Network Working Group                                          T. Nadeau
Request for Comments: 4377                                     M. Morrow
Category: Informational                                       G. Swallow
                                                     Cisco Systems, Inc.
                                                                D. Allan
                                                         Nortel Networks
                                                           S. Matsushima
                                                           Japan Telecom
                                                           February 2006
Network Working Group                                          T. Nadeau
Request for Comments: 4377                                     M. Morrow
Category: Informational                                       G. Swallow
                                                     Cisco Systems, Inc.
                                                                D. Allan
                                                         Nortel Networks
                                                           S. Matsushima
                                                           Japan Telecom
                                                           February 2006

Operations and Management (OAM) Requirements for Multi-Protocol Label Switched (MPLS) Networks


Status of This Memo


This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.


Copyright Notice


Copyright (C) The Internet Society (2006).




This document specifies Operations and Management (OAM) requirements for Multi-Protocol Label Switching (MPLS), as well as for applications of MPLS, such as pseudo-wire voice and virtual private network services. These requirements have been gathered from network operators who have extensive experience deploying MPLS networks.


Table of Contents


   1. Introduction ....................................................2
   2. Document Conventions ............................................2
   3. Motivations .....................................................4
   4. Requirements ....................................................4
   5. Security Considerations ........................................11
   6. References .....................................................12
   7. Acknowledgements ...............................................13
   1. Introduction ....................................................2
   2. Document Conventions ............................................2
   3. Motivations .....................................................4
   4. Requirements ....................................................4
   5. Security Considerations ........................................11
   6. References .....................................................12
   7. Acknowledgements ...............................................13
1. Introduction
1. 介绍

This document describes requirements for user and data plane Operations and Management (OAM) for Multi-Protocol Label Switching (MPLS). These requirements have been gathered from network operators who have extensive experience deploying MPLS networks. This document specifies OAM requirements for MPLS, as well as for applications of MPLS.


Currently, there are no specific mechanisms proposed to address these requirements. The goal of this document is to identify a commonly applicable set of requirements for MPLS OAM at this time. Specifically, a set of requirements that apply to the most common set of MPLS networks deployed by service provider organizations at the time this document was written. These requirements can then be used as a base for network management tool development and to guide the evolution of currently specified tools, as well as the specification of OAM functions that are intrinsic to protocols used in MPLS networks.

目前,没有针对这些要求提出的具体机制。本文档的目标是确定目前MPLS OAM的一组普遍适用的需求。具体来说,这是一组要求,适用于编写本文档时服务提供商组织部署的最常见的一组MPLS网络。然后,这些需求可以用作网络管理工具开发的基础,并指导当前指定工具的发展,以及MPLS网络中使用的协议固有的OAM功能的规范。

2. Document Conventions
2. 文件惯例
2.1. Terminology
2.1. 术语

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].

本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照RFC 2119[RFC2119]中所述进行解释。

Queuing/buffering Latency: The delay caused by packet queuing (value is variable since it is dependent on the packet arrival rate, the packet length, and the link throughput).


Probe-based-detection: Active measurement tool that can measure the consistency of an LSP [RFC4379].


Defect: Any error condition that prevents a Label Switched Path (LSP) from functioning correctly. For example, loss of an Interior Gateway Protocol (IGP) path will most likely result in an LSP not being able to deliver traffic to its destination. Another example is the interruption of the path for a TE tunnel. These may be due to physical circuit failures or failure of switching nodes to operate as expected.


Multi-vendor/multi-provider network operation typically requires agreed upon definitions of defects (when it is broken and when it is not) such that both recovery procedures and service level specification impact can be specified.


Head-end Label Switching Router (LSR): The beginning of an LSP. A head-end LSR is also referred to as an ingress LSR.


Tail-end Label Switching Router (LSR): The end of an LSP. A tail-end LSR is also referred to as an egress LSR.


Propagation Latency: The delay added by the propagation of the packet through the link (fixed value that depends on the distance of the link and the propagation speed).


