02 Tw2104eu01 Eg0001 Protocol Architecture

8/13/2019 02 Tw2104eu01 Eg0001 Protocol Architecture

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Protocol Architecture of V5 Interface Siemens

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Contents

1 Introduction to Protocol Architecture 3

2 Frame Formats 8

2.1 Flag 10

2.2

FCS (Frame Check Sequence Field) 10

2.3 EFA (Envelope Function Address) 10

2.4 V5 Data Link Address 12

2.5 Data Link Connection Identifier (DLCI) 14

2.6 Control Field 18

2.7 Protocol Discriminator 22

2.8 Layer 3 Address 24

2.9 Message Types 28

2.10 Information Elements 31

Protocol Architecture of V5 Interface


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Siemens Protocol Architecture of V5 Interface

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1 Introduction to Protocol Architecture

D16

LAPV5-DL

data link sublayer

AN

FrameRelay

1

89

5

6

6

4

D16

Layer 3:Network

Layer

Layer 2:Data

Link

Layer

Layer 1:Phys.

Layer

ISDN-TE AN LE

PSTNprotocol

2

CON-TROL

protocol

LAPD

ETS

300125

EDSS1

C64

3

LAPV5-

EF

7

Mapping

function

C64

LAPV5-

EF

7

Mapping

function

LAPV5-DL

data link sublayer

PSTNprotocol

2

CON-TROL

protocol

p- and f-data

V5.1 interface

Communication

channel

Fig. 1 Protocol architecture for V5.1 interface


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ISDN-TE AN

T V5.2

PhysicalLayer

DataLink

Layer

NetworkLayer

LAPV5-DL

BCCControlLink

ControlProt.PSTN

LAPV5-DL

BCCControlLink

ControlProt.PSTN

D16/64 D16/64 C64

LAPV5-EFAN framerelay funct.

p- andf-data

Mapping function Mapping function

C64

LAPV5-EF

LE

ETS3

00125(DSS1)

Fig. 2 Protocol architecture for V5.2 interface


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The AN protocol is structured in the lower 3 layers according to OSI 7 layer model.

The PSTN protocol(belongs to layer 3) has to convert the analog subscriberinterface functions into digital messages.

No standardization has been done by ETSI for the analog subscriber connections inthe form of a functional protocol like DSS1in the case of digital subscribers. ThePSTN protocol does not control the call procedure in the AN, but it transmits thesignals and states of the a/b wire over the V5IF.

The AN has no information about the state of a call, the call processing is done bythe local exchange. The AN has to detect line conditions according to a nationalstandard and it has to map those to the PSTN protocol.

The PSTN protocol by ETSI defines a superset of messages and informationelements out of which a national subset has to be defined, which is mandatory for AN

and LE.ISDN D-channel messages according to EDSS1 LAPD-protocol are not modifiedthroughout the whole transmission, only the transmission safeguarding (layer 2)changes.

The AN frame relay for ISDN D-channel embeds the D-Channel messages into theV5 protocol.

The layer 3 of D-channel p-data (SAPI=16) is not processed in the LE, but forwardedto the packet network.

The layer 2 is subdivided into two parts, the higher one being the LAPD-V5 data link

sublayer, the lower one the V5 envelope function. The information of the data linksublayer is embedded into the EFA function as shown in the diagram below.

The higher sublayer of layer 2, the data link sublayer, is only used for PSTN andcontrol protocol, the LAPD has this sublayer implemented. The sublayer provides alogical link address for the communication between the different peer entities in ANand LE. It especially allows to separate PSTN signaling from control procedures. Thepossible values for that field are shown below.

The communication for signaling and packet data between the ISDN terminal (via NTand Uk0) runs via the 16 kbit/s D-channel.

All messages run between AN and LE on a 64 kbit/s communication channel (1 out of

max. 3, the first one being in time slot 16).


