1、 International Telecommunication Union ITU-T G.998.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2005) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Access networks Ethernet-based multi-pair bonding ITU-T Recommendation G.998.2
2、 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 INTERNATIONAL CARRIER TELEPHON
3、E 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 CHARACTERISTICS G.600G.699 DI
4、GITAL 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.929 Digital line transmis
5、sion 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 submarine cable systems G.970G.979
6、 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 NETWORKS G.8000G.8999 For furt
7、her details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.998.2 (01/2005) i ITU-T Recommendation G.998.2 Ethernet-based multi-pair bonding Summary This Recommendation describes a method for bonding of multiple digital subscriber lines (DSL) for Ethernet transport. This Recommendat
8、ion can support SHDSL, VDSL and ADSL transport as well as future xDSL technologies as they emerge. This Recommendation builds on the IEEE 802.3ah-2004 methods and extends Ethernet transport over other xDSL technologies, including ADSL. The Recommendation does not describe the details of the specific
9、 xDSL transport technology. Rather, it focuses on the aspects of the PCS layer modifications required for bonding. Source ITU-T Recommendation G.998.2 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.998.2 (01/2005) FOR
10、EWORD 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 tariff questions and iss
11、uing 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 Recommendations on these to
12、pics. 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 Recommendation, the expressio
13、n “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. interoperability or applicability)
14、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 compliance with the Recomme
15、ndation 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 or applicability of c
16、laimed 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 implement this Recomme
17、ndation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2005 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permiss
18、ion of ITU. ITU-T Rec. G.998.2 (01/2005) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Technologies addressed and architecture . 4 5.1 Technologies nomenclature 4 5.2 System considerations 4 5.3 Relationship between IEEE 802.3ah-2004 terminology and lay
19、ering (informative). 4 5.4 Multiple bearers 6 6 Exceptions to IEEE 802.3ah-2004, clause 61. 6 6.1 Exceptions to 802.3ah-2004, clause 61.1 . 6 6.2 Exceptions to 802.3ah-2004, clause 61.2 . 7 6.3 Exceptions to clause 61.3 . 8 7 Management . 9 8 Handshake 10 Annex A Ethernet bonding with 64/65-octet en
20、capsulation . 10 Annex B Ethernet bonding with HDLC encapsulation. 10 ITU-T Rec. G.998.2 (01/2005) 1 ITU-T Recommendation G.998.2 Ethernet-based multi-pair bonding 1 Scope This Recommendation specifies portions of clause 61 of IEEE Standard 802.3ah-2004 amendment to Carrier Sense Multiple Access wit
21、h Collision Detection (CSMA/CD) access method and physical layer specification as a normative reference and identifies the requirements for multi-pair bonding in IEEE 802.3ah-2004 that are different in the United States. Further, this Recommendation specifies the requirements for extending the bondi
22、ng methods in IEEE 802.3ah-2004 to xDSL technologies other than VDSL and SHDSL. The following are the objectives this Recommendation: a) To provide support for operation of xDSL technologies on multiple pairs of voice grade twisted pair cable. b) To provide 100 Mbit/s burst data rate at the Ethernet
23、 media independent interface using Rate Matching. c) To provide full duplex operation. d) To provide a communication channel with a mean BER at the / service interface of less than 107. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference
24、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 therefore encouraged to investigate the possibility of applying the most recen
25、t 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 stand-alone document, the status of a Recommendation. 1 ITU-T Recommendation G
26、.991.2 (2001), Single-pair high-speed digital subscriber line (SHDSL) transceivers. 2 ITU-T Recommendation G.991.2 (2003), Single-pair high-speed digital subscriber line (SHDSL) transceivers. 3 ITU-T Recommendation G.992.1 (1999), Asymmetric digital subscriber line (ADSL) transceivers. 4 ITU-T Recom
27、mendation G.992.3 (2005), Asymmetric digital subscriber line transceivers 2 (ADSL2). 5 ITU-T Recommendation G.992.5 (2005), Asymmetric Digital Subscriber Line (ADSL) transceivers Extended bandwidth ADSL2 (ADSL2+). 6 ITU-T Recommendation G.993.1 (2004), Very high speed digital subscriber line transce
28、ivers. 7 ITU-T Recommendation G.994.1 (2003), Handshake procedures for digital subscriber line (DSL) transceivers. 8 IEEE 802.3 (2002), Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method and physical layer specification. 2 ITU-T Rec. G.998.2 (01/2005) 9 IEEE 802.3ah (2004
29、), Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method and physical layer specification Amendment: Media Access Control Parameters, Physical Layers, and Management Parameters for Subscriber Access Networks. 10 T1.424*(2004), Interface between Networks and Customer Installa
30、tions Very-high-bit-rate Digital Subscriber Lines (VDSL) Metallic Interface (DMT-Based). 3 Definitions This Recommendation defines the following terms: 3.1 10PASS-TS: The IEEE 802.3 standard for delivering single and multi-pair Ethernet transport over G.993.1 (MCM) transceivers. 3.2 2BASE-TL: The IE
