1、 STD-ETSI ETS 300 B2L-ENGL 3998 3400855 0343242 3b7 = t UROPEAN T I ELECOMMUNICATION STANDARD ETS 300 821 September 1998 Source: NA Reference: DE/NA-052627 ICs: 33.020 Key words: ATM, B-ISDN, layer 2 Broad band Integrated Services Digital Network (B-ISDN); ATM Adaptation Layer (AAL); Support of the
2、High Level Data Link Control (HDLC) core service by AAL type 5 (AALS) ITU-T Recommendation 1.365.4 (1 996) ETSI European Telecommunications Standards Institute ETSI Secretariat Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonn
3、e - FRANCE Internet: secretariatetsi.fr - http:/www.etsi.fr - http:/www.etsi.org Tel.: +33 4 92 94 42 O0 - Fax: +33 4 93 65 47 16 Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the foregoing restriction extend to reproduction in all me
4、dia. O European Telecommunications Standards Institute 1998. All rights reserved. STD=ETSI ETS 300 82L-ENGL 1998 3400855 0343243 2T3 D Page 2 ETS 300 821 : September 1998 Whilst every care has been taken in the preparation and publication of this document, errors in content, typographical or otherwi
5、se, may occur. If you have comments concerning its accuracy, please write to “ETSI Standards Making Support Dept.“ at the address shown on the title page. - . STDmETSI ETS 300 821-ENGL 1998 = 3400855 03Y1244 L3T Page 3 ETC 300 821 : September 1998 Contents Foreword . 5 1 Scope 7 2 Normative referenc
6、es 7 3 Definitions and abbreviations 7 3.1 Definitions 7 3.2 Abbreviations . 8 4 General Description . 8 5 Functions of the DL-FRAME SSCS . 8 6 Specification of the DL-FRAME SSCS 9 6.1 The service of the DL-FRAME SSCS 9 6.2 The CPCS service of the AAL type 5 . 9 6.3 PDU format 10 6.4 Mapping the DL-
7、FRAME primitive into the AAL type 5 CPCS signal (transmitter) 10 6.5 Mapping the AAL type 5 CPCS signal into the DL-FRAME primitive (receiver) 11 6.6 Layer Management 11 History 12 STD-ETSI ETS 300 821-ENGL 1978 m 3400855 0343245 076 m Page 5 ETS 300 821 : September 1998 Foreword This European Telec
8、ommunication Standard (ETS) has been produced by the Network Aspects (NA) Technical Committee of the European Telecommunications Standards Institute (ETSI). This ETS reproduces and endorses the ITU-T Recommendation 1.365.4 5. Transposition dates Date of adoption of this ETS: Date of latest announcem
9、ent of this ETC (doa): Date of latest publication of new National Standard or endorsement of this ETS (dop/e): 18 September 1998 31 December 1998 30 June 1999 I I Date of withdrawal of any conflicting National Standard (dow): 30 June 1999 Previous page is blank STD.ETS1 ETS 300 821-ENGL 1998 3400855
10、 0341246 TO2 Page 7 ETS 300 821: September 1998 1 Scope This European Telecommunication Standard (ETS) specifies a function that allows data communication applications utilizing protocol stacks which include High Level Data Link Control (HDLC) procedures (ITU-T Recommendation X.25, 2) also to be dep
11、loyed in a Broadband Integrated Services Digital Network (B-ISDN) environment. The required mapping function specified in this ETS is called “Service Specific Convergence Subiayer for HDLC Applications“. This ETS makes use of the fact that the functionality of the HDLC framing, .e., the flag and abo
12、rt sequences, the zero-bit insertion, and the Frame Checking Sequence (FCS) can be interpreted as a subset of the services offered by the ATM Adaptation Layer type 5 (AAL 5) as specified in ITU-T Recommendation 1.363.5 l. This ETS is applicable to equipment to be attached to a B-ISDN network when pr
13、otocol stacks developed for an HDLC-based environment are to be deployed. 2 Normative references This ETS incorporates by dated and undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereaf
14、ter. For dated references, subsequent amendments to or revisions of any of these publications apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. 31 41 51 ITU-T Recommendation 1.363.5: “B-ISDN ATM
15、Adaptation Layer specification: Type 5 AAL“. ITU-T Recommendation X.25: “Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit“. ITU-T Recommendation X.200: “I
16、nformation technology; Open Systems Interconnection; Basic reference model: The basic model“. ITU-T Recommendation X.210: “Information technology; Open systems interconnection; Basic Reference Model: Conventions for the definition of OS1 services“. ITU-T Recommendation 1.365.4: “B-ISDN ATM adaptatio
17、n layer sublayers: Service specific convergence sublayer for HDLC applications“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of this ETS, the following definitions apply: The term “HDLC framing“ refers to the framing, transparency, and bit error detection functions of HDLC, .e.,
18、 the flag and abort sequences, the zero-bit insertion, and the FCS. Extensive use is also made of the layering concepts defined in ITU-T Recommendation X.200 3 and the service primitive concepts defined in ITU-T Recommendation X.210 4. The HDLC framing usually is not considered as a separate sublaye
