1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.7042/Y.1305TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Corrigendum 1(08/2004) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments General SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL A
2、SPECTS AND NEXT GENERATION NETWORKS Internet protocol aspects Transport Link capacity adjustment scheme (LCAS) for virtual concatenated signals Corrigendum 1 ITU-T Recommendation G.7042/Y.1305 (2004) Corrigendum 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NET
3、WORKS 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 SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER
4、 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 CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.8
5、00G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.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 General G.7000G.7099 Coding of analogue signals by pulse code modula
6、tion G.7100G.7199 Coding of analogue signals by methods other than PCM G.7200G.7299 Principal characteristics of primary multiplex equipment G.7300G.7399 Principal characteristics of second order multiplex equipment G.7400G.7499 Principal characteristics of higher order multiplex equipment G.7500G.7
7、599 Principal characteristics of transcoder and digital multiplication equipment G.7600G.7699 Operations, administration and maintenance features of transmission equipment G.7700G.7799 Principal characteristics of multiplexing equipment for the synchronous digital hierarchy G.7800G.7899 Other termin
8、al equipment G.7900G.7999 DIGITAL NETWORKS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) i ITU-T Recommendation G.7042/Y.1305 Link capacity adjustment scheme (LCAS) for virtual concatenated signals Corrigendum 1 S
9、ummary This corrigendum contains modifications to both normative text and Appendix I to ITU-T Rec. G.7042/Y.1305 (02/2004). Source Corrigendum 1 to ITU-T Recommendation G.7042/Y.1305 (2004) was approved on 6 August 2004 by ITU-T Study Group 15 (2001-2004) under the ITU-T Recommendation A.8 procedure
10、. ii ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) FOREWORD 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 st
11、udying 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 study gr
12、oups 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 basis with
13、 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 mandatory provis
14、ions (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 use of such
15、 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 no position
16、 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 not received notice of intellectual property, protected
17、 by patents, which may be required to implement this Recommendation. 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
18、, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) iii CONTENTS Page 1) Clause 4, Abbreviations 1 2) Clause 6 1 3) Annex A 4 4) Appendix I 10 ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) 1 ITU-T Recommendation G.7042/Y.1305 Link
19、 capacity adjustment scheme (LCAS) for virtual concatenated signals Corrigendum 1 1) Clause 4, Abbreviations Apply the following changes in abbreviations: LOM Loss of Multiframe TSF Trail Signal Fail 2) Clause 6 Apply the following changes in clause 6: 6 LCAS for virtual concatenation 6.1 Methodolog
20、y LCAS in the virtual concatenation source and sink adaptation functions provides a control mechanism to smoothly increase or decrease the capacity of a VCG link to meet the bandwidth needs of the application. It also provides the capability of temporarily removing member links that have experienced
21、 a failure. The LCAS assumes that in cases of capacity initiation, increase or decrease, the construction or destruction of the end-to-end path of each individual member is the responsibility of the Network and Element Management Systems. A VCG capacity increase or decrease can be initiated at eithe
22、r end. However, the initiation of a VCG capacity decrease at the Sk may result in temporary loss of data, see 6.5. 6.2.1 MultiFrame Indicator (MFI) field At the So side the MFI is equal for all members of the VCG and it will be incremented each frame. At the Sk side the MFI shall be used to realign
23、the payload for all the members in the group. The MFI is used to determine the differential delay between members of the same VCG. 6.2.2 Sequence Indicator (SQ) field The SQ of a member removed fromof the VCG sending IDLE in the control field shall be set to the highest possible value. 6.2.4 Group I
24、dentification (GID) bit Used for identification of the VCG. The GID bit of all members of the same VCG has the same value in the frames control packets with the same MFI. NOTE The GID is not valid for members sending IDLE in the control field. 6.2.5.1 CRC Multiplication/division process The bits of
25、the control packet can be regarded as the coefficients of a polynomial where the first bit of the control packet to be transmitted is the most significant bit. A particular CRC-n block is the remainder after multiplication of all bits in a control packet by xXnand then division (modulo 2) by the app
26、lication specific generator polynomial. The remainder is a polynomial of at most degree (n 1). 2 ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) 6.2.6 Member Status (MST) field At initiation of a VCG sink all members shall report MST = FAIL. A transition to MST = OK occurs when a control packet is r
27、eceived for that member with a control field of ADD (or NORM or EOS after it has been added, or DNU after recovery from a network failure). All unused MST and members that have a control field of IDLE shall be set to FAIL. 6.2.7 Re-Sequence Acknowledge (RS-Ack) bit The expiration of the time-out is
28、equivalent to the detection of a toggling toggled of the RS-Ack bit at So (see refer to SDL protocol description, shown in Figures A.1 and A.4, for details). NOTE 2 No new change in the VCG should be committed executed, i.e., no member should be added or removed from the VCG, until the RS-Ack is rec
29、eived or the RS-Ack time out has expired for the currently active change request. 6.3 VCG capacity increase (Addition of member(s) When a member is added it shall always be assigned a sequence number one larger than the currently highest sequence number that has EOS or DNU in the CTRL code. When mul
