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 Series G TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Supplement 60 (09/2016) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Ethernet linear protection switching with dual node interconnection ITU
2、-T G-series Recommendations Supplement 60 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTE
3、RISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER 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 TRANSMI
4、SSION 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.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERIS
5、TICS 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 to the list of ITU-T Recommendations. G series Supplement 60 (09/2016) i Supplement 60 to ITU-T G-series Recommendations Ethern
6、et linear protection switching with dual node interconnection Summary Supplement 60 to ITU-T G-series Recommendations describes potential solutions to support dual node interconnection (DNI) based on the ITU-T G.8031 Ethernet linear protection switching to support resilient interconnection with an a
7、djacent recovery domain. Other viable means of supporting dual node interconnection for Ethernet are known to exist. This Supplement is intended to give examples based on Recommendation ITU-T G.8031 only. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G Suppl. 60 2016-09-30
8、 15 11.1002/1000/13124 Keywords Dual node interconnection, Ethernet, protection. * To access the Recommendation, 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 G serie
9、s Supplement 60 (09/2016) 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
10、-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), which meets every four years, establishes the topics for stu
11、dy 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 ITU-Ts purview, the necessary standards are prepared on a
12、collaborative basis with ISO and IEC. NOTE In this publication, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this publication is voluntary. However, the publication may contain certain m
13、andatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the publication 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. T
14、he use of such words does not suggest that compliance with the publication is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this publication may involve the use of a claimed Intellectual Property Right. ITU takes no p
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16、 patents, which may be required to implement this publication. 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 2016 All rights reserved. No part of this pub
17、lication may be reproduced, by any means whatsoever, without the prior written permission of ITU. G series Supplement 60 (09/2016) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Supplement 1 4 Abbreviations and acronyms
18、 2 5 Conventions 2 6 Introduction . 2 7 Network objectives . 3 8 Failure scenarios . 3 9 Solutions for Ethernet linear protection switching with DNI . 4 9.1 Solution A . 4 9.2 Solution B . 9 G series Supplement 60 (09/2016) 1 Supplement 60 to ITU-T G-series Recommendations Ethernet linear protection
19、 switching with dual node interconnection 1 Scope Supplement 60 to ITU-T G-series Recommendations describes potential solutions to support dual node interconnection (DNI) based on the ITU-T G.8031 Ethernet linear protection switching, inside a recovery domain. The dual node interconnection is betwee
20、n this recovery domain, which can be protected by one of the Ethernet linear protection-based mechanisms described in this Supplement, and an adjacent recovery domain via two nodes. This Supplement describes only solutions where the traffic between these two recovery domains passes through the same
21、node in both directions. Description of the survivability mechanism within the adjacent recovery domain is outside the scope of this Supplement. 2 References ITU-T G.808 Recommendation ITU-T G.808 (2016), Terminology for protection and restoration. ITU-T G.808.1 Recommendation ITU-T G.808.1 (2014),
22、Generic protection switching Linear trail and subnetwork protection. ITU-T G.7701 Recommendation ITU-T G.7701 (2016), Common control aspects. ITU-T G.8013 Recommendation ITU-T G.8013/Y.1731 (2015), Operations, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks.
23、 ITU-T G.8031 Recommendation ITU-T G.8031/Y.1342 (2015), Ethernet linear protection switching. ITU-T G.8081 Recommendation ITU-T G.8081/Y.1353 (2012), Terms and definitions for automatically switched optical networks. 3 Definitions 3.1 Terms defined elsewhere This Supplement uses the following terms
24、 defined elsewhere: 3.1.1 transfer time, Tt: ITU-T G.808.1 3.1.2 shared risk group (SRG): ITU-T G.8081 3.1.3 recovery domain: ITU-T G.7701 3.2 Terms defined in this Supplement This Supplement defines the following terms: 3.2.1 dual node interconnection: An architecture where two interconnected nodes
25、 provide node resiliency at the boundary between two recovery domains. 3.2.2 adjacent recovery domain: A recovery domain adjacent to the Ethernet linear protection DNI domain. 3.2.3 Ethernet linear protection DNI domain: A recovery domain where one of the solutions described in this Supplement is us
26、ed to support reliable transfer of information. 2 G series Supplement 60 (09/2016) 4 Abbreviations and acronyms This Supplement uses the following abbreviations and acronyms: APS Automatic Protection Switching CCM Continuity Check Message DNI Dual Node Interconnection EDNI Ethernet linear protection
27、 DNI ETH Ethernet layer network FS Forced Switch LO Lockout of protection LOC Loss of Continuity MEP Maintenance Entity Group End Point NR No Request OAM Operation, Administration and Maintenance SNC Subnetwork Connection SNC/S Subnetwork Connection with Sublayer monitoring SRG Shared Risk Group SF-
28、V Signal Fail on the vertical path SF-W Signal Failure on the working path TSF Trial Signal Fail 5 Conventions The terms bridge, permanent bridge, selector bridge, selector and selective selector, are used in this Supplement as defined in ITU-T G.808 without qualifying the input and output signals a
29、s normal signal or working/protection transport entities. 6 Introduction Ethernet linear protection switching with dual node interconnection involves using three distinct points: node N1 is an end point behaving as defined in ITU-T G.8031, and nodes N2 and N3 are interconnection points that provide