19、r but integrated into the HDLC Data 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 sublaye
20、r are called “DL-FRAME“ primitives. STD-ETSI ETS 300 821-ENGL 1998 3400855 0341247 949 v) Y o $3 cn .2 gz o o, 2 a -c oc Page 8 ETS 300 821 : September 1998 3.2 Abbreviations Higher Layers S i- DLC Control Procedure e.g., X.25 Layer 2 For the purposes of this ETS, the following abbreviations apply:
21、AAL ATM CP CPCS CPCS-CI CPCS-LP CPCS-uu DL HDLC FCS M PCI PDU RS sscs SDU ATM Adaptation Layer Asynchronous Transfer Mode Common Part CP Convergence Sublayer CPCS-Congestion Indication CPCS-Loss Priority CPCS-User-to-User-Indication Data Link High Level Data Link Control Frame Checking Sequence More
22、 Protocol Control Information Protocol Daia Unit Reception Status Service Specific Convergence Sublayer Service Data Unit 4 General Description The Service Specific Convergence Sublayer (SSCS) for HDLC applications provides for the possibility, to deploy applications developed for an HDLC-based envi
23、ronment also in a B-ISDN environment (see figure 1 / ITU-T Recommendation 1.365.4 ti); HDLC framing is replaced by the services of the AAL type 5 (ITU-T Recommendation 1.363.5 l). 5 Functions of the DL-FRAME SSCS The purpose of the DL-FRAME SSCS is to map DL-FRAME primitives onto a subset of the AAL
24、 type 5 CPCS (Common Part Convergence Sublayer) service. An HDLC frame structure consisting of an Address field, a Control field and possibly an Information field is transported as a CPCS-SDU. I c I Physical Layer ATM I X.25 or other Higher Layers - HDLC Control Procedu e.g., X.25 Layer 2 DL-FRAME s
25、ervice . HDLC Framing i I Phvsical Laver I Figure 1: ITU-T Recommendation 1.365.4 5: Environment for the DL-FRAME SSCS for HDLC Applications STD-ETSI ETS 300 BZL-ENGL 1998 3400855 0341248 885 W Interface Data Page 9 ETC 300 821 : September 1998 DL-FRAME-UNITDATA- DL-FRAME-UNITDATA- request indicatio
26、n K 6 Specification of the DL-FRAME SSCS Interface Data (ID) More (M) (note 1) CPCS-Loss Priority (CPCS-LP) CPCS-Congestion Indication (CPCS-Ci) CPCS-User-to-User-Indication (CPCS-VU) Reception Status (RS) (note 2) 6.1 The service of the DL-FRAME SSCS CPCS-UNITDATA.invoke CPCS-UNITDATA.signa1 X X X
27、X X X X X T The DL-FRAME SSCS 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, .e., the HDLC control procedure sublayer, and the DL-FRAME SSCS are
28、shown in table 1 / ITU-T Recommendation 1.365.4 5. The length 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
29、 is determined by the capability of the AAL type 5 CPCS. NOTE: 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. 6.2 The CPCS service of the AAL type 5 is defined in ITU-T Recom
30、mendation 1.363.51. Table 2 / ITU-T Recommendation 1.365.4 5 summarizes the primitives and parameters in the AAL type 5 CPCS service. Where there are differences between the definitions in this ETS and those in ITU-T Recommendation 1.363.5 l, the one in ITU-T Recommendation 1.363.5 l is definitive.
31、The CPCS service of the AAL type 5 STD-ETSI ETS 300 823-ENGL 1998 3400855 0343249 733 Page 10 ETS 300 821 : September 1998 6.3 PDU format The AAL type 5 CPCS SDU is equivalent to the Interface Data parameter of the DL-FRAME-UNITDATA primitive; no further PCI is added. DL-FRAME-UNITDATA-request I f D
32、L-FRAME-UNITDATA-indication CPCS-UN ITDATA-invoke CPCS-UNITDATA-signal Figure 2: ITU-T Recommendation 1.365.4 5: Relationship of DL-FRAME primitives and AAL type 5 CPCS signals 6.4 Mapping the DL-FRAME primitive into the AAL type 5 CPCS signal (transmitter) As shown in figure 2 / ITU-T Recommendatio
33、n 1.365.4 5, upon receipt of a DL-FRAME-UNITDATA-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): a) The ID parameter is formed as specified in subclause 6.3; b) The CP
34、CS-LP parameter is set to “O“; c) d) The CPCS-CI parameter is set to “O“; The CPCS-UU parameter is set to “o. 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
35、 is required. STDmETSI ETS 300 BZI-ENGL 3998 3400855 0343250 433 = Page 11 ETS 300 821: September 1998 6.5 Mapping the AAL type 5 CPCS signal into the DL-FRAME primitive (receiver) As shown in figure 2 / ITU-T Recommendation 1.365.4 5, upon receipt of a CPCS-UNITDATA-signal from the CPCS, a DL-FRAME
36、-UNITDATA-indication primitive is formed 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 subclause 6
37、.3); b) The CPCS-LP parameter is ignored; c) d) The CPCS-CI parameter is ignored: 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. 6.6 Layer Management The
38、re are no interactions with Layer Management defined. Interactions to report the values of the congestion management parameter of the AAL type 5 CPCS (.e., the CPCS-CI parameter) are for further study. - - STDmETSI ETS 300 821-ENGL 1998 3400855 0341251 37T July 1998 Page 12 ETS 300 821: September 1998 History Document history Vote v 9837: 1998-07-1 4 to 1998-09-1 1 I December 1996 I Public Enquiry PE 120: 1996-12-16 to 1997-04-11 I September 1998 I First Edition ISBN 2-7437-2529-X Dpt lgal : Septembre 1998
