Network Working Group J. Ash
Request for Comments: 3213 AT&T
Category: Informational M. Girish
Atoga Systems
E. Gray
Sandburst
B. Jamoussi
G. Wright
Nortel Networks Corp.
January 2002
Network Working Group J. Ash
Request for Comments: 3213 AT&T
Category: Informational M. Girish
Atoga Systems
E. Gray
Sandburst
B. Jamoussi
G. Wright
Nortel Networks Corp.
January 2002
Applicability Statement for CR-LDP
CR-LDP适用性声明
Status of this Memo
本备忘录的状况
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2002). All Rights Reserved.
版权所有（C）互联网协会（2002年）。版权所有。
Abstract
摘要
This document discusses the applicability of Constraint-Based LSP Setup using LDP. It discusses possible network applications, extensions to Label Distribution Protocol (LDP) required to implement constraint-based routing, guidelines for deployment and known limitations of the protocol. This document is a prerequisite to advancing CR-LDP on the standards track.
本文讨论了使用LDP的基于约束的LSP设置的适用性。它讨论了可能的网络应用、实现基于约束的路由所需的标签分发协议（LDP）扩展、部署指南以及协议的已知限制。本文件是在标准轨道上推进CR-LDP的先决条件。
As the Internet evolves, additional capabilities are required to ensure proper treatment of data [3], voice, video and other delay sensitive traffic [4]. MPLS enhances source routing and allows for certain techniques, used in circuit switching, in IP networks. This permits a scalable approach to handling these diverse transmission requirements. CR-LDP [1] is a simple, scalable, open, non-proprietary, traffic engineering signaling protocol for MPLS IP networks.
随着互联网的发展，需要额外的功能来确保正确处理数据[3]、语音、视频和其他对延迟敏感的流量[4]。MPLS增强了源路由，并允许IP网络中用于电路交换的某些技术。这允许采用可扩展的方法来处理这些不同的传输需求。CR-LDP[1]是一种用于MPLS IP网络的简单、可扩展、开放、非专有的流量工程信令协议。
CR-LDP provides mechanisms for establishing explicitly routed Label Switched Paths (LSPs). These mechanisms are defined as extensions to LDP [2]. Because LDP is a peer-to-peer protocol based on the
CR-LDP提供了建立显式路由标签交换路径（LSP）的机制。这些机制被定义为LDP的扩展[2]。因为LDP是基于
establishment and maintenance of TCP sessions, the following natural benefits exist:
在建立和维护TCP会话时，存在以下自然好处：
CR-LDP messages are reliably delivered by the underlying TCP, and State information associated with explicitly routed LSPs does not require periodic refresh.
CR-LDP消息由底层TCP可靠地传递，与显式路由LSP关联的状态信息不需要定期刷新。
CR-LDP messages are flow controlled (throttled) through TCP.
CR-LDP消息通过TCP进行流控制（节流）。
CR-LDP is defined for the specific purpose of establishing and maintaining explicitly routed LSPs. Additional optional capabilities included have minimal impact on system performance and requirements when not in use for a specific explicitly routed LSP. Optional capabilities provide for negotiation of LSP services and traffic management parameters over and above best-effort packet delivery including bandwidth allocation, setup and holding priorities. CR-LDP optionally allows these parameters to be dynamically modified without disruption of the operational (in-service) LSP [4].
CR-LDP的定义是为了建立和维护显式路由LSP的特定目的。当不用于特定的显式路由LSP时，包含的附加可选功能对系统性能和需求的影响最小。可选功能提供LSP服务和流量管理参数的协商，包括带宽分配、设置和保持优先级。CR-LDP可选地允许动态修改这些参数，而不会中断操作（在用）LSP[4]。
CR-LDP allows the specification of a set of parameters to be signaled along with the LSP setup request. Moreover, the network can be provisioned with a set of edge traffic conditioning functions (which could include marking, metering, policing and shaping). This set of parameters along with the specification of edge conditioning functions can be shown to be adequate and powerful enough to describe, characterize and parameterize a wide variety of QoS scenarios and services including IP differentiated services [5], integrated services [6], ATM service classes [7], and frame relay [8].
CR-LDP允许将一组参数的规范与LSP设置请求一起发送信号。此外，网络可配备一组边缘流量调节功能（可包括标记、计量、监管和整形）。这组参数以及边缘调节功能的规范足以描述、表征和参数化各种QoS场景和服务，包括IP区分服务[5]、综合服务[6]、ATM服务类别[7]和帧中继[8]。
CR-LDP is designed to adequately support the various media types that MPLS was designed to support (ATM, FR, Ethernet, PPP, etc.). Hence, it will work equally well for Multi-service switched networks, router networks, or hybrid networks.