30、tiple members are added, they must each use a unique sequence number so there will be a unique MST response for each additionalrequesting member. In case more than one member (e.g., x) is being added, and MST = OK is being simultaneously received for more than one those members, then the allocation
31、of sequence indicators is arbitrary provided they are the next x sequence numbers after the currently highest sequence number (which has CTRL code EOS or DNU). The newly added members will have CTRL code NORM or EOS. 6.4 Temporary removal of member When a member sending a NORM or EOS experiences a f
32、ailure in the Network this is detected at the Sk (aTSF, aTSD, dLOM) the Sk will send in the MST of that particular member the status FAIL. The So will then either replace the NORM condition by a DNU condition, or replace the EOS condition with an DNU condition and the preceding member will send EOS
33、in the CTRL field. When the defect causing the temporary removal is cleared this is detected at the Sk. The Sk will send in the MST of that particular member the status OK. The So will then either replace the DNU condition by an NORM condition, or replace the DNU condition with an EOS condition and
34、the preceding member will send NORM in the CTRL field. 6.4.1 Temporary removal of member payload The final step for temporary removal of a member is to remove the payload area of that particular member from the VCG. The last container frame that contains payload of the removed member shall be the co
35、ntainer frame containing the last bit(s) of the control packet containing the first DNU control field. The following container frames will contain all ZEROes in the payload area. Upon reception at the Sk of the DNU control field the payload of this particular member shall not be used to reconstruct
36、the original VCG payload. The final step after recovering from a temporary removal is to start using the payload area of that member again. The first container frame to contain payload data for the member shall be the container frame immediately following the container frame that contained the last
37、bit(s) of the control packet containing the first NORM or EOS control field for that member. ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) 3 6.4 VCG Capacity Decrease: Member(s) temporary removed by the LCAS procedure (due to failure) 6.4.1 Temporary removal of a member When a member sending a NOR
38、M or EOS experiences a failure in the Network this is detected at the Sk (MSU_L, TSD) and the Sk will send MST = FAIL for that particular member. The reporting of the MST = FAIL can be delayed by a Hold-Off time to limit the number of switch actions in case of nested protection mechanisms. Upon dete
39、ction of the MST = FAIL, the So will either replace the NORM condition by a DNU condition, or replace the EOS condition with a DNU condition. The active member with the highest sequence number will send EOS in the CTRL field. 6.4.1.1 Temporary removal of member payload There are two reasons for a te
40、mporary removal of a members payload: In case of a received MSU_L, the final step for temporary removal of a member is to remove that particular member from the VCG. At the Sk side, the removal shall start immediately after detection of the MSU_L defect. At the So side, the last container frame that
41、 contains payload of the removed member shall be the container frame containing the last bit(s) of the control packet containing the first DNU control field. The following container frames will contain all ZEROes in the payload area. Upon reception at the Sk of the DNU control field, the payload of
42、this particular member shall not be used to reconstruct the original VCG payload. In case of a received TSD, the final step for temporary removal of a member is to remove that particular member from the VCG. At the Sk side, the payload area of that particular member will continue to be used for the
43、reconstruction of the original VCG payload. The bit errors in the payload area of the member have to be handled by the server to client adaptation function at the sink side of the VCG. At the So side, the last container frame that contains payload of the removed member shall be the container frame c
44、ontaining the last bit(s) of the control packet containing the first DNU code in the control field. The following container frames will contain all ZEROes in the payload area. Upon reception at the Sk of DNU in the control field, the payload area of that particular member is removed from the VCG. 6.
45、4.2 Reinstatement of temporarily removed member When the defect causing the temporary removal is cleared this is detected at the Sk. The Sk will send MST = OK for that particular member. The reporting of the MST = OK can be delayed by a Wait-To-Restore time to avoid unwanted effects due to intermitt
46、ent defects. Upon detection of the MST = OK, the So will either replace the DNU condition by an NORM condition, or replace the DNU condition with an EOS condition and the preceding member, that was sending CTRL code EOS, will send NORM in the CTRL field. 6.4.2.1 Reinstatement of temporarily removed
47、members payload The final step after recovering from a temporary removal is to start using the payload area of that member again. The first container frame to contain payload data for the member shall be the container frame immediately following the container frame that contained the last bit(s) of
48、the control packet containing the first CTRL code NORM or EOS in the control field for that member. 6.5 VCG Capacity Decrease: Removal (permanent) Deletion of member(s) When members are deleted, the sequence numbers and corresponding member status number of the other members shall be renumbered. If
49、the deleted permanently removed member contains contained the highest sequence number of that group, the active member containing the next highest sequence number shall change its control field to EOS in its control packet coinciding with the 4 ITU-T Rec. G.7042/Y.1305 (2004)/Cor.1 (08/2004) permanently removed deleted members control packet with the IDLE control field. If the permanently removed deleted member contains contained the highest sequence number of that group and sends DNU in the control field, the sequence numbering and control fields o
