1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Y.1561TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2004) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT GENERATION NETWORKS Internet protocol aspects Quality of service and network performance Performance and availa
2、bility parameters for MPLS networks ITU-T Recommendation Y.1561 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 aspec
3、ts Y.300Y.399 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, n
4、etwork capabilities 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 a
5、nd 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.2300Y.2399 Netw
6、ork management Y.2400Y.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. ITU-T Rec. Y.1561 (05/2004) i ITU-T Recommendation Y.1561 Performance and availability
7、parameters for MPLS networks Summary This Recommendation defines parameters that may be used in specifying and assessing the performance of speed, accuracy, dependability, and availability of packet transfer over a Label Switched Path on a Multi-Protocol Label Switching (MPLS) network. The defined p
8、arameters apply to end-to-end, point-to-point and multipoint-to-point LSP and to any MPLS domain that provides, or contributes to the provision of, packet transfer services. Two categories of MPLS networks are considered: 1) TE-LSP: Traffic Engineering Label Switched Path, or configured LSP. These a
9、re point-point paths. 2) LDP-based LSP: This includes point-to-point and multipoint to point LSPs. Source ITU-T Recommendation Y.1561 was approved on 7 May 2004 by ITU-T Study Group 13 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. Y.1561 (05/2004) FOREWORD The International
10、 Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. 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
11、 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 Recommendations on these topics. The approval of I
12、TU-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, the expression “Administration“ is u
13、sed 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 applicability) and compliance with the
14、 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 with the Recommendation is required of
15、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 applicability of claimed Intellectual Pro
16、perty 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 implement this Recommendation. However, i
17、mplementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T R
18、ec. Y.1561 (05/2004) iii CONTENTS Page 1 Scope 1 2 References. 2 3 Definitions 3 4 Abbreviations 3 5 Layered protocol reference model and performance model for MPLS 4 5.1 Network components 5 5.2 Exchange links and network sections. 7 5.3 Measurement points and measurable sections 7 5.4 Packet trans
19、fer reference events (PREs). 8 5.5 Packet transfer outcomes 9 6 Packet transfer performance parameters. 13 6.1 Populations of interest 13 6.2 Packet Transfer Delay (PTD) . 14 6.3 Packet Error Ratio (PER) . 16 6.4 Packet Loss Ratio (PLR) 16 6.5 Spurious Packet Rate (SPR) . 16 6.6 Packet Severe Loss B
20、lock Ratio (PSLBR). 16 6.7 Recovery Time . 17 7 Availability . 17 7.1 Availability service function for connection-oriented services 17 7.2 Availability parameters 17 8 Security. 18 BIBLIOGRAPHY 18 ITU-T Rec. Y.1561 (05/2004) 1 ITU-T Recommendation Y.1561 Performance and availability parameters for
21、MPLS networks 1 Scope This Recommendation defines parameters that may be used in specifying and assessing the performance of speed, accuracy, dependability, and availability of packet (labelled or not in the latter case, Penultimate Hop Popping (PHP) may cause loss of Label Switched Paths (LSP) iden
22、tity at the network edges) transfer over an LSP on a Multi-Protocol Label Switching (MPLS) network. The defined parameters apply to end-to-end, point-to-point and multipoint-to-point LSP and to any MPLS domain that provides, or contributes to the provision of, packet transfer services in accordance
23、with the normative references specified in clause 2. Figure 1/Y.1561 Scope of this Recommendation The scope of this Recommendation is summarized in Figure 1. The MPLS network performance parameters are defined on the basis of packet transfer reference events that may be observed at measurement point
24、s (MPs) associated with specified functional and jurisdictional boundaries. The 2 ITU-T Rec. Y.1561 (05/2004) measurement points may be at the ends of LSPs. For comparability and completeness, MPLS network performance is considered in the context of the 3 3 performance matrix defined in ITU-T Rec. I
25、.350. Three protocol-independent communication functions are identified in the matrix: access, user information transfer and disengagement. Each function is considered with respect to three general performance concerns (or “performance criteria“): speed, accuracy and dependability. An associated two
26、-state model provides a basis for describing MPLS network availability. The performance of MPLS networks providing access and disengagement functions (e.g., Resource ReserVation Protocol Traffic Engineering, RSVP-TE) and supporting capabilities (e.g., Label Distribution Protocol, LDP, as per RFC 303
27、6) may be addressed in separate Recommendations. Two categories of MPLS networks will be considered here: 1) TE-LSP: Traffic Engineering Label Switched Path, or configured LSP. These are point-point paths. The paths are connection-oriented, explicitly routed, and fixed. 2) LDP-based LSP: This includ
28、es point-to-point and multipoint to point LSPs. The paths behave more like IP, using the Interior Gateway Protocol (IGP), such as Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS) for routing. The LSPs are connectionless. The point-to-point and multipoint-to-point
