1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.804TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2004) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital networks General aspects ATM cell mapping into plesiochronous digital hierarchy (PDH) ITU-T Recommendation G.804
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 TELEPHONE
3、 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 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA
4、CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 General aspects G.800G.809 Design objectives for digital networks G.810G.819 Quality and availability targets G.820G.829 Network capabilities and functions G.830G.839 SDH network characteristics G.840G.849
5、Management of transport network G.850G.859 SDH radio and satellite systems integration G.860G.869 Optical transport networks G.870G.879 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERIST
6、ICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWORKS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.804 (06/2004) i ITU-T Recommendation G.804 ATM cell mapping into plesiochronous digital hierarchy (PDH) Summary This Recommenda
7、tion provides the mapping to be used for the transport of ATM cells over PDH at the various hierarchical bit rates defined in ITU-T Rec. G.702. These mappings cover both the 1544 kbit/s and 2048 kbit/s-based hierarchies and are used in conjunction with the frame structures defined in ITU-T Rec. G.83
8、2. Source ITU-T Recommendation G.804 was approved on 13 June 2004 by ITU-T Study Group 15 (2001-2004) under the ITU-T Recommendation A.8 procedure. Keywords AAL2, ATM, mapping, PDH. ii ITU-T Rec. G.804 (06/2004) FOREWORD The International Telecommunication Union (ITU) is the United Nations specializ
9、ed 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 issuing Recommendations on them with a view to standardizing telecommunications on a wor
10、ldwide 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 topics. The approval of ITU-T Recommendations is covered by the procedure laid down in
11、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 expression “Administration“ is used for conciseness to indicate both a telecommunication admin
12、istration 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) and compliance with the Recommendation is achieved when all of these mandatory provis
13、ions 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 Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to
14、 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 claimed Intellectual Property Rights, whether asserted by ITU members or others outsid
15、e 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 Recommendation. However, implementors are cautioned that this may not represent the latest i
16、nformation 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 permission of ITU. ITU-T Rec. G.804 (06/2004) iii CONTENTS Page 1 Introduction 1 1.1 Scope 1
17、 1.2 References 1 1.3 Definitions 1 1.4 Abbreviations . 2 1.5 Conventions 2 2 Mapping of ATM cells into 1544 kbit/s . 2 2.1 Frame format 2 2.2 Cell rate adaptation. 3 2.3 Header Error Control (HEC) generation 3 2.4 Scrambling of the ATM cell payload (optional) 3 2.5 Cell delineation. 3 2.6 Cell head
18、er verification and extraction. 3 2.7 Physical layer OAM . 3 3 Mapping of ATM cells into 2048 kbit/s . 3 3.1 Frame format 4 3.2 Cell rate adaptation. 4 3.3 Header Error Control (HEC) generation 4 3.4 Scrambling of the ATM cell payload . 4 3.5 Cell delineation. 4 3.6 Cell header verification and extr
19、action. 4 3.7 Physical layer OAM . 4 4 Mapping of ATM cells into 6312 kbit/s . 5 4.1 Frame format 5 4.2 Cell rate adaptation. 5 4.3 Header Error Control (HEC) generation 5 4.4 Scrambling of the ATM cell payload . 5 4.5 Cell delineation. 5 4.6 Cell header verification and extraction. 6 4.7 Physical l
20、ayer OAM . 6 5 Mapping of ATM cells into 8448 kbit/s . 6 6 Mapping of ATM cells into 34 368 kbit/s 6 6.1 Frame format 6 6.2 Cell rate adaptation. 6 6.3 Header Error Control (HEC) 6 6.4 Scrambling of the ATM cell payload . 6 6.5 Cell delineation. 7 6.6 Cell header verification and extraction. 7 iv IT
21、U-T Rec. G.804 (06/2004) Page 6.7 Physical layer OAM . 7 7 Mapping of ATM cells into 44 736 kbit/s 7 7.1 Frame format 7 7.2 PLCP-based mapping of ATM cells. 7 7.3 HEC-based mapping of ATM into 44 736 kbit/s . 10 8 Mapping of ATM cells into 97 728 kbit/s 11 8.1 Frame format 11 8.2 Cell rate adaptatio
