSEQTMO`|`CA_K_WARNING`|59|59|Virtual circuit connection sequence aborted
+|====================
+
+
+== Example conversation
+
+This is example conversation between client and server. Client first 
+establishes TCP connection to the server and immediately requests creation of 
+a channel. After server aknowledges channel creation, client reads the value 
+of the channel twice. First as a single string value and second as a 
+`DBR_GR_INT16` type. After the response to both queries has been received, 
+the channel is destroyed.
+
+----
+Client to Server
+CA_PROTO_VERSION (handshake)
+00 00  00 00  00 00  00 0b  00 00 00 00  00 00 00 00
+    0      0      0     11            0            0
+CA_PROTO_CLIENT_NAME (handshake)
+00 14  00 08  00 00  00 00  00 00 00 00  00 00 00 00  61 70 75 63 65 6c 6a 00
+   20      8      8      0            0            0   a  p  u  c  e  l  j \0
+CA_PROTO_HOST_NAME (handshake)
+00 15  00 08  00 00  00 00  00 00 00 00  00 00 00 00  63 73 6c 30 36 00 00 00
+   21      8      0      0            0            0   c  s  l  0  6 \0 \0 \0
+CA_PROTO_CREATE_CHAN (request)
+00 12  00 18  00 00  00 00  00 00 00 01  00 00 00 0b
+   18     24      0      0            1           11
[phone]c 6a 3a  61 69 45 78 61 6d 70 6c 65 31 00 00 00 00 00 00
+ a  p  u  c  e  l  j  :   a  i  E  x  a  m  p  l  e  1 \0 \0 \0 \0 \0 \0
+
+Server to Client
+CA_PROTO_ACCESS_RIGHTS (handshake)
+00 16  00 00  00 00  00 00  00 00 00 01  00 00 00 03
+   22      0      0      0            1            3
+CA_PROTO_CREATE_CHAN (response)
+00 12  00 00  00 06  00 01  00 00 00 01  00 00 00 04
+   18      0      6      1            1            4
+|
+Client to Server
+CA_PROTO_READ_NOTIFY (request)
+00 0f  00 00  00 00  00 01  00 00 00 04  00 00 00 01
+   15      0      0      1            4            1
+CA_PROTO_READ_NOTIFY (request)
+00 0f  00 00  00 16  00 01  00 00 00 04  00 00 00 02
+   15      0     22      1            4           02
+
+Server to Client
+CA_PROTO_READ_NOTIFY (response)
+00 0f  00 08  00 00  00 01  00 00 00 01  00 00 00 01  30 00 00 00 00 06 00 01
+   15      8      0      1            1            1   0
+CA_PROTO_READ_NOTIFY (response)
+00 0f  00 20  00 16  00 01  00 00 00 01  00 00 00 02
+   15     32     22      1            1           02
+00 05  00 02  43 6f 75 6e 74 73 00 00  00 0a  00 00
+    5      2   C  o  u  n  t  s \0 \0     10      0
+00 08  00 06  00 04  00 02  00 00  00 00  00 00 00 00
+    8      6      4      2      0      0      0     0
+
+Client to Server
+CA_PROTO_CLEAR_CHANNEL (request)
+00 0c  00 00  00 00  00 00  00 00 00 04  00 00 00 01
+   12      0      0      0            4            1
+
+Server to Client
+CA_PROTO_CLEAR_CHANNEL (response)
+00 0c  00 00  00 00  00 00  00 00 00 04  00 00 00 01
+   12      0      0      0            4            1
+----
+
+[[glossary]]
+== Glossary of Terms
+
+IOC::
+    Input/Output Controller.
+PV::
+    Process variable.
+Virtual circuit::
+    Reusable TCP connection between client and server, through which all PVs 
+    hosted by the server can be conveyed to the client.