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A single V5.2 interface may consist of up to sixteen (16) 2 048 kbit/s links. Accordingto the protocol architecture and multiplexing structure a communication path maycarry information associated to several 2 048 kbit/s links (non-associated information

transfer). The failure of a communication path could therefore impact the service of alarge number of customers in an unacceptable way. This is in particular true for theBCC protocol, the control protocol, and the link control protocol, where all user portsare affected in case of a failure of the relevant communication path.

In order to improve the reliability of the V5.2 interface, protection procedures for theswitch-over of communication paths under failure are provided. The protectionmechanisms will be used to protect all active C-channels. The protection mechanismwill also protect the protection protocol C-path (itself) which is used to control theprotection switch-over procedures.

Theprotection protocoldoes not protect bearer channels, or allow the

reconfiguration of bearer channels in the event of failure of their associated 2 048kbit/s link. In the event of such failures, customers connections on these bearerchannels will fail. This is deemed acceptable, given the low predicted level of suchfailures.

In the V5.2 interface the link control protocolprovides the communication betweenAN and LE to coordinate the following functions at both sides for each individual 2048kbit/s link:

the 2 048 kbit/s layer 1 link status and link identification as relevant;

the blocking and co-ordinated unblocking of a layer 1 link by the management;

the verification of the link continuity by the link identification;

The control protocolprovides the communication between AN and LE to coordinatethe following functions at both sides:

control of user ports: to provide the bi-directional transmission capability to carrythe status and control of each individual user port;

control of layer 2 links: to provide bi-directional communication capability to carrycontrol and PSTN signaling information;

control for the support of common functions: to provide synchronized application of

provisioning data and restart capability;

The V5.2 BCC protocolprovides the means for the LE to request the AN to establishand release connections between specified AN user ports and specified V5.2interface time slots. It enables V5.2 interface bearer channels to be allocated or de-allocated by a trigger from the national PSTN or DSS1 entities, where the LE shallhave sole responsibility for time slot allocation.


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2 Frame Formats

Flag

FCS

Informationelements

Message type

L3

address field

Protrocol Discr.

Control

field

V5DLA

Flag

.

1

2

10

9

8

7

6

4

3

1

5

BCC

protocol

PSTN

protocol

ISDN

LAPD frame

FCS

Informationelements

Message type

Call

Reference

Protrocol Discr.

Control

field

DLCI

EFA

FLAG

EFA

FLAG

Flag

FCS

Informationelements

Message type

BCC ref.

number

Protrocol Discr.

Controlfield

V5DLA

EFA

FLAG

Fig. 3 Frame formats used in the V5 interface (part 1)


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Flag

FCS

Information

elements

Message type

logical C-channel

ID

FlagFlag

FCS

Information

elements

Message type

L3

address field

Protocol Discr.

Control

field

V5DLA

EFA

FLAG

for ISDN port

or common

Protection

protocol

Link control

protocol

Control protocol

for PSTN port

1

2

9

8

5

6

4

3

1

FCS

Information

elements

Message type

L3

address field

Protocol Discr.

Control

field

V5DLA

EFA

FLAG

Protocol Discr.

Control

field

V5DLA

EFA

FLAG

Flag

FCS

Information

elements

Message type

L3

address field

Protocol Discr.

Control

field

V5DLA

EFA

FLAG

10

Fig. 4 Frame formats used in the V5 interface (part 2)


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2.1 Flag

The flag identifies the beginning and end of a frame is uniformly represented by thebinary signal 01111110. The flag which opens the frame is described as the openingflag, the one that closes the frame as the closing flag. However, a closing flag mayalso serve as opening flag for the next frame.

The special significance of the opening and closing flags makes it necessary toprevent their bit patterns being reproduced by the information content in a transmittedframe.

To preclude such a possibility but still allow the transmission of any desired bitpattern, the transmitting Layer 2 checks the information contained between theopening and closing flags for sequences of five consecutive "1" bits and if necessary

inserts a "0" bit (insert bit).The receiving Layer 2 checks the frame contents between the opening and closingflags likewise, and eliminates any "0" bit directly following five consecutive "1" bits.