CR-LDP设计用于充分支持MPLS设计用于支持的各种媒体类型（ATM、FR、以太网、PPP等）。因此，它同样适用于多业务交换网络、路由器网络或混合网络。
This applicability statement does not preclude the use of other signaling and label distribution protocols for the traffic engineering application in MPLS based networks. Service providers are free to deploy whatever signaling protocol meets their needs.
本适用性声明不排除在基于MPLS的网络中使用其他信令和标签分发协议进行流量工程应用。服务提供商可以自由部署满足其需求的任何信令协议。
In particular CR-LDP and RSVP-TE [9] are two signaling protocols that perform similar functions in MPLS networks. There is currently no consensus on which protocol is technically superior. Therefore, network administrators should make a choice between the two based upon their needs and particular situation. Applicability of RSVP-TE is described in [10].
特别是CR-LDP和RSVP-TE[9]是两种在MPLS网络中执行类似功能的信令协议。目前还没有就哪种协议在技术上更优越达成共识。因此，网络管理员应该根据他们的需要和具体情况在两者之间做出选择。[10]中描述了RSVP-TE的适用性。
To provide support of additional LSP services, CR-LDP extensions are defined in such a way as to be directly translatable to objects and messages used in other protocols defined to provide similar services [9]. Implementations can take advantage of this fact to:
为了提供对附加LSP服务的支持，CR-LDP扩展的定义方式应确保可直接翻译为用于提供类似服务的其他协议中的对象和消息[9]。实施可以利用这一事实：
Setup LSPs for provision of an aggregate service associated with the services being provided via these other protocols.
设置LSP以提供与通过这些其他协议提供的服务相关联的聚合服务。
Directly translate protocol messages to provide services defined in a non-CR-LDP portion of the network.
直接翻译协议消息以提供在网络的非CR LDP部分中定义的服务。
Describe, characterize and parameterize a wide variety of QoS scenarios and services including IP differentiated services, integrated services, ATM service classes, and frame relay.
描述、描述和参数化各种QoS场景和服务，包括IP区分服务、集成服务、ATM服务类别和帧中继。
Steady state information required for proper maintenance of an LSP may be as little as 200 bytes or less. It is not unreasonable to anticipate that CR-LDP implementations may support in excess of one hundred thousand or one million LSPs switched through a single Label Switching Router (LSR) under fairly stable conditions.
正确维护LSP所需的稳态信息可能少至200字节或更少。在相当稳定的条件下，预计CR-LDP实现可能支持通过单标签交换路由器（LSR）交换的超过十万或一百万个LSP并非不合理。
Because CR-LDP provides for low overhead per LSP - both in terms of needed state information and control traffic - CR-LDP is applicable in those portions of the Internet where very large numbers of LSPs may need to be switched at each LSR. An example of this would be large backbone networks using MPLS exclusively to transport very large numbers of traffic streams between a moderately large number of MPLS edge nodes.
由于CR-LDP在所需的状态信息和控制流量方面为每个LSP提供了较低的开销，因此CR-LDP适用于在每个LSR可能需要交换大量LSP的互联网部分。这方面的一个例子是专门使用MPLS在数量适中的MPLS边缘节点之间传输大量流量流的大型骨干网络。
CR-LDP may also be applicable as a mediating service between networks providing similar service extensions using widely varying signaling models.
CR-LDP还可以用作使用广泛变化的信令模型提供类似服务扩展的网络之间的中介服务。
LDP specifies the following label distribution and management modes (which can be combined in various logical ways described in LDP):
LDP规定了以下标签分发和管理模式（可以通过LDP中描述的各种逻辑方式进行组合）：
. Downstream On Demand label distribution . Downstream Unsolicited label distribution . Independent Label Distribution Control . Ordered Label Distribution Control . Conservative Label Retention Mode . Liberal Label Retention Mode
. 下游按需标签分发。下游未经请求的标签分发。独立的标签分发控制。有序标签分发控制。保守的标签保留模式。自由标签保留模式
The applicability of LDP is described in [11].
