1、 International Telecommunication Union ITU-T Y.2174TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2008) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Next Generation Networks Quality of Service and performance Distributed RACF architecture f
2、or MPLS networks Recommendation ITU-T Y.2174 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.399 Inter
3、faces 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 capabilities
4、 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 NEXT GENERATION NETWORKS Frameworks and functional archi
5、tecture 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.2300Y.2399 Network management Y.24
6、00Y.2499 Network control architectures and protocols Y.2500Y.2599 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T Y.2174 (06/2008) i Recommendation ITU-T Y.2174 Distributed RACF architecture for MPLS networks
7、Summary The architectural structure of a distributed resource admission and control function (RACF) is considered in this Recommendation. RACF is comprised of a transport resource control functional entity (TRC-FE) and a policy decision functional entity (PD-FE). This Recommendation defines an archi
8、tecture, which considers a distributed RACF resulting from a distributed TRC-FE, it specifies supporting requirements, and it describes the resource reservation process for this specific architecture. Source Recommendation ITU-T Y.2174 was approved on 29 June 2008 by ITU-T Study Group 13 (2005-2008)
9、 under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T Y.2174 (06/2008) 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
10、 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 Telecommunication Standardization Assembly (WTSA), which meets
11、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 information technology which fall within ITU-Ts pur
12、view, 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 operating agency. Compliance with this Recommendation is vol
13、untary. 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 some other obligatory language such as “must“ and th
14、e 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 or implementation of this Recommendation may involve
15、 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 process. As of the date of approval of this Recomme
16、ndation, 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 and are therefore strongly urged to consult the TSB patent database at h
17、ttp:/www.itu.int/ITU-T/ipr/. ITU 2009 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 Y.2174 (06/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Con
18、ventions 3 6 Distributed RACF architecture and supporting requirements 3 6.1 Distributed TRC-FE functions in MPLS-TE core networks 4 6.2 Requirements to support distributed architecture. 6 7 Security considerations. 6 Appendix I MPLS traffic engineering capabilities to support CAC. 7 Appendix II Adm
19、ission control process with a distributed TRC-FE 9 Bibliography. 13 Rec. ITU-T Y.2174 (06/2008) 1 Recommendation ITU-T Y.2174 Distributed RACF architecture for MPLS networks 1 Scope ITU-T Y.2111 defines general requirements for resource and admission control functions for next generation networks (N
20、GN). These requirements are independent of the underlying transport technology. Multiprotocol label switching (MPLS) is considered to be a key transport technology in core networks. In particular, networks which use MPLS with traffic engineering (MPLS-TE) capabilities provide significant assurance t
21、hat the delivery of the desired quality of service (QoS) for a variety of services and applications will occur. Resource and admission control functions (RACF) are used to control the flow of traffic from access networks into the MPLS core ITU-T Y.2111. A distributed architectural structure of one R
22、ACF functional entity, the transport resource control functional entity (TRC-FE) is considered in this Recommendation. In this architectural arrangement, MPLS transport resource information is available in label edge routers (LER) and gateways connected to the LERs. This Recommendation defines the d
23、istributed architecture for the TRC-FE and specifies supporting requirements. 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 indicat
24、ed 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 currently valid ITU-T Reco
25、mmendations 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 Y.2012 Recommendation ITU-T Y.2012 (2006), Functional requirements and architecture of the NGN release 1. ITU-T Y.2111 Recomme
26、ndation ITU-T Y.2111 (2006), Resource and admission control functions in Next Generation Networks. ITU-T Y.2171 Recommendation ITU-T Y.2171 (2006), Admission control priority levels in Next Generation Networks. ITU-T Y.2172 Recommendation ITU-T Y.2172 (2007), Service restoration priority levels in N
27、ext Generation Networks. IETF RFC 3175 IETF RFC 3175 (2001), Aggregation of RSVP for IPv4 and IPv6 Reservations . IETF RFC 3209 IETF RFC 3209 (2001), RSVP-TE: Extensions to RSVP for LSP Tunnels . IETF RFC 3814 IETF RFC 3814 (2004), Multiprotocol Label Switching (MPLS) Forwarding Equivalence Class To
28、 Next Hop Label Forwarding Entry (FEC-To-NHLFE) Management Information Base (MIB) . IETF RFC 4090 IETF RFC 4090 (2005), Fast Reroute Extensions to RSVP-TE for LSP Tunnels . 2 Rec. ITU-T Y.2174 (06/2008) IETF RFC 4125 IETF RFC 4125 (2005), Maximum Allocation Bandwidth Constraints Model for DiffServ-a
29、ware MPLS Traffic Engineering . IETF RFC 4126 IETF RFC 4126 (2005), Max Allocation with Reservation Bandwidth Constraints Model for DiffServ-aware MPLS Traffic Engineering and Performance Comparisons . IETF RFC 4127 IETF RFC 4127 (2005), Russian Dolls Bandwidth Constraints Model for DiffServ-aware M
30、PLS Traffic Engineering . IETF RFC 4804 IETF RFC 4804 (2007), Aggregation of Resource ReSerVation Protocol (RSVP) Reservations over MPLS TE/DS-TE Tunnels . 3 Definitions The definitions for the terms used in this Recommendation can be found in ITU-T Y.2111. 4 Abbreviations and acronyms This Recommen