This precaution guarantees that frame contents will not be mistaken for opening orclosing flags. Any desired bit combination can therefore be included in the framecontents (code transparency).

2.2 FCS (Frame Check Sequence Field)

The frame check sequence (FCS) field is made up of 16 bits and is generated by thetransmitter on the basis of a set computing instruction using the contents of theaddress field, control field and information field. The FCS is transmitted as the lastfield before the closing flag.

The receiver in turn calculates from the received message the FCS according to thesame instruction and compares its own FCS with the received one. This check allowstransmission errors to be detected reliably. The frame check sequence field analysisis used to check the transmission quality in the D channel.

2.3 EFA (Envelope Function Address)

The envelope function address field consists of two octets. The EFA identifies theintended receiver of a command frame and the transmitter of a response frame. TheEFA address has 13 bits.

The range from 0 to 8175 is used to uniquely identify an ISDN user part within the V5interface.

Value 8176 is used to identify an PSTN user part.

Value 8177 is used to identify a control V5 layer 2 entity to a layer 3.


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EFA

EFA = 8177 H'FCE3

Control Protocol user

1 1 1 1 1 1 0 01 1 1 0 0 0 1 1

High byte

Low byte

EFA = 8176 HFCE1PSTN user

1 1 1 1 1 1 0 01 1 1 0 0 0 0 1

EFA = 8175 HFCD7ISDN user

EFA = 0 H00010 0 0 0 0 0 0 0

0 0 0 0 0 0 0 1

1 1 1 1 1 1 0 01 1 0 1 0 1 1 1

EFA = 8178 HFCE5BCC user

EFA = 8180 HFCE9

Link control user

EFA = 8179 HFCE7

Protection Protocol User

1 1 1 0 0 1 0 11 1 1 1 1 1 0 0

1 1 1 1 1 1 0 0

1 1 1 0 1 0 0 1

1 1 1 1 1 1 0 01 1 1 0 0 1 1 1

Fig. 5 EFA (envelope function address) layout


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2.4 V5 Data Link Address

Basically the V5DLA has the same value as the EFA. Additionally it contain the C/Rbit. The C/R (Command/Response) bit indicates whether the frame is a command(i.e. transmission self-initiated) or a response (i.e. reaction to previously transmittedcommand). If the terminal equipment (USER SIDE) transmits a command, the C/R bitis set to 0; if a response is transmitted, the bit is set to 1. The network side uses theopposite procedure, i.e. command C/R = 1, response C/R = 0.


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V5DLA

V5DLA = 8176

PSTN Signaling

C/R 0

1

V5DLA = 8177

Control protocol

V5DLA = 8178

BCC protocol

V5DLA = 8179

Protection protocol

V5DLA = 8180

Link control protocol

1 1 1 1 1 1 1 1

1 1 1 0 0 0 0 0

1 1 1 1 1 1 1 1

1 1 1 0 0 0 1 0

1 1 1 1 1 1 1 1

1 1 1 0 0 1 0 0

1 1 1 1 1 1 1 1

1 1 1 0 0 1 1 0

1 1 1 1 1 1 1 1

1 1 1 0 1 0 0 0

Fig. 6 V5DLA (V5 data link address) layout

Command/response

Transmission direction Binary valueof C/R bit

Command Networkterminal equipment 1

Terminal equipmentnetwork 0

Response Networkterminal equipment 0

Terminal equipmentnetwork 1

Fig. 7 Meaning of the C/R bit


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2.5 Data Link Connection Identifier (DLCI)

Several Layer 2 connections can be set up at the same time, whereby each individualconnection must be uniquely identifiable. Identification takes place with the Layer 2address (address field or DLCI (Data Link Connection Identifier), which is acombination of two components: the SAPI(Service Access Point Identifier) and TEI(Terminal End-Point Identifier).

