1、 International Telecommunication Union ITU-T G.709/Y.1331TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(10/2013) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments General SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPE
2、CTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Transport Interfaces for the optical transport network Amendment 2 Recommendation ITU-T G.709/Y.1331 (2012) Amendment 2 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNE
3、CTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY O
4、R SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 General G.700G.709Coding of voice and audio signals G.710G.729 Pr
5、incipal characteristics of primary multiplex equipment G.730G.739 Principal characteristics of second order multiplex equipment G.740G.749 Principal characteristics of higher order multiplex equipment G.750G.759 Principal characteristics of transcoder and digital multiplication equipment G.760G.769
6、Operations, administration and maintenance features of transmission equipment G.770G.779 Principal characteristics of multiplexing equipment for the synchronous digital hierarchy G.780G.789 Other terminal equipment G.790G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900
7、G.999 MULTIMEDIA 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.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer
8、 to the list of ITU-T Recommendations. Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) i Recommendation ITU-T G.709/Y.1331 Interfaces for the optical transport network Amendment 2 Summary Amendment 2 to Recommendation ITU-T G.709/Y.1331 (2012) contains extensions related to the: addition of a low lat
9、ency 1.25G OTU0 for deployment at the edge of an optical transport network (clauses 2, 3.2, 4, 11.1 and Annex G), addition of overhead (OH) type, trail trace identifier (TTI) and nominal central frequency overhead and transport of this overhead plus OCh FDI-P, FDI-O and OCI overhead over a multi-ven
10、dor IaDI (clauses 15.5.4, 15.5.4.1 and 15.5.4.2). History Edition Recommendation Approval Study Group 1.0 ITU-T G.709/Y.1331 2001-02-09 15 1.1 ITU-T G.709/Y.1331 (2001) Amd. 1 2001-11-29 15 2.0 ITU-T G.709/Y.1331 2003-03-16 15 2.1 ITU-T G.709/Y.1331 (2003) Amd. 1 2003-12-14 15 2.2 ITU-T G.709/Y.1331
11、 (2003) Cor. 1 2006-12-14 15 2.3 ITU-T G.709/Y.1331 (2003) Amd. 2 2007-11-22 15 2.4 ITU-T G.709/Y.1331 (2003) Cor.2 2009-01-13 15 2.5 ITU-T G.709/Y.1331 (2003) Amd. 3 2009-04-22 15 3.0 ITU-T G.709/Y.1331 2009-12-22 15 3.1 ITU-T G.709/Y.1331 (2009) Cor. 1 2010-07-29 15 3.2 ITU-T G.709/Y.1331 (2009) A
12、md. 1 2010-07-29 15 3.3 ITU-T G.709/Y.1331 (2009) Amd. 2 2011-04-13 15 4.0 ITU-T G.709/Y.1331 2012-02-13 15 4.1 ITU-T G.709/Y.1331 (2012) Cor. 1 2012-10-29 15 4.2 ITU-T G.709/Y.1331 (2012) Amd. 1 2012-10-29 15 4.3 ITU-T G.709/Y.1331 (2012) Amd. 2 2013-10-22 15 ii Rec. ITU-T G.709/Y.1331 (2012)/Amd.2
13、 (10/2013) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsib
14、le 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 Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T
15、 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 fall within ITU-Ts purview, the necessary standards are prepared on a collaborative b
16、asis 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 Recommendation is voluntary. However, the Recommendation may contain certain mandato
17、ry 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 such as “must“ and the negative equivalents are used to express requirements. The
18、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 Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes
19、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 approval of this Recommendation, ITU had received notice of intellectual property, pr
20、otected by patents, which may be required to 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 2013 All rights reserved. No par
21、t of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) iii Table of Contents Page 1) Introduction 1 2) Additions 1 2.1) Clause 2 1 2.2) Clause 3.2 . 1 2.3) Clause 4 1 2.4) Clause 11.1 . 1 2.5) Clau
22、se 15.5 . 2 2.6) New Annex G . 3 2.7) Bibliography . 5 Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) 1 Recommendation ITU-T G.709/Y.1331 Interfaces for the optical transport network Amendment 2 1) Introduction This amendment contains extensions to the fourth version (2012) of Recommendation ITU-T G
23、.709/Y.1331, related to the: addition of a low latency 1.25G OTU0 for deployment at the edge of an optical transport network (clauses 2, 3.2, 4, 11.1 and Annex G); addition of overhead (OH) type, trail trace identifier and nominal central frequency overhead and transport of this overhead plus OCh FD
24、I-P, FDI-O and OCI overhead over a multi-vendor IaDI (clauses 15.5.4, 15.5.4.1 and 15.5.4.2). 2) Additions 2.1) Clause 2 Add the following references to clause 2: ITU-T G.698.3 Recommendation ITU-T G.698.3 (2012), Multichannel seeded DWDM applications with single-channel optical interfaces. ITU-T G.
25、7712 Recommendation ITU-T G.7712/Y.1703 (2010), Architecture and specification of data communication network. 2.2) Clause 3.2 Add the following term to clause 3.2: 3.2.2 OTU0 low latency: The OTU0 low latency (OTU0LL) is the information structure used for transport of an ODU0 over a multi-vendor opt
26、ical network IaDI at the edge of the optical transport network. NOTE The OTU0LL is not transported over an OTM-0 IrDI, OTM-n IaDI, OTM-nr IaDI. 2.3) Clause 4 Add the following abbreviations to clause 4: OTU0LL Completely standardized Optical channel Transport Unit-0 Low Latency TTI Trail Trace Ident
27、ifier 2.4) Clause 11.1 Replace the NOTE in clause 11.1 with the following text: NOTE This Recommendation does not specify an OTUk frame structure for k=0, k=2e or k=flex. See Annex G for the specification of OTU0LL. 2 Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) 2.5) Clause 15.5 Add the following
28、subclauses to clause 15.5: 15.5.4 Optical channel non-associated overhead (OCh OH) transport over OTM-1 multi-vendor IaDI Figure 15-5bis illustrates the information and representation to be used when the OCh overhead is to be transferred across a multi-vendor IaDI. This information consists of OCh o
29、verhead primitives and of additional information including an OH type field, a trail trace identifier field to check for misconnections over the OCN and a field indicating the nominal central frequency of the associated OCh payload. In the case of single-vendor IaDI, the coding and method of informa
30、tion transfer is vendor specific. For multi-vendor IaDI, the overhead is transferred over the overhead communication network (OCN) as described in ITU-T G.7712. NOTE A multi-vendor IaDI which transfers OCh overhead over an OCN cannot provide fate-sharing of the OCh overhead with the OCh payload acro
31、ss this interface. Each OCh overhead primitive is represented by a bit that is set to one if the respective condition is present, and will be set to zero when it is not. The specification of the encapsulation and transmission of this information is outside the scope of this Recommendation. This info
32、rmation must be communicated with the peers such that the OCh overhead primitives come into sync within one second in the absence of changes to OCh FDI-P, FDI-O or OCI. In the event of changes to any OCh overhead primitive, the update must be sent within 10 ms of the change and with a mechanism to g
33、uarantee receipt in the event of packet loss. Size Contents 2 octets OH type, 0x0001=OCh overhead 64 octets Trail trace identifier (TTI): 16 octets SAPI 16 octets DAPI 32 octets operator specific 4 octets Nominal central frequency (NCF) Encoded as a “DWDM Wavelength Label” per Section 3.2 of b-IETF
34、RFC 6205 1 octet OAM bits The OAM bits are represented as follows: 1 2 3 4 5 6 7 8 FDI-P FDI-O OCI Reserved Figure 15-5bis OCh overhead information elements to be used for multi-vendor 15.5.4.1 Trail trace identifier (TTI) The TTI is defined to transport a 64-byte TTI as specified in clause 15.2 ove
35、r a multi-vendor IaDI to ensure there are no misconnections across the OCN. Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) 3 15.5.4.2 Nominal central frequency (NCF) The NCF encodes the nominal central frequency of the intended OCh payload. This is sent explicitly across a multi-vendor IaDI to ensur
36、e there are no misconnections across the OCN. The coding for this information for a multi-vendor IaDI is specified in clause 15.5.4. 2.6) New Annex G Add new Annex G as follows: Annex G Mapping ODU0 into a low latency OTU0 (OTU0LL) (This annex forms an integral part of this Recommendation.) G.1 Intr
37、oduction Optical networks at the edge of the optical transport network have 1.25 Gbit/s applications that benefit from a low latency FEC, see e.g., ITU-T G.698.3. Within the optical transport network client signals with a bit rate up to 1.25 Gbit/s are transported within an ODU0 and the ODU0 is tran