29、 topologies are accommodated through the concept of populations of interest, defined in 6.1. The case of PHP causing loss of LSP identity is specifically addressed in 5.4, where there are three optional criteria for packet transfer reference events. Correspondence between ingress and egress referenc
30、e events has been dealt with here to the same degree as in different Recommendations (e.g., ITU-T Rec. Y.1540), in 5.5.2. In this Recommendation, the general term packet refers to an IP packet with header and information field, or to other protocols with combinations of header and information fields
31、, so long as there is a standard that describes the encapsulation as an MPLS packet. 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
32、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 currently valid ITU
33、-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 Recommendation I.350 (1993), General aspects of quality of service and network performance in digital networks, includi
34、ng ISDNs. ITU-T Recommendation I.353 (1996), Reference events for defining ISDN and B-ISDN performance parameters. ITU-T Recommendation Y.1540 (2002), Internet protocol data communication service IP packet transfer and availability performance parameters. ITU-T Recommendation Y.1711 (2004), Operatio
35、n and maintenance mechanism for MPLS networks. IETF RFC 3031 (2001), Multiprotocol Label Switching Architecture. IETF RFC 3032 (2001), MPLS Label Stack Encoding. IETF RFC 3036 (2001), LDP Specification. IETF RFC 3107 (2001), Carrying Label Information in BGP-4. ITU-T Rec. Y.1561 (05/2004) 3 IETF RFC
36、 3429 (2002), Assignment of the OAM Alert Label for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions. 3 Definitions This Recommendation defines the following terms: 3.1 Forwarding Equivalence Class (FEC): A category of IP packets that receive the same forwa
37、rding treatment. 3.2 Label Switched Path (LSP): The path through one or more LSRs at one level of the hierarchy followed by a packet in a particular FEC. 3.3 Penultimate Hop Popping (PHP): An optional feature in MPLS, where the label stack may be popped (removed) at the penultimate Label Switching R
38、outer of the LSP, rather than at the LSP Egress. 4 Abbreviations This Recommendation uses the following abbreviations: CE Customer Edge Router CR-LDP Constraint-based Routing Label Distribution Protocol DSCP Differentiated Services Code Point DST Destination EL Exchange Link EXP Experimental FEC For
39、warding Equivalence Class IGP Interior Gateway Protocol IP Internet Protocol IS-IS Intermediate System to Intermediate System LDP Label Distribution Protocol LSP Label Switched Path LSR Label Switching Router MP Measurement Point MPLS Multi-Protocol Label Switching NS Network Section NSE Network Sec
40、tion Ensemble OSPF Open Shortest Path First PDV Packet Delay Variation PE Provider Edge Label Switching Router PER Packet Error Ratio PHP Penultimate Hop Popping PIA Percent service availability PIU Percent service unavailability 4 ITU-T Rec. Y.1561 (05/2004) PLR Packet Loss Ratio PRE Packet Transfe
41、r Reference Event PSLBR Packet Severe Loss Block Ratio PTD Packet Transfer Delay RSVP-TE Resource ReserVation Protocol Traffic Engineering RTPTD Round Trip Packet Transfer Delay SLB Severe Loss Block SPR Spurious Packet Rate SRC Source TLV Type-Length-Value-tuple ToS Type of Service TTL Time To Live
42、 UDP User Datagram Protocol UNI User Network Interface 5 Layered protocol reference model and performance model for MPLS Figure 2 illustrates the layered nature of MPLS transport service. The performance provided to layers above MPLS depends both on the MPLS layer performance and the layers below MP
43、LS: Lower layers that provide connection-oriented or connection transport supporting the MPLS layer. The MPLS layer that transports packets. This layer has significance across the MPLS Domain(s), and provides the Label Switched Path (LSP). In the case where Penultimate Hop Popping is employed, the l
44、abel stack is returned to the depth on ingress in the penultimate node. Higher Layers, including the IP layer, that further enable end-to-end communication. This clause defines a generic MPLS transport network performance model, composed of network sections and exchange links that interconnect netwo
45、rk sections. The performance parameters defined here may be applied to the unidirectional transfer of packets on a network section, or across a single MPLS Domain, as defined below (this is the scope of OA or 2) a router in one network section with a router in another network section. Note that the
46、responsibility for an exchange link, its capacity, and its performance is typically shared between the connected parties. NOTE “Exchange link“ is equivalent to the term “label switched hop“ as defined in RFC 3031. 5.2.2 Network Section (NS) A set of MPLS nodes together with all of their interconnect
47、ing links that together provide all or part of the MPLS network between an ingress node and an egress node, and are under a single (or collaborative) jurisdictional responsibility. Some network sections consist of a single host with no interconnecting links. Source NS and Destination NS are particul
48、ar cases of network sections. Pairs of network sections are connected by exchange links. NOTE “Network Section“ is synonymous with the term “MPLS Domain“ as defined in RFC 3031. 5.3 Measurement points and measurable sections 5.3.1 Measurement Point (MP) The boundary between a host or MPLS Edge Node
49、and an adjacent link at which performance reference events can be observed and measured. Consistent with ITU-T Rec. I.353, any of the standard Internet protocols can be observed at measurement points. NOTE The exact location of the MPLS MP within the protocol stack is for further study. A section or a combination of sections is measurable if it is bounded by a set of MPs. In this Recommendation, the following sections are measurable. 5.3.2 Basic section An EL, NS, a SRC, or a DST. Basic sections are delimited by MP. T
