1、 - STD=ITU-T RECMN I-460-ENGL 1999 4862591 Ob57336 187 m INTERNATIONAL TELECOMMUN KATION UN I ON ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU I .460 (02/99) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK ISDN user-network interfaces - Multiplexing, rate adaption and support of existing inter
2、faces Multiplexing, rate adaption and support of existi ng in terfaces ITU-T Recommendation I A60 (Previously CCITT Recommendation) STD-ITU-T RECMN 1-4bO-ENGL 1999 9 YBb259b Ob57337 Ob3 I TU-T I -S E R I ES RE C O M M EN DATI O N S INTEGRATED SERVICES DIGITAL NEMIORK GENERAL STRUCTURE Terminology De
3、scription of ISDNs I. 1 1 0-1. I 19 I. 120-1.129 General modelling methods I. 130-1.139 Telecommunication network and service attributes I. 140-1.149 /1 General description of asynchronous transfer mode SERVICE CAPABILITIES II I. 150-1. I99 Scope 1.200-1.209 General aspects of services in ISDN 1.210
4、-1.219 Common aspects of services in the ISDN I .220-1.229 1.230-1.239 Teleservices supported by an ISDN 1.240-1.249 Supplementary services in ISDN 1.250-1.299 Bearer services supported by an ISDN OVERALL NETWORK ASPECTS AND FUNCTIONS Network functional principles I .310-I.319 Reference models Numbe
5、ring, addressing and routing Connection types Performance objectives Protocol layer requirements General network requirements and functions I .320-1.329 I. 3304.339 I. 3404.349 I .350-1.359 1.360-1.369 1.370-1.399 ISDN USER-NETWORK INTERFACES Application of I-series Recommendations to ISDN user-netw
6、ork interfaces 1.420-1.429 Layer 1 Recommendations Layer 2 Recommendations I .430-1.439 1.440-1.449 Layer 3 Recommendations 1.450-1.459 INTERNETWORK INTERFACES 1.500-1.599 MAINTENANCE PRINCIPLES 1.600-1.699 B-ISDN EQUIPMENT ASPECTS ATM equipment 1.730-1.739 Transport functions 1.740-1.749 Management
7、 of ATM equipment I .750-1.799 For further details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION 1.460 MULTIPLEXING, RATE ADAPTION AND SUPPORT OF EXISTING INTERFACES Source ITU-T Recommendation 1.460 was revised by ITU-T Study Group 13 (1997-2000) and was approved under the WT
8、SC Resolution No. 1 procedure on the 1 5Ih of February 1999. i Recommendation 1.460 (02/99) STD-ITU-T RECMN 1.4bO-ENGL Lqq7 4862591 Ob57337 996 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication
9、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 them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Confer
10、ence (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 approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some are
11、as of information technology which fall within ITU-T?s purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation the term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that opera
12、tes a public correspondence service. The terms Adnzinistration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the
13、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 development process. As of the date of approval of this Recommen
14、dation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, impleinentors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
15、 O ITU 1999 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 Recommendation 1.460 (02/99) . . STD-ITU-T RECMN 1.4bO-ENGL 1799 II 4
16、8b2591 Ob57340 bOB II CONTENTS Page 1 1.1 1.2 Rate adaption to a 64 kbit/s channel . Rate adaption of 8, 16 and 32 kbit/s streams Rate adaption of streams other than 8, 16 and 32 kbits . 2 2.1 Multiplexing into a 64 kbit/s channel . Time division multiplexing of 8. 16 and 32 kbits . 2.1.1 Fixed form
17、at multiplexing . 2.1.2 Flexible format multiplexing . Multiplexing of rates other than 8, 16 and 32 kbit/s . 2.2 2 2 2 2 3 . Recommendation 1.460 (02199) 111 STDOITU-T RECflN 1.4bO-ENGL 1999 4862591 Ob57342 544 M Recommendation 1.460 MULTIPLEXING, RATE ADAPTION AND SUPPORT OF EXISTING INTERFACES (M
18、alaga-Torremolinos, 1984; amended at Melbourne, 1988; revised in 1999) This Recommendation describes procedures to be used to: a) b) The rates lower than 64 kbits are of two types: 1) binary rates of 8, 16 and 32 kbit/s; and 2) other rates including those associated with DTEs conforming to the X- an
19、d V-series Recommendations. The detailed procedures for support of X-series circuit mode DTEs, X-series packet mode DTEs, and V-series DTEs are given in Recommendations 1.461K.30, I.462K.3 1, 1.463/V.110 and 1.465/V. 120), respectively. Rate adaption, multiplexing and support of existing interfaces
20、for restricted 64 kbits transfer capability is covered in Recommendation 1.464. adapt the rate of one stream, of rate lower than 64 kbit/s, into a 64 kbit/s B-channel; multiplex several streams, of rates lower than 64 kbit/s, into a 64 kbits B-channel. 1 Rate adaption to a 64 kbit/s channel 1.1 The
21、procedure in this subclause will be used to adapt the rate of a single stream at 8, 16 or 32 kbit/s into a 64 kbius B-channel. In this Recommendation, bit positions in the B-channel octet are assumed to be numbered from 1 to 8 with bit position 1 being the first transmitted. The procedure requires t
22、hat: i) Rate adaption of 8,16 and 32 kbit/s streams the 8 kbit/s stream occupies bit position 1, the 16 kbit/s stream occupies bit positions (1,2), the 32 kbit/s stream occupies bit positions (i, 2,3,4); the order of transmission of the bits of the subrate stream is identical before and after rate a
23、daption; and all unused bit positions be set to binary “1“. ii) iii) 1.2 Information streams at bit rates less than 64 kbit/s need to be rate adapted to be carried on the B-channel. The approaches in this subclause are for adapting single information streams. 1.2.1 The rate adaption of bit rates of
