1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECT0 R OF ITU SERIES Q: SWITCHING AND SIGNALLING Broadband ISDN - ATM adaptation layer Q.2119 (07/96) 6-ISDN ATM adaptation layer - Convergence function for SSCOP above the frame relay core service ITU-T Recommendation Q.
2、21 I9 (Previously CCITT Recommendation) STD-ITU-T RECMN Q*211S-ENGL L7Sb m 48b257L Ob27157 3q5 m ITU-T Q-S E R I ES RECOM MEN DATI ON S SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE Q.1-Q.3 INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING Q .4-Q. 59 CLAUSES APPLICABLE TO
3、ITU-T STANDARD SYSTEMS Q. 1 OO-(2.119 SPECIFICATION OF SIGNALLING SYSTEMS No. 4 AND No. 5 SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 SPECIFICATIONS OF SIGNALLING SYSTEM RI SPECIFICATIONS OF SIGNALLING SYSTEM R2 DIGITAL EXCHANGES INTERWORKING OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM N
4、o, 7 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. I PUBLIC LAND MOBILE NETWORK INTERWORKING WITH SATELLITE MOBILE SYSTEMS Q.120-Q.249 Q.250-Q.309 Q .3 1 O-Q. 399 Q.400-Q.499 Q.500-Q.599 Q.600-Q.699 Q.700-Q.849 Q.850-Q.999 Q.1000-Q.1099 Q.?lOO-Q.I199 INTELLIGENT NETWORK Q.1200-Q.1999 BROADBAND ISDN Q.200
5、0-Q.2999 General aspects Q.2000-Q.2099 .210-Q.2199 Signalling network protocols Q.2200-Q.2599 Common aspects of B-ISDN application protocols for access signalling and Q.2600-Q.2699 B-ISDN application protocols of the network B-ISDN application protocols for access signalling network signalling and i
6、nterworking Q.2700-Q.2899 Q.2900-Q.2999 For further details, please refer to ITU-T List of Recommendations. STD-ITU-T RECMN Q-ZLLS-ENGL 177b Li8b257L 0b27158 281 9 ITU-T RECOMMENDATION 4.2119 B-ISDN ATM ADAPTATION LAYER - CONVERGENCE FUNCTION FOR SSCOP ABOVE THE FRAME RELAY CORE SERVICE Summary This
7、 Recommendation specifies a mapping function that allows B-ISDN data communications applications utilizing protocol stacks which include SSCOP (Recommendation 4.21 10) also to be deployed in an HDLC-based environment. The required mapping function is called “convergence function for SSCOP above the
8、fiame relay core service“. This Recommendation makes use of the fact that the subset of services provided by AAL type 5 (Recommendation 1.363.5) that SSCOP uses can also be provided by the services of the core service for the frame mode bearer services (Annex NQ.922). This Recommendation also provid
9、es, in Annex A, suggested parameter values for use in support of SS No. 7 applications. Such an arrangement would allow one approach to a migration from N-ISDN This Recommendation is applicable to equipment to be attached to a frame relay network when protocol stacks developed for a B-ISDN environme
10、nt are deployed in a narrow-band environment, to B-ISDN. Source ITU-T Recommendation Q.2119 was prepared by ITU-T Study Group 11 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 9th of July 1996. Keywords AAL, B-ISDN, frame relay, N-ISDN, SSCOP and SS No. 7 STD-ITU-T REC
11、MN Q-2117-ENGL L99b 4Ab2571 Ob27159 11A FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying te
12、chnical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups wh
13、ich, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a
14、 collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice
15、 or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation develo
16、pment process. As of the date of approval of this Recommendation, the ITU hadhad not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are
17、therefore strongly urged to consult the TSB patent database. O ITU 1997 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. II Recommend
18、ation Q.2119 (07/96) CONTENTS 1 Scope 2 Normative references 3 Definitions 4 Abbreviations . 5 General descnption . 6 Functions of the convergence function . 7 7.1 7.2 The core service of the frame mode bearer service 7.3 PDU format 7.4 Mapping the AAL type 5 CPCS signal into the frame relay core se
19、rvice primitives (transmitter) Mapping the frame relay core service primitives into the AAL type 5 CPCS signal (receiver) . 7.6 Layer management . Specification of the convergence function . The CPCS service of the AAL type 5 . 7.5 Annex A . Use of the frame relay core service for SS No . 7 signalli
20、ng links at the NNI . Appendix I . Impact of 32-bit alignment in SSCOP on the DL-CORE-DATA-PDU format Page 1 1 2 2 3 3 3 4 4 5 7 . Recommendation 4.21 19 (07/96) 111 STD-ITU-T RECMN Q-ZLLS-ENGL 177b - 48b2571 Db272bl 87b . , e. .,- rid - STD-ITU-T RECMN Q-2117-ENGL 177b gBb257L Ob27Lb2 72 m Recommen