+
+
+[[references]]
+== References
+
+[options="header"]
+|====================
+|ID|Author|Reference|Revision|Date|Publisher
+|1|Jeffrey O. Hill|Channel Access Reference Manual|R3.14|2003|
+|2| |Java Channel Access|2.0.1|2003|
+|3|Bradner, S.|RFC 2119: Key words for use in RFCs to Indicate Requirement Levels| |1997-03|
+|====================

=== added directory 'ca_protocol/dia'
=== added file 'ca_protocol/dia/README.txt'
--- ca_protocol/dia/README.txt	1970-01-01 00:00:00 +0000
+++ ca_protocol/dia/README.txt	2014-09-29 14:22:53 +0000
@@ -0,0 +1,2 @@
+The diagrams are created with Dia.
+See http://sourceforge.net/projects/dia-installer/
\ No newline at end of file

=== added file 'ca_protocol/dia/connection-states.dia'
--- ca_protocol/dia/connection-states.dia	1970-01-01 00:00:00 +0000
+++ ca_protocol/dia/connection-states.dia	2014-09-29 14:22:53 +0000
@@ -0,0 +1,614 @@
+<?xml version="1.0" encoding="UTF-8"?>
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+    <dia:attribute name="background">
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+        <dia:attribute name="is_portrait">
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+        <dia:attribute name="fitto">
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+    <dia:attribute name="guides">
+      <dia:composite type="guides">
+        <dia:attribute name="hguides"/>
+        <dia:attribute name="vguides"/>
+      </dia:composite>
+    </dia:attribute>
+  </dia:diagramdata>
+  <dia:layer name="Hintergrund" visible="true" active="true">
+    <dia:object type="UML - State Term" version="0" id="O0">
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+      <dia:attribute name="line_colour">
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+      <dia:attribute name="fill_colour">
+        <dia:color val="#ffffff"/>
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+      <dia:attribute name="is_final">
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+    <dia:object type="UML - State" version="0" id="O1">
+      <dia:attribute name="obj_pos">
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+      <dia:attribute name="obj_bb">
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+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
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+      <dia:attribute name="elem_corner">
+        <dia:point val="7.24437,14.3625"/>
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+      <dia:attribute name="elem_width">
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+      <dia:attribute name="elem_height">
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+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
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+      <dia:attribute name="fill_colour">
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+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#NEVER_CONN#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.80000000000000004"/>
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+          <dia:attribute name="pos">
+            <dia:point val="9.72938,15.5025"/>
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+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
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+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="entry_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="do_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="exit_action">
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+      <dia:attribute name="meta">
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+      <dia:attribute name="line_colour">
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+      <dia:attribute name="fill_colour">
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+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
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+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
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+          <dia:attribute name="pos">
+            <dia:point val="9.72938,21.14"/>
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+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="entry_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="do_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="exit_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="UML - State" version="0" id="O3">
+      <dia:attribute name="obj_pos">
+        <dia:point val="6.90938,26"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="6.85938,25.95;12.5994,27.85"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="6.90938,26"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="5.6399999999999997"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="1.8"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="fill_colour">
+        <dia:color val="#ffffff"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#DISCONNECTED#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.80000000000000004"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="9.72938,27.14"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="entry_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="do_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="exit_action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="UML - Transition" version="2" id="O4">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9.72938,11.8003"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="8.98438,10.9062;10.2294,14.362"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="9.72938,11.8003"/>
+        <dia:point val="9.72938,12.3003"/>
+        <dia:point val="9.72938,13.812"/>
+        <dia:point val="9.72938,14.312"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+      </dia:attribute>