Transmission Latency: The delay added by the transmission of the packet over the link, i.e., the time it takes to put the packet over the media (value that depends on the link throughput and packet length).


Processing Latency: The delay added by all the operations related to the switching of labeled packets (value is node implementation specific and may be considered fixed and constant for a given type of equipment).


Node Latency: The delay added by the network element resulting from of the sum of the transmission, processing, and queuing/buffering latency.


One-hop Delay: The fixed delay experienced by a packet to reach the next hop resulting from the of the propagation latency, the transmission latency, and the processing latency.


Minimum Path Latency: The sum of the one-hop delays experienced by the packet when traveling from the ingress to the egress LSR.


Variable Path Latency: The variation in the sum of the delays experienced by packets transiting the path, otherwise know as jitter.


2.2. Acronyms
2.2. 缩略词

ASBR: Autonomous System Border Router


CE: Customer Edge


PE: Provider Edge


SP: Service Provider


ECMP: Equal-Cost Multi-path


LSP: Label Switched Path


LSP Ping: Label Switched Path Ping

LSP Ping:标签交换路径Ping

LSR: Label Switching Router


OAM: Operations and Management


RSVP: Resource reSerVation Protocol


LDP: Label Distribution Protocol


DoS: Denial of Service


3. Motivations
3. 动机

This document was created to provide requirements that could be used to create consistent and useful OAM functionality that meets operational requirements of those service providers (SPs) who have deployed or are deploying MPLS.


4. Requirements
4. 要求

The following sections enumerate the OAM requirements gathered from service providers who have deployed MPLS and services based on MPLS networks. Each requirement is specified in detail to clarify its applicability. Although the requirements specified herein are defined by the IETF, they have been made consistent with requirements gathered by other standards bodies such as the ITU [Y1710].


4.1. Detection of Label Switched Path Defects
4.1. 标签交换路径缺陷的检测

The ability to detect defects in a broken LSP MUST not require manual hop-by-hop troubleshooting of each LSR used to switch traffic for that LSP. For example, it is not desirable to manually visit each LSR along the data plane path transited by an LSP; instead, this function MUST be automated and able to be performed at some operator specified frequency from the origination point of that LSP. This implies solutions that are interoperable to allow for such automatic operation.


Furthermore, the automation of path liveliness is desired in cases where large numbers of LSPs might be tested. For example, automated ingress LSR to egress LSR testing functionality is desired for some LSPs. The goal is to detect LSP path defects before customers do, which requires detection and correction of LSP defects in a manner that is both predictable and within the constraints of the service level agreement under which the service is being offered. Simply put, the sum of the time it takes an OAM tool to detect a defect and the time needed for an operational support system to react to this defect, by possibly correcting it or notifying the customer, must fall within the bounds of the service level agreement in question.


Synchronization of detection time bounds by tools used to detect broken LSPs is required. Failure to specify defect detection time bounds may result in an ambiguity in test results. If the time to detect broken LSPs is known, then automated responses can be specified with respect and regard to resiliency and service level specification reporting. Further, if synchronization of detection time bounds is possible, an operational framework can be established to guide the design and specification of MPLS applications.


Although an ICMP-based ping [RFC792] can be sent through an LSP as an IP payload, the use of this tool to verify the defect-free operation of an LSP has the potential of returning erroneous results (both positive and negative) for a number of reasons. For example, in some cases, because the ICMP traffic is based on legally addressable IP addressing, it is possible for ICMP messages that are originally transmitted inside of an LSP to "fall out of the LSP" at some point along the path. In these cases, since ICMP packets are routable, a falsely positive response may be returned. In other cases, where the data plane of a specific LSP needs to be tested, it is difficult to guarantee that traffic based on an ICMP ping header is parsed and hashed to the same equal-cost multi-paths (ECMP) as the data traffic.