21、dation 4.21 19 B-ISDN ATM ADAPTATION LAYER - CONVERGENCE FUNCTION FOR SSCOP ABOVE THE FRAME RELAY CORE SERVICE (Geneva, 1996) 1 Scope This Recommendation specifies a function that allows B-ISDN data communication applications utilizing protocol stacks which include SSCOP 3 also to be deployed in an
22、HDLC-based environment. The required mapping function specified in this Recommendation is called “convergence function for SSCOP above the frame relay core service“. This Recommendation makes use of the fact that SSCOP uses only a subset of the services offered by the preferred underlying (sub)layer
23、, the AAL type 5 i. This particular service subset can also be derived as a subset from the service of the core service for the frame mode bearer service as specified in Annex AQ.922 2. This Recommendation is applicable to equipment to be attached to a frame relay network when protocol stacks develo
24、ped for a B-ISDN environment are deployed in a narrow-band environment. If this Recommendation is applied to signalling at a B-ISDN Network Node Interface (“I), Annex A specifies further restrictions on the use of the frame relay core service. 2 Normative references The following ITU-T Recommendatio
25、ns and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision: all users of this Recommendation are theref
26、ore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. ITU-T Recommendation 1.363 (1993), B-ISDN ATMAdaptation Layer (AAL) spec$cation. CCI
27、TT Recommendation 4.922 (1 992), ISDN data link layer specification for kame mode bearer services. ITU-T Recommendation 4.21 1 O (1 994), B-ISDN signalling ATM Adaptation - Service SpeciJic Connection Oriented Protocol (SSCOP). ITU-T Recommendation X.200 (1 994), Information technology - Open System
28、s Interconnection - Basic reference model: The basic model. ITU-T Recommendation X.2 1 O (i 993), Information technology - Open Systems Interconnection - Basic reference model: Conventions for the definition of OSI Services. ITU-T Recommendation 1.365.1 (1 993), B-ISDN ATM adaptation layer sublayers
29、: Frame Relaying Service SpeclJic Conversion Sublayer (FR-SSCS). CCITT Recommendation 1.233.1 (1991), Frame mode bearer services: ISDN - Frame relaying bearer sewice. ITU-T Recommendation X.263 (1995) 1 ISOOEC TR 9577: 1996, Information technology - Protocol identijkation in the Network Layer. Recom
30、mendation 4.2119 (07/96) 1 STD-ITU-T RECMN Q-2117-ENGL L77b W 48b259L Ob27Lb3 b49 W 9 ITU-T Recommendation 4.704 (1 996), Signalling network functions and messages. 3 Definitions The term “frame relay core service“ refers to the core aspects of the frame relaying bearer service (see Annex NQ.922 2).
31、 Otherwise, this Recommendation introduces no new terms beyond the ones defined in Recommendations Q.2110 3 and 4.922 2. As in those Recommendations, extensive use is made of the layering concepts defined in Recommendation X.200 4 and the service primitive concepts defined in Recommendation X.210 5.
32、 4 Abbreviations This Recommendation uses the following abbreviations. AAL ATM Adaptation Layer ATM Asynchronous Transfer Mode CP Common Part CPCS Common Part Convergence Sublayer CPC S -CI CPCS-LP CPCS-Loss Priority CPCS-UU CPCS-User-to-User-Indication DLCI Data Link Connection Identifier HDLC High
33、-level Data Link Control IPI Initial Protocol Identifier PCI Protocol Control Information PDU Protocol Data Unit SAAL AAL for Signalling SAP Service Access Point SS No. 7 SSCOP Service Specific Connection-Oriented Protocol CPC S -Congestion Indication Signalling System No. 7 5 General description Th
34、e convergence function for SSCOP above the frame relay core service provides for the possibility, to deploy SSCOP (Recommendation Q.2110 3) on top of the frame relay core service. The frame relay core service is implemented as frame relay services utilizing the protocol according to Annex NQ.922 2 (
35、used on leased lines or narrow-band ISDN) or utilizing the protocol according to Recommendation 1.365.1 6 (as an AAL type 5 on B-ISDN). All protocol stacks that include SSCOP can, therefore, also be used in a frame relay environment (see Figure 1). For an intermediate period of time, a particular ap