+      <dia:attribute name="orth_autoroute">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="text_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="trigger">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="guard">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="trigger_text_pos">
+        <dia:point val="9.22938,11.5562"/>
+      </dia:attribute>
+      <dia:attribute name="guard_text_pos">
+        <dia:point val="9.22938,12.5562"/>
+      </dia:attribute>
+      <dia:attribute name="direction_inverted">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O0" connection="8"/>
+        <dia:connection handle="1" to="O1" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="UML - Transition" version="2" id="O5">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9.72938,16.2125"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="6.01813,16.1625;10.2294,20"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="9.72938,16.2125"/>
+        <dia:point val="9.72938,18.0812"/>
+        <dia:point val="9.72938,18.0812"/>
+        <dia:point val="9.72938,19.95"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+      </dia:attribute>
+      <dia:attribute name="orth_autoroute">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:attribute name="text_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="trigger">
+        <dia:string>#CONN_UP#</dia:string>
+      </dia:attribute>
+      <dia:attribute name="action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="guard">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="trigger_text_pos">
+        <dia:point val="7.42563,18"/>
+      </dia:attribute>
+      <dia:attribute name="guard_text_pos">
+        <dia:point val="9.22938,17.5812"/>
+      </dia:attribute>
+      <dia:attribute name="direction_inverted">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O1" connection="8"/>
+        <dia:connection handle="1" to="O2" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="UML - Transition" version="2" id="O6">
+      <dia:attribute name="obj_pos">
+        <dia:point val="7.37534,20.9"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="1.13812,20.4;7.42534,27.4"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="7.37534,20.9"/>
+        <dia:point val="5.40938,20.9"/>
+        <dia:point val="5.40938,26.9"/>
+        <dia:point val="6.90938,26.9"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+      </dia:attribute>
+      <dia:attribute name="orth_autoroute">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="text_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="trigger">
+        <dia:string>#CONN_DOWN#</dia:string>
+      </dia:attribute>
+      <dia:attribute name="action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="guard">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="trigger_text_pos">
+        <dia:point val="3.10562,23.5"/>
+      </dia:attribute>
+      <dia:attribute name="guard_text_pos">
+        <dia:point val="4.90938,23.4"/>
+      </dia:attribute>
+      <dia:attribute name="direction_inverted">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O2" connection="8"/>
+        <dia:connection handle="1" to="O3" connection="3"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="UML - State Term" version="0" id="O7">
+      <dia:attribute name="obj_pos">
+        <dia:point val="17,14.5125"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="16.95,14.4625;18.55,16.0625"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="17,14.5125"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="1.5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="1.5"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="fill_colour">
+        <dia:color val="#ffffff"/>
+      </dia:attribute>
+      <dia:attribute name="is_final">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="UML - Transition" version="2" id="O8">
+      <dia:attribute name="obj_pos">
+        <dia:point val="12.2634,15.2625"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="12.2134,13.1125;17,15.7625"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="12.2634,15.2625"/>
+        <dia:point val="14.3943,15.2625"/>
+        <dia:point val="14.3943,15.2625"/>
+        <dia:point val="16.95,15.2625"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+      </dia:attribute>
+      <dia:attribute name="orth_autoroute">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:attribute name="text_colour">
+        <dia:color val="#ff0000"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="trigger">
+        <dia:string>#FAILED#</dia:string>
+      </dia:attribute>
+      <dia:attribute name="action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="guard">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="trigger_text_pos">
+        <dia:point val="13.8943,13.7625"/>
+      </dia:attribute>
+      <dia:attribute name="guard_text_pos">
+        <dia:point val="13.8943,14.7625"/>
+      </dia:attribute>
+      <dia:attribute name="direction_inverted">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O1" connection="8"/>
+        <dia:connection handle="1" to="O7" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="UML - Transition" version="2" id="O9">
+      <dia:attribute name="obj_pos">
+        <dia:point val="12.0331,20.9"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="11.5331,16.0127;18.25,21.05"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="12.0331,20.9"/>
+        <dia:point val="12.0331,21"/>
+        <dia:point val="17.75,21"/>
+        <dia:point val="17.75,16.0627"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+      </dia:attribute>
+      <dia:attribute name="orth_autoroute">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:attribute name="text_colour">
+        <dia:color val="#ff0000"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="trigger">