22、n. 11 8.3 Header Error Control (HEC) generation 11 8.4 Scrambling of the ATM cell payload . 11 8.5 Cell delineation. 12 8.6 Cell header verification and extraction. 12 8.7 Physical layer OAM . 12 9 Mapping of ATM cells into 139 264 kbit/s 12 9.1 Frame format 12 9.2 Cell rate adaptation. 12 9.3 Heade
23、r Error Control (HEC) generation 12 9.4 Scrambling of the ATM cell payload . 12 9.5 Cell delineation. 13 9.6 Cell header verification and extraction. 13 9.7 Physical layer OAM . 13 Annex A Transport of AAL2 CPS-packets in 2048 kbit/s frames 13 A.1 General . 13 A.2 Description of the method for trans
24、porting AAL2 channels in 2048 kbit/s frames . 13 A.3 Scrambling of the AAL2 CPS-packets. 14 A.4 N 64 kbit/s case . 14 A.5 Utilization of the Channel Identification Field (CIF). 15 ITU-T Rec. G.804 (06/2004) 1 ITU-T Recommendation G.804 ATM cell mapping into plesiochronous digital hierarchy (PDH) 1 I
25、ntroduction This Recommendation identifies the way of transporting ATM cells over PDH networks at different hierarchical bit rates. 1.1 Scope Existing transmission networks are based on Plesiochronous Digital Hierarchy (PDH) as defined in ITU-T Rec. G.702. ATM is considered as the suitable technique
26、 to support B-ISDN. The Synchronous Digital Hierarchy (SDH) will form the basis of transport of the ATM cells. During the transition period, there is a need to transport ATM cells using existing PDH transmission networks. This Recommendation provides the mapping to be used for this transport of ATM
27、cells on the different PDH bit rates for both 1544 and 2048 kbit/s hierarchies. 1.2 References The following ITU-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 ind
28、icated 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 recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T
29、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. ITU-T Recommendation G.702 (1988), Digital hierarchy bit rates. ITU-T Recommendation G.704 (1998), Synchronous frame structures
30、used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels. ITU-T Recommendation G.706 (1991), Frame alignment and cyclic redundancy check (CRC) procedures relating to basic frame structures defined in Recommendation G.704. ITU-T Recommendation G.832 (1998), Transport of SDH elements on PD
31、H networks Frame and multiplexing structures. ITU-T Recommendation I.363.2 (2000), B-ISDN ATM Adaptation Layer specification: Type 2 AAL. ITU-T Recommendation I.432.1 (1999), B-ISDN user-network interface Physical layer specification: General characteristics. 1.3 Definitions This Recommendation defi
32、nes the following terms: 1.3.1 idle cell: A cell which is inserted and extracted by the physical layer in order to adapt the cell flow rate at the boundary between the ATM layer and the physical layer to the available payload capacity of the transmission used. 1.3.2 valid cell: A cell whose header h
33、as no errors or has been modified by the cell Header Error Control (HEC) verification process. 1.3.3 nibble: A nibble is a group of four bits. 2 ITU-T Rec. G.804 (06/2004) 1.4 Abbreviations This Recommendation uses the following abbreviations: AAL ATM Adaptation Layer AAL2-CPS AAL type 2 Common Part
34、 Sublayer AIS Alarm Indication Signal ATM Asynchronous Transfer Mode BIP-8 Bit Interleaved Parity-8 B-ISDN Broadband aspects of Integrated Services Digital Network CID Channel Identifier CIF Channel Identification Field CRC Cyclic Redundancy Check FEAC Far-End Alarm and Control FEBE Far-End Block Er
35、ror FERF Far-End Receive Failure HEC Header Error Control LCD Loss of Cell Delineation OAM Operation, Administration and Maintenance PDH Plesiochronous Digital Hierarchy PLCP Physical Layer Convergence Protocol POH Path OverHead POI Path Overhead Identifier RAI Remote Alarm Indication SDH Synchronou
36、s Digital Hierarchy SYF Synchronization Field TS Time Slot 1.5 Conventions The order of transmission of information in all diagrams in this Recommendation is first from left to right and then top to bottom. Within each byte the most significant bit is transmitted first. The most significant bit (bit
37、 1) is illustrated at the left of all diagrams. 2 Mapping of ATM cells into 1544 kbit/s 2.1 Frame format The multiframe structure for the 24-frame multiframe as described in ITU-T Rec. G.704 shall be used. The ATM cell is mapped into bits 2 to 193 (i.e., time slots 1 to 24 described in ITU-T Rec. G.