The SAPIin the address field describes the class of information to be transmitted, i.e.it identifies the Layer 3 entity. These information classes allow the discriminationbetween signaling, Layer 2 management functions and packet data. The 6 bits in theaddress field can differentiate 64 information classes numbered through from 0 to 63.Bit 3 in octet 2 is the least significant bit, bit is the most significant bit. The followingtable shows the meaning of the SAPI values.

The TEIin the address field identifies the transmitting or receiving terminalequipment, and therefore allows the discrimination within one information class ofterminal equipments.

If a multiterminal configuration is connected to a basic access, the TEI identifies theterminal equipment (TE). This means each TE can set up Layer 2 connections ableto be uniquely identified by the SAPI and TEI. The TEI values 1 to 126 are used forthis purpose, with 1 to 63 being set in the terminal equipment, and 64 to 126 beingassigned by the exchange.

The TEI in the address field identifies the transmitting or receiving terminal

equipment, and therefore allows the discrimination within one information class ofterminal equipments.

If a multiterminal configuration is connected to a basic access, the TEI identifies theterminal equipment (TE). This means each TE can set up Layer 2 connections ableto be uniquely identified by the SAPI and TEI. The TEI values 1 to 126 are used forthis purpose, with 1 to 63 being set in the terminal equipment, and 64 to 126 beingassigned by the exchange.

A supplementary TEI value exists. This TEI value (TEI=127) is used to address allterminal equipments at once (broadcasting, e.g. call setup on the called side).


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TEI 1

SAPI

8 7 6 5 4 3 2 1 Bit numbering

C/R 0 Octet 2

Octet 3

C/R 0

Fig. 8 Data link connection identifier

SAPI Information class

0

16

63

Signaling

Packet data (currently used for BA only)

Layer 2 management function (TEI management)

Fig. 9 SAPI values


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TEI Meaning

0..63

64...126

127

given by terminal

given by exchange

broadcast

Fig. 10 TEI values

In compliance with the rules of the HDLC procedure the commands must always

include the address field of the destination and the responses must always includethe address field of the originator. This means that both peer entities use the sameDLCI, which is composed of SAPI and TEI.

A supplementary TEI value exists. This TEI value (TEI=127) is used to address allterminal equipments at once (broadcasting, e.g. call setup on the called side).


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SAPI=0

TEI=71

TEI=127

SAPI=0TEI=64TEI=127

Packet

data

SAPI=16TEI=64TEI=127

SAPI=0D channel (16 kbit/s)

Terminal unit 2

ExchangeSubscriber lineTerminal units

Terminal unit 1

B channels (64 kbit/s)

SAPI=16

SAPI=16

TEI=71

TEI=127

Voice

Text

Data

Image

Signaling

Voice

Text

Data

Image

Packet

data

Signaling

Signaling

SAPI=16

TEI=71

TEI=127

SAPI=0

TEI=71

TEI=127

Packet data

Fig. 11 Multiterminal configuration


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2.6 Control Field

The main task of the control fieldis to number the frames and thus to provide themeans to send a positive or a negative acknowledgment to a particular frame. Thereare three types of frames:

Information frames (I-frames) are used to transmit layer 3 data along with anumber. The number is incremented with each I-frame, and an I-frame must beacknowledged (positively) before the same number can be used simultaneouslyfor I-frame terminal. Of course, the same number can be used simultaneously for I-frames from resp. to different terminals; in this case, the distinction is given by theTEI.

Supervisory frames (S-frames) are used to acknowledge a previously received I-

frame (positively or negatively). In case of a negative acknowledgment, the I-framemust be transmitted (accordingly, the sender of an I-frame must store the frameintermediately until the final acknowledgment); in the case of a positiveacknowledgment, the intermediate storage can be cleared. S-frames do notcontain any layer 3 data, but their control field includes the number of the previousI-frame.

Unnumbered frames (U-frames) are used whenever neither a sending number oran acknowledgment number is included. This applies, for example, for globalmessages (calls to all terminals at a given subscriber line); here, layer 3 data aretransmitted without any number because no acknowledgment can be expected. U-

frames are stored intermediately.