尽管基于ICMP的ping[RFC792]可以作为IP有效负载通过LSP发送,但由于多种原因,使用此工具验证LSP的无缺陷操作有可能返回错误结果(正面和负面)。例如,在某些情况下,由于ICMP流量基于合法可寻址的IP寻址,因此最初在LSP内部传输的ICMP消息可能在路径上的某个点“脱离LSP”。在这些情况下,由于ICMP数据包是可路由的,因此可能会返回错误的肯定响应。在其他情况下,在需要测试特定LSP的数据平面的情况下,很难保证基于ICMP ping报头的流量被解析并散列到与数据流量相同的等成本多路径(ECMP)。

Any detection mechanisms that depend on receiving the status via a return path SHOULD provide multiple return options with the expectation that one of them will not be impacted by the original


defect. An example of a case where a false negative might occur would be a mechanism that requires a functional MPLS return path. Since MPLS LSPs are unidirectional, it is possible that although the forward LSP, which is the LSP under test, might be functioning, the response from the destination LSR might be lost, thus giving the source LSR the false impression that the forward LSP is defective. However, if an alternate return path could be specified -- say IP for example -- then the source could specify this as the return path to the destination, and in this case, would receive a response indicating that the return LSP is defective.

缺点可能出现假阴性的情况的一个示例是需要功能性MPLS返回路径的机制。由于MPLS LSP是单向的,因此尽管前向LSP(即被测LSP)可能正在工作,但来自目的地LSR的响应可能丢失,从而给源LSR留下前向LSP有缺陷的错误印象。但是,如果可以指定备用返回路径(例如IP),则源可以将其指定为到目标的返回路径,在这种情况下,将收到一个指示返回LSP有缺陷的响应。

The OAM packet MUST follow the customer data path exactly in order to reflect path liveliness used by customer data. Particular cases of interest are forwarding mechanisms, such as ECMP scenarios within the operator's network, whereby flows are load-shared across parallel paths (i.e., equal IGP cost). Where the customer traffic may be spread over multiple paths, the ability to detect failures on any of the path permutations is required. Where the spreading mechanism is payload specific, payloads need to have forwarding that is common with the traffic under test. Satisfying these requirements introduces complexity into ensuring that ECMP connectivity permutations are exercised and that defect detection occurs in a reasonable amount of time.


4.2. Diagnosis of a Broken Label Switched Path
4.2. 标签交换路径断裂的诊断

The ability to diagnose a broken LSP and to isolate the failed component (i.e., link or node) in the path is required. For example, note that specifying recovery actions for mis-branching defects in an LDP network is a particularly difficult case. Diagnosis of defects and isolation of the failed component is best accomplished via a path trace function that can return the entire list of LSRs and links used by a certain LSP (or at least the set of LSRs/links up to the location of the defect). The tracing capability SHOULD include the ability to trace recursive paths, such as when nested LSPs are used. This path trace function MUST also be capable of diagnosing LSP mis-merging by permitting comparison of expected vs. actual forwarding behavior at any LSR in the path. The path trace capability SHOULD be capable of being executed from the head-end Label Switching Router (LSR) and may permit downstream path components to be traced from an intermediate mid-point LSR. Additionally, the path trace function MUST have the ability to support ECMP scenarios described in Section 4.1.


4.3. Path Characterization
4.3. 路径表征

The path characterization function is the ability to reveal details of LSR forwarding operations. These details can then be compared during subsequent testing relevant to OAM functionality. This includes but is not limited to:


- consistent use of pipe or uniform time to live (TTL) models by an LSR [RFC3443].

- LSR一致使用管道或统一生存时间(TTL)模型[RFC3443]。

- sufficient details that allow the test origin to exercise all path permutations related to load spreading (e.g., ECMP).

- 足够详细的信息,允许测试原点执行与负载扩展相关的所有路径排列(例如ECMP)。

- stack operations performed by the LSR, such as pushes, pops, and TTL propagation at penultimate hop LSRs.

- LSR执行的堆栈操作,如倒数第二跳LSR的推送、pops和TTL传播。

4.4. Service Level Agreement Measurement
4.4. 服务水平协议度量

Mechanisms are required to measure the diverse aspects of Service Level Agreements, which include:


- latency - amount of time required for traffic to transit the network

- 延迟-流量通过网络所需的时间量

- packet loss

- 丢包

- jitter - measurement of latency variation

- 抖动-延迟变化的测量

- defect free forwarding - the service is considered to be available, or the service is unavailable and other aspects of performance measurement do not have meaning.

