1、STD-ITU-T RECMN 1-3b5.4-ENLL 179b D LiAb2571 0632135 02b D INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 1.365.4 (08/96) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions - Protocol layer req u i remen ts B-ISDN ATM adap
2、tation layer sublayers: Service specific convergence sublayer for HDLC applications ITU-T Recommendation 1.365.4 (Previously CCIlT Recommendation) STD-ITU-T RECMN 1.3h5.q-ENGL 1b m LIBb25L 0632336 Tb2 General network requirements and functions Application of I-series Recommendations to ISDN user-net
3、work interfaces Layer 1 Recommendations Layer 2 Recommendations Layer 3 Recommendations Multiplexing, rate adaption and support of existing interfaces Aspects of ISDN affecting terminal requirements ISDN USER-NETWORK INTERFACES INTERNETWORK INTERFACES MAINTENANCE PRINCIPLES B-ISDN EQUIPMENT ASPECTS
4、, ATM equipment 1 Management of ATM equipment I ITU-T I-SERIES RECOMMENDATIONS INTEGRATED SERVICES DIGITAL NETWORK GENERAL STRUCTURE Terminology Description of ISDNs General modelling methods Telecommunication network and service attributes General description of asynchronous transfer mode Scope Gen
5、eral aspects of services in ISDN Common aspects of services in the ISDN Bearer services supported by an ISDN Teleservices supported by an ISDN Supplementary services in ISDN Network functional principles Reference models Numbering, addressing and routing Connection types Performance objectives SERVI
6、CE CAPABILITIES OVERALL NETWORK ASPECTS AND FUNCTIONS I. 100-1. I99 1.110-1.119 I. 120-1.129 I. 130-1.139 I. 140-1.149 I. 150-1.199 I .200-1.299 1.200-1.209 I .2 1 0-1 -21 9 1.220-1.229 1.230-1.239 I .240-1.249 1.250-1.299 1.300-1.399 I .310-I .319 1.320-1.329 1.330-1.339 1.340-1.349 I .350-1.359 (1
7、 Pratocoi layer requirements 1.3604.369 1.370-1.399 1.400-1.499 1.420-1.429 1.430-1.439 I .440-1.449 I .450-1.459 1.460-1.469 1.470-1.499 I .500-l. 599 1.600-1.699 I. 700-1.799 I .73O-l.749 1.750-1.799 For further details, please refer to ITU-T List of Recommendations STD-ITU-T RECMN 1-3bS.4-ENGL 19
8、9b 48b259L Ob32137 7T7 ITU-T RECOMMENDATION 1.365.4 B-ISDN ATM ADAPTATION LAYER SUBLAYERS: SERVICE SPECIFIC CONVERGENCE SUBLAYER FOR HDLC APPLICATIONS Summary This Recommendation specifies a mapping function that allows narrow-band data communication applications utilizing protocol stacks which incl
9、ude one of the HDLC protocols also to be deployed in a B-ISDN environment. The required mapping function is called “Service Specific Convergence Sublayer for HDLC Applications“. This Recommendation makes use of the fact that the subset of services provided by AAL type 5 (Recommendation 1.363.5) can
10、replace the framing and bit error detection part of HDLC. This Recommendation is applicable to equipment to be attached to an ATM network when protocol stacks developed for a narrow-band environment are deployed in a B-ISDN environment. Source ITU-T Recommendation 1.365.4 was prepared by ITU-T Study
11、 Group 13 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 27th of August 1996. Keywords ATM Adaptation Layer (AAL), Asynchronous Transfer Mode (ATM), Broadband ISDN (B-ISDN), High Level Data Link Control (HDLC), Narrow-band ISDN (N-ISDN). FOREWORD ITU (International Tel
12、ecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The IT Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on t
13、hem 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 which, in their turn, produce Recommendations on these topics. The approva
14、l 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 collaborative basis with IS0 and IEC. NOTE In this Recommendation, the
15、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 or implementation of this Recommendation may involve the use of a claim
16、ed 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 development process. As of the date of approval of this Recommendation, the IT
17、U hadhad not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, impiementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 1997
18、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. 1 2 3 4 5 6 7 7.1 7.2 7.3 7.4 7.5 7.6 STD-ITU-T RECMN 1.3b5.4-ENGL 177b 9 LiAb2571 O
19、b32137 771 CONTENTS Page Scope Normative references Definitions Abbreviations . General description . Functions of the DL-FRAME SSCS Specification of the DL-FRAME SSCS . The CPCS service ofthe AAL type 5 . The service of the DL-FRAME SSCS PDU format Mapping the DL-FRAME-primitive into the AAL type 5
20、 CPCS Mapping the AAL type 5 CPCS signal into the DL-FRAME-primitive (receiver) . Layer management . signal (transmitter) 1 1 1 2 2 2 Recommendation 1.365.4 B-ISDN ATM ADAPTATION LAYER SUBLAYERS: SERVICE SPECIFIC CONVERGENCE SUBLAYER FOR HDLC APPLICATIONS (Geneva, 1996) 1 Scope This Recommendation s