The length of the control field is 2 bytes for I- and S-frames and 1 byte for U-frames.If the transmission has been erroneous, in case of an I-frame a retransmission isnecessary. In the case of an S-frame or a U-frame, the frame is lost.


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M P/F M 11

N(R)

N(S)

P

0

Control

Field

U-Format

S-Format

I-Format

N(R)

0 0 0 0 S S 0 1

N(S) send sequence number

N(R) receive sequence number

P/F poll/final bitM modifier function bit

S S-frame type bit

Fig. 12 Control field layout


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Some bits must be defined in the I-, U- or S-frames as follow:

P/F bit: This bit is used for a "polling" procedure whose function is to determinewhether the partner is still in normal service. One partner does this by sending a

frame with the P-bit set to 1 (default value is 0), which indicates to the oppositeside that an immediate response is requested. The opposite side responds bysending a frame with the F-bit set to 1. This response is time-monitored.

Modifier function (M) bits indicate the U-frame types (SABME, DISC, UA, ...).

S-frame function (S) bits distinguish the three S-type frames: Receive Ready,Receive Not Ready and Reject).

The N (R) is used for expect the send sequence number of the next receiver I-frame and S-frame.

The N (S) is used for expect the received sequence number or the next received I-

frame.

The receive sequence number confirms the error-free reception of all I-frame typesincluding the send sequence number N(S)=N(R)-1.


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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Example:

Including

frame

N(S) = 37,

everything o.k.

N(S) = 37

N(R) = 38

Fig. 13 Acknowledgement procedure


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2.7 Protocol Discriminator

The purpose of the Protocol Discriminator information element is to distinguishmessages corresponding to one of the V5 protocols (PSTN protocol, Controlprotocol, Link control protocol, BCC protocol or Protection protocol) from othermessages corresponding to other protocols making use of the same V5 data linkconnections.

It provides a mechanism for future compatibility, allowing the use of the same V5data link connection for other Layer 3 protocols not yet identified.

The protocol discriminator occupies the first octet in every Layer 3 message. Itidentifies the Layer 3 protocol regulating the meaning and usage (message type) ofthe message.

The table lists the meanings of the various protocol discriminator values in conformitywith CCITT. Individual operating companies are permitted to freely define themeanings of the protocol discriminators within the scope of the predefinedframework, meaning the definition of customized protocols is possible.


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Protocoldiscriminator octet

(hexadecimal)

Meaning

H00 - H07 Protocol discriminators in user-user information elements. Notavailable for messages employed for user-network call control.

H08 Messages for user-network call control

(CCITT Recommendation Q.931)

H08 ISDN DSS1

H10 - H3F Reserved for other network layer protocols or Layer 3protocols (including X.25 protocol)

H40 - H47 National usages

H48 - H4F Reserved for ETSI: H48 V5 Protocols

H50 - HFE Reserved for other Layer 3 protocols

(including X.25 protocol)

Fig. 14 Protocol discriminators


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2.8 Layer 3 Address

The purpose of theLink IDis to identify the 2 048 kbit/s link to which the link controlmessage refers. The numbering is done with the MML command CR V5LINKparameter V5LINKID.

For a particular V5 2 048 kbit/s link the same value is used in the BCC protocolinformation elements.

The purpose of the BCC Reference Numberis to identify the BCC protocol process,within the V5.2 interface, to which the transmitted or received message applies. TheBCC reference number value shall be a random value generated by the AN or LE,whoever is creating the new BCC protocol process.

It is essential that values are not repeated in messages for which a different BCC

process is required (in the same direction), until the old BCC process has beenfinished and the number deleted. In the case of any process generating errorindications, the BCC reference number should not be reused until sufficient time haselapsed for delayed arrival of messages containing the same BCC reference number.

The Source Identification bit is specifying the entity (LE or AN) that has created theBCC reference number (i.e. the entity that has created the BCC protocol process).The coding of this field shall be ZERO for an LE created process and ONE for an ANcreated process.

