1、STD-ITU-T RECMN G-708-ENGl L999 48b259L Obb482L 497 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZAT ION SECTOR OF ITU G.708 (06/99) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Terminal equipments - General Sub S
2、TM-O network node interface for the synchronous digital hierarchy (SDH) ITU-T Recommendation G.708 (Previously CCITT Recommendation) _ - STD-ITU-T RECMN G.708-ENGL 3999 4862593 0664822 323 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEP
3、HONE CONNECTIONS AND CIRCUITS G . 1 00-G.199 INTERNA TIONAL ANALOGUE CARRIER SYSTEM TRANSMISSION SYSTEMS GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- G ,200-G 299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE G .300-G. 399 SYSTEMS ON METALLIC LINES Il GENERAL CHARACTERISTI
4、CS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION G .400-G ,449 WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TES TING EQUIPMEN TS TRANS MISSI0 N MEDIA CHA RA C TERIS TICS DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS G.450
5、-G.499 G.600-G.699 G .700-G ,799 Coding of analogue signals by pulse code modulation Coding of analogue signals by methods other than PCM Principal characteristics of primary multiplex equipment Principal characteristics of second order multiplex equipment Principal characteristics of higher order m
6、ultiplex equipment Principal characteristics of transcoder and digital multiplication equipment Operations, administration and maintenance features of transmission equipment Principal characteristics of multiplexing equipment for the synchronous digital hierarchy Other terminal equipment DIGITAL NET
7、WORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.710-G.719 G .720-G .729 G .730-G, 739 G .740-G .749 G ,750-G . 759 G .760-G I 769 G .770-G, 779 G .780-G. 789 G .790-G .79 9 G .800-G .899 G, 900-G. 999 I For further details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION G.708 S
8、UB STM-O NETWORK NODE INTERFACE FOR THE SYNCHRONOUS DIGITAL HIERARCHY (SDH) Summary This Recommendation is an extension of Recommendation G.707. It provides the requirements for the sub STM-O signals at the Network Node Interface of a synchronous digital network in terms of: - bit rates; - frames st
9、ructures; - - functionalities of the overheads. formats for mapping and multiplexing elements; Source ITU-T Recommendation G.708 was prepared by ITU-T Study Group 15 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 22nd of June 1999. Recommendation 6.708 (06/99) 1 FOREWO
10、RD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITV-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and is
11、suing 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 which, in their turn, produce Recommendations on
12、 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 collaborative basis with IS0 and IEC. NOTE In
13、 this Recommendation the term recognized operating agency (ROA) includes any individual, company, corporation or govemrnental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defmed in the Constitution of the ITU (Geneva, 1992).
14、INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice 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 Proper
15、ty Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, impl
16、ementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. o ITU 1999 All rights reserved. No part of this publication may be reproduced or utilized in any fom or by any means, electronic or mechanical, including pho
17、tocopying and microfilm, without permission in writing from the ITU. Recommendation G.708 (06199) 11 - 1 2 3 4 5 5.1 5.2 5.3 5.4 6 6.1 6.2 6.3 7 I 8 8.1 8.2 STD-ITU-T RECMN G.708-ENGL 1999 m 4862591 0664825 032 CONTENTS Scope References Definitions sSTM interface rates . Transport formats . Section
18、overhead Scrambling Frame structure for the sSTM-2n interface n x TUG-2 payloads . Overhead functions . Interface layers . 6.1.1 Physical layer 6.1.3 Path layer . sSTM section overhead 6.2.1 Regenerator section overhead . 6.2.2 Multiplex section overhead . sSTM maintenance signals . 6.1.2 Section la
19、yer 6.3 . 1 6.3.2 6.3.3 VC-n Path layer maintenance signals sSTM multiplex section remote defect indication (MS-RDI) . sSTM multiplex section alarm indication signal (MS-AIS) . sSTM-2n interface APS Multiplexing and numbering structure . Numbering structure . Multiplexing structure Annex A . Structu