- 无缺陷转发-服务被视为可用,或服务不可用,而性能度量的其他方面没有意义。

Such measurements can be made independently of the user traffic or via a hybrid of user traffic measurement and OAM probing.


At least one mechanism is required to measure the number of OAM packets. In addition, the ability to measure the quantitative aspects of LSPs, such as jitter, delay, latency, and loss, MUST be available in order to determine whether the traffic for a specific LSP is traveling within the operator-specified tolerances.


Any method considered SHOULD be capable of measuring the latency of an LSP with minimal impact on network resources. See Section 2.1 for definitions of the various quantitative aspects of LSPs.


4.5. Frequency of OAM Execution
4.5. 执行OAM的频率

The operator MUST have the flexibility to configure OAM parameters to meet their specific operational requirements.


This includes the frequency of the execution of any OAM functions. The ability to synchronize OAM operations is required to permit a consistent measurement of service level agreements. To elaborate, there are defect conditions, such as mis-branching or misdirection of traffic, for which probe-based detection mechanisms that incur significant mismatches in their detection frequency may result in flapping. This can be addressed either by synchronizing the rate or having the probes self-identify their probe rate. For example, when the probing mechanisms are bootstrapping, they might negotiate and ultimately agree on a probing rate, therefore providing a consistent probing frequency and avoiding the aforementioned problems.


One observation would be that wide-spread deployment of MPLS, common implementation of monitoring tools, and the need for inter-carrier synchronization of defect and service level specification handling will drive specification of OAM parameters to commonly agreed on values. Such values will have to be harmonized with the surrounding technologies (e.g., SONET/SDH, ATM) to be useful. This will become particularly important as networks scale and mis-configuration can result in churn, alarm flapping, etc.


4.6. Alarm Suppression, Aggregation, and Layer Coordination
4.6. 报警抑制、聚合和层协调

Network elements MUST provide alarm suppression functionality that prevents the generation of a superfluous generation of alarms by simply discarding them (or not generating them in the first place), or by aggregating them together, thereby greatly reducing the number of notifications emitted. When viewed in conjunction with the requirement in Section 4.7 below, this typically requires fault notification to the LSP egress that may have specific time constraints if the application using the LSP independently implements path continuity testing (for example, ATM I.610 Continuity check (CC)[I610]). These constraints apply to LSPs that are monitored. The nature of MPLS applications allows for the possibility of having multiple MPLS applications attempt to respond to defects simultaneously, e.g., layer-3 MPLS VPNs that utilize Traffic Engineered tunnels where a failure occurs on the LSP carrying the Traffic Engineered tunnel. This failure would affect the VPN traffic that uses the tunnel's LSP. Mechanisms are required to coordinate network responses to defects.

网络元件必须提供报警抑制功能,通过简单地丢弃报警(或不首先生成报警)或将其聚合在一起,从而大大减少发出的通知数量,从而防止生成多余的报警。当结合下面第4.7节中的要求查看时,这通常需要向LSP出口发出故障通知,如果使用LSP的应用程序独立地执行路径连续性测试(例如,ATM I.610连续性检查(CC)[I610]),则LSP出口可能具有特定的时间限制。这些约束适用于受监视的LSP。MPLS应用程序的性质允许多个MPLS应用程序尝试同时响应缺陷的可能性,例如,第3层MPLS VPN利用流量工程隧道,其中在承载流量工程隧道的LSP上发生故障。此故障将影响使用隧道LSP的VPN流量。需要机制来协调网络对缺陷的响应。

4.7. Support for OAM Inter-working for Fault Notification
4.7. 支持用于故障通知的OAM互操作

An LSR supporting the inter-working of one or more networking technologies over MPLS MUST be able to translate an MPLS defect into the native technology's error condition. For example, errors occurring over an MPLS transport LSP that supports an emulated ATM VC MUST translate errors into native ATM OAM Alarm Indication Signal (AIS) cells at the termination points of the LSP. The mechanism SHOULD consider possible bounded detection time parameters, e.g., a "hold off" function before reacting to synchronize with the OAM functions.

