ETSI ETR 117 ed.1 (1993-12)

SLOVENSKI STANDARD
SIST-TP ETSI/ETR 117 E1:2005
01-april-2005
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Broadband Integrated Services Digital Network (B-ISDN); Asynchronous Transfer Mode

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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Whilst every care has been taken in the preparation and publication of this document, errors in content,

typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to

"ETSI Editing and Committee Support Dept." at the address shown on the title page.

Foreword .......................................................................................................................................................5

1 Scope ..................................................................................................................................................7

2 References..........................................................................................................................................7

3 Definitions, symbols and abbreviations...............................................................................................7

4 General................................................................................................................................................8

4.1 Concept and terminology.....................................................................................................8

4.2 AAL structure for signalling applications............................................................................10

5 Service specific part ..........................................................................................................................11

5.1 SSP-AAL services..............................................................................................................11

5.2 Operational attributes.........................................................................................................12

6 Common part ....................................................................................................................................13

6.1 CP-AAL services................................................................................................................13

6.2 Operational attributes.........................................................................................................13

6.3 Primitives ...........................................................................................................................14

7 Service specific part functions...........................................................................................................14

8 Definition of the AAL boundary..........................................................................................................15

8.1 Definition of the AAL boundary at the UNI .........................................................................15

8.1.1 Primitives.......................................................................................................15

8.1.2 State diagram................................................................................................16

8.2 Definition of the AAL boundary at the NNI .........................................................................17

8.2.1 Primitives.......................................................................................................17

8.2.2 State diagram................................................................................................19

Annex A: Example flow diagrams...........................................................................................................20

Annex B: Bibliography ............................................................................................................................26

History..........................................................................................................................................................27

This ETSI Technical Report (ETR) has been produced by the Signalling Protocols and Switching (SPS)

Technical Committee of the European Telecommunications Standards Institute (ETSI).

ETRs are informative documents resulting from ETSI studies which are not appropriate for European

Telecommunication Standard (ETS) or Interim European Telecommunication Standard (I-ETS) status. An

ETR may be used to publish material which is either of an informative nature, relating to the use or the

application of ETSs or I-ETSs, or which is immature and not yet suitable for formal adoption as an ETS or

This ETR describes the Broadband Integrated Services Digital Network (B-ISDN) Asynchronous Transfer

Mode (ATM) ATM Adaptation Layer (AAL) requirements to support the transfer of signalling messages.

The AAL operates over an ATM virtual channel connection to provide a signalling link for the transfer of

messages between two signalling entities. This is applicable for both User Network Interfaces (UNIs) and

Network Node Interfaces (NNIs). As such, the Signalling ATM Adaptation Layer (SAAL) shall be able to

provide the services provided by both Link Access Procedure on the D-channel (LAPD) and Message

This ETR specifies the SAAL requirements. It is designed to assist the protocol experts in the design of a

service specific SAAL. These are minimum requirements, i.e. based on services provided by the existing

link layers of the UNI (ITU-T Recommendation Q.921 [5]) and NNI (ITU-T Recommendation Q.703 [4]).

The requirements are not intended to limit the protocol definition to only these capabilities, but form a

NOTE: ITU-T Recommendation I.363 [3] includes the specification of the Common Part (CP)

The basic structuring technique in the Open Systems Interconnection (OSI) reference model is layering.

According to this technique, communication among application processes is viewed as being logically

partitioned into an ordered set of layers represented in a vertical sequence as shown in figure 1.

A SAAL Service Access Point (SAP) is the point at which the SAAL provides services to layer 3.

Associated with each SAAL SAP are one or more SAAL connection endpoints, see figure 2.

Entities exist in each layer. Entities in the same layer but in different systems which need to exchange

information to achieve a common objective are called "peer entities". Entities in adjacent layers interact

through their common boundary. The services provided by the data link layer are the combination of the

services and functions provided by the SAAL Service Specific Part (SSP), SAAL Common Part (CP) and

Cooperation between SAAL entities is governed by a peer-to-peer protocol specific to the layer.

SAAL Signalling Data Units (SDUs) are conveyed between SAAL entities by means of a physical

Layer 3 requests services from the SAAL via service primitives. The same applies for the interaction

between the SAAL and the ATM layer. The primitives represent, in an abstract way, the logical exchange

of information and control between the SAAL and the adjacent layers and between the SAAL SSP and the

The primitives that are exchanged between the SAAL and adjacent layers are of the following four types

The request primitive type is used when a higher layer is requesting a service from the next lower layer.

The indication primitive type is used by a layer providing a service to notify the next higher layer of any

specific activity which is service related. The indication primitive may be the result of an activity of the

The response primitive type is used by a layer to acknowledge receipt from a lower layer of the primitive

The confirm primitive type is used by the layer providing the requested service to confirm that the activity

Information is transferred, in various types of SDUs, between peer entities and between entities in

adjacent layers (and sublayers) that are attached to a specific SAP. The SDUs are of two types:

- SDUs that contain layer-to-layer information concerning status and specialized service requests.

The SDUs of the layer 3 peer-to-peer protocol are carried by the SAAL connection. The SDUs containing

layer-to-layer information concerning status and specialized service requests are never conveyed over a

The CP may be used by different SSPs; the SSP is specific to the needs of the service application. The

requirements in this ETR address the SSP. The CP protocol is specified in ITU-T Recommendation

Figure 5 shows the application topology of the CP and the SSP of the AAL. The CP and SSP are both

peer-to-peer protocols with as much commonality between them as possible. Commonality between the

NOTE 1: One of the overall objectives in B-ISDN studies has been to achieve as much

It is hoped that this commonality, without increasing the complexity at the UNI, will have the following

- allow for flexibility in network operation and configuration (due to a common signalling mechanism);

However, the above should be taken into account with the need to have a SAAL available for release 1.