+        <dia:string>#CLOSED#</dia:string>
+      </dia:attribute>
+      <dia:attribute name="action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="guard">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="trigger_text_pos">
+        <dia:point val="14.3916,19.5"/>
+      </dia:attribute>
+      <dia:attribute name="guard_text_pos">
+        <dia:point val="14.3916,20.5"/>
+      </dia:attribute>
+      <dia:attribute name="direction_inverted">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O2" connection="4"/>
+        <dia:connection handle="1" to="O7" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="UML - Transition" version="2" id="O10">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9.72938,25.9495"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="8.98438,21.8005;12.8331,25.9995"/>
+      </dia:attribute>
+      <dia:attribute name="meta">
+        <dia:composite type="dict"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="9.72938,25.9495"/>
+        <dia:point val="9.72938,25.4495"/>
+        <dia:point val="9.72938,22.3505"/>
+        <dia:point val="9.72938,21.8505"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+      </dia:attribute>
+      <dia:attribute name="orth_autoroute">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="text_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="line_colour">
+        <dia:color val="#000000"/>
+      </dia:attribute>
+      <dia:attribute name="trigger">
+        <dia:string>#CONN_UP#</dia:string>
+      </dia:attribute>
+      <dia:attribute name="action">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="guard">
+        <dia:string>##</dia:string>
+      </dia:attribute>
+      <dia:attribute name="trigger_text_pos">
+        <dia:point val="11.4256,23.5"/>
+      </dia:attribute>
+      <dia:attribute name="guard_text_pos">
+        <dia:point val="9.22938,23.4"/>
+      </dia:attribute>
+      <dia:attribute name="direction_inverted">
+        <dia:boolean val="false"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O3" connection="8"/>
+        <dia:connection handle="1" to="O2" connection="8"/>
+      </dia:connections>
+    </dia:object>
+  </dia:layer>
+</dia:diagram>

=== added file 'ca_protocol/dia/repeater.dia'
--- ca_protocol/dia/repeater.dia	1970-01-01 00:00:00 +0000
+++ ca_protocol/dia/repeater.dia	2014-09-29 14:22:53 +0000
@@ -0,0 +1,458 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<dia:diagram xmlns:dia="http://www.lysator.liu.se/~alla/dia/">
+  <dia:diagramdata>
+    <dia:attribute name="background">
+      <dia:color val="#ffffff"/>
+    </dia:attribute>
+    <dia:attribute name="pagebreak">
+      <dia:color val="#000099"/>
+    </dia:attribute>
+    <dia:attribute name="paper">
+      <dia:composite type="paper">
+        <dia:attribute name="name">
+          <dia:string>#A4#</dia:string>
+        </dia:attribute>
+        <dia:attribute name="tmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="bmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="lmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="rmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="is_portrait">
+          <dia:boolean val="true"/>
+        </dia:attribute>
+        <dia:attribute name="scaling">
+          <dia:real val="1"/>
+        </dia:attribute>
+        <dia:attribute name="fitto">
+          <dia:boolean val="false"/>
+        </dia:attribute>
+      </dia:composite>
+    </dia:attribute>
+    <dia:attribute name="grid">
+      <dia:composite type="grid">
+        <dia:attribute name="width_x">
+          <dia:real val="1"/>
+        </dia:attribute>
+        <dia:attribute name="width_y">
+          <dia:real val="1"/>
+        </dia:attribute>
+        <dia:attribute name="visible_x">
+          <dia:int val="1"/>
+        </dia:attribute>
+        <dia:attribute name="visible_y">
+          <dia:int val="1"/>
+        </dia:attribute>
+        <dia:composite type="color"/>
+      </dia:composite>
+    </dia:attribute>
+    <dia:attribute name="color">
+      <dia:color val="#d8e5e5"/>
+    </dia:attribute>
+    <dia:attribute name="guides">
+      <dia:composite type="guides">
+        <dia:attribute name="hguides"/>
+        <dia:attribute name="vguides"/>
+      </dia:composite>
+    </dia:attribute>
+  </dia:diagramdata>
+  <dia:layer name="Hintergrund" visible="true" active="true">
+    <dia:object type="Standard - Box" version="0" id="O0">
+      <dia:attribute name="obj_pos">
+        <dia:point val="-1,-1"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="-1.05,-1.05;16.05,11.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="-1,-1"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="17"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Flowchart - Box" version="0" id="O1">
+      <dia:attribute name="obj_pos">
+        <dia:point val="1,3"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="0.95,2.95;6.05,4.95"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="1,3"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="1.9000000000000001"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="padding">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Repeater#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.80000000000000004"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="3.5,4.19"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Flowchart - Box" version="0" id="O2">
+      <dia:attribute name="obj_pos">
+        <dia:point val="10,0"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="9.95,-0.05;15.05,1.95"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="10,0"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="1.9000000000000001"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="padding">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#CA Server 1#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.80000000000000004"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="12.5,1.19"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Flowchart - Box" version="0" id="O3">