21、pecifies a function that allows data communication applications utilizing protocol stacks which include HDLC procedures 2 also to be deployed in a B-ISDN environment. The required mapping function specified in this Recommendation is called “Service Specific Convergence Sublayer for HDLC Applications
22、“. This Recommendation makes use of the fact that the functionality of the HDLC framing, i.e. the flag and abort sequences, the zero-bit insertion, and the frame checking sequence (FCS) can be interpreted as a subset of the services offered by the AAL type 5 i. This Recommendation is applicable to e
23、quipment to be attached to a B-ISDN network when protocol stacks developed for an HDLC-based environment are to be deployed. 2 Normative references The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recomme
24、ndation. 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 therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other refe
25、rences listed below. A list of the currently valid ITU-T Recommendations is regularly published. i ITU-T Recommendation 1,363.5 (1996), B-ISDN ATA4 Adaptation Layer specification: Type 5 AAL. 2 ITU-T Recommendation X.25 (1 996), Interference between Data Terminal Equipment (DTE) and Data Circuit-ter
26、minating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuits, 3 ITU-T Recommendation X.200 (1 994), Information technology - Open Systems Interconnection - Basic Reference Model: The Basic Model. 4 ITU-T Recommendation X.210 (1993),
27、Information Technology - Open Systems Interconnection - Basic Reference Model: Conventions for the de$nition of OSI services. 3 Definitions The term “HDLC framing“ refers to the framing, transparency, and bit error detection functions of HDLC, i.e., the flag and abort sequences, the zero-bit inserti
28、on, and the Frame Checking Sequence (FCS). Extensive use is also made of the layering concepts defined in Recommendation X.200 3 and the service primitive concepts defined in Recommendation X.2 1 O 4. The HDLC fiaming usually is not considered as a separate sublayer but integrated into the HDLC Data
29、 Link layer; however, as the definition of HDLC procedures is beyond the scope of this Recommendation, a division into an HDLC control procedure sublayer and a HDLC framing sublayer is necessary. The primitives for accessing the services of the HDLC framing sublayer are called “DL-FRAME“ primitives.
30、 4 Abbreviations This Recommendation uses the following abbreviations. AAL ATM Adaptation Layer ATM Asynchronous Transfer Mode CP Common Part CPCS Common Part Convergence Sublayer CPCS-CI CPCS-Congestion Indication CPCS-LP CPCS-Loss Priority CPCS-W CPCS-User-to-User-Indication DL Data Link DLCI Data
31、 Link Connection Identifier FCS Frame Checking Sequence HDLC High Level Data Link Control PCI Protocol Control Information PDU Protocol Data Unit SAP Service Access Point SDU Service Data Unit sscs Service Specific Convergence Sublayer 5 General description The Service Specific Convergence Sublayer
32、for HDLC Applications provides for the possibility to deploy applications developed for an HDLC-based environment also in a B-ISDN environment (see Figure 1); HDLC framing is replaced by the services of the AAL type 5 (Recommendation 1.363.5 il). 6 The purpose of the DL-FRAME SSCS is to map DL-FRAME
33、 primitives onto a subset of the AAL type 5 CPCS (Common Part Convergence Sublayer) service. An HDLC fi-ame structure consisting of an Address field, a Control field and possibly an Information field is transported as a CPCS-SDU. Functions of the DL-FRAME SSCS STD-ITU-T RECMN 1.3b5.4-ENGL 177b m 4b2
34、571 b32142 2bb m 1 DL-FRAME-UNITDATA-request B-ISDN X.25 or other DL-FRAME service DL-FRAME service AAL !ype 5 CPCS service DL-FRAME F-UNITDATA- indication TI 307010-95 Figure 1D.365.4 - Environment for the DL-FRAME SSCS for HDLC applications 7 Specification of the DL-FRAME SSCS 7.1 The DL-FRAME SSC
35、S provides a framing and bit error detection service to its user. The DL-FRAME SSCS sublayer preserves the DL-FRAME-SDU sequence integrity. The primitives across the boundary from the DL-FRAME SSCS user, Le. the HDLC control procedure sublayer, and the DL-FRAME SSCS are shown in Table 1. The length
36、of the Interface Data parameter is an integral number of octets. It carries the HDLC Address, Control, and Information field as a PDU constructed and interpreted by the HDLC control procedure sublayer. The maximum length of this parameter is determined by the capability of the AAL type 5 CPCS. NOTE
37、- Although the absolute maximum length of a CPCS-PDU is 65 535 octets, the actual maximum CPCS-PDU length deployed depends on the error characteristics of the ATM connection. The service of the DL-FRAME SSCS Table 1n.365.4 - DL-FRAME SSCS service primitives and parameters I Interface Data I X I X I
38、7.2 The CPCS service of the AAL type 5 is defined in Recommendation 1.363.5 i. Table 2 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 Recommendation 1.363.5, the one in Recommendation 1.