LDP的适用性如[11]所述。
In networks where only Traffic Engineered LSPs are required, the CR-LDP implementation and deployment does NOT require all the functionality defined in the LDP specification. The basic Discovery, Session, and Notification messages are required. However, CR-LDP requires one specific combination of the label distribution modes:
在只需要流量工程LSP的网络中，CR-LDP实施和部署不需要LDP规范中定义的所有功能。需要基本的发现、会话和通知消息。然而，CR-LDP需要标签分发模式的一种特定组合：
. Downstream On Demand Ordered label distribution and conservative Label Retention Mode
. 下游按需有序标签分发和保守的标签保留模式
Although CR-LDP is defined as an extension to LDP, support for Downstream Unsolicited Label Advertisement and Independent Control modes is not required for support of Strict Explicit Routes. In addition, implementations of CR-LDP MAY be able to support Loose Explicit Routes via the use of 'Abstract Nodes' and/or 'Hierarchical Explicit Routing', without using LDP for hop-by-hop LSP setup.
尽管CR-LDP被定义为LDP的扩展，但支持严格的显式路由并不需要支持下游未经请求的标签广告和独立控制模式。此外，CR-LDP的实现可能能够通过使用“抽象节点”和/或“分层显式路由”来支持松散显式路由，而无需将LDP用于逐跳LSP设置。
CR-LDP also includes support for loose explicit routes. Use of this capability allows the network operator to define an 'explicit path' through portions of their network with imperfect knowledge of the entire network topology. Proper use of this capability may also allow CR-LDP implementations to inter-operate with 'vanilla' LDP implementations - particularly if it is desired to set up an explicitly routed LSP for best-effort packet delivery via a loosely defined path.
CR-LDP还包括对松散显式路由的支持。使用此功能允许网络运营商在不完全了解整个网络拓扑的情况下，通过其网络的各个部分定义“显式路径”。正确使用此功能还可以允许CR-LDP实现与“普通”LDP实现相互操作-特别是如果希望通过松散定义的路径设置显式路由LSP以尽最大努力交付数据包。
Finally, in networks where both Routing Protocol-driven LSPs (a.k.a. hop-by-hop LSPs) and Traffic Engineered LSPs are required, a single protocol (LDP, with the extensions defined in CR-LDP) can be used for both TE and Hop-by-Hop LSPs. New protocols do not have to be introduced in the network to provide TE-LSP signaling.
最后，在既需要路由协议驱动的LSP（也称为逐跳LSP）又需要流量工程LSP的网络中，TE和逐跳LSP都可以使用单个协议（LDP，具有CR-LDP中定义的扩展）。不必在网络中引入新协议来提供TE-LSP信令。
CR-LDP specification only supports point-to-point LSPs. Multi-point-to-point and point-to-multi-point are for further study (FFS).
CR-LDP规范仅支持点对点LSP。多点对点和点对多点用于进一步研究（FFS）。
CR-LDP specification only supports unidirectional LSP setup. Bi-directional LSP setup is FFS.
CR-LDP规范仅支持单向LSP设置。双向LSP设置为FFS。
CR-LDP specification only supports a unique label allocation per LSP setup. Multiple label allocations per LSP setup are FFS.
CR-LDP规范仅支持每个LSP设置的唯一标签分配。每个LSP设置的多个标签分配是FFS。
No additional security issues are introduced in this document. As an extension to LDP, CR-LDP shares the security concerns associated with LDP.
本文档中未介绍其他安全问题。作为LDP的延伸，CR-LDP与LDP有着共同的安全顾虑。
The authors would like to thank the following people for their careful review of the document and their comments: Loa Andersson, Peter Ashwood-Smith, Anoop Ghanwani, Juha Heinanen, Jon Weil and Adrian Farrel.
作者要感谢以下人士对该文件及其评论的仔细审查：Loa Andersson、Peter Ashwood Smith、Anoop Ghanwani、Juha Heinanen、Jon Weil和Adrian Farrel。
[1] Jamoussi, B., Andersson, L., Callon, R., Dantu, R., Wu, L., Doolan, P., Worster, T., Feldman, N., Fredette, A., Girish, M., Gray, E., Heinanen, J., Kilty, T. and A. Malis, "Constraint-based LSP Setup Using LDP", RFC 3212, January 2002.
[1] Jamoussi，B.，Andersson，L.，Callon，R.，Dantu，R.，Wu，L.，Doolan，P.，Worster，T.，Feldman，N.，Fredette，A.，Girish，M.，Gray，E.，Heinanen，J.，Kilty，T.和A.Malis，“使用LDP的基于约束的LSP设置”，RFC 3212，2002年1月。
[2] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B. Thomas, "LDP Specification", RFC 3036, January 2001.