38、704) of the 1544 kbit/s frame with the octet structure of the cell aligned with the octet structure of the frame (see Figure 2-1). ITU-T Rec. G.804 (06/2004) 3 Figure 2-1/G.804 Frame structure for 1544 kbit/s used to transport ATM cells 2.2 Cell rate adaptation The cell rate adaptation to the payloa
39、d capacity of the frames is performed by the insertion of idle cells, as described in ITU-T Rec. I.432.1, when valid cells are not available from the ATM layer. 2.3 Header Error Control (HEC) generation The Header Error Control (HEC) value is generated and inserted in the specific field in complianc
40、e with ITU-T Rec. I.432.1. 2.4 Scrambling of the ATM cell payload (optional) As an option, the ATM cell payload (48 bytes) can be scrambled before mapping into the 1544 kbit/s signal. If this option is used, then, in the reverse operation, following the termination of 1544 kbit/s signal, the ATM cel
41、l payload will be descrambled before being passed to the ATM layer. The self-synchronizing scrambler with the generator polynomial x43+ 1, as described in ITU-T Rec. I.432.1, is used. If this option is not used, then no descrambling is done in the reverse operation. 2.5 Cell delineation The cell del
42、ineation shall be performed using the Header Error Control (HEC) mechanism as defined in ITU-T Rec. I.432.1. 2.6 Cell header verification and extraction The cell header verification shall be performed in compliance with ITU-T Rec. I.432.1. All physical layer cells shall be extracted and only valid c
43、ells are passed to the ATM layer. 2.7 Physical layer OAM The error detection and performance reporting functions described in ITU-T Rec. G.704 are used. In addition, the Loss of Cell Delineation (LCD) is to be reported by a priority data link message. The specific 16-bit codeword is for further stud
44、y. 3 Mapping of ATM cells into 2048 kbit/s The mapping of ATM cells in a G.704 2048 kbit/s frame is described below. Annex A contains the description of an alternative method that can optionally be used when AAL2 CPS-packets are contained in the ATM cells. 4 ITU-T Rec. G.804 (06/2004) 3.1 Frame form
45、at The basic frame structure at 2048 kbit/s as described in ITU-T Rec. G.704 shall be used. The ATM cell is mapped into bits 9 to 128 and bits 137 to 256 (i.e., time slots 1 to 15 and time slots 17 to 31 described in ITU-T Rec. G.704) of the 2048 kbit/s frame with the octet structure of the cell ali
46、gned with the octet structure of the frame (see Figure 3-1). HeaderHeader256 bits/125 sATM cell mapping field: 30 octets (TS1 TS15 and TS17 TS31)ATMcell53 octetsProvides F3 OAM functions: Detection of loss of frame alignment Performance monitoring (CRC-4) Transmission of FERF and LOC Performance rep
47、ortingHeaderHeaderHeaderTS16: Reserved for signallingTS0Figure 3-1/G.804 Frame structure for 2048 kbit/s used to transport ATM cells 3.2 Cell rate adaptation The cell rate adaptation to the payload capacity of the frames is performed by the insertion of idle cells, as described in ITU-T Rec. I.432.1
48、, when valid cells are not available from the ATM layer. 3.3 Header Error Control (HEC) generation The Header Error Control (HEC) value is generated and inserted in the specific field in compliance with ITU-T Rec. I.432.1. 3.4 Scrambling of the ATM cell payload The ATM cell payload (48 bytes) shall
49、be scrambled before mapping into the 2048 kbit/s signal. In the reverse operation, following the termination of the 2048 kbit/s signal, the ATM cell payload will be descrambled before being passed to the ATM layer. A self-synchronizing scrambler with the generator polynomial x43+ 1, as described in ITU-T Rec. I.432.1, shall be used. Cell payload field scrambling is required to provide security against false cell delineation and replication of the 2048 kbit/s frame alignment word. 3.5 Cell delineation The cell delineation shall be pe