支持MPLS上一种或多种网络技术交互工作的LSR必须能够将MPLS缺陷转化为本机技术的错误状况。例如,在支持模拟ATM VC的MPLS传输LSP上发生的错误必须在LSP的终止点将错误转换为本机ATM OAM报警指示信号(AIS)信元。该机制应考虑可能的有界检测时间参数,例如,在与OAM功能同步之前,先进行“暂存”功能。

One goal would be alarm suppression by the upper layer using the LSP. As observed in Section 4.5, this requires that MPLS perform detection in a bounded timeframe in order to initiate alarm suppression prior to the upper layer independently detecting the defect.


4.8. Error Detection and Recovery
4.8. 错误检测与恢复

Recovery from a fault by a network element can be facilitated by MPLS OAM procedures. These procedures will detect a broader range of defects than that of simple link and node failures. Since MPLS LSPs may span multiple routing areas and service provider domains, fault recovery and error detection should be possible in these configurations as well as in the more simplified single-area/domain configurations.

通过MPLS OAM过程,可以促进网元从故障中恢复。这些程序将检测到比简单链路和节点故障更广泛的缺陷。由于MPLS LSP可能跨越多个路由区域和服务提供商域,因此在这些配置以及更简化的单区域/域配置中,故障恢复和错误检测应该是可能的。

Recovery from faults SHOULD be automatic. It is a requirement that faults SHOULD be detected (and possibly corrected) by the network operator prior to customers of the service in question detecting them.


4.9. Standard Management Interfaces
4.9. 标准管理界面

The wide-spread deployment of MPLS requires common information modeling of management and control of OAM functionality. Evidence of this is reflected in the standard IETF MPLS-related MIB modules (e.g., [RFC3813][RFC3812][RFC3814]) for fault, statistics, and configuration management. These standard interfaces provide operators with common programmatic interface access to Operations and Management functions and their statuses. However, gaps in coverage of MIB modules to OAM and other features exist; therefore, MIB modules corresponding to new protocol functions or network tools are required.

MPLS的广泛部署要求对OAM功能的管理和控制进行公共信息建模。故障、统计和配置管理的标准IETF MPLS相关MIB模块(例如,[RFC3813][RFC3812][RFC3814])反映了这一点。这些标准接口为操作员提供对操作和管理功能及其状态的公共编程接口访问。然而,MIB模块对OAM和其他功能的覆盖范围存在差距;因此,需要与新协议功能或网络工具相对应的MIB模块。

4.10. Detection of Denial of Service Attacks
4.10. 拒绝服务攻击的检测

The ability to detect denial of service (DoS) attacks against the data or control planes MUST be part of any security management related to MPLS OAM tools or techniques.

检测针对数据或控制平面的拒绝服务(DoS)攻击的能力必须是与MPLS OAM工具或技术相关的任何安全管理的一部分。

4.11. Per-LSP Accounting Requirements
4.11. 根据LSP会计要求

In an MPLS network, service providers can measure traffic from an LSR to the egress of the network using some MPLS related MIBs, for example. This means that it is reasonable to know how much traffic is traveling from location to location (i.e., a traffic matrix) by analyzing the flow of traffic. Therefore, traffic accounting in an MPLS network can be summarized as the following three items:


(1) Collecting information to design network

(1) 收集信息设计网络

For the purpose of optimized network design, a service provider may offer the traffic information. Optimizing network design needs this information.


(2) Providing a Service Level Specification

(2) 提供服务级别规范

Providers and their customers MAY need to verify high-level service level specifications, either to continuously optimize their networks, or to offer guaranteed bandwidth services. Therefore, traffic accounting to monitor MPLS applications is required.


(3) Inter-AS environment

(3) 内部AS环境

Service providers that offer inter-AS services require accounting of those services.