[2] Andersson，L.，Doolan，P.，Feldman，N.，Fredette，A.和B.Thomas，“LDP规范”，RFC 3036，2001年1月。
[3] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M. and J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC 2702, September 1999.
[3] Awduche，D.，Malcolm，J.，Agogbua，J.，O'Dell，M.和J.McManus，“MPLS上的流量工程要求”，RFC 2702，1999年9月。
[4] Ash, B., Lee, Y., Ashwood-Smith, P., Jamoussi, B., Fedyk, D., Skalecki, D. and L. Li, "LSP Modification using CR-LDP", RFC 3214, January 2002.
[4] Ash，B.，Lee，Y.，Ashwood Smith，P.，Jamoussi，B.，Fedyk，D.，Skalecki，D.和L.Li，“使用CR-LDP的LSP改性”，RFC 32142002年1月。
[5] Blake S., Black, D., Carlson, M., Davies, E., Wang, Z. and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998.
[5] Blake S.，Black，D.，Carlson，M.，Davies，E.，Wang，Z.和W.Weiss，“差异化服务架构”，RFC 24751998年12月。
[6] Shenker, S. and J. Wroclawski, "General Characterization Parameters for Integrated Service Network Elements", RFC 2215, September 1997.
[6] Shenker，S.和J.Wroclawski，“综合业务网络元件的一般特征参数”，RFC 2215，1997年9月。
[7] ATM Forum Traffic Management Specification Version 4.1 (AF-TM-0121.000), March 1999.
[7] ATM论坛流量管理规范版本4.1（AF-TM-0121.000），1999年3月。
[8] CONGESTION MANAGEMENT FOR THE ISDN FRAME RELAYING BEARER SERVICE, ITU (CCITT) Recommendation I.370, 1991.
[8] ISDN帧中继承载业务的拥塞管理，ITU（CCITT）建议I.370，1991。
[9] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001.
[9] Awduche，D.，Berger，L.，Gan，D.，Li，T.，Srinivasan，V.和G.Swallow，“RSVP-TE：LSP隧道RSVP的扩展”，RFC 3209，2001年12月。
[10] Awduche, D., Hannan, A. and X. Xiao, "Applicability Statement for Extensions to RSVP for LSP-Tunnels", RFC 3210, December 2001.
[10] Awduche，D.，Hannan，A.和Xiao，“LSP隧道RSVP扩展的适用性声明”，RFC 3210，2001年12月。
[11] Thomas, B. and E. Gray, "LDP Applicability", RFC 3037, January 2001.
[11] Thomas，B.和E.Gray，“LDP适用性”，RFC 3037，2001年1月。
Gerald R. Ash AT&T Room MT D5-2A01 200 Laurel Avenue Middletown, NJ 07748 USA Phone: 732-420-4578 Fax: 732-368-8659 EMail: gash@att.com
Gerald R.Ash AT&T室MT D5-2A01美国新泽西州劳雷尔大道中城200号07748电话：732-420-4578传真：732-368-8659电子邮件：gash@att.com
Eric Gray Sandburst 600 Federal Drive Andover, MA 01810 Phone: (978) 689-1610 EMail: eric.gray@sandburst.com
Eric Gray Sandburst马萨诸塞州安多弗联邦大道600号电话：（978）689-1610电子邮件：Eric。gray@sandburst.com
Gregory Wright Nortel Networks Corp. P O Box 3511 Station C Ottawa, ON K1Y 4H7 Canada Phone: +1 613 765-7912 EMail: gwright@nortelnetworks.com
Gregory Wright Nortel Networks Corp.加拿大渥太华C站3511号邮政信箱K1Y 4H7电话：+1 613 765-7912电子邮件：gwright@nortelnetworks.com
M. K. Girish Atoga Systems 49026 Milmont Drive Fremont, CA 94538 EMail: muckai@atoga.com
M.K.Girish Atoga Systems 49026加利福尼亚州弗里蒙特市密尔蒙特大道94538电子邮件：muckai@atoga.com
Bilel Jamoussi Nortel Networks Corp. 600 Technology Park Drive Billerica, MA 01821 USA phone: +1 978-288-4506 EMail: Jamoussi@nortelnetworks.com
Billel Jamoussi Nortel Networks Corp.美国马萨诸塞州比尔里卡科技园大道600号电话：+1 978-288-4506电子邮件：Jamoussi@nortelnetworks.com
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Acknowledgement
确认
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