The logical C-channel is used by the protection protocol. The numbering is donewith the command CR V5CMCHAN parameter V5CHANID. ETSI allows total of 44logical C-channel: 3 (timeslots) x 16 (PCM Links) - 1 (STB group 1) - 3 (STB group2). In EWSD the maximum 4.

The PSTN Port IDand the ISDN Port IDare use to identify a particular subscriber.The numbering is done with the MML command CR SUB and the parameterCOSDAT with the value V5ACCID-x. The range x=0...32767 is used for PSTNsubscribers and x=0...8175 for ISDN subscribers.


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TW2104EU01EG-0001 25

Layer 3

Address Field

BCC protocol

for ISDN port or

common

Control protocol

for PSTN port

PSTN protocol

ISDN protocol

Protection protocol

Link control protocol

PSTN Port ID1

Call reference

Logical

C-channel ID

0 0 0 0 0 0 0 0

Link ID

BCC reference

number

S

o o

ISDN Port ID0 0

1

PSTN Port ID1

Fig. 15 Layer 3 address field layout


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The Call Referenceis used to identify Layer 3 connections (known as"transactions"). Each call reference refers uniquely to one TEI, and in Layer 3establishes the unique relationship between a Layer 3 message and a Layer 3

connection (transaction). A transaction of this type is set up during normal call setup,for example, or to control a supplementary service.

A specific call reference value is assigned to a transaction when it is established (i.e.at transaction setup). The call reference value remains dedicated to this transactionuntil the latter is terminated (i.e. transaction cleardown), after which the call referencevalue is released once more and can be assigned to a different connection(transaction).

The layout of the call reference is shown in the following figure.

The call reference value is freely selected between 0 and 127 by the initiating side ina transaction setup, whereby the most significant bit (M-bit) serves as direction flag.

The originating end (TE or exchange) sets the M-bit to 0. The opposite end theninverts the respective M-bits. This procedure allows both ends to allocate callreference values independently of each other without ever duplicating the values (i.e.M-bit + call reference value + direction is unique).

Example:

An ISDN subscriber has two simultaneous active calls. For one call (1st call) thesubscriber is the calling party, for the other (2nd call) the called party. This means

one call reference is selected by the exchange and one call reference is selected bythe terminal.


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0

Call reference value

1000000

M

Fig. 16 Layout of call reference

Exchange

- Selection of CR

value 0111010

- These twoI-frames relateto the secondcall

TE

- These two

I-frames relateto the first call

- Selection of CRvalue 0111010

I-frame (CR=10111010)

I-frame (CR=00111010)

I-frame (CR=00111010)

I-frame (CR=10111010)

Fig. 17 Allocation of a call reference value


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2.9 Message Types

The message type defines the function of the message and at the same timestipulates its format, i.e. specifies which information elements must or, as applicable,may be included in the message.

For the ISDN Protocol CCITT defined the various message types in Q.931 andQ.932. The messages combine to form groups that are specified by the three mostsignificant bits. The groups describe the application of the messages.

The message types allocated to the V5 Interface are listed in figure 18, the ones forthe ISDN Protocol in figure 19.


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Byte

(hex.)