39、363.5 is definitive. The CPCS service of the AAL type 5 CPCS-UNITD ATA.invo ke Interface Data (ID) X More (M) (Note 1) - CPCS-UNITDATA.signa1 X - I CPCS-LOSS Priority (CPCS-LP) I X I X I (CPCS-CI) CPCS-User-to-User-Indication (CPCS-uu) -I I CPCS-Congestion Indication I X 1- X X X Reception Status (R
40、S) (Note 2) - - NOTE 1 - Not present in message mode. NOTE 2 -Not present as the corrupted data delivery option is not utilized. 7.3 PDU format The AAL type 5 CPCS SDU is equivalent to the Interface Data parameter of the DL-FFUME- UNITDATA primitive; no further PCI is added. DL-FRAME-UNITD ATA-reque
41、s t DL-FRAME-UNITDATA-indication i .L I l 4 I I I I 1 I 1.365.4 I as defined in 7.5 I I as defined in 7.4 I I CPCS-UNITDATA-invoke CPCS-UNITDATA-signal T1307020-95 Figure 2n.365.4 - Relationship of DL-FRAME primitives and AAL type 5 CPCS signals 7.4 As shown in Figure 2, upon receipt of a DL-FRAME-U
42、NITDATA-request from the HDLC control procedure sublayer, a CPCS-UNITDATA-invoke signal is formed with the parameters noted below and submitted to the CPCS (only message mode is utilized): Mapping the DL-FRAME-primitive into the AAL type 5 CPCS signal (transmitter) STD-ITU-T RECMN 1.3bS.Y-ENGL 377b
43、486259L O632344 O37 a) b) c d) NOTE 1 - The value “O“ for the CPCS-LP is the default value; the value “1“ may also be used by layer management decision. NOTE 2 - Further study on the relationship with ATM layer flow control is required. The ID paramter is formed as specified in 7.3. The CPCS-LP para
44、meter is set to “O“. The CPCS-CI parameter is set to “O“. The CPCS-UU parameter is set to “O“. 7.5 Mapping the AAL type 5 CPCS signal into the DL-FRAME-primitive (receiver) As shown in Figure 2, upon receipt of a CPCS-UNITDATA-signal fi-om the CPCS, a DL-FRAME- UNITDATA-indication primitive is forme
45、d with the parameters noted below and sent to the HDLC control procedure sublayer (only message mode without the corrupted data delivery option is utilized) : a) The Interface Data parameter is set to the ID parameter of the CPCS-UNITDATA-signal (see 7.3). b) The CPCS-LP parameter is ignored. c The
46、CPCS-CI parameter is ignored. d) The CPCS-UU parameter is ignored. NOTE - Flow control in HDLC procedures may be activated by link layer management functions on the receipt of congestion indications at the DL-FRAME SSCS entity. 7.6 Layer management No interactions with Layer Management are defined.
47、Interactions to report the values of the congestion management parameter of the AAL type 5 CPCS (i.e. the CPCS-CI parameter) are for fixther study. STD-ITU-T RECMN 1.3b5.4-ENGL L77b W 4b257L Ob32145 T75 W Series A Series B Series C Series D Series E Series F Series G Series H Series I Series J Serie
48、s K Series L Series M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Series X Series Z ITU-T RECOMMENDATIONS SERIES Organization of the work of the ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff pr
49、inciples Overall network operation, telephone service, service operation and human factors Non-telephone telecommunication services Transmission systems and media, digital systems and networks Audiovisual and multimedia systems Integrated services digital network Transmission of television, sound programme and other multimedia signals Protection against interference Construction, installation and protection of cables and other elements of outside plant Maintenance: international transmission systems, telephone circuits, telegraphy facsimile and leased
