1、 International Telecommunication Union ITU-T G.998.3TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2005) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Access networks Multi-pair bonding using time-division inverse multiplexing IT
2、U-T Recommendation G.998.3 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTE
3、RNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA CHA
4、RACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 General G.900G.909 Parameters for optical fibre cable systems G.910G.919 Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s G.920G
5、.929 Digital line transmission systems on cable at non-hierarchical bit rates G.930G.939 Digital line systems provided by FDM transmission bearers G.940G.949 Digital line systems G.950G.959 Digital section and digital transmission systems for customer access to ISDN G.960G.969 Optical fibre submarin
6、e cable systems G.970G.979 Optical line systems for local and access networks G.980G.989 Access networks G.990G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWOR
7、KS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.998.3 (01/2005) i ITU-T Recommendation G.998.3 Multi-pair bonding using time-division inverse multiplexing Summary This Recommendation describes a method for bonding of multiple digital subscriber li
8、nes (DSL) using Time-Division Inverse Multiplexing (TDIM). This Recommendation provides a specification of the TDIM protocol in sufficient detail, to allow development and testing of interoperable implementations for both transmitter and receiver. It includes a multi-pair synchronization frame forma
9、t, Bonding Communication Channel (BCC), byte-oriented dispatching, hitless addition and removal of pairs, fast removal of pair upon pair failure, using IEEE 802.3ah handshake for pair discovery, parameter negotiation and setup, and an optional FEC and interleaver. Source ITU-T Recommendation G.998.3
10、 was approved on 13 January 2005 by ITU-T Study Group 15 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.998.3 (01/2005) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommuni
11、cation Standardization Sector (ITU-T) is a permanent organ of ITU. 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 Assembl
12、y (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which
13、fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this
14、 Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language
15、 such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Reco
16、mmendation may involve the use of a claimed Intellectual Property Right. 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 ap
17、proval of this Recommendation, ITU had 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 therefore strongly urged to consult the TSB pa
18、tent database. ITU 2005 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.998.3 (01/2005) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations, Acronyms, and Symbols 2 5 Data f
19、low 3 6 Multi-pair synchronization . 4 6.1 Introduction 4 6.2 Frame format 4 6.3 Multi-pair synchronization state machine 7 7 Dispatching. 10 7.1 Principles 10 7.2 Algorithm . 10 7.3 Pseudo code 10 8 Differential delay 12 9 Clock synchronization 12 9.1 Scope 12 9.2 TDM service synchronization and cl
20、ock transfer. 13 9.3 Aggregation layer synchronization. 13 9.4 Pair synchronization . 14 10 Service encapsulation . 14 10.1 Reference model. 14 10.2 Service mux 15 10.3 Asynchronous services . 18 10.4 TDM service stuffing . 22 11 FEC and interleaver 24 11.1 FEC. 24 11.2 Interleaver. 27 12 Processes.