+      <dia:attribute name="obj_pos">
+        <dia:point val="10,3"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="9.95,2.95;15.05,4.95"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="10,3"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="1.9000000000000004"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="padding">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#CA Client#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.80000000000000004"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="12.5,4.19"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O4">
+      <dia:attribute name="obj_pos">
+        <dia:point val="6,3.95"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="5.95,3.5882;10.1118,4.3118"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="6,3.95"/>
+        <dia:point val="10,3.95"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="22"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O1" connection="8"/>
+        <dia:connection handle="1" to="O3" connection="7"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - ZigZagLine" version="1" id="O5">
+      <dia:attribute name="obj_pos">
+        <dia:point val="6.05031,3.95"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="6.00031,0.588197;10.1118,4"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="6.05031,3.95"/>
+        <dia:point val="8.02516,3.95"/>
+        <dia:point val="8.02516,0.95"/>
+        <dia:point val="10,0.95"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+      </dia:attribute>
+      <dia:attribute name="autorouting">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="22"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O1" connection="16"/>
+        <dia:connection handle="1" to="O2" connection="7"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Flowchart - Box" version="0" id="O6">
+      <dia:attribute name="obj_pos">
+        <dia:point val="10,6"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="9.95,5.95;15.05,7.95"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="10,6"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="1.9000000000000001"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="padding">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#CA Server 2#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.80000000000000004"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="12.5,7.19"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - ZigZagLine" version="1" id="O7">
+      <dia:attribute name="obj_pos">
+        <dia:point val="6.05031,3.95"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="6.00031,3.9;10.1118,6.8368"/>
+      </dia:attribute>
+      <dia:attribute name="orth_points">
+        <dia:point val="6.05031,3.95"/>
+        <dia:point val="8.02516,3.95"/>
+        <dia:point val="8.02516,6.475"/>
+        <dia:point val="10,6.475"/>
+      </dia:attribute>
+      <dia:attribute name="orth_orient">
+        <dia:enum val="0"/>
+        <dia:enum val="1"/>
+        <dia:enum val="0"/>
+      </dia:attribute>
+      <dia:attribute name="autorouting">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="22"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O1" connection="16"/>
+        <dia:connection handle="1" to="O6" connection="5"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O8">
+      <dia:attribute name="obj_pos">
+        <dia:point val="7.5,10"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="6.37125,8.87;8.62875,10.2325"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Host#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="1.4111111193350803"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="7.5,10"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="3"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O9">
+      <dia:attribute name="obj_pos">
+        <dia:point val="-3,3.96847"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="-3.05023,3.59103;1.1118,4.31462"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="-3,3.96847"/>
+        <dia:point val="1,3.95"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="22"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="1" to="O1" connection="7"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O10">
+      <dia:attribute name="obj_pos">
+        <dia:point val="10,7.37045"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="-3.1118,7.01201;10.05,7.73561"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="10,7.37045"/>
+        <dia:point val="-3,7.37398"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="22"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O6" connection="7"/>
+      </dia:connections>
+    </dia:object>
+  </dia:layer>
+</dia:diagram>

=== added file 'ca_protocol/dia/virtual-circuit.dia'
--- ca_protocol/dia/virtual-circuit.dia	1970-01-01 00:00:00 +0000
+++ ca_protocol/dia/virtual-circuit.dia	2014-09-29 14:22:53 +0000
@@ -0,0 +1,1368 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<dia:diagram xmlns:dia="http://www.lysator.liu.se/~alla/dia/">
+  <dia:diagramdata>
+    <dia:attribute name="background">
+      <dia:color val="#ffffff"/>
+    </dia:attribute>
+    <dia:attribute name="pagebreak">
+      <dia:color val="#000099"/>
+    </dia:attribute>
+    <dia:attribute name="paper">
+      <dia:composite type="paper">
+        <dia:attribute name="name">
+          <dia:string>#A4#</dia:string>
+        </dia:attribute>
+        <dia:attribute name="tmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="bmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="lmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="rmargin">