30、node resiliency at the boundary between the two recovery domains. This is illustrated in Figure 6-1. The protection mechanism used within the Ethernet linear protection dual node interconnection (DNI) domain is based on 1:1 SNC/S linear protection mechanism, as defined in ITU-T G.8031, with a select
31、or bridge being used in node N1. The traffic in both directions passes through the same interconnection point. G series Supplement 60 (09/2016) 3 Figure 6-1 Reference network for Ethernet linear protection switching with dual node interconnection Regarding the adjacent recovery domain, it is assumed
32、 that: 1) Under normal conditions, it delivers traffic to/from node N2. 2) It is capable of indicating if N2 or N3 is isolated in it. 3) It is capable of ensuring no traffic loops are created in it as a result of switching actions in the Ethernet linear protection DNI domain. 4) When N2 is isolated
33、in the Ethernet linear protection DNI domain, N2 isolation information can be transmitted to node N3 through the adjacent recovery domain. 5) It is capable of recovering traffic from N2 node isolation conditions in the Ethernet linear protection DNI domain when the Ethernet linear protection DNI dom
34、ain informs the adjacent recovery domain of the N2 node isolation conditions via node N2, node N3, or both nodes. Using Figure 6-1 as the reference network, subsequent clauses provide network objectives and example protection mechanisms for Ethernet linear protection DNI domain. 7 Network objectives
35、 The following network protection objectives apply for the Ethernet linear protection DNI domain: 1) Transfer time (Tt) in response to a single failure should be less than 50 ms in the Ethernet linear protection DNI domain. 2) The Ethernet linear protection DNI domain shall inform the adjacent recov
36、ery domain of the isolation status of N2 and N3 in the Ethernet linear protection DNI domain, so that the adjacent recovery domain can decide which interconnection point to use for traffic delivery. 8 Failure scenarios This Supplement describes how each solution addresses the following failure scena
37、rios. 4 G series Supplement 60 (09/2016) Figure 8-1 Failure scenarios These six cases are also considered when either N2 or N3 is isolated in the adjacent recovery domain. 9 Solutions for Ethernet linear protection switching with DNI This clause provides descriptions of potential solutions to suppor
38、t DNI based on the Ethernet linear protection switching defined in ITU-T G.8031. Other viable means of supporting dual node interconnection for Ethernet are known to exist. This Supplement is intended to give examples based on ITU-T G.8031 only. 9.1 Solution A 9.1.1 Assumptions This solution has the
39、 following detailed assumptions regarding common assumption 2) listed in clause 6: Node N3 is informed from the adjacent recovery domain when N3 is isolated in that domain. Node N3 is informed from the adjacent recovery domain when N2 is isolated in that domain. 9.1.2 Architecture Figure 9-1 shows t
40、he architecture of Ethernet linear protection DNI Solution A. The working path is defined between nodes N1 and N2 and the protection path is defined between nodes N1 and N3. There is a third path called vertical path defined between nodes N2 and N3. The status of the working path, the protection pat
41、h and the vertical path are monitored by continuity check message (CCM) mechanisms, respectively. G series Supplement 60 (09/2016) 5 Figure 9-1 Ethernet linear protection DNI architecture of solution A N1 is the same as the end point of an ITU-T G.8031 protected domain. N3 also has the same automati
42、c protection switching (APS) process as defined in ITU-T G.8031 and exchanges APS messages with N1 through the protection path to perform protection switching between the working path and the protection path. All aspects of APS processes in N1 and N3, including APS messages and APS state machines, a
43、re exactly the same as those in the APS process defined in ITU-T G.8031. Ethernet linear protection DNI (EDNI) processes in N2 and N3 exchange EDNI messages through the vertical path to coordinate the Ethernet linear protection DNI operation. The EDNI process in N2 is defined as EDNI slave process a
44、nd the EDNI process in N3 is defined as EDNI master process. The EDNI master process determines the status of the working path based on the status of the working path received from N2, the status of the vertical path and the isolation status of N2 and N3 in the adjacent recovery domain, and sends th
45、e working path status to the APS process as a local request (ETH_CI_SSF(W). N2 and N3 have multiple selector bridges and selective selectors to provide connectivity among the working path (in case of N2), the protection path (in case of N3), the vertical path and the adjacent recovery domain as illu
46、strated in Figure 9-2. 6 G series Supplement 60 (09/2016) Figure 9-2 Bridges and selectors in N2 and N3 The bridges and selectors in N2 and N3 are controlled by the EDNI master process based on the status of the APS process, the status of the vertical path and the isolation status of N2 and N3 in th
47、e adjacent recovery domain. Possible sets of the connectivity provided by the bridges and selectors are as follows: Bridges and selectors in N2 connect the working path to the adjacent recovery domain (W-AD) (default position) connect the working path to the vertical path (W-V) connect the vertical
48、path to the adjacent recovery domain (V-AD) Bridges and selectors in N3 connect the protection path to the adjacent recovery domain (P-AD) (default position) connect the protection path to the vertical path (P-V) connect the vertical path to the adjacent recovery domain (V-AD) 9.1.3 Process In addit
49、ion to the ITU-T G.8031 processes in N1 and N3, this solution defines the EDNI master and slave processes in N3 and N2, respectively. The protocol message format and the operations of the EDNI processes are described in this subclause. 9.1.3.1 EDNI message The format and the rule for transmission and acceptance of EDNI message are the same as those of APS message in ITU-T G.8031. Figure 9-3 shows the APS-specific information in the EDNI message. 1 2 3 4 8 7 6 5 4 3 2 1 8 7 6 5 4
