1、 International Telecommunication Union ITU-T Y.2615TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2012) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Next Generation Networks Packet-based Networks Routing mechanisms in public packet telecomm
2、unication data networks Recommendation ITU-T Y.2615 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Network aspects Y.300Y.39
3、9 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 applications Y.1100Y.1199 Architecture, access, network capab
4、ilities and resource management Y.1200Y.1299 Transport Y.1300Y.1399 Interworking 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.1899 IPTV over NGN Y.1900Y.1999 NEXT GENERATION NETWOR
5、KS 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 NGN Y.2250Y.2299 Numbering, naming and addressing Y.
6、2300Y.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Packet-based Networks Y.2600Y.2699Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 Carrier grade open environment Y.2900Y.2999 FUTURE NETWORKS Y.3000Y.3499 CLOUD COMPUTING Y.3500Y.3999 For furt
7、her details, please refer to the list of ITU-T Recommendations. Rec. ITU-T Y.2615 (07/2012) i Recommendation ITU-T Y.2615 Routing mechanisms in public packet telecommunication data networks Summary As one hierarchical packet data network which can meet requirements of future packet-based networks (F
8、PBNs), the public packet telecom data network (PTDN) provides a solution of efficient and reliable routing mechanisms. Recommendation ITU-T Y.2615 illustrates the PTDN routing architecture, routing models and the corresponding routing mechanisms, such as topology construction, intra-domain routing,
9、inter-domain routing and routing procedures. History Edition Recommendation Approval Study Group 1.0 ITU-T Y.2615 2012-07-29 13 Keywords Alternative routing, dual path routing, PTDN, routing architecture, shortest path routing. ii Rec. ITU-T Y.2615 (07/2012) FOREWORD The International Telecommunicat
10、ion 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-T is responsible for studying technical, operating and tariff ques
11、tions 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 groups which, in turn, produce Recommendation
12、s 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 ISO and IEC. NOTE In this Recommendation,
13、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 provisions (to ensure, e.g., interoperability or
14、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 words does not suggest that compliance w
15、ith 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 concerning the evidence, validity or app
16、licability 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 by patents, which may be required to imp
17、lement this Recommendation. 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 2013 All rights reserved. No part of this publication may be reproduced, by any
18、means whatsoever, without the prior written permission of ITU. Rec. ITU-T Y.2615 (07/2012) 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 Recommendation . 2 4 Abbreviations and acronyms 2 5 Routing architecture . 3 5.1 Int
19、ra-domain routing mechanism . 3 5.2 Inter-domain routing mechanism . 4 6 Routing models . 4 6.1 Shortest path routing model 4 6.2 Dual path routing model . 5 6.3 Alternative routing model . 5 7 Shortest path routing model 5 7.1 Construction of topology 5 7.2 The intra-domain routing 6 7.3 The inter-
20、domain routing 6 8 Dual path routing model . 6 8.1 Construction of topology 6 8.2 The intra-domain routing 6 8.3 The inter-domain routing 7 9 Alternative routing model . 7 9.1 Construction of topology 7 9.2 The intra-domain routing 7 9.3 The inter-domain routing 8 10 Routing procedure 8 11 Security
21、considerations . 8 11.1 Security guarantee of control plane 9 11.2 Security guarantee of network connectivity . 9 Annex A Path calculation in the dual path routing model 10 A.1 Construction of protection paths 10 A.2 Ear decomposition 10 A.3 Generation of ST number . 11 A.4 Construction of protectio
22、n routes . 11 A.5 Construction of link state database . 12 A.6 Forwarding table . 14 Bibliography. 15 Rec. ITU-T Y.2615 (07/2012) 1 Recommendation ITU-T Y.2615 Routing mechanisms in public packet telecommunication data networks 1 Scope This Recommendation identifies the routing mechanisms of the pub
23、lic packet telecom data network (PTDN), including routing architecture, routing models and corresponding routing mechanisms, such as topology construction, intra-domain routing, inter-domain routing and routing procedure. 2 References The following ITU-T Recommendations and other references contain
24、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 to revision; users of this Recommendation are therefore encouraged to investigate the po
25、ssibility 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 within this Recommendation does not give it, as a stand-alone document, the status of a Reco
26、mmendation. ITU-T Y.2601 Recommendation ITU-T Y.2601 (2006), Fundamental characteristics and requirements of future packet based networks. ITU-T Y.2611 Recommendation ITU-T Y.2611 (2006), High-level architecture of future packet-based networks. ITU-T Y.2612 Recommendation ITU-T Y.2612 (2009), Generi
27、c requirements and framework of addressing, routing and forwarding in future, packet-based networks. ITU-T Y.2613 Recommendation ITU-T Y.2613 (2010), General technical architecture for public packet telecommunication data network. ITU-T Y.2614 Recommendation ITU-T Y.2614 (2011), Network reliability
28、in public telecommunication data networks. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 address ITU-T Y.2601: An address is the identifier for a specific termination point and is used for routing to this termination point. NOTE Ident
29、ifiers can be used for registration or authorization. They can be either public to all networks, shared between a limited number of networks or private to a specific network (private identifiers are normally not disclosed to third parties). 3.1.2 alternative routing model ITU-T Y.2614: A routing mod
30、el providing multiple paths between a source public packet telecommunication data network (PTDN) node and a destination PTDN node. NOTE These paths are not required to be deterministic and unique. In this model, the sending path and the receiving path are not necessarily composed of the same nodes a
31、nd links. 2 Rec. ITU-T Y.2615 (07/2012) 3.1.3 dual path routing model ITU-T Y.2614: A routing model providing two totally disjoint paths between a source public packet telecommunication data network (PTDN) node and a destination PTDN node. NOTE The two paths may not be the shortest paths. 3.1.4 publ
32、ic packet telecommunication data network (PTDN) ITU-T Y.2613: A packet data network designed for the NGN transport stratum, which should be secure, trustworthy, controllable, and manageable, can meet all the requirements described in ITU-T Y.2601. PTDN is a hierarchical network, which can be subdivi
33、ded into several network layers. 3.1.5 shortest path routing model ITU-T Y.2614: A routing model providing a deterministic and unique path, which is the shortest path from a source PTDN node to a destination PTDN node. NOTE In this model, the path from the source node to the destination node results
34、 in the same as the path from the destination node to the source node. 3.1.6 trail protection b-ITU-T G.780: Normal traffic is carried over/selected from a protection trail instead of a working trail if the working trail fails, or if its performance falls below a required level. 3.2 Terms defined in
35、 this Recommendation This Recommendation defines the following terms: 3.2.1 dominant node: A PTDN node in a domain, which is responsible for calculating routing and generating a routing table for every PTDN node in the domain. 3.2.2 ear decomposition: An ear decomposition D = P0; P1; Pr1 of an undir
36、ected graph G = (V, E) is a partition of E into an ordered collection of edge-disjoint simple paths P0; P1; Pr1, called ears, such that: P0is a simple cycle. Pi(i0) is a simple path with the end-points belonging to lower-numbered ears, and with no internal vertices belonging to lower-numbered ears.
37、Pi(i0) may also be a simple cycle. If it is a cycle consisting of only one edge, it is called a trivial ear. 3.2.3 potential energy: A numerical value derived from the PTDN node address, which should be unique to the node and can be used for selecting one path from multiple redundant paths. In the s
38、hortest path routing model, the potential energy values of the nodes on the paths are used to choose one path when several paths have the same cost as the shortest path. 3.2.4 ST number: After ear decomposition, the nodes in a domain will be renumbered according to the results of decomposition with
39、spanning tree (ST) numbers, which are used to form two node-disjoint paths from source node to destination node. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: NNI Network to Network Interface PTDN Public packet Telecom Data Network QoS Quality of Ser
40、vice ST Spanning Tree TTL Time To Live Rec. ITU-T Y.2615 (07/2012) 3 UNI User to Network Interface VPN Virtual Private Network 5 Routing architecture The address space of the PTDN is hierarchical, and the addresses of the PTDN are allocated subject to geographical distribution. The prefix of the PTD
41、N address contains the hierarchical information. In the PTDN, a domain is composed of a group of nodes under a single administration and with common routing policies. The nodes in a domain usually have an identical address prefix, use common metrics to route packets and share the same routing table
42、information. The relationship between nodes which are in the same domain is called intra-domain and the relationship between nodes which are in different domains is called inter-domain. The example given in Figure 1 illustrates the concept of domains. There are four domains in this PTDN network: dom
43、ain 1, domain 2, domain 3 and domain 4. The nodes in domain 1, which are located in the core layer, has the address prefix “1000 0000 0000“. There are two domains in the access layer: domain 3 and domain 4, and the prefixes are “1000 1000 1000“ and “1000 1000 2000“, respectively. The routing mechani
44、sm of the PTDN is divided into two levels: the intra-domain routing mechanism and inter-domain routing mechanism. The routing within a domain, such as from node d to node h, is called intra-domain routing. The routing across domains, such as from node f to node m and from node g to node j, is called
45、 inter-domain routing. Y.2615(12)_F01abcnm lki jDomain 1:1000 0000 0000Core layerDomain 2:1000 1000 0000Convergence layerAccess layerDomain 4:1000 1000 2000Domain 3:1000 1000 1000fdehgFigure 1 Illustration of domains in the PTDN 5.1 Intra-domain routing mechanism The intra-domain routing mechanism c
46、an be divided into two parts: one part establishes the intra-domain routing table, the other produces two kinds of forwarding tables the inter-domain forwarding table and the intra-domain forwarding table. 4 Rec. ITU-T Y.2615 (07/2012) (1) When a boundary node in a domain transfers routing informati
47、on (e.g., domain prefix or address) of other domains within the domain, the inter-domain forwarding table will be established based on the intra-domain routing table. Then the routing information of these other domains will be transferred based on the inter-domain forwarding table to other boundary
48、nodes in the current domain, which connects to other domains. (2) When packets arrive at the destination domain or the source PTDN node and the destination PTDN node is located in the same domain, the node will establish the intra-domain forwarding table based on the intra-domain routing table. Pack
49、ets will be forwarded to the destination PTDN node based on the intra-domain forwarding table. In the PTDN intra-domain routing mechanism, the potential energy of PTDN nodes will be used to construct the routing table. 5.2 Inter-domain routing mechanism The inter-domain routing mechanism can be divided into two parts: one is the within-domain part; the other is the cross-domain part. The within-domain part establishes intra-domain forwarding tables which are usually used for transferrin
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