31、EE 802.3 standard for delivering single and multi-pair Ethernet transport over G.991.2 transceivers. 3.3 aggregation group: A collection of lines that may be aggregated into a single Ethernet interface. 3.4 carrier sense: In a local area network, an ongoing activity of a data station to detect wheth
32、er another station is transmitting. NOTE The carrier sense signal indicates that one or more DTEs are currently transmitting. 3.5 collision: A condition that results from concurrent transmissions from multiple data terminal equipment (DTE) sources within a single collision domain. 3.6 downstream: Di
33、rection from central office to remote terminal. 3.7 media independent interface: In IEEE 802.3, a transparent signal interface at the bottom of the Reconciliation sublayer. 3.8 physical medium attachment: That portion of the physical layer that contains the functions for transmission, reception coll
34、ision detection, clock recovery and skew alignment. 3.9 physical medium dependent: That portion of the physical layer responsible for interfacing to the transmission medium. The PMD is located just above the Medium Dependent Interface (MDI). 3.10 physical media entity: In IEEE 802.3ah-2004, a refere
35、nce to an individual loop contained with an aggregate group. 3.11 remote terminal: A terminal located downstream from a central office switching system. 3.12 upstream: Direction from remote terminal to central office. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations:
36、 the interface between the PMS-TC and TPS-TC layers at a CO the interface between the PMS-TC and TPS-TC layers in CPE the interface between the TPS-TC layer and the PCS layer ADSL Asymmetric Digital Subscriber Line ANSI American National Standards Institute _ *T1 standards are maintained since Novem
37、ber 2003 by ATIS. ITU-T Rec. G.998.2 (01/2005) 3 ATIS Alliance for Telecommunications Industry Solutions BER Bit Error Ratio CL Capabilities List CLR Capabilities List Request CO Central Office CPE Customer Premises Equipment CRC Cyclic Redundancy Check CS Carrier Sense CSMA/CD Carrier Sense Multipl
38、e Access/Collision Detection DSL Digital Subscriber Line DTE Data Terminal Equipment EFM Ethernet in the First Mile FEC Forward Error Correction FIFO First In, First Out HDLC High-level Data Link Control IEEE Institute of Electrical and Electronics Engineers ITU-T International Telecommunication Uni
39、on Telecommunication Standardization Sector MAC Media Access Control MCM Multi-Carrier Modulation MII Medium Independent Interface MP Mode Proposal Message MS Mode Select Message MSB Most Significant Bit PAF PMA Aggregation Function PCS Physical Coding Sublayer PHY Physical Layer Entity Sublayer PMA
40、 Physical Medium Attachment PMD Physical Medium Dependent PME Physical Media Entity PMS-TC Physical Media-Specific TC Layer PTM Packet Transfer Mode SFD Start Frame Delimiter SHDSL Single-Pair High-bit-rate DSL TC Transmission Convergence layer TC-CRC Transmission Convergence Cyclic Redundancy Check
41、 TPS-TC Transmission Protocol-Specific TC Layer 4 ITU-T Rec. G.998.2 (01/2005) VDSL Very High-speed Digital Subscriber Line xDSL a collective term referring to any of the various types of DSL technologies 5 Technologies addressed and architecture This clause addresses technology specific parameters
42、for some bonded PHYs. The values presented here were derived from the rules set forth in clause 61 of IEEE 802.3ah-2004. Other PHYs may be addressed by following these rules. 5.1 Technologies nomenclature Large portions of this Recommendation reference the IEEE 802.3ah-2004 specification. A cross-re
43、ference to the technology nomenclature, and a reference to the relevant Recommendations, are given in Table 1. Table 1/G.998.2 Technology nomenclature Reference in this Recommendation IEEE 802.3ah-2004 Reference Relevant Recommendation VDSL 10PASS-TS T1.424 10 SHDSL 2BASE-TL G.991.2 1 ADSL N/A G.992
44、.1 3 As shown in the table, the IEEE reference to 10PASS-TS is the IEEE 802.3 standard for transporting Ethernet using a MCM-VDSL-based PHY. Likewise, 2BASE-TL is the IEEE 802.3 standard for transporting Ethernet using a SHDSL-based PHY. There is no IEEE standard for transporting Ethernet over ADSL,
45、 though that operation is clarified in this Recommendation. 5.2 System considerations The Copper PHYs addressed by this Recommendation are only defined for full duplex operation as defined in the IEEE 802.3 specification. 5.3 Relationship between IEEE 802.3ah-2004 terminology and layering (informati
46、ve) The Physical Coding Sublayer (PCS) contains two functions: MAC-PHY rate matching and PME aggregation. The functional position of the PCS is shown in Figure 1. The -interface and the ()-interface are generic interfaces used in various xDSL specifications such as the ones referenced in clause 2. T
47、he ()-interface is a simple octet-synchronous date interface; the -interface add protocol-awareness. Note that the bit rates in the shaded area labelled “PMD rate domain“ are derived from the DSL bit rates. Data is transferred across the -interface at the rate imposed by the lower layers. The bit ra
48、tes in the shaded area labelled “100 Mbit/s rate domain“ are synchronous to the MII rate. Data is transferred across the MII at the rate of one nibble per MII clock cycle. The MAC-PHY rate matching function adjusts the inter-packet gap so that the net data rate across this interface matches the sum
49、of rates across the -interface.1In the transmit direction, frames are transferred from the MAC to the PCS across the MII when the MAC-PHY rate matching function allows this. In the PCS, preamble and SFD octets are removed. _ 1Bit domains and physical clock domains do not necessarily coincide. The TC sublayer receives as clock signal from the PMA via the ()-interface, and a clock signal from the optional PAF or the MAC-PHY Rate Matching function via the -interface. T