20、res for radio-relay applications A.l Scope A.2 Interface rates . A.3 k x TU- 12 payloads A.4 Media-dependent overhead functions . A.5 Multiplexing and numbering structure . A.5.1 . Multiplexing structure . A.5.2 Numbering structure Recommendation 6.708 (06/99) Page 1 1 1 2 3 3 4 5 5 5 5 5 5 5 5 5 6
21、8 8 8 8 8 8 8 10 11 11 11 11 11 11 11 12 . 111 Page Annex B - Frame format of a reduced functionality sSTM- 1 1 for intra-station crossconnects 13 14 C.l Numbering of TU-2s in a sSTM-2n 14 of TU-1 2 using existing office wiring Annex C - Numbering structure of TUS into sSTM frame formats C.2 Numberi
22、ng of TU-12s in a sSTM-2n . 14 C.3 Numbering of TU-1 1s in a sSTM-2n . 14 Numbering of TU- 12s in a sSTM- 1 k . . C.4 14 iv Recommendation G.708 (06/99) - Recommendation G.708 SUB STM-O NETWORK NODE INTERFACE FOR THE SYNCHRONOUS DIGITAL HIERARCHY (SDH) (Geneva, 1999) 1 Scope Network node interface (
23、“1) specifications are necessary to enable interconnection of synchronous digital hierarchy (SDH) network elements for the transport of payloads. Therefore, this Recommendation specifies: - the bit rates for sub STM-O signals; - the fiame structures for sub STM-O signals; - the functionalities to be
24、 implemented in the different overheads of a sub STM-O fiame at the NNI of a synchronous digital network. Annex A specifies bit rates, frame structures and overhead functionalities to be used at radio interfaces to ensure consistent transport of SDH payloads and overhead functionalities when low/med
25、ium capacity (sub STM-O) radio systems are used. 2 References The following UIT-T Recommendations 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 Recommenda
26、tions 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 references listed below. A list of the currently valid ITU-T Recommendations is regularly
27、published. - ITU-T Recommendation G.707 (1 996), Network node interface for the synchronous digital hierarchy (SOH). ITU-T Recommendation G.861 (1 996), Principles and guidelines for the integration of satellite and radio systems in SDH transport networks. This Recommendation is an extension of Reco
28、mmendation G.707 (1 996), Network node interface for the synchronous digital hierarchy (SOH). It must be used in conjunction with Recommendation G.707 and thus all the relevant references in Recommendation G.707 are also references of this Recommendation, - 3 Definitions This Recommendation defines
29、the following terms: 3.1 tributary unit group-2: A %row by 12-column structure (108 bytes) that carries one or more TUS of the same size, as defined by Recommendation G.707. 3.2 sSTM-2n interface: A SDH transmission interface which transports one or more TU Group(s)-2, as defined by Recommendation G
30、.707, with Section overhead (9 bytes per fiame). sSTM-2n interfaces may be defined for optical, electrical or radio transport technologies. Recommendation 6.708 (06/99) 1 STDmITU-T RECMN G-708-ENGL %997 = 4862573 0664828 B4L m - M S O H The number (n) of TUG in sSTM-2n interfaces provided by this Re
31、commendation is limited to n = 1, 2 and 4. 4Ch (#), JO,Zl,Z2 Ch: S1, Kl,Z3,Z B2 BE-8 M1 status 3.3 sSTM-lk interface: A SDH transmission interface which transports one or more TU-12, as defined by Recommendation G.707, with Section overhead (9 bytes per frame). sSTM-lk interfaces are defined for rad
32、io transport technologies (sSTM-lk interfaces are defined in Annex A), and the sSTM-11 interface may also be used for reduced functionality, intra-station connections, as defined in Annex B. The number (k) of TU-12 in sSTM-lk interfaces provided by this Recommendation is limited to k= 1,2,4, 8 and 1
33、6. 4 sSTM interface rates As illustrated in Figure 1, for the n = 1 case, the sSTM-2n frame consists of nine overhead bytes and 108 payload bytes (i.e. one column of overhead and 12 columns of payload). The frame duration is 125 p, for a resulting signal rate of 7.488 Mbit/s. For the other rates, se
34、e Table 1. TUG-2 9 rows x 12 columns Figure UG.708 - sSTM interface frame format 2 Recommendation G.708 (06/99) - STD-ITU-T RECMN G.7D-ENGL 1999 Y862591 DbbY829 788 m TU structure TUG 2 Table UG.708 - Interface rates for sSTM systems # Overhead Payload envelope Bit rate 1 9 bytes 1 O8 7.488 Mbit/s 2
35、 21 6 14.400 Mbit/s r I I I 1 Tu12 _ 4 432 28.224 Mbit/s 1 9 bytes 36 2.88 Mbit/s 2 72 5.184 Mbit/s 4 8 16 _ 144 9.792 Mbit/s 288 19.008 Mbit/s 576 37.44 Mbit/s 5 Transport formats 5.1 Section overhead The sSTM interface has an associated Section overhead of 9 bytes. The location of the Section over