+          <dia:real val="2.8222000598907471"/>
+        </dia:attribute>
+        <dia:attribute name="is_portrait">
+          <dia:boolean val="true"/>
+        </dia:attribute>
+        <dia:attribute name="scaling">
+          <dia:real val="1"/>
+        </dia:attribute>
+        <dia:attribute name="fitto">
+          <dia:boolean val="false"/>
+        </dia:attribute>
+      </dia:composite>
+    </dia:attribute>
+    <dia:attribute name="grid">
+      <dia:composite type="grid">
+        <dia:attribute name="width_x">
+          <dia:real val="1"/>
+        </dia:attribute>
+        <dia:attribute name="width_y">
+          <dia:real val="1"/>
+        </dia:attribute>
+        <dia:attribute name="visible_x">
+          <dia:int val="1"/>
+        </dia:attribute>
+        <dia:attribute name="visible_y">
+          <dia:int val="1"/>
+        </dia:attribute>
+        <dia:composite type="color"/>
+      </dia:composite>
+    </dia:attribute>
+    <dia:attribute name="color">
+      <dia:color val="#d8e5e5"/>
+    </dia:attribute>
+    <dia:attribute name="guides">
+      <dia:composite type="guides">
+        <dia:attribute name="hguides"/>
+        <dia:attribute name="vguides"/>
+      </dia:composite>
+    </dia:attribute>
+  </dia:diagramdata>
+  <dia:layer name="Hintergrund" visible="true" active="true">
+    <dia:object type="Standard - Polygon" version="0" id="O0">
+      <dia:attribute name="obj_pos">
+        <dia:point val="11,12"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="10.95,11.95;23.05,22.05"/>
+      </dia:attribute>
+      <dia:attribute name="poly_points">
+        <dia:point val="11,12"/>
+        <dia:point val="23,12"/>
+        <dia:point val="23,22"/>
+        <dia:point val="21,22"/>
+        <dia:point val="21,14"/>
+        <dia:point val="11,14"/>
+      </dia:attribute>
+      <dia:attribute name="line_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#90ee90"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O1">
+      <dia:attribute name="obj_pos">
+        <dia:point val="40,18"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="39.95,17.95;50.05,31.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="40,18"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="10"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="13"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O2">
+      <dia:attribute name="obj_pos">
+        <dia:point val="11,23"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="10.95,22.95;23.05,28.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="11,23"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="5"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#90ee90"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O3">
+      <dia:attribute name="obj_pos">
+        <dia:point val="11,6"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="10.95,5.95;23.05,11.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="11,6"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="5"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#90ee90"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O4">
+      <dia:attribute name="obj_pos">
+        <dia:point val="1,5"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="0.95,4.95;10.05,15.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="1,5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="9"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="10"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#1e90ff"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O5">
+      <dia:attribute name="obj_pos">
+        <dia:point val="24,5"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="23.95,4.95;36.05,17.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="24,5"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#1e90ff"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O6">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,16"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="27.8863,14.8359;32.1478,16.3006"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Server A#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="1.4111111193350803"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,16"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="3"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O7">
+      <dia:attribute name="obj_pos">
+        <dia:point val="26,6"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="25.95,5.95;34.05,8.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="26,6"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O8">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,7"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="29.2937,6.575;30.7063,7.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#PV 1#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,7.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O7" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O9">
+      <dia:attribute name="obj_pos">
+        <dia:point val="26,9"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="25.95,8.95;34.05,11.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="26,9"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O10">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,10"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="29.2937,9.575;30.7063,10.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#PV 2#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,10.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O9" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O11">
+      <dia:attribute name="obj_pos">
