1、 International Telecommunication Union ITU-T G.7042/Y.1305TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2006) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Data over Transport Generic aspects General SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECT
2、S AND NEXT-GENERATION NETWORKS Internet protocol aspects Transport Link capacity adjustment scheme (LCAS) for virtual concatenated signals ITU-T Recommendation G.7042/Y.1305 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTION
3、S 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 OR SAT
4、ELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF
5、 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.7099 Transport network control aspects G.7700G.7799 PACKET OVER TRANSPORT ASPECTS G.8000G.8999ACCESS NETWORKS G.9000
6、G.9999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.7042/Y.1305 (03/2006) i ITU-T Recommendation G.7042/Y.1305 Link capacity adjustment scheme (LCAS) for virtual concatenated signals Summary This Recommendation specifies a methodology for dynamically changing
7、(i.e., increasing and decreasing) the capacity of a container that is transported in a generic transport network (e.g., over SDH or OTN network using Virtual Concatenation). In general, this change of capacity does not affect the traffic. In addition, the methodology also provides survivability capa
8、bilities, automatically decreasing the capacity if a member experiences a failure in the network, and increasing the capacity when the network fault is repaired. Source ITU-T Recommendation G.7042/Y.1305 was approved on 29 March 2006 by ITU-T Study Group 15 (2005-2008) under the ITU-T Recommendation
9、 A.8 procedure. Keywords Link capacity adjustment scheme, optical transport network, synchronous digital hierarchy, virtual concatenation. ii ITU-T Rec. G.7042/Y.1305 (03/2006) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommu
10、nications. 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 worldwide basis. The World Telecommuni
11、cation 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 WTSA Resolution 1. In some areas of
12、 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 administration and a recognized operatin
13、g 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 provisions are met. The words “shall“ or
14、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 the possibility that the practice
15、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 outside of the Recommendation development
16、 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 information and are therefore strong
17、ly urged to consult the TSB patent database. ITU 2007 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.7042/Y.1305 (03/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and definitions . 1 4
18、 Abbreviations 2 5 Conventions 2 6 LCAS for virtual concatenation 2 6.1 Methodology. 2 6.2 Control packet 3 6.3 VCG capacity increase (Addition of member(s). 6 6.4 VCG capacity decrease: Member(s) temporary removed by the LCAS procedure (due to failure) . 7 6.5 VCG capacity decrease: Removal (perman
19、ent) of member(s). 8 6.6 LCAS to non-LCAS interworking 8 6.7 Asymmetric connections 9 6.8 Symmetric connection 9 Annex A LCAS protocol. 10 A.1 LCAS protocol 10 A.2 LCAS protocol partitioning 12 A.3 State diagram of member(i) in the Virtual Concatenated Group . 14 A.4 Procedures state diagrams 16 A.5
20、 State diagram for the VCG. 20 Appendix I LCAS Time Sequence Diagrams. 22 I.1 Nomenclature . 22 I.2 Numbering system 22 I.3 Provisioning 22 I.4 Commands 22 Appendix II Non hit-less bandwidth modifications during Hold Off periods 29 II.1 Introduction 29 II.2 Removal of a group member at Source 29 II.
21、3 TSD conditions raised while performing ADD commands . 29 II.4 Enhanced HO procedure. 29 ITU-T Rec. G.7042/Y.1305 (03/2006) 1 ITU-T Recommendation G.7042/Y.1305 Link capacity adjustment scheme (LCAS) for virtual concatenated signals 1 Scope This Recommendation specifies a link capacity adjustment s
22、cheme that should be used to increase or decrease the capacity of a container that is transported in an SDH/OTN network using Virtual Concatenation. In addition, the scheme will automatically decrease the capacity if a member experiences a failure in the network and increase the capacity when the ne
23、twork fault is repaired. The scheme is applicable to every member of the Virtual Concatenation group. This Recommendation defines the required states at the source and at the sink side of the link as well as the control information exchanged between both the source and the sink side of the link to e
24、nable the flexible resizing of this Virtual Concatenated signal. The actual information fields used to convey the control information through the transport network are defined in their respective Recommendations, ITU-T Recs G.707/Y.1322 1 and G.783 3 for SDH and ITU-T Recs G.709/Y.1331 2 and G.798 4
25、 for OTN. 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
26、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 Recommendations is regularly published. The reference to a document with
27、in this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. 1 ITU-T Recommendation G.707/Y.1322 (2003), Network node interface for the synchronous digital hierarchy (SDH). 2 ITU-T Recommendation G.709/Y.1331 (2003), Interfaces for the Optical Transport Network
28、 (OTN). 3 ITU-T Recommendation G.783 (2006), Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks. 4 ITU-T Recommendation G.798 (2004), Characteristics of optical transport network hierarchy equipment functional blocks. 5 ITU-T Recommendation G.806 (2006), Characteristi
29、cs of transport equipment Description methodology and generic functionality. 6 ITU-T Recommendation Z.100 (2002), Specification and Description Language (SDL). 3 Terms and definitions This Recommendation defines the following terms: 3.1 link: A connection through a network from termination function