36、plication of this Recommendation is in a protocol stack for SS No. 7 signalling. This option is defined further in Annex A. 2 Recommendation Q.2119 (07/96) B-ISDN ?I Higher Layers Rec 0.21 10 AAL type 5 CPCS service =-, I CPCS I AAL type 5 Common li, Higher Layers II 37- Rec.Q.2110 AAL type 5 CPCS s
37、ervice -1 Frame Relay Core Service Frame Relay Core Service . Physical Layer T1175410-95 Figure 1/4-2119 - Environment for the convergence function for SSCOP above the frame relay core service 6 The purpose of the convergence function is to map SSCOP signals that use a subset of the AAL type 5 Commo
38、n Part Convergence Sublayer (CPCS) service into a subset of the frame relay core service. In addition, a protocol identifier is added at the beginning of the frame relay core service PDU as is customarily done in the frame relay environment. Functions of the convergence function 7 7.1 Specification
39、of the convergence function The CPCS service of the AAL type 5 I The CPCS service of the AAL type5 is defined ,I clause 64.363 Table 1 summarizes the primitives and parameters in the AAL type 5 CPCS service. Where there are differences between the definitions in this Recommendation and those in Reco
40、mmendation 1.363, the one in Recommendation 1.363 is definitive. SSCOP (Recommendation Q.2110) defines the use of the parameters as follows: Recommendation 4.2119 (07/96) 3 STD-ITU-T RECMN Q-ZLLS-ENGL L79b 48b257L Ob27Lb5 411 Interface Data (ID) CPCS-Loss Priority (CPCS-LP) CPCS-Congestion-Indicatio
41、n (CPCS-CI) CPCS-User-to-User-Indication (CPCS-UU) More (M) (Note 1) Table 1/Q.2119 - AAL type 5 CPCS service primitives and parameters CPCS-UNITDATA.invoke CPCS-UNITDATA.signa1 X X X X X X X X Discard eligibility (optional) Congestion encountered backward (optional) Reception Status (RS) mote 2) X
42、- X 1 -Not present in message mode. NOTE 2 -Not present as the corrupted data delivery option is not utilized. Only message mode is utilized. The CPCS-LP parameter is set to “O“ at the transmitter and ignored at the receiver. The CPCS-CI parameter is set to “O“ at the transmitter and its use by the
43、receiver is for further study. The CPCS-UU parameter is set to “O“ at the transmitter and ignored at the receiver. The corrupted data delivery option is not utilized. Congestion encountered forward (optional) Core service user protocol control information 7.2 The core service of the frame mode beare
44、r service X X X The fiame relay core service is defined in Annex NQ.922 2 and in Annex DI.233.1 7. Table 2 summarizes the primitives and parameters in the fiame relay core service. Where there are differences between the definitions in this Recommendation and those in Recommendation 4.922 or 1.233.1
45、, the one in Recommendation Q.922 is definitive. Table 2lQ.2119 - Core service primitives and parameters I I Core-DATA.request 1 Core-DATA.indication 1 I Core-user-data I X I X I 7.3 PDU format SSCOP PDUs are prepended with two octets of PCI information. This is required to carry the protocol identi
46、fier; this situation is depicted in Figure 2. The coding of these two octets is as follows: 1) Octet I: Unnumbered Information “UI“ This octet shall be coded as 0000-001 12. 2) Octet 2: Protocol identifier This octet contains an Initial Protocol Identifier (IPI) and shall be coded as 0000-1010, (thi
47、s value is specified in ITU-T Rec. X.263 1 ISO/IEC TR 9577 SI). NOTE - Discussion of the impact of 32-bit alignment in SSCOP on the DL-CORE-DATA-PDU format can be found in Appendix I. 4 Recommendation Q.2119 (07/96) STD-ITU-T RECMN Q.ZLL7-ENGL L79b U8b259L Ob27Lbb 358 H 1 “UI“ Octets 3 ton 2 Protoco
48、l SSCOP PDU Identifier T1175420-95 Figure 2/Q.2119 - PDU format to embed an SSCOP PDU in a frame relay SDU 7.4 Mapping the AAL type5 CPCS signal into the frame relay core service primitives (transmitter) As shown in Figure 3, upon receipt of a CPCS-UNITDATAhvoke signal from SSCOP, a DL-CORE-DATA.req
49、uest primitive is formed with the parameters noted below and submitted to the frame relay core service: a) The “core-user-data“ parameter is formed as specified in 7.3 using the “interface data“ parameter of the CPCS-UNITDATAhvoke signal (SSCOP PDU). b) The “discard eligibility“ parameter is set to “O“. c) The “core service user protocol control information“ parameter is set to “O“. 7.5 Mapping the frame relay core service primitives into the AAL type5 CPCS signal (receiver) As shown in Figure 3, upon receipt of a DL-CORE-DATA