+        <dia:point val="26,12"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="25.95,11.95;34.05,14.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="26,12"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O12">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,13"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="29.1675,12.575;30.8325,13.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#PV ...#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,13.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O11" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O13">
+      <dia:attribute name="obj_pos">
+        <dia:point val="5.48297,14"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="3.57047,12.87;7.39547,14.2325"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Client A#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="1.4111111193350803"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="5.48297,14"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="3"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O14">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9,7"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="8.92929,6.67929;27.0707,7.32071"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="9,7"/>
+        <dia:point val="27,7"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O15">
+      <dia:attribute name="obj_pos">
+        <dia:point val="24,19"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="23.95,18.95;36.05,31.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="24,19"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="12"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#1e90ff"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O16">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,30"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="27.8925,28.87;32.1075,30.2325"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Server B#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="1.4111111193350803"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,30"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="3"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O17">
+      <dia:attribute name="obj_pos">
+        <dia:point val="26,20"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="25.95,19.95;34.05,22.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="26,20"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O18">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,21"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="29.2937,20.575;30.7063,21.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#PV 3#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,21.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O17" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O19">
+      <dia:attribute name="obj_pos">
+        <dia:point val="26,23"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="25.95,22.95;34.05,25.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="26,23"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O20">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,24"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="29.2937,23.575;30.7063,24.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#PV 4#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,24.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O19" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O21">
+      <dia:attribute name="obj_pos">
+        <dia:point val="26,26"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="25.95,25.95;34.05,28.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="26,26"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O22">
+      <dia:attribute name="obj_pos">
+        <dia:point val="30,27"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="29.2937,26.575;30.7063,27.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#PV 5#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="30,27.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O21" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O23">
+      <dia:attribute name="obj_pos">
+        <dia:point val="1,21"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="0.95,20.95;10.05,31.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="1,21"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="9"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="10"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#1e90ff"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O24">
+      <dia:attribute name="obj_pos">
+        <dia:point val="5.5,30"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="3.59375,28.87;7.40625,30.2325"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Client B#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="1.4111111193350803"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="5.5,30"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="3"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O25">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9,10"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="8.92929,9.67929;27.0707,10.3207"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="9,10"/>
+        <dia:point val="27,10"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O26">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9,24"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="8.92929,23.6793;27.0707,24.3207"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="9,24"/>
+        <dia:point val="27,24"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O27">
+      <dia:attribute name="obj_pos">
+        <dia:point val="9,27"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="8.92929,26.6793;27.0707,27.3207"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="9,27"/>
+        <dia:point val="27,27"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O28">
+      <dia:attribute name="obj_pos">