30、to termination function. This can be related to the members of a virtual concatenation group as well as the virtual concatenation group itself. 3.2 member: An individual server layer container that belongs to a virtual concatenated group. 2 ITU-T Rec. G.7042/Y.1305 (03/2006) 3.3 virtual concatenatio
31、n group (VCG): A group of co-located member trail termination functions that are connected to the same virtual concatenation link. 4 Abbreviations This Recommendation uses the following abbreviations: CRC Cyclic Redundancy Check CTRL Control field sent from source to sink DNU Do Not Use EOS End of S
32、equence GID Group Identification HO Hold Off LCAS Link Capacity Adjustment Scheme MFI MultiFrame Indicator MI Management Information MST Member Status MSU Member Signal Unavailable MSU_L Member Signal Unavailable, LCAS-enabled criteria NORM Normal Operating Mode RS-Ack Re-Sequence Acknowledge Sk Sin
33、k So Source SQ Sequence Indicator TSD Trail Signal Degrade VCG Virtual Concatenation Group WTR Wait-To-restore XAActual number of members of a virtual concatenated group XMMaximum size of a virtual concatenated group XPNumber of provisioned members in a virtual concatenated group 5 Conventions The o
34、rder of transmission of information in all the diagrams in this Recommendation is first from left to right, and then from top to bottom. Within each byte the most significant bit is transmitted first. The most significant bit (bit 1) is shown at the left in all the diagrams. 6 LCAS for virtual conca
35、tenation 6.1 Methodology LCAS in the virtual concatenation source and sink adaptation functions provides a control mechanism to hitlessly increase or decrease the capacity of a VCG link to meet the bandwidth needs of the application. Hitless bandwidth modification can only be achieved when the trans
36、mission of ITU-T Rec. G.7042/Y.1305 (03/2006) 3 the active members belonging to the VCG before and after the bandwidth modification is error free (see Appendix II for details). It also provides the capability of temporarily removing member links that have experienced a failure. The LCAS assumes that
37、 in cases of capacity adjustment (i.e., creation, increase, decrease or deletion), 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 either end.
38、 6.2 Control packet Synchronization of changes in the capacity of the transmitter (So) and the receiver (Sk) shall be achieved by a control packet. Each control packet describes the state of the link during the next control packet. Changes are sent in advance so that the receiver can switch to the n
39、ew configuration as soon as it arrives. The control packet consists of fields dedicated to a specific function. The control packet contains information sent from So to Sk and information sent from Sk to So, see also Figure 1. Forward direction, So to Sk: MultiFrame Indicator (MFI) field; Sequence In
40、dicator (SQ) field; Control (CTRL) field; Group Identification (GID) bit. Return direction, Sk to So: Member Status (MST) field; Re-Sequence Acknowledge (RS-Ack) bit. NOTE 1 MST and RS-Ack are identical in the control packets of all members of the VCG. Both directions: CRC field; Unused bits are res
41、erved and shall be set to “0“. NOTE 2 To allow consistent timing relationships, it is assumed that the LCAS control packets are processed at the Sk after differential delay compensation. Figure 1/G.7042/Y.1305 Allocation of information in a control packet 4 ITU-T Rec. G.7042/Y.1305 (03/2006) 6.2.1 M
42、ultiFrame Indicator (MFI) field At the So side, the MFI is equal for all members of the VCG. At the Sk side, the MFI shall be used to realign the payload for all the members in the group. The MFI is used to determine the differential delay between members of the same VCG. See ITU-T Rec. G.806 for mo
43、re details. 6.2.2 Sequence Indicator (SQ) field Contains the sequence number assigned to a specific member. Each member of the same VCG is assigned a unique sequence number, starting at 0, similar to the Recommendations for Virtual Concatenation in ITU-T Recs G.707/Y.1322 1 and G.709/Y.1331 2. The S
44、Q is ignored at the Sk end for members sending IDLE in the control field. The SQ of a member of the VCG sending IDLE in the control field shall be set to the highest possible value. 6.2.3 Control (CTRL) field The control field is used to transfer information from So to Sk. It shall be used to synchr
45、onize the Sk with the So and provide the status of the individual member of the group. Table 1/G.7042/Y.1305 LCAS CTRL words Value msblsb Command Remarks 0000 FIXED This is an indication that this end uses fixed bandwidth (non-LCAS mode) 0001 ADD This member is about to be added to the group 0010 NO
46、RM Normal transmission 0011 EOS End of Sequence indication and Normal transmission 0101 IDLE This member is not part of the group or about to be removed 1111 DNU Do Not Use (the payload) the Sk side reported FAIL status At initiation of a VCG source, all members shall send CTRL = IDLE until they are
47、 added to the VCG (and send CTRL = ADD). 6.2.4 Group Identification (GID) bit Used for identification of the VCG. The GID bit of all members of the same VCG has the same value in the control packets with the same MFI. The GID provides the receiver with a means of verifying that all the arriving memb
48、ers originated from one transmitter. The contents are pseudo-random, but the receiver is not required to synchronize with the incoming stream. The pseudo-random pattern used is 215 1. 6.2.5 CRC field To simplify the validation of the changes in the virtual concatenation overhead, a CRC is used to pr
49、otect each control packet. The CRC check is performed on every control packet after it has been received, and the contents rejected if the test fails. If the control packet passes the CRC test, then its contents are used immediately. To simplify MFI multi-framing, it is allowed to disregard the result of the control packet CRC check for the MFI element checked by the CRC so that the multi-framing process may use the MFI element equivalently with the non-LCAS virtual concatenation processing case. ITU-T