36、head bytes within the sSTM frame is shown in Figure 1. Some of these bytes are further subdivided into separated 16 kbit/s transmission capacity, using the multifiame structure, as shown in Figure 2. The detailed definitions and functions of these nine overhead bytes are described in clause 6. Recom
37、mendation 6.708 (06/99) 3 (Example for the sSTM-21 case) TU Mapping area s1 B2 v2s-, l+l I z1 I I 23 I TU Mapping IZT Mapping area H D1 v4s+ I Ei I TU Mapping area 24 B2 M1 (*) Media-dependent bytes (#) Media-specific error detection code byte (see 6.2.1.4) 125 bis 250 ps 375 ps 500 ps Figure 2/6.70
38、8 - sSTM multiframe format 5.2 Scrambling A frame synchronous scrambler equal to that recommended in Recommendation G.707 for STM-N frame should be used to prevent long sequences of “1 Is or “0“s. The frame alignment byte An should be excluded from the scrambling. The scrambler shall be reset to “11
39、1111 1“ on the most significant bit of the byte following the An. 4 Recommendation G.708 (06/99) - 5.3 The sSTM-2n interface frame structure, for the N = 1 case as illustrated in Figure 1, consists of thirteen columns and nine rows of %bit bytes for a total of 117 bytes (936 bits). The frame duratio
40、n is 125 ps (i.e. 8000 fiames per second), which results in a bit rate of 7.488 Mbits. As with the STM-1 signal, the order of transmission bytes is row by row, from left to right. In each byte, the most significant bit is transmitted first. Frame structure for the sSTM-2n interface 5.4 n x TUG-2 pay
41、loads The payload portion of the sSTM-2n interface follows the TUG structure and interleaving format of the STM-1 signal described in Recommendation G.707. Specifically, the TUG payload may consist of four TU-1 Is, three TU-l2s, or a single TU-2. 6 Overhead functions 6.1 Interface layers 6.1.1 Physi
42、cal layer Physical layer specifications are defined in other Recommendations. 6.1.2 Section layer The Section overhead deals with the reliable transport of the TU or sSTM frame and overhead across the physical medium. 6.1.3 Path layer The VC Path layer for the sSTM interface is specified in Recommen
43、dation G.707 6.2 * sSTM section overhead The Section overhead is subdivided into regenerator section overhead (RSOH) and multiplex section overhead (MSOH) as shown in Figure 1. Any bytes or bits in the SOH defined as reserved or not required should be coded as all “O“ and receivers should be able to
44、 ignore their content. 6.2.1 Regenerator section overhead 6.2.1.1 This byte combines the framing and multiframe alignment functions for the sSTM signal. The byte values alternate betweenF6,28, F7, and 29 Hex (11110110,00101000,11110111, and 00101001) as shown in Figure 3. The multiframe alignment fu
45、nction is required to identie the phase of the V1-V4 bytes of the TUS. The first byte transmitted directly afier Al is the V1 byte associated with the first TU; similarly the V2, V3 and V4 bytes, associated with the first TU, are transmitted directly after A2, A3 and A4 bytes, respectively, NOTE-The
46、 byte An values in sSTM frames 1 and 2 are the same as the STM-1 byte Al and A2 values, respectively. The seven MSBs of the byte alternate between the two patterns, and the LSB is used to provide the additional multiframe information. Framing and multiframe indicator (An) Recommendation G.708 (06199
47、) 5 I Frame I An I Value I Hex I V bvte I 1 2 3 4 AI 111 101 10 F6 v1 A2 001 01000 28 v2 A3 11110111 F7 v3 A4 00101001 29 v4 6.2.1.2 Section trace (JO) This byte is used for the same purpose and with the same codes provided for JO byte in Recommendation G.707. 6.2.1.3 Data communications channel 01)
48、 A 64 kbit/s channel is defined using byte D1 as a section data communication channel (DCC). 6.2.1.4 Media-dependent error detection code This byte is reserved for implementation-dependent methods of error detection for operation and maintenance purposes. 6.2.1.5 Growth (Zl, 22) These bytes are rese
49、rved for overhead functions. 6.2.1.6 Media-dependent bytes These bytes are reserved for media-specific use. 6.2.2 Multiplex section overhead 6.2.2.1 Multiplex section status (Mi) This byte provides a combination of performance status, and maintenance functions. The partitioning of the byte is shown in Figure 4. The four-bit REI field (bits 1-4) shall be set to convey the count of interleaved bit blocks that have been detected in error by the BIP-8 in the range of O, 81 received in the B2 byte
