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.808 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2016) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital networks General aspects Terms and definitions for network protection and restor
2、ation Recommendation ITU-T G.808 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 CHARACTERISTICS O
3、F 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 TRANSMISSION MED
4、IA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 General aspects G.800G.809 Design objectives for digital networks G.810G.819 Synchronization, quality and availability targets G.820G.829 Network capabilities and functions G.830G.839
5、 SDH network characteristics G.840G.849 Management of transport network G.850G.859 SDH radio and satellite systems integration G.860G.869 Optical transport networks G.870G.879 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED A
6、SPECTS 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 further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.808 (11/2016) i Recommenda
7、tion ITU-T G.808 Terms and definitions for network protection and restoration Summary Recommendation ITU-T G.808 provides terms, definitions and abbreviations used in Recommendations that describe network protection and restoration. It contains a list of the definitions and abbreviations introduced
8、in Recommendations associated with network protection and restoration. This Recommendation can be considered to be a companion to Recommendations ITU-T G.870/Y.1352, ITU-T G.8001/Y.1354, ITU-T G.8081/Y.1353 and ITU-T G.8101/Y.1355. The goal of this Recommendation is to be a single normative source f
9、or terms in this subject area. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.808 2016-11-13 15 11.1002/1000/13083 Keywords Acronyms, protection, restoration, terminology, terms. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of yo
10、ur web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.808 (11/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and comm
11、unication 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 with a view to standardizing telecommunications on a worldwide basis. T
12、he 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 Recommendations is covered by the procedure laid down in WTSA Resolution
13、 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 for conciseness to indicate both a telecommunication administration and a
14、 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 Recommendation is achieved when all of these mandatory provisions are met.
15、 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 party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibili
16、ty 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 Property Rights, whether asserted by ITU members or others outside of the Recom
17、mendation development process. As of the date of approval of this Recommendation, ITU had not 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
18、 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 permission of ITU. Rec. ITU-T G.808 (11/2016) iii Table of Contents Pa
19、ge 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 9 5 Conventions 9 Annex A Terms specific to ring protection . 10 Bibliography. 11 Rec. ITU-T G.808 (11/2016) 1 Recommendation ITU-T G.808 Terms and
20、definitions for network protection and restoration 1 Scope This Recommendation contains a complete listing of the terms, definitions and abbreviations introduced in the Recommendations associated with network protection and restoration in a generic manner. Terms specific to particular types of prote
21、ction or restoration, or to protection and restoration of specific technologies, are not included. 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,
22、 the editions indicated were valid. All Recommendations and other references are subject 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 curre
23、ntly valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.780 Recommendation ITU-T G.780/Y.1351 (2010), Terms and definitions for synchronous digital hierarchy (
24、SDH) networks. ITU-T G.805 Recommendation ITU-T G.805 (2000), Generic functional architecture of transport networks. ITU-T G.806 Recommendation ITU-T G.806 (2012), Characteristics of transport equipment Description methodology and generic functionality. 3 Definitions 3.1 Terms defined elsewhere This
25、 Recommendation uses the following terms defined elsewhere: 3.1.1 adaptation function (A) ITU-T G.806 3.1.2 adapted information (AI) ITU-T G.805 3.1.3 characteristic information ITU-T G.805 3.1.4 connection ITU-T G.805 3.1.5 connection function (C) ITU-T G.806 3.1.6 defect ITU-T G.806 3.1.7 failure
26、ITU-T G.806 3.1.8 fault ITU-T G.806 3.1.9 function ITU-T G.806 3.1.10 layer ITU-T G.780 3.1.11 link connection ITU-T G.805 3.1.12 network connection ITU-T G.805 3.1.13 process ITU-T G.806 2 Rec. ITU-T G.808 (11/2016) 3.1.14 reference point ITU-T G.780 3.1.15 section ITU-T G.806 3.1.16 signal degrade
27、 (SD) ITU-T G.806 3.1.17 signal fail (SF) ITU-T G.806 3.1.18 subnetwork connection ITU-T G.805 3.1.19 trail ITU-T G.805 3.1.20 transport entity ITU-T G.805 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 General protection terms 3.2.1.1 hitless protect
28、ion switch: A protection switch that does not cause characteristic or adapted information loss, duplication, disorder, or bit errors upon protection switching action. 3.2.1.2 impairment: Fault or performance degradation, which may lead to triggering of SF or SD. 3.2.1.3 network survivability: The se
29、t of capabilities that allow a network to restore affected traffic in the event of an impairment. 3.2.1.4 protection: The use of pre-assigned capacity between nodes. 3.2.1.5 protection control: The information and set of processes for providing control of protection switching for a trail or subnetwo
30、rk connection. 3.2.1.6 protected domain: The protected domain defines one or more transport entities (trails, subnetwork connections), for which a survivability mechanism is provided in the event of impairment affecting that or those transport entities. 3.2.1.7 protection group: The collection of he
