1、 International Telecommunication Union ITU-T G.7041/Y.1303TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(10/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Data over Transport Generic aspects General SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROT
2、OCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Transport Generic framing procedure Amendment 2 Recommendation ITU-T G.7041/Y.1303 (2011) Amendment 2 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AN
3、D 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 OR SATELLI
4、TE 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 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900
5、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 General G.7000G.7099Transport network control aspects G.7700G.7799 PACKET OVER TRANSPORT ASPECTS G.8000G.
6、8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.7041/Y.1303 (2011)/Amd.2 (10/2012) i Recommendation ITU-T G.7041/Y.1303 Generic framing procedure Amendment 2 Summary Amendment 2 to Recommendation ITU-T G.7041/Y.1301 contains text
7、 for a new generic framing procedure (GFP) frame delineation algorithm alternative and a modification to the timing requirements for the initial transmission of client signal fail (CSF), forward defect indication (FDI) and reverse defect indication (RDI) frames. History Edition Recommendation Approv
8、al Study Group 1.0 ITU-T G.7041/Y.1303 2001-12-14 15 1.1 ITU-T G.7041/Y.1303 (2001) Amd. 1 2002-06-13 15 1.2 ITU-T G.7041/Y.1303 (2001) Cor. 1 2003-03-16 15 1.3 ITU-T G.7041/Y.1303 (2001) Amd. 2 2003-03-16 15 2.0 ITU-T G.7041/Y.1303 2003-12-14 15 2.1 ITU-T G.7041/Y.1303 (2003) Amd. 1 2004-10-07 15 2
9、.2 ITU-T G.7041/Y.1303 (2003) Amd. 2 2004-06-13 15 2.3 ITU-T G.7041/Y.1303 (2003) Cor. 1 2005-01-13 15 2.4 ITU-T G.7041/Y.1303 (2003) Amd. 3 2005-01-13 15 3.0 ITU-T G.7041/Y.1303 2005-08-22 15 3.1 ITU-T G.7041/Y.1303 (2005) Amd. 1 2006-03-29 15 3.2 ITU-T G.7041/Y.1303 (2005) Cor. 1 2006-12-14 15 3.3
10、 ITU-T G.7041/Y.1303 (2005) Amd. 2 2007-07-29 15 4.0 ITU-T G.7041/Y.1303 2008-10-07 15 4.1 ITU-T G.7041/Y.1303 (2008) Amd. 1 2009-01-13 15 4.2 ITU-T G.7041/Y.1303 (2008) Amd. 2 2010-07-29 15 5.0 ITU-T G.7041/Y.1303 2011-04-13 15 5.1 ITU-T G.7041/Y.1303 (2011) Amd. 1 2012-02-13 15 5.2 ITU-T G.7041/Y.
11、1303 (2011) Amd. 2 2012-10-29 15 ii Rec. ITU-T G.7041/Y.1303 (2011)/Amd.2 (10/2012) 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 Stand
12、ardization 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 worldwide basis. The World Telecommunication Standardization Assembly (WTSA), wh
13、ich 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 WTSA Resolution 1. In some areas of information technology which fall within
14、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 administration and a recognized operating agency. Compliance with this Recommendat
15、ion 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 provisions are met. The words “shall“ or some other obligatory language such as “
16、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 the possibility that the practice or implementation of this Recommendation
17、 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 outside of the Recommendation development process. As of the date of approval of
18、this Recommendation, ITU had received notice of intellectual property, protected 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 datab
19、ase at http:/www.itu.int/ITU-T/ipr/. ITU 2013 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.7041/Y.1303 (2011)/Amd.2 (10/2012) 1 Recommendation ITU-T G.7041/Y.1303 Generic framing procedure Amend
20、ment 2 Modifications to Recommendation ITU-T G.7041/Y.1301 1) 6.3.1 GFP frame delineation algorithm Modify clause 6.3.1 and subclauses as follows: GFP uses a modified version of the HEC algorithm specified in clause 7.3.3.2 of ITU-T I.432.1 to provide GFP frame delineation. The frame delineation alg
21、orithm used in GFP differs from that in ITU-T I.432.1 in two basic ways: a) the algorithm uses the payload length indicator field of the GFP core header to find the end of the GFP frame; and b) HEC field calculation uses a 16-bit polynomial and, consequently, generates a two-octet cHEC field. GFP fr
22、ame delineation is performed based on the correlation between the first two octets of the GFP frame and the embedded two-octet cHEC field. There are two alternative frame delineation methods. 6.3.1.1 Frame delineation alternative using only the Core header Figure 6-13 shows the state diagram for the
23、 GFP frame delineation method based on only using the Core header. The state diagram works as follows: 1) In the HUNT state, the GFP process performs frame delineation by searching, octet-by-octet, for a correctly formatted core header over the last received sequence of four octets. The core header
24、single error correction is disabled while in this state. Once a correct cHEC match is detected in the candidate PLI and cHEC fields, a candidate GFP frame is identified and the receive process enters the PRESYNC state. 2) In the PRESYNC state, the GFP process performs frame delineation by checking,
25、frame-by-frame, for a correct cHEC match in the presumed core header of the next candidate GFP frame. The PLI field in the core header of the preceding GFP frame is used to find the beginning of the next candidate GFP frame. Core header single error correction remains disabled while in this state. T
26、he process repeats until DELTA consecutive correct cHECs are confirmed, at which point the process enters the SYNC state. If an incorrect cHEC is detected, the process returns to the HUNT state. The total number of consecutive correct cHECs required to move from the HUNT state to the SYNC state is t
27、herefore DELTA + 1. 2 Rec. ITU-T G.7041/Y.1303 (2011)/Amd.2 (10/2012) 3) In the SYNC state, the GFP process performs frame delineation by checking for a correct cHEC match on the next candidate GFP frame. The PLI field in the core header of the preceding GFP frame is used to find the beginning of th
