1、 International Telecommunication Union ITU-T G.998.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(12/2006) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Access networks Ethernet-based multi-pair bonding Amendment 1 ITU-T
2、 Recommendation G.998.2 (2005) Amendment 1 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 CHARACT
3、ERISTICS OF INTERNATIONAL 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 TRANSM
4、ISSION MEDIA CHARACTERISTICS 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 20
5、48 kbit/s G.920G.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 Optica
6、l fibre submarine 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 DATA OVER TRANSPORT GENERIC ASPECTS G.7
7、000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.998.2 (2005)/Amd.1 (12/2006) i ITU-T Recommendation G.998.2 Ethernet-based multi-pair bonding Amendment 1 Summary This amendment to IT
8、U-T Rec. G.998.2 addresses differential delay for aggregation of ADSL2plus links and of VDSL2 links. Source Amendment 1 to ITU-T Recommendation G.998.2 (2005) was approved on 14 December 2006 by ITU-T Study Group 15 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.998.2 (200
9、5)/Amd.1 (12/2006) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and ta
10、riff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recom
11、mendations 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 fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recomme
12、ndation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperabil
13、ity 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 such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compl
14、iance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity
15、 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, ITU had received notice of intellectual property, protected by patents, which may be required to
16、implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be reproduced, by a
17、ny means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.998.2 (2005)/Amd.1 (12/2006) 1 ITU-T Recommendation G.998.2 Ethernet-based multi-pair bonding Amendment 1 Insert new clause 6.2.3: 6.2.3 Exceptions to clause 61.2.2.5 IEEE 802.3-2005 clause 61.2.2.5 requires the receiving
18、 PCS to be able to handle a maxDifferentialDelay of 15 000-bit times between the slowest link (i.e., link with the lowest net data rate) and the fastest link (i.e., link with the highest net data rate) in an N-pair bonding group. This allows to operate at a slowest link fragment size value (max. 512
19、 octets) and at a fastest link speed value (max. 400/(N+3) Mbit/s) and at a speed ratio value (fastest to slowest net data rate ratio, max. 4:1), all close to their maximum allowed values, with the transmitting PCS assuring that: (8 * slowest_link_fragment_size) * (speed_ratio) 15 000 and in case th
20、e transceiver jitter does not significantly contribute to the differential delay to be handled by the receiving PCS. A low transceiver jitter is particularly achieved by G.992.1 (SHDSL) transceivers. However, in the case of ADSL2plus and VDSL2, transceiver jitter is caused e.g., by buffering inside
21、the transmitting or receiving transceiver (number of octets jitter), by symbol rate (1 symbol jitter = 250 s), by sync symbols (1 symbol jitter = 250 s), and by FEC (KFECoctets jitter). Transceiver jitter is further increased by differences over the transceivers in the bonding group in interleaving
22、delay (number of s jitter) and processing time (number of s jitter). While ITU-T Recs G.992.3/5 and G.993.2 provide means to reduce the interleaving delay difference over the links in the bonding group down to some low value depending on granularity, these Recommendations do not define transceiver j
23、itter bounds. The remaining transceiver jitter can be estimated as an additional differential delay (in bit times) at the receiving PCS up to about: (KFEC* 8/slowest_link_net_data_rate + 500 s) * fastest_link_net_data_rate depending on whether or not the transceiver jitter is reduced by the receivin
24、g transceiver. If such differential delay is input to a receiving PCS capable of handling only 15 000-bit times of differential delay, then the net data rate of each link in the bonding group is limited between 0 and 25 Mbit/s, depending on the transmitting PCSs choice of maximum or minimum fragment
25、 size and speed ratio respectively. To avoid such limitations on the net data rate of ADSL2plus or VDSL2 links, the receiving PCS should be able to handle the additional differential delay introduced by the transceiver jitter. NOTE For example, to support the full 100 Mbit/s aggregate net data rate
26、for a 2-pair bonding group at a 4:1 speed ratio, the receiving PCS may need to be able to handle a total differential delay of approximately 65 000-bit times, in case the receiving transceiver does not reduce the transceiver jitter. Printed in Switzerland Geneva, 2007 SERIES OF ITU-T RECOMMENDATIONS
27、 Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H A
28、udiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements
29、 of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installations, loc
30、al line networks Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks, open system communications and security Series Y Global information infrastructure, Internet protocol aspects and next-generation networks Series Z Languages and general software aspects for telecommunication systems