These three motivations need to satisfy the following:


- In (1) and (2), collection of information on a per-LSP basis is a minimum level of granularity for collecting accounting information at both of ingress and egress of an LSP.

- 在(1)和(2)中,基于每个LSP的信息收集是在LSP入口和出口收集会计信息的最小粒度级别。

- In (3), SP's ASBR carry out interconnection functions as an intermediate LSR. Therefore, identifying a pair of ingress and egress LSRs using each LSP is needed to determine the cost of the service that a customer is using.

- 在(3)中,SP的ASBR作为中间LSR执行互连功能。因此,需要使用每个LSP识别一对入口和出口lsr来确定客户正在使用的服务的成本。

4.11.1. Requirements
4.11.1. 要求

Accounting on a per-LSP basis encompasses the following set of functions:


(1) At an ingress LSR, accounting of traffic through LSPs that begin at each egress in question.

(1) 在入口LSR处,通过LSP的流量核算,该LSP从所讨论的每个出口开始。

(2) At an intermediate LSR, accounting of traffic through LSPs for each pair of ingress to egress.

(2) 在中间LSR,对每对进出口通过LSP的流量进行核算。

(3) At egress LSR, accounting of traffic through LSPs for each ingress.

(3) 在出口LSR处,对每个入口通过LSP的流量进行核算。

(4) All LSRs containing LSPs that are being measured need to have a common identifier to distinguish each LSP. The identifier MUST be unique to each LSP, and its mapping to LSP SHOULD be provided whether from manual or automatic configuration.

(4) 所有包含正在测量的LSP的LSR都需要有一个公共标识符来区分每个LSP。标识符对于每个LSP都必须是唯一的,无论是手动配置还是自动配置,都应提供其到LSP的映射。

In the case of non-merged LSPs, this can be achieved by simply reading traffic counters for the label stack associated with the LSP at any LSR along its path. However, in order to measure merged LSPs, an LSR MUST have a means to distinguish the source of each flow so as to disambiguate the statistics.


4.11.2. Location of Accounting
4.11.2. 会计地点

It is not realistic for LSRs to perform the described operations on all LSPs that exist in a network. At a minimum, per-LSP based accounting SHOULD be performed on the edges of the network -- at the edges of both LSPs and the MPLS domain.


5. Security Considerations
5. 安全考虑

Provisions to any of the network mechanisms designed to satisfy the requirements described herein are required to prevent their unauthorized use. Likewise, these network mechanisms MUST provide a means by which an operator can prevent denial of service attacks if those network mechanisms are used in such an attack.


LSP mis-merging has security implications beyond that of simply being a network defect. LSP mis-merging can happen due to a number of potential sources of failure, some of which (due to MPLS label stacking) are new to MPLS.


The performance of diagnostic functions and path characterization involve extracting a significant amount of information about network construction that the network operator MAY consider private.


6. References
6. 工具书类
6.1. Normative References
6.1. 规范性引用文件

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2119]Bradner,S.,“RFC中用于表示需求水平的关键词”,BCP 14,RFC 2119,1997年3月。

6.2. Informative References
6.2. 资料性引用

[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.

[RFC4379]Kompella,K.和G.Swallow,“检测多协议标签交换(MPLS)数据平面故障”,RFC 4379,2006年2月。

[RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau, "Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Management Information Base (MIB)", RFC 3812, June 2004.

[RFC3812]Srinivasan,C.,Viswanathan,A.,和T.Nadeau,“多协议标签交换(MPLS)流量工程(TE)管理信息库(MIB)”,RFC 3812,2004年6月。

[RFC3813] Srinivasan, C., Viswanathan, A., and T. Nadeau, "Multiprotocol Label Switching (MPLS) Label Switching Router (LSR) Management Information Base (MIB)", RFC 3813, June 2004.