+        <dia:point val="41,22"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="40.95,21.95;49.05,24.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="41,22"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#e5e5e5"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O29">
+      <dia:attribute name="obj_pos">
+        <dia:point val="45,23"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="42.4675,22.575;47.5325,23.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Process Variable#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="45,23.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
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+      <dia:connections>
+        <dia:connection handle="0" to="O28" connection="8"/>
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+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O30">
+      <dia:attribute name="obj_pos">
+        <dia:point val="41,25"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="40.95,24.95;49.05,27.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="41,25"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#1e90ff"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O31">
+      <dia:attribute name="obj_pos">
+        <dia:point val="45,26"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="43.825,25.575;46.175,26.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Process#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="45,26.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O30" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Box" version="0" id="O32">
+      <dia:attribute name="obj_pos">
+        <dia:point val="41,28"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="40.95,27.95;49.05,30.05"/>
+      </dia:attribute>
+      <dia:attribute name="elem_corner">
+        <dia:point val="41,28"/>
+      </dia:attribute>
+      <dia:attribute name="elem_width">
+        <dia:real val="8"/>
+      </dia:attribute>
+      <dia:attribute name="elem_height">
+        <dia:real val="2"/>
+      </dia:attribute>
+      <dia:attribute name="border_width">
+        <dia:real val="0.10000000149011612"/>
+      </dia:attribute>
+      <dia:attribute name="inner_color">
+        <dia:color val="#90ee90"/>
+      </dia:attribute>
+      <dia:attribute name="show_background">
+        <dia:boolean val="true"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O33">
+      <dia:attribute name="obj_pos">
+        <dia:point val="45,29"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="42.9137,28.575;47.0862,29.425"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#Virtual Circuit#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="45,29.28"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="2"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O32" connection="8"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Line" version="0" id="O34">
+      <dia:attribute name="obj_pos">
+        <dia:point val="41,20"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="40.9293,19.6793;49.0707,20.3207"/>
+      </dia:attribute>
+      <dia:attribute name="conn_endpoints">
+        <dia:point val="41,20"/>
+        <dia:point val="49,20"/>
+      </dia:attribute>
+      <dia:attribute name="numcp">
+        <dia:int val="1"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="start_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow">
+        <dia:enum val="8"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_length">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+      <dia:attribute name="end_arrow_width">
+        <dia:real val="0.5"/>
+      </dia:attribute>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O35">
+      <dia:attribute name="obj_pos">
+        <dia:point val="45,20"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="42.2875,19.15;47.7125,20"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#(CID, name, SID)#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="45,19.855"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="1"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O34" connection="0"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O36">
+      <dia:attribute name="obj_pos">
+        <dia:point val="18,7"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="15.36,6.08625;20.6612,7"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#(1, Channel 1, 1)#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="18,6.8125"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>
+      <dia:attribute name="valign">
+        <dia:enum val="1"/>
+      </dia:attribute>
+      <dia:connections>
+        <dia:connection handle="0" to="O14" connection="0"/>
+      </dia:connections>
+    </dia:object>
+    <dia:object type="Standard - Text" version="1" id="O37">
+      <dia:attribute name="obj_pos">
+        <dia:point val="18,10"/>
+      </dia:attribute>
+      <dia:attribute name="obj_bb">
+        <dia:rectangle val="15.36,9.08625;20.6612,10"/>
+      </dia:attribute>
+      <dia:attribute name="text">
+        <dia:composite type="text">
+          <dia:attribute name="string">
+            <dia:string>#(2, Channel 2, 2)#</dia:string>
+          </dia:attribute>
+          <dia:attribute name="font">
+            <dia:font family="sans" style="0" name="Helvetica"/>
+          </dia:attribute>
+          <dia:attribute name="height">
+            <dia:real val="0.88194444958442519"/>
+          </dia:attribute>
+          <dia:attribute name="pos">
+            <dia:point val="18,9.8125"/>
+          </dia:attribute>
+          <dia:attribute name="color">
+            <dia:color val="#000000"/>
+          </dia:attribute>
+          <dia:attribute name="alignment">
+            <dia:enum val="1"/>
+          </dia:attribute>
+        </dia:composite>
+      </dia:attribute>