Bits Message types

0 0 0 0 x x x x PSTN protocol message types

00 0 0 0 0 0 0 0 0 ESTABLISH

01 0 0 0 0 0 0 0 1 ESTABLISH ACKNOWLEDGE

02 0 0 0 0 0 0 1 0 SIGNAL

03 0 0 0 0 0 0 1 1 SIGNAL ACKNOWLEDGE

08 0 0 0 0 1 0 0 0 DISCONNECT

09 0 0 0 0 1 0 0 1 DISCONNECT COMPLETE

0C 0 0 0 0 1 1 0 0 STATUS ENQUIRY

0D 0 0 0 0 1 1 0 1 STATUS

0E 0 0 0 0 1 1 1 0 PROTOCOL PARAMETER

0 0 0 1 0 x x x Control protocol message types

10 0 0 0 1 0 0 0 0 PORT CONTROL

11 0 0 0 1 0 0 0 1 PORT CONTROL ACKNOWLEDGE

12 0 0 0 1 0 0 1 0 COMMON CONTROL

13 0 0 0 1 0 0 1 1 COMMON CONTROL ACKNOWLEDGE

0 0 0 1 1 x x x Protection protocol message types

18 0 0 0 1 1 0 0 0 SWITCH-OVER REQ

19 0 0 0 1 1 0 0 1 SWITCH-OVER COM

1A 0 0 0 1 1 0 1 0 OS-SWITCH-OVER COM

1B 0 0 0 1 1 0 1 1 SWITCH-OVER ACK

1C 0 0 0 1 1 1 0 0 SWITCH-OVER REJECT

1D 0 0 0 1 1 1 0 1 PROTOCOL ERROR

1E 0 0 0 1 1 1 1 0 RESET SN COM

1F 0 0 0 1 1 1 1 1 RESET SN ACK

0 0 1 0 x x x x BCC protocol message types

20 0 0 1 0 0 0 0 0 ALLOCATION

21 0 0 1 0 0 0 0 1 ALLOCATION COMPLETE

22 0 0 1 0 0 0 1 0 ALLOCATION REJECT23 0 0 1 0 0 0 1 1 DE-ALLOCATION

24 0 0 1 0 0 1 0 0 DE-ALLOCATION COMPLETE

25 0 0 1 0 0 1 0 1 DE-ALLOCATION REJECT

26 0 0 1 0 0 1 1 0 AUDIT

27 0 0 1 0 0 1 1 1 AUDIT COMPLETE

28 0 0 1 0 1 0 0 0 AN FAULT

29 0 0 1 0 1 0 0 1 AN FAULT ACKNOWLEDGE

2A 0 0 1 0 1 0 1 0 PROTOCOL ERROR

0 0 1 1 0 x x x Link control protocol message types

30 0 0 1 1 0 0 0 0 LINK CONTROL

31 0 0 1 1 0 0 0 1 LINK CONTROL ACK

Fig. 18 Message types used within the V5.2 interface


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Message-type octet(bit numbering) Hex. Meaning

0 0 0 0 0 0 0 0 00 National usage: message type defined in the

follow-on octets

0 0 0 -

0000000

-

0001001

-

0011011

-

0111100

-

1011111

0102070F03050D

Messages for call setup

ALERTINGCALL PROCEEDINGCONNECTCONNECT ACKNOWLEDGEPROGRESSSETUPSETUP ACKNOWLEDGE

0 0 1 -

0

011110000000

-

0

100000100100

-

1

000011101100

-

0

000111110000

-

0

001110001110

24

2830313337262E22252D2120

Messages during active call phases

HOLD

HOLD ACKNOWLEDGEHOLD REJECTRETRIEVERETRIEVE ACKNOWLEDGERETRIEVE REJECTRESUMERESUME ACKNOWLEDGERESUME REJECTSUSPENDSUSPEND ACKNOWLEDGESUSPEND REJECTUSER INFORMATION

0 1 0 -

00100

-

01101

-

11011

-

00111

-

11000

454D5A464E

Messages for call cleardown

DISCONNECTRELEASERELEASE COMPLETERESTARTRESTART ACKNOWLEDGE

0 1 1 -

01100110

-

01101100

-

00001111

-

00111000

-

01100110

60797B626E7D7564

Other messages

SEGMENTCONGESTION CONTROLINFORMATIONFACILITYNOTIFYSTATUSSTATUS ENQUIRYREGISTER

Fig. 19 Message types as specified by Q.931 for ISDN protocol


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2.10 Information Elements

The final part of a message is made up by the information elements assigned to themessage type. These information elements contain the information requiring to betransferred, e.g. information necessary for call setup. The following chapters give thelayout for the information elements required by each protocol type.


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02 Tw2104eu01 Eg0001 Protocol Architecture