21、 28 12.1 Pair management and control . 28 12.2 Aggregation group management and control . 31 12.3 Procedures 33 13 TDIM Bonding Communication Channel (BCC). 38 13.1 Introduction 38 13.2 Events . 39 13.3 Messages. 41 iv ITU-T Rec. G.998.3 (01/2005) Page 14 Handshaking . 53 14.1 Overview 53 14.2 Bondi
22、ng Npar(2) codepoint 54 14.3 Pair discovery . 54 15 Performance monitoring . 54 Annex A Modem rate matching 55 A.1 Introduction 55 A.2 Work principles 56 A.3 Coordination between BTU-C and BTU-R 57 A.4 Framing format. 57 A.5 Modem rate matching operation. 58 Appendix I Clock synchronization examples
23、 . 59 I.1 Clock domains 59 I.2 Rate adaptation between clock domains. 60 I.3 Timing operation modes. 60 I.4 Examples 61 Appendix II Management objects. 64 ITU-T Rec. G.998.3 (01/2005) 1 ITU-T Recommendation G.998.3 Multi-pair bonding using time-division inverse multiplexing 1 Scope This Recommendati
24、on defines the bonding function for the TDIM-based bonding method, the purpose of which is to provide inverse multiplexing of various service data streams (Ethernet, ATM, TDM) over multiple DSL physical links and to retrieve the original stream at the far-end from these physical links. This Recommen
25、dation is a detailed specification of the TDIM protocol in sufficient detail to allow development and testing of interoperable implementations for both transmitter and receivers. It includes: 1) Multi-pair synchronization frame format. 2) Bonding Communication Channel (BCC). 3) Dispatching algorithm
26、 4) Hitless addition and removal of pairs. 5) Fast removal of pair upon pair failure. 6) Using IEEE 802.3ah handshake for pair discovery, parameter negotiation and setup. This Recommendation defines a new TPS-TC for DSL transceivers. Architecturally, this TPS-TC should be placed above the PMS-TC (at
27、 the alpha/beta-interface) of existing or future DSL transceivers. Practically, the exact same result can be obtained by stacking the new TPS-TC defined in this Recommendation on top of the Clear Channel or STM TPS-TC as defined in existing DSL Recommendations. 2 References The following ITU-T Recom
28、mendations 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; users of this Recommendation are th
29、erefore 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. The reference to a document within this Recommendation does not give it, as a st
30、and-alone document, the status of a Recommendation 1 ITU Recommendation G.704 (1998), Synchronous frame structures used at 1544, 6312, 2048, 8488 and 44 736 kbit/s hierarchical levels. 2 ITU-T Recommendation G.7041/Y.1303 (2003), Generic framing procedure (GFP). 3 ITU-T Recommendation G.991.2 (2003)
31、, Single-pair high-speed digital subscriber line (SHDSL) transceivers. 4 ITU-T Recommendation G.992.1 (1999), Asymmetric digital subscriber line (ADSL) transceivers. 5 ITU-T Recommendation G.992.3 (2005), Asymmetric digital subscriber line (ADSL) transceivers 2 (ADSL2). 6 ITU-T Recommendation G.993.
32、1 (2004), Very-high-speed digital subscriber line transceivers. 7 ITU-T Recommendation G.994.1 (2003), Handshake procedures for digital subscriber line (DSL) transceivers. 2 ITU-T Rec. G.998.3 (01/2005) 8 ITU-T Recommendation I.432.1 (1999), B-ISDN user-network interface Physical layer specification
33、: General characteristics. 9 IEEE 802.3ah (2004), Telecommunications and Information Exchange Between Systems LAN/MAN Specific Requirements Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method and physical layer specifications, Amendment: Media Access Control Parame
34、ters, Physical Layers, and Product Type. 3 Definitions There are no additional definitions required in this Recommendation. 4 Abbreviations, Acronyms, and Symbols This Recommendation uses the following abbreviations: ADSL Asymmetric Digital Subscriber Line ANSI American National Standards Institute
35、ATIS Alliance for Telecommunications Industry Solutions ATM Asynchronous Transfer Mode BCC Bonding Communication Channel bps bits per second BTU-C Bonding Terminating Unit, CO side BTU-R Bonding Terminating Unit, RT (or CPE) side BW Bandwidth Clk Clock CPE Customer Premises Equipment CO Central Offi