24、less than 24 kbits uses a multi-stage approach. One stage is described in Recommendations I.461K.30, 1.462K.3 1, 1.463N. 1 1 O. For example, user rates of 4.8 kbits and below are mapped to 8 kbit/s, 9.6 kbits is mapped to 16 kbit/s, and 19.2 kbit/s is mapped to 32 kbits. Another stage of rate adapti
25、on is from 8 kbits, 16 kbits, or 32 kbit/s to 64 kbit/s and is described in 1.1. Rate adaption of streams other than 8,16 and 32 kbit/s Recommendation 1.460 (02/99) 1 A third stage for asynchronous data is described in Recommendation I.463N. 110. 1.2.2 Rate adaption of bit rates equal to or greater
26、than 24 kbits uses a single-stage approach as described in Recommendations 1.461K.30 and 1.463N.110. For example, 48 kbit/s and 56 kbits rates are adapted to 64 kbit/s in one stage. 1.2.3 Rate adaption for packet mode operation may be performed in two ways as described in Recommendation 1.462K.3 1 :
27、 a) the preferred method: in using HDLC flag stuffing between HDLC frames; or b) using the two-stage approach. 1.2.4 HDLC frames as described in Recommendation 1.465N. 120. Rate adaption of bit rates up to 48 kbit/s on a B-channel may be performed by insertion of 2 Multiplexing into a 64 kbit/s chan
28、nel 2.1 Multiplexing of 8, 16 and 32 kbit/s streams is done by interleaving the subrate streams within each B-channel octet. Time division multiplexing of 8,16 and 32 kbit/s Using the procedures described in 2.1.2, any number of 8, 16 and 32 kbits streams may be combined up to the limit of 64 kbits
29、aggregate bit rate in one B-channel. Using the procedure described in 2.1.1 can lead to situations where the full 64 kbith capacity cannot be utilized; however, this will not occur if the mixture of substreams is known in advance. The procedures in 2.1.2 are recommended when the mixture will change
30、during the duration of the 64 kbits connection. 2.1.1 Fixed format multiplexing This procedure will multiplex any combination of 8, 16 and 32 kbit/s streams by allocating bit positions in each B-channel octet to each subrate stream. The fixed format procedure requires that: i) an 8 kbits stream be a
31、llowed to occupy any bit position; a 16 kbith stream occupies bit positions (1,2) or (3,4) or (5, 6) or (7, 8); a 32 kbith stream occupies bit positions (1,2, 3, a subrate stream occupies the same bit position(s) in each successive B-channel octet; the order of transmission of the bits at each subra
32、te stream is identical before and after multiplexing; and all unused bit positions be set to binary I 1 I. 4) or (5,6,7, 8); ii) iii) iv) 2.1.2 Flexible format multiplexing This procedure will multiplex any combination of 8, 16 and 32 kbit/s streams by allocating bits in each B-channel octet to each
33、 subrate stream. This procedure always allows subrate streams to be multiplexed up to the 64 kbits limit of the B-channel. This procedure first attempts to accommodate the subrate streams by using the fixed format procedure of 2.1.1. Although there may be a sufficient number of available bits in the
34、 B-channel octet, the attempt may fail because nile i) of 2.1,l cannot be satisfied. If this attempt does fail, then flexible format procedure requires that: i a subrate stream occupy the same bit position(s) in each successive B-channel octet; ii) the new subrate stream be added to the existing mul
35、tiplex by inserting each successive bit of the new subrate stream into the earliest (lowest numbered) available bit position in the B-channel octet; and 2 Recommendation 1.460 (02/99) STD.ITU-T RECMN 1-4bO-ENGL 1999 R YAb2571i Ob57343 317 m iii) all unused bit positions be set to binary “1“. 2.2 Two
36、 technical approaches for multiplexing lower bit rate information streams (e.g. Recommendation X. 1 rates) can be used: i) Time division multiplexing Multiplexing of rates other than 8,16 and 32 kbit/s In this case, the two-stage approach (rate adaption up to 8, 16 or 32 kbits followed by multiplexi
37、ng to 64 kbits) as defined in 1.2 and 2.1 should be used. NOTE - Multiplexing schemes according to X-series Recommendations (e.g. X.50) may be used only in the context of 64 kbits access through the ISDN to existing dedicated networks. ii) Statistical multiplexing a) for supporting packet mode termi
38、nals using either the D-channel or b) for circuit mode terminals or terminal adaptors on the B-channel, see Recommendation X.25 protocols; Recommendation V. 120. Recommendation 1.460 (02/99) 3 STD-ITU-T RECMN 1.4bO-ENGL 1777 U 4862573 Ob57344 253 . . . STD-ITU-T RECMN I.4bO-ENGL 1799 4Bb2593 Ob57345
39、 17T leries A ieries B ieries C ;cries D ;cries E 3eries F Series G Series H series I Series J Series 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 Y Series Z ITU-T RECOMMENDATIONS SERIES Organization of the work of the ITU-T Mea
40、ns of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors Non-telephone telecommunication services Transmission systems and media, digital systems and network
41、s 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 TMN and network maintenance: inter
42、national transmission systems, telephone circuits telegraphy, facsimile and leased circuits Maintenance: international sound programme and television transmission circuits Specifications of measuring equipment Telephone transmission quality, telephone installations, local line networks Switching and
43、 signalling Telegraph transmission Telegraph services terminal equipment Terminals for telematic services Telegraph switching Data communication over the telephone network Data networks and open system communications Global information infrastructure Programming languages Printed in Switzerland Geneva, 1999