28、e next candidate GFP frame. Single-bit core header error correction is enabled while in this state. Frame delineation is lost whenever multiple bit errors are detected in the core header by the cHEC. In this case, a GFP loss of frame delineation event is declared, the framing process returns to the
29、HUNT state, and a client server signal failure (SSF) is indicated to the client adaptation process. 4) Idle GFP frames participate in the delineation process and are then discarded. G.7041/Y.1303(08)_F6-13PRESYNC(cHEC )1DPRESYNC(cHEC )M1PRESYNC(cHEC )11Frame-by-frame(error correction disabled)Deltac
30、onsecutivecorrectcHECsVirtualframers(up to )MIncorrectcHECCorrectcHECCorrectcHECIncorrect HEC(multi-bit-errors)PRESYNC(cHEC )MDFrame-by-frame(error correction enabled)Octet-by-octet(error correction disabled)HUNT SYNCFigure 6-13 GFP frame delineation state diagram Robustness against false delineatio
31、n in the re-synchronization process depends on the value of DELTA. A value of DELTA = 1 is suggested. Frame delineation acquisition speed can be improved by the implementation of multiple “virtual framers“, whereby the GFP process remains in the HUNT state and a separate PRESYNC sub-state is spawned
32、 for each candidate GFP frame detected in the incoming octet stream, as depicted in Figure 6-13. 6.3.1.2 Frame delineation alternative using both the Core and Type headers An alternative algorithm uses both the Core and Type headers, as illustrated in Figure 6-13bis. This algorithm can be advantageo
33、us for high-speed interfaces that are typically protected by FEC and where circuit implementations often use wide data bus structures. The state machine works the same as the one shown in Figure 6-13, except for the PRESYNC state operation. That operation works as follows: In the PRESYNC state, the
34、four octets following the candidate cHEC are checked. o If the candidate cHEC corresponds to a GFP Idle frame (i.e., PLI=0), and the subsequent four octets contain a valid cHEC, proceed to the SYNC state. o If the candidate cHEC does not correspond to a GFP Idle frame (i.e., PLI0), and the subsequen
35、t four octets contain a valid tHEC, proceed to the SYNC state. o Otherwise, go back to the HUNT state. Rec. ITU-T G.7041/Y.1303 (2011)/Amd.2 (10/2012) 3 Error correction continues to be disabled for both the Core and Type Headers during this state. The tHEC check requires retaining the 43 data bits
36、immediately prior to the candidate cHEC so that the tHEC value can be properly descrambled. PRESYNCHUNT SYNCCorrect cHECIncorrect cHEC(multiple bit errors)Octet-by-octet(error correction disabled)Frame-by-frame(error correction enabled)Frame-by-frame(error correction disabled)Incorrect cHEC or tHECC
37、orrect tHEC or 2ndconsecutive cHECFigure 6-13bis GFP frame delineation state diagram using cHEC and tHEC NOTE The choice between the frame delineation algorithm alternatives is left to the implementer, and shall not be a provisional option. Equipment developed prior to the 2012 version of this Recom
38、mendation used the frame delineation algorithm method based on only using the Core header. Equipment developed subsequently may use either alternative. 2) 6.3.3.1 Client signal fail indication Modify the second full paragraph of clause 6.3.3.1 (after the dashes) as follows: Upon detection of the CSF
39、 condition, the GFP client-specific source adaptation process should send CSF indications to the far-end GFP client-specific sink adaptation process once every 100 ms T 1000 ms, beginning at the next GFP frame as soon as possible. Interim frames shall be GFP idle frames. When no client frames are av
40、ailable, GFP idle frames shall be transmitted before and between CSF frames. 3) 6.3.3.2 Client link fault status indications Modify the second full paragraph of 6.3.3.2 (after the dashes) with the following text: Detection rules for local and remote defect indications are client-specific and specifi
41、ed in clause 7. The format of these client link fault status signals is specified in the associated standards for the client signal. Upon detection of the explicit forward (reverse) client link fault status signal, the GFP client-specific source adaptation process should send an FDI (RDI) signal to
42、the far-end GFP client-specific sink adaptation process. The FDI/RDI signal shall be sent once every 100 ms T 1000 ms, beginning as soon as possible. at the next GFP frame as soon as possible. Interim frames with FDI or RDI shall be GFP idle frames when no client data frames are available. When no c
43、lient frames are available, GFP idle frames shall be transmitted before and between FDI and RDI frames. ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications
44、 and middleware Y.200Y.299 Network aspects Y.300Y.399 Interfaces and protocols Y.400Y.499 Numbering, addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applicati
45、ons Y.1100Y.1199 Architecture, access, network capabilities and resource management Y.1200Y.1299 Transport Y.1300Y.1399Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.189
46、9 IPTV over NGN Y.1900Y.1999 NEXT GENERATION NETWORKS Frameworks and functional architecture models Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in N
47、GN Y.2250Y.2299 Numbering, naming and addressing Y.2300Y.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Packet-based Networks Y.2600Y.2699 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 Carrier grade open environment Y.2900Y.2999 FUTURE NETWORK
48、S Y.3000Y.3499 CLOUD COMPUTING Y.3500Y.3999 For further details, please refer to the list of ITU-T Recommendations. Printed in Switzerland Geneva, 2013 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall network operation, te
49、lephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual 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 of outside plant Series M Teleco