[RFC3813]Srinivasan,C.,Viswanathan,A.,和T.Nadeau,“多协议标签交换(MPLS)标签交换路由器(LSR)管理信息库(MIB)”,RFC 38132004年6月。

[RFC3814] Nadeau, T., Srinivasan, C., and A. Viswanathan, "Multiprotocol Label Switching (MPLS) Forwarding Equivalence Class To Next Hop Label Forwarding Entry (FEC-To-NHLFE) Management Information Base (MIB)", RFC 3814, June 2004.

[RFC3814]Nadeau,T.,Srinivasan,C.,和A.Viswanathan,“多协议标签交换(MPLS)转发等价类到下一跳标签转发条目(FEC到NHLFE)管理信息库(MIB)”,RFC 3814,2004年6月。

[Y1710] ITU-T Recommendation Y.1710, "Requirements for OAM Functionality In MPLS Networks"


[I610] ITU-T Recommendation I.610, "B-ISDN operations and maintenance principles and functions", February 1999


[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

[RFC2434]Narten,T.和H.Alvestrand,“在RFCs中编写IANA注意事项部分的指南”,BCP 26,RFC 2434,1998年10月。

[RFC792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981.

[RFC792]Postel,J.,“互联网控制消息协议”,STD 5,RFC 792,1981年9月。

[RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, January 2003.

[RFC3443]Agarwal,P.和B.Akyol,“多协议标签交换(MPLS)网络中的生存时间(TTL)处理”,RFC 3443,2003年1月。

7. Acknowledgements
7. 致谢

The authors wish to acknowledge and thank the following individuals for their valuable comments to this document: Adrian Smith, British Telecom; Chou Lan Pok, SBC; Mr. Ikejiri, NTT Communications; and Mr. Kumaki, KDDI. Hari Rakotoranto, Miya Kohno, Cisco Systems; Luyuan Fang, AT&T; Danny McPherson, TCB; Dr. Ken Nagami, Ikuo Nakagawa, Intec Netcore, and David Meyer.

作者希望感谢以下个人对本文件的宝贵意见:Adrian Smith,英国电信;周兰博,SBC,;Ikejiri先生,NTT通信公司;和KDDI Kumaki先生。Hari Rakotoranto、Miya Kohno、思科系统公司;美国电话电报公司(AT&T)方绿园,;丹尼·麦克弗森,TCB;Ken Nagami博士、Ikuo Nakagawa、Intec Netcore和David Meyer。

Authors' Addresses


Comments should be made directly to the MPLS mailing list at


Thomas D. Nadeau Cisco Systems, Inc. 300 Beaver Brook Road Boxboro, MA 01719

Thomas D.Nadeau Cisco Systems,Inc.马萨诸塞州Boxboro市比弗布鲁克路300号,邮编01719

   Phone: +1-978-936-1470
   Phone: +1-978-936-1470

Monique Jeanne Morrow Cisco Systems, Inc. Glatt-Com, 2nd Floor CH-8301 Switzerland

Monique Jeanne Morrow思科系统有限公司Glatt Com二楼瑞士CH-8301

Phone: (0)1 878-9412 EMail:


George Swallow Cisco Systems, Inc. 300 Beaver Brook Road Boxboro, MA 01719


   Phone: +1-978-936-1398
   Phone: +1-978-936-1398

David Allan Nortel Networks 3500 Carling Ave. Ottawa, Ontario, CANADA


Phone: 1-613-763-6362 EMail:


Satoru Matsushima Japan Telecom 1-9-1, Higashi-Shinbashi, Minato-ku Tokyo, 105-7316 Japan


   Phone: +81-3-6889-1092
   Phone: +81-3-6889-1092

Full Copyright Statement


Copyright (C) The Internet Society (2006).


This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.

本文件受BCP 78中包含的权利、许可和限制的约束,除其中规定外,作者保留其所有权利。



Intellectual Property


The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.

IETF对可能声称与本文件所述技术的实施或使用有关的任何知识产权或其他权利的有效性或范围,或此类权利下的任何许可可能或可能不可用的程度,不采取任何立场;它也不表示它已作出任何独立努力来确定任何此类权利。有关RFC文件中权利的程序信息,请参见BCP 78和BCP 79。

Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at


The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at




Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA).