1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.709.1/Y.1331.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2017) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments General SERIES Y: GLOBAL INFORMATION INFRASTRUCTU
2、RE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES Internet protocol aspects Transport Flexible OTN short-reach interface Recommendation ITU-T G.709.1/Y.1331.1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERN
3、ATIONAL 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 SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE S
4、YSTEMS 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 AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 General G.700G.709 Coding of voice and aud
5、io signals G.710G.729 Principal 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 multiplicati
6、on equipment G.760G.769 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 D
7、IGITAL LINE SYSTEM G.900G.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 furth
8、er details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.709.1/Y.1331.1 (01/2017) i Recommendation ITU-T G.709.1/Y.1331.1 Flexible OTN short-reach interface Summary Recommendation ITU-T G.709.1/Y.1331.1 specifies functions associated with the n x 100 Gbit/s FlexO Group interface a
9、pplication. The intent is to keep it separate from the main ITU-T G.709 text. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.709.1/Y.1331.1 2017-01-12 15 11.1002/1000/13082 Keywords B100G, FlexO, Flex OTN, IrDI, KP4 FEC, SR or short reach. * To access the Recommendation,
10、type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.709.1/Y.1331.1 (01/2017) FOREWORD The International Telecommunication Union (ITU) is the United Nations spe
11、cialized 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 responsible for studying technical, operating and tariff questions and issuing Recommendations on them
12、 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 topics. The approval of ITU-T
13、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 expression “Administration“ is used f
14、or 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) and compliance with the Re
15、commendation 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 Recommendation is required of any
16、 party. INTELLECTUAL PROPERTY RIGHTSITU 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 claimed Intellectual Propert
17、y 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 Recommendation. However, implement
18、ers 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 2017 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written pe
19、rmission of ITU. Rec. ITU-T G.709.1/Y.1331.1 (01/2017) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Introduction and applications . 4 6.1 FlexO consi
20、derations 4 6.2 Sample applications 4 7 Structure and processes . 5 7.1 Basic signal structure 6 7.2 Process flow 6 8 FlexO frame 6 8.1 Frame structure . 7 8.2 Multi-frame structure 7 8.3 Bit rates . 8 8.4 FEC . 8 9 Alignment markers and overhead . 9 9.1 Lane alignment markers (AM) . 9 9.2 Overhead
21、description 11 10 OTUCn mapping 16 10.1 Dividing and combining OTUCn . 16 10.2 FlexO frame payload 17 10.3 Mapping of OTUC into FlexO frame . 17 10.4 FlexO group alignment and deskewing 18 10.5 Scrambling 18 11 FOIC interface 19 11.1 FOIC1.4 interface . 19 Bibliography. 21 Rec. ITU-T G.709.1/Y.1331.
22、1 (01/2017) 1 Recommendation ITU-T G.709.1/Y.1331.1 Flexible OTN short-reach interface 1 Scope This Recommendation specifies a flexible interoperable short-reach OTN interface, over which an OTUCn (n 1) is transferred, using bonded interfaces. The FlexO interfaces are covered by application codes wh
23、ich are at the time of publication 4I1-9D1F, 4L1-9C1F, C4S1-9D1F and 4L1-9D1F in ITU-T G.695 and ITU-T G.959.1. A FlexO group interface complements the existing functions specified in ITU-T G.709, such as B100G OTUCn frame, ODUk/flex, with new functions such as physical interface bonding, group mana
24、gement and OTUCn (de)mapping. The intent of the FlexO Recommendation is to capture links to existing ITU-T G.709/ITU-T G.798 functions and to provide specifications for new functions that are applicable to FlexO groups. In addition, some introduction material for the addressed application is include
25、d. 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 indicated were valid. All Recommendations and other references are subject to revi
26、sion; 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 Recommendations is regularly published. The reference to a document within this
27、 Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.695 Recommendation ITU-T G.695 (2015), Optical interfaces for coarse wavelength division multiplexing applications. ITU-T G.709 Recommendation ITU-T G.709/Y.1331 (2016), Interfaces for the optical tr
28、ansport network. ITU-T G.798 Recommendation ITU-T G.798 (2012), Characteristics of optical transport network hierarchy equipment functional blocks. ITU-T G.870 Recommendation ITU-T G.870/Y.1352 (2016), Terms and definitions for optical transport networks (OTN). ITU-T G.872 Recommendation ITU-T G.872
29、 (2017), Terms and definitions for optical transport networks. ITU-T G.959.1 Recommendation ITU-T G.959.1 (2016), Optical transport network physical layer interfaces. ITU-T G.7041 Recommendation ITU-T G.7041/Y.1303 (2016), Generic framing procedure (GFP). ITU-T G.8260 Recommendation ITU-T G.8260 (20
30、15), Definitions and terminology for synchronization in packet networks. IEEE 802.3 IEEE Std. 802.3:2015, IEEE Standard for Information Technology Telecommunications and Information Exchange Between Systems Local and Metropolitan Area Networks Specific Requirements Part 3: Carrier Sense Multiple Acc
31、ess With Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications. OIF FlexE IA Optical Interworking Forum, OIF (2016), FlexEthernet Implementation Agreement. 2 Rec. ITU-T G.709.1/Y.1331.1 (01/2017) 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following
32、 term defined elsewhere: 3.1.1 Terms defined in ITU-T G.870 completely standardized OTUCn (OTUCn) optical data unit (ODUCn) optical payload unit (OPUCn) optical transport network (OTN) 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 FlexO frame: Consis
33、ts of frame alignment (markers), OH, FEC and payload area. 3.2.2 FlexO lane: Refers to an electrical/optical lane of a FlexO interface, used to carry OTUC transport signals. 3.2.3 FlexO interface: Refers to an individual interface that is part of a FlexO group. The acronym used for FlexO interface i
34、s FOICx.k. The term Cx signifies the FlexO interface rate. The term k refers to the number of lanes in the interface. NOTE The terms member and PHY are often used to refer to a FlexO interface. 3.2.4 FlexO group: Refers to the group of m * FlexO interfaces. 4 Abbreviations and acronyms This Recommen
35、dation uses the following abbreviations and acronyms: AM Alignment Marker B100G Beyond 100G BMP Bit-synchronous Mapping Procedure CAUI (Chip to) 100 Gb/s Attachment Unit Interface CM Common Marker CRC Cyclic Redundancy Check FA Frame Alignment FAS Frame Alignment Signal FCC FlexO Communications Chan
36、nel FEC Forward Error Correction FlexE Flexible Ethernet FlexO Flexible Optical Transport Network FOIC FlexO Interface GFP Generic Framing Procedure GID Group Identification IA Implementation Agreement LSB Least Significant Bit Rec. ITU-T G.709.1/Y.1331.1 (01/2017) 3 MAP PHY Map field MFAS Multi-Fra
37、me Alignment Signal MS Multiplexed Section MSB Most Significant Bit NNI Network Node Interface ODU Optical Data Unit OH Overhead OPU Optical Payload Unit OSMC OTN synchronization messaging channel OTL Optical Transport Lane OTLk.n Group of n Optical Transport Lanes that carry one OTUk OTLC.n Group o
38、f n Optical Transport Lanes that carry one OTUC of an OTUCn OTN Optical Transport Network OTU Optical Transport Unit PCS Physical Coding Sublayer PHY Physical Layer PID Physical Identification PTP Precise Timing Protocol RES Reserved for future international standardization RPF Remote Physical Layer
39、 Fault RS Regeneration Section RS Reed-Solomon SM Section Monitoring SSM Source Sync Message STAT Status UM Unique Marker UP Unique Padding 5 Conventions This Recommendation uses the following conventions defined in ITU-T G.870: k Cn m n r Transmission order: The order of transmission of information
40、 in all the diagrams in this Recommendation is first from left to right and then from top to bottom. Within each byte the most 4 Rec. ITU-T G.709.1/Y.1331.1 (01/2017) significant bit is transmitted first. The most significant bit (bit 1) is illustrated on the left side of all diagrams. Value of rese
41、rved bit(s): The value of an overhead bit, which is reserved for future international standardization, shall be set to “0. Value of non-sourced bit(s): Unless stated otherwise, any non-sourced bits shall be set to “0“. 6 Introduction and applications A FlexO (Flexible OTN) group is defined for inter
42、operable interfacing applications. It complements B100G (beyond 100G) ITU-T G.709 Edition 5, by providing an interoperable interface for OTUCn transport signals. The FlexO group interface provides modularity by bonding standard-rate interfaces (e.g., m * 100G), over which the OTUCn (n 1) signal is a
43、dapted. The value of m is not standardized. The specification of OTUCn in ITU-T G.709 excludes interface specific functions such as FEC, scrambling, and bit alignment. The FlexO interface wraps OTUCn, abstracting the transport signal from the interface. FlexO enables ODUflex services 100Gbit/s to be
44、 supported across multiple interfaces, ahead of next-gen interface standards (e.g., 400GE b-IEEE 802.3bs). FlexO provides OTN interfaces with comparable functionality as to what was introduced in OIF FlexE IA for Ethernet interfaces. 6.1 FlexO considerations The considerations and capabilities for a
45、 FlexO group: provides an interoperable system interface for OTUCn transport signals; enables higher capacity ODUflex and OTUCn, by means of bonding m standard-rate interfaces; provides interface rate modularity and flexibility; provides a frame, alignment, deskew, group management, management commu
46、nication channel, and such functions that are not associated with the OTUCn transport signal; and reuses 100G modules (e.g., CFP2, QSFP28) by matching the interface rate to OTU4 as specified in ITU-T G.709 The FlexO interface is specified in this recommendation at the external reference point. The l
47、ogical signal format FOIC can be reused on a system internal interface. These requirements and the optimizations to the FlexO groups (e.g., lower latency by removing FEC) are beyond the scope of this recommendation and covered in b-ITU-T G-Sup.58. 6.2 Sample applications FlexO group interfaces can b
48、e used for a variety of applications. Example applications for a FlexO interoperable interface are shown in Figure 6-1 and Figure 6-2. An interoperable interface might represent an OTN handoff between router (R) and transport (T) nodes, or could be a handoff between different administrative domains.
49、 Rec. ITU-T G.709.1/Y.1331.1 (01/2017) 5 Figure 6-1 Example FlexO handoff router-transport The R-T topology is used in Figure 6-1, to draw an analogy between FlexO and FlexE use cases presented in OIF FlexE IA. The ODUk/flex (which can be a rate higher than 100Gbit/s) is the transport service (path) and maintenance entity in the OTN transport/switch network. The ODUCn/OTUCn is the section and FlexO provides the interfacing capabilities (e.g., FEC,