31、ad-end and tail-end functions, 1 to n normal traffic signals, optionally an extra traffic signal, 1 to n working transport entities, and a single protection transport entity that are used to provide extra reliability for the transport of normal traffic signals. 3.2.1.8 protection ratio: The quotient
32、 of the actually protected bandwidth divided by the traffic bandwidth, which is intended to be protected. 3.2.1.9 restoration: The use of any capacity available between nodes for protection. In general, the algorithms used for restoration will involve re-routing. When restoration is used, a percenta
33、ge of the transport network capacity will be reserved for the re-routing of normal traffic. 3.2.1.10 signal degrade group (SDG): A signal indicating the associated group data has degraded. 3.2.1.11 signal fail group (SFG): A signal indicating the associated group has failed. 3.2.1.12 switch: 1) (For
34、 the selector) The action of selecting normal traffic from the (current) standby transport entity rather than the (current) active transport entity. 2) (For the bridge in the case of permanent connection to working) The action of connecting or disconnecting the normal traffic to the protection trans
35、port entity. 3) (For the case of non-permanent connection to working) The action of connecting the normal traffic signal to the (current) standby transport entity. 3.2.1.13 switch event: A switch event exists if either a fault condition on a working transport entity or an external command exists, an
36、d the protection algorithm has concluded that this fault condition or external command is the highest priority event. Rec. ITU-T G.808 (11/2016) 3 3.2.2 Transport entities related to protection 3.2.2.1 active transport entity: The transport entity from which the protection selector selects the norma
37、l traffic signal. 3.2.2.2 protection transport entity: The transport entity allocated to transport the normal traffic signal during a switch event. The protection transport entity may be used to carry extra traffic in the absence of a switch event. When there is a switch event, normal traffic on the
38、 affected working transport entity is bridged onto the protection transport entity, pre-empting the extra traffic (if present). 3.2.2.3 standby transport entity: The transport entity from which the protection selector does not select the normal traffic signal. 3.2.2.4 transport entity protection: A
39、method that allows transporting a traffic signal via more than one pre-assigned transport entity. The transport of a normal traffic signal via a working transport entity is replaced by the transport of this normal traffic signal via a protection transport entity if the working transport entity fails
40、 (SF condition), or if its performance falls below a required level (SD condition). 3.2.2.5 working transport entity: The transport entity over which the normal traffic signal is transported. 3.2.3 Signal types 3.2.3.1 extra traffic signal: Traffic signal that is carried over the protection transpor
41、t entity and/or bandwidth when that transport entity/bandwidth is not being used for the protection of a normal traffic signal; i.e., when the protection transport entity is on standby. Whenever the protection transport entity/bandwidth is required to protect or restore the normal traffic on the wor
42、king transport entity, the extra traffic is pre-empted. Extra traffic is not protected. 3.2.3.2 normal traffic signal: Traffic signal that is protected by two alternative transport entities, called working and protection transport entities. 3.2.3.3 null signal: The null signal can be any kind of sig
43、nal that conforms to the signal structure (characteristic or adapted information) of the reference point in the specific layer. By default, it is the signal inserted by a connection function on an output, which is not connected to one of its inputs. The null signal is ignored (not selected) at the s
44、ink end of the protection. The null signal is indicated in the APS protocol if the protection transport entity is not used to carry the normal or extra traffic signal. 3.2.4 Protection architecture terms 3.2.4.1 1+1 (protection) architecture: A 1+1 protection architecture has one normal traffic sign
45、al, one working transport entity, one protection transport entity and a permanent bridge. At the source end, the normal traffic signal is permanently bridged to both the working and the protection transport entities. At the sink end, the normal traffic signal is selected from the better of the two t
46、ransport entities. Due to the permanent bridging, the 1+1 (protection) architecture does not allow an unprotected extra traffic signal to be provided. 3.2.4.2 1:n (protection) architecture (n 1): A 1:n protection architecture has n normal traffic signals, n working transport entities and one protect
47、ion transport entity. It may have one extra traffic signal. At the source end, a normal traffic signal is either permanently connected to its working transport entity and may be connected to the protection transport entity (in the case of a broadcast bridge), or is connected to either its working or
48、 the protection transport entity (in the case of a selector bridge). 4 Rec. ITU-T G.808 (11/2016) At the sink end, the normal traffic signal is selected from either the working or the protection transport entity. An unprotected extra traffic signal can be transported via the protection transport ent
49、ity, whenever the protection transport entity is not used to carry a normal traffic signal. 3.2.4.3 (1:1)n protection architecture: n parallel 1:1 protection architectures, which have their n protection transport entities share (and compete for) the protection bandwidth. It has n normal traffic signals, n working transport entities and n protection transport entities. It may have an extra traffic signal, in which case an additional protection transport entity will be present. NOTE This architecture