31、dation uses the following abbreviations and acronyms: BG-FE Border Gateway Functional Entity CAC Connection Admission Control CPE Customer Premises Equipment CPN Customer Premises Network DSCP DiffServ Code Point DS-TE Diffserv-aware MPLS Traffic Engineering EF Expedited Forwarding IP Internet Proto
32、col LDP Label Distribution Protocol LER Label Edge Router LSP Label Switched Path MAM Maximum Allocation Model MAR Maximum Allocation with Reservation MPLS MultiProtocol Label Switching MPLS-TE MPLS Traffic Engineering NAPT/FW Network Address and Port Translation/Firewall NGN Next Generation Network
33、 PD-FE Policy Decision Functional Entity PE-FE Policy Enforcement Functional Entity QoS Quality of Service RDM Russian Dolls Model RIR Resource Initiation Request Rec. ITU-T Y.2174 (06/2008) 3 RIP Resource Initiation Response RSVP Resource Reservation Protocol RSVP-TE RSVP Traffic Engineering TE Tra
34、ffic Engineering TRC-FE Transport Resource Control Functional Entity VoIP Voice-over-IP 5 Conventions None. 6 Distributed RACF architecture and supporting requirements Real-time traffic is aggregated by access networks prior to entry into the MPLS core network; there may be multiple core networks al
35、so referred to as autonomous administrative domains. Inside the MPLS core network, label edge routers are assumed to be connected via pre-provisioned label switched paths (LSP) or traffic engineering (TE) tunnels. Note that an LSP may be treated as an LSP tunnel IETF RFC 3209 when the LSP flow is co
36、mpletely identified by the label applied at the ingress node of the path. Hence, the terms LSP, LSP tunnels, and TE tunnels are considered synonymous in this Recommendation. A brief overview of MPLS-TE capabilities which support admission control is provided in Appendix I. Admission of traffic flows
37、 into the TE tunnels requires careful attention in order to achieve the required QoS. The admission control process needs to determine the type of incoming service/application flows (real-time calls, interactive sessions, or data flows) as well as their QoS and bandwidth requirements. The initial po
38、int of contact for incoming flows from an access network is the border gateway functional entity (BG-FE) ITU-T Y.2012 which is connected to the LER. The BG-FE is defined as a key node for support of dynamic QoS, network address and port translation/firewall (NAPT/FW) control and NAPT traversal. The
39、BG-FE resides at the boundary between an access network and a core network or between two core networks. This Recommendation recommends the use of a specific implementation of the BG-FE, namely a session border controller (SBC) b-ITU-T Y-Sup.2. For the purpose of this Recommendation, the SBC is thus
40、 synonymous with the BG-FE all SBC requirements defined here for admission control purposes are also applicable to generic BG-FEs. The processing of incoming flows commences at the SBC prior to admission control processing at the policy decision functional entity (PD-FE). The PD-FE needs to interact
41、 with the service/application layer to determine the following QoS requirements about incoming calls/sessions: 1) Terminating SBC 2) Priority requirements for connection admission control (CAC) ITU-T Y.2171 and restoration ITU-T Y.2172, IETF RFC 4090 3) Bandwidth requirement (based on appropriate co
42、dec negotiation between originating and terminating SBC as well as call/session QoS requirements, if any) 4) DiffServ code point (DSCP) based on the type of call/session and priority requirements. The PD-FE then needs to relay these requirements to the TRC-FE which then proceeds to determine the ava
43、ilability of the required bandwidth. In this Recommendation, the PD-FE is depicted as a single functional entity (see Figure 1). However, it is recognized that from an architectural perspective, the PD-FE could be developed into a single centralized entity (per administrative domain), or, alternatel
44、y, some PD-FE functions could 4 Rec. ITU-T Y.2174 (06/2008) be distributed across a number of physical elements. The precise nature of an architecture that allows for a distributed PD-FE and the resulting reference point signalling flows with the TRC-FE and PE-FE are for further study. In this Recom
45、mendation, the PD-FE is depicted as a single functional entity (see Figure 1) regardless of the ultimate form of the PD-FE architecture. Once the QoS and priority requirements have been established by the PD-FE, the flows are directed to the LER where they are mapped into the proper tunnels. Informa
46、tion on tunnel status and bandwidth utilization conditions is assumed to be available at the LERs and the connected gateways tunnel selection for incoming flows is based on this information. This clause defines a distributed architecture for the TRC-FE and specifies supporting requirements. In this
47、architecture, MPLS transport resource information is available in the LERs and gateways connected to the LERs. 6.1 Distributed TRC-FE functions in MPLS-TE core networks A distributed implementation of a TRC-FE is shown in Figure 1. It is based on the capabilities of the MPLS LER and the SBC which se
48、rves as the gateway connected to the LER. The TRC-FE functionality is distributed across SBCs and LERs. Y.2174(08)_F01RACFService control functionsPD-FEOtherNGNsNetwork attachmentcontrol functionService stratumTransport stratum RsRwRuRtSBCSBCEnd-userequipmentRwIngressLEREgressLERMPLS CoreLSRLSRLSRLS
49、RDS-TE LSPRdRtPD-FESBCLERLSRSession border controller: This physical element contains the CACfunction which forms a subset of the distributed TRC-FE.Label edge router: This physical element maintains TE tunnel states.It forms a subset of the distributed TRC-FE.Label switched routers: This physical element is part of the MPLScore backbone.Policy decision functional entity: The physical architecture of thisfunctional entity is for further study.Figure 1 Architecture showing a