36、ce CRC Cyclic Redundancy Check DS1 Digital Signal 1, (1.544 Mbit/s) DS3 Digital Signal 3, (44.736 Mbit/s) DSL Digital Subscriber Line E1 Electrical interface signal, Level 1, (2.048 Mbit/s) E3 Electrical interface signal, Level 3, (34.368 Mbit/s) EFM Ethernet in the First Mile enum Enumerated EOC Em
37、bedded Operations Channel FCS Frame Check Sequence FE Far End FEC Forward Error Correction GF Galois Field GFP Generic Framing Procedure HEC Header Error Check ITU-T Rec. G.998.3 (01/2005) 3 HS Handshake IEEE Institute of Electrical and Electronics Engineers IL Interleaver IMA Inverse Multiplexing f
38、or ATM ITU-T International Telecommunication Union Telecommunication Standardization Sector kbit/s kilobits per second LSB Least Significant Bit/Byte Mbit/s megabits per second MSB Most Significant Bit/Byte MUX Multiplexer NE Near End NS Number of Services PLI Packet Length Identifier PM Performance
39、 Monitor PMI Physical Medium Independent PSD Power Spectral Density RS Reed Solomon RT Remote Terminal rx Receive/receiver SDH Synchronous Digital Hierarchy SF Super-Frame SHDSL Single-Pair High-Speed Digital Subscriber Line STM Synchronous Transfer Mode TC Transmission Convergence TDIM Time-Divisio
40、n Inverse Multiplexing TDM Time Division Multiplexing TPS-TC Transport Protocol Specific Transmission Convergence Tx Transmit/transmitter uint 8 Unsigned Integer 8 bits uint 16 Unsigned Integer 16 bits UTC Unable To Comply VDSL Very high speed Digital Subscriber Line 5 Data flow Figure 1 represents
41、the data flow model which is defined in this proposed text. Data from a mix of services is encapsulated into a single data stream. The data stream can then optionally pass through forward error correction and interleaving, and then be dispatched (inverse multiplexed) over multi-pair modems. 4 ITU-T
42、Rec. G.998.3 (01/2005) Figure 1/G.998.3 Data flow model The data flow model using modem rate matching is illustrated in Annex A. 6 Multi-pair synchronization 6.1 Introduction The multi-pair aggregation group synchronization is done in the aggregation layer, independently from the underlying physical
43、 layer. Time-Division Inverse Multiplexing (TDIM) bonding uses a super frame format for multi-pair synchronization, as described below. 6.2 Frame format The multi-pair synchronization frame, called super-frame, is made of smaller entities. Figure 2 describes the frame format for the super-frame. Not
44、e that wherever applicable, Most Significant Bit/Byte (MSB) bits are always transmitted first in time and Least Significant Bit/Byte (LSB) bits are always transmitted last. ITU-T Rec. G.998.3 (01/2005) 5 Figure 2/G.998.3 Multi-pair synchronization Frame format 6.2.1 Bonding sub-block and mini-frames
45、 The bonding sub-block has a fixed time period of 125 s. A sub-block duration of 125 s yields a rate granularity of 8 kbit/s. A mini-frame contains 8 bonding sub-blocks and has a period of 1 ms. The start of a mini-frame is synchronized to the start of a bonding sub-block. The first byte in each min
46、i-frame (in each DSL pair) is taken for header. The mini-frame header is used to indicate the start of a super-frame and to transferring events and messages to the far end. The amount of bits in each sub-block is a function of the sub-block location, the number of bonded pairs and on the total data
47、rate of all the bonded pairs. The amount of bonding payload bits carried by each of the last 7 bonding sub-blocks of every mini-frame is equal to N(Rate) = Rate/8 kbit/s, while: N(Rate) is the number of bits in each sub-block, depending on the accumulated link data rate. Rate is the accumulated data
48、 rate of all the pairs measured in bits-per-second bps. The amount of bonding payload bits carried by the first bonding sub-block in each mini-frame is N(Rate) 8M where M is the number of individual pairs in the bonded system. NOTE If rate matching is used (see Annex A), then: The amount of bits ava
49、ilable for bonding payload in the first bonding sub-block of every min-frame is N(Rate) 16M. The amount of bits available for bonding payload in the 8-th bonding sub-block of every mini-frame is N(Rate) + 8, where = i=1Mi, and each iis dependent on the rate variation on pair i and can take the values 1, 0, 1, 2. Moreover, each may take different values in each Mini-Frame (see Annex A for details). 6 ITU-T Rec. G.998.3 (01/2005) 6.2.2 Frame A frame is built from 2 mini-frames and therefore has a perio