38、sported within a HO ODUk and OTUk (k = 1,2,3,4). This annex specifies a low latency 1.25G OTU0 (OTU0LL) frame format in which one ODU0 is transported which carries a client (e.g., 1G Ethernet) signal as specified in this Recommendation. G.2 Optical channel transport unit 0 low latency (OTU0LL) The O
39、TU0LL conditions the ODU0 for transport over a multi-vendor optical network IaDI at the edge of the optical transport network. The OTU0LL frame structure, including the OTU0LL FEC is completely standardized. The optical aspects of the multi-vendor optical network IaDI at the edge of the optical tran
40、sport network are outside the scope of this Recommendation. NOTE 1 Transport of the OTU0LL over the OTM-0 IrDI, OTM-nr IrDI and OTM-n IaDI specified in this Recommendation is not supported. NOTE 2 An ODU0 which is transported within an OTU0LL may be passed through the OTN and terminated at the far e
41、nd edge of the OTN. G.2.1 OTUk frame structure The OTU0LL frame structure is based on the ODU0 frame structure and extends it with a distributed forward error correction (FEC) as shown in Figure G.1. Sixteen times 16 columns are added to the ODU0 frame for the FEC and the reserved overhead bytes in
42、row 1, columns 8 to 14 of the ODU0 overhead are used for an OTU0LL specific overhead, resulting in an octet-based block frame structure with four rows and 4080 columns. The MSB in each octet is bit 1, the LSB is bit 8. The OTU0LL overhead is the same as the OTUk overhead. The bit rate of the OTU0LL
43、signal is 255/239 1 244 160 kbit/s (1 327 451.046 kbit/s). The frame period of the OTU0LL signal is approximately 98.354 s. The sixty-four 16-byte RS(255,239) FEC fields in the OTL0LL frame contain the Reed-Solomon RS(255,239) FEC code. Each RS(255,339) FEC is computed over the previous 239 OTU0LL b
44、ytes. Transmission of the OTU0LL FEC is mandatory. NOTE The distribution of the RS(255,239) FEC fields over the OTU0LL frame minimizes the transfer delay introduced by the processing of this FEC and the number of codecs to compute this FEC. 4 Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) The RS(255
45、,239) FEC code shall be computed as specified in Annex A with the notion that each FEC is computed over the previous 239 OTU0LL bytes instead of over a sub-row as described in this annex for the case of an OTUk (k=1,2,3,4). G.709-Y.1331(12)-Amd.2(13)_FG.1. . . .11 12 13 14RESGCC0123456 7 8910Column
46、#FAS MFAS SM3826 408014 15(4 239 bytes)FA OHOTU0LLOH11112233443824(4 239 bytes)ODU0239 240 255 4065RS(255,239)FECRS(255,239)FECRS(255,239)FECRS(255,239)FECRS(255,239)FECRS(255,239)FECRS(255,239)FECRS(255,239)FEC406414 blocks of 4 (239 + 16) bytes OTU0LLFigure G.1 OTU0LL frame structure, overhead and
47、 ODU0 mapping The transmission order of the bits in the OTU0LL frame is left to right, top to bottom, and MSB to LSB (see Figure G.2). G.709-Y.1331(12)_F11-2112344080ColumnRowMSB12345678LSBFigure G.2 Transmission order of the OTU0LL frame bits G.2.2 Scrambling The OTU0LL signal must have sufficient
48、bit timing content at the NNI. A suitable bit pattern, which prevents a long sequence of “1“s or “0“s, is provided by using a scrambler. The operation of the scrambler shall be functionally identical to that of a frame synchronous scrambler of sequence length 65535 operating at the OTU0LL rate. The
49、generating polynomial shall be 1 + x + x3+ x12+ x16. Figure G.3 shows a functional diagram of the frame synchronous scrambler. Rec. ITU-T G.709/Y.1331 (2012)/Amd.2 (10/2013) 5 + + +G.709-Y.1331(12)-Amd.2(13)_FG.3DDDDDDDDDDDDDDDDQQ QQQQQQQQQQQQQQSS SSSSSSSSSSSSSSOTU0LLclockOTU0LL MSB of MFAS byteData inScrambleddata outFigure G.3 Frame synchronous scrambler The scrambler shall be reset to “FFFF“ (HEX) on the most significant bit of the byte following the last framing byte in the OTU0LL frame, i.e., the MSB
