Network Working Group L. Berger
Request for Comments: 4003 Movaz Networks
Updates: 3473 February 2005
Category: Standards Track
Network Working Group L. Berger
Request for Comments: 4003 Movaz Networks
Updates: 3473 February 2005
Category: Standards Track
GMPLS Signaling Procedure for Egress Control
出口控制的GMPLS信号程序
Status of This Memo
关于下段备忘
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2005).
版权所有（C）互联网协会（2005年）。
Abstract
摘要
This document clarifies the procedures for the control of the label used on an output/downstream interface of the egress node of a Label Switched Path (LSP). This control is also known as "Egress Control". Support for Egress Control is implicit in Generalized Multi-Protocol Label Switching (GMPLS) Signaling. This document clarifies the specification of GMPLS Signaling and does not modify GMPLS signaling mechanisms and procedures.
本文件阐明了标签交换路径（LSP）出口节点的输出/下游接口上使用的标签控制程序。该控制也称为“出口控制”。广义多协议标签交换（GMPLS）信令隐含了对出口控制的支持。本文件澄清了GMPLS信令规范，并未修改GMPLS信令机制和程序。
The ability to control the label used on the output/downstream interface of an egress node was one of the early requirements for GMPLS. In the initial GMPLS documents, this was called "Egress Control". As the GMPLS documents progressed, the ability to control a label on an egress interface was generalized to support control of a label on any interface. This generalization is seen in Section 6 of [RFC3471] and Section 5.1 of [RFC3473]. When this functionality was generalized, the procedures to support control of a label at the egress were also generalized. Although the result was intended to cover egress control, this intention is not clear to all. This note reiterates the procedures to cover control of a label used on an egress output/downstream interface.
控制出口节点输出/下游接口上使用的标签的能力是GMPLS的早期要求之一。在最初的GMPLS文件中，这被称为“出口控制”。随着GMPLS文档的发展，控制出口接口上标签的能力被推广到支持控制任何接口上的标签。这一概括见[RFC3471]第6节和[RFC3473]第5.1节。当这个功能被推广时，支持在出口处控制标签的程序也被推广。虽然其结果旨在涵盖出口控制，但并非所有人都清楚这一意图。本说明重申了涵盖出口输出/下游接口上使用的标签控制的程序。
For context, the following is the text from the GMPLS signalling document dated June 2000 about how ERO (Explicit Route Object) for egress control:
以下是2000年6月GMPLS信令文件中关于如何使用ERO（显式路由对象）进行出口控制的文本：
6. Egress Control
6. 出口控制
The LSR at the head-end of an LSP can control the termination of the LSP by using the ERO. To terminate an LSP on a particular outgoing interface of the egress LSR, the head-end may specify the IP address of that interface as the last element in the ERO, provided that interface has an associated IP address.
LSP前端的LSR可以使用ERO控制LSP的终止。为了在出口LSR的特定输出接口上终止LSP，只要接口具有相关联的IP地址，则前端可以将该接口的IP地址指定为ERO中的最后一个元素。
There are cases where the use of IP address doesn't provide enough information to uniquely identify the egress termination. One case is when the outgoing interface on the egress LSR is a component link of a link bundle. Another case is when it is desirable to "splice" two LSPs together, i.e., where the tail of the first LSP would be "spliced" into the head of the second LSP. This last case is more likely to be used in the non-PSC classes of links.
在某些情况下，IP地址的使用不能提供足够的信息来唯一标识出口终端。一种情况是，出口LSR上的传出接口是链路包的组件链路。另一种情况是希望将两个LSP“拼接”在一起，即，第一LSP的尾部将“拼接”到第二LSP的头部。最后一种情况更可能用于非PSC类的链路。
6.2. Procedures
6.2. 程序
The Egress Label subobject may appear only as the last subobject in the ERO/ER. Appearance of this subobject anywhere else in the ERO/ER is treated as a "Bad strict node" error.
出口标签子对象只能作为ERO/ER中的最后一个子对象出现。此子对象在ERO/ER中任何其他位置的外观都被视为“错误严格节点”错误。
During an LSP setup, when a node processing the ERO/RR performs Next Hop selection finds that the second subobject is an Egress Label Subobject, the node uses the information carried in this subobject to determine the handling of the data received over that LSP. Specifically, if the Link ID field of the subobject is non zero, then this field identifies a specific (outgoing) link of the node that should be used for sending all the data received over the LSP. If the Label field of the subobject is not Implicit NULL label, this field specifies the label that should be used as an outgoing label on the data received over the LSP.
在LSP设置期间，当处理ERO/RR的节点执行下一跳选择时发现第二个子对象是出口标签子对象，该节点使用该子对象中携带的信息来确定通过该LSP接收的数据的处理。具体地说，如果子对象的Link ID字段为非零，则该字段标识节点的特定（传出）链路，该链路应用于发送通过LSP接收的所有数据。如果子对象的标签字段不是隐式空标签，则此字段指定应在通过LSP接收的数据上用作传出标签的标签。
Procedures by which an LSR at the head-end of an LSP obtains the information needed to construct the Egress Label subobject are outside the scope of this document.
LSP前端的LSR获取构造出口标签子对象所需信息的过程不在本文档范围内。
This section is intended to complement Sections 5.1.1 and 5.2.1 of [RFC3473]. The procedures described in those sections are not modified. This section clarifies procedures related to the label used on an egress output/downstream interface.
本节旨在补充[RFC3473]第5.1.1节和第5.2.1节。这些章节中描述的程序不作修改。本节阐明了与出口输出/下游接口上使用的标签相关的程序。
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 [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
Egress Control occurs when the node processing an ERO is the egress and the ERO contains one or more subobjects related to the output/downstream interface. In this case, the outgoing/downstream interface is indicated in the ERO as the last listed local interface. Note that an interface may be numbered or unnumbered.
当处理ERO的节点是出口且ERO包含与输出/下游接口相关的一个或多个子对象时，发生出口控制。在这种情况下，输出/下游接口在ERO中指示为最后列出的本地接口。请注意，接口可以编号，也可以不编号。
To support Egress Control, an egress checks to see whether the received ERO contains an outgoing/downstream interface. If it does, the type of the subobject or subobjects following the interface is examined. If the associated LSP is unidirectional, one subobject is examined. Two subobjects are examined for bidirectional LSPs. If the U-bit of the subobject being examined is clear (0), then the value of the label MUST be used for transmitting traffic associated with the LSP on the indicated outgoing/downstream interface.
为了支持出口控制，出口检查以查看接收到的ERO是否包含输出/下游接口。如果是，则检查接口后面的一个子对象或多个子对象的类型。如果关联的LSP是单向的，则检查一个子对象。检查双向LSP的两个子对象。如果正在检查的子对象的U位为清除（0），则标签的值必须用于传输与所指示的输出/下游接口上的LSP相关联的通信量。
If the U-bit of the subobject being examined is set (1), then the value of the label is used for upstream traffic associated with the bidirectional LSP. Specifically, the label value will be used for the traffic associated with the LSP that will be received on the indicated outgoing/downstream interface.
如果正在检查的子对象的U位设置为（1），则标签的值用于与双向LSP相关联的上游流量。具体地说，标签值将用于与LSP相关联的通信量，该LSP将在指示的出站/下游接口上接收。
Per [RFC3473], any errors encountered while processing the ERO, including if the listed label(s) are not acceptable or cannot be supported in forwarding, SHOULD result in the generation of a PathErr message with the error code "Routing Error" and error value of "Bad Explicit Route Object".
根据[RFC3473]，处理ERO时遇到的任何错误，包括所列标签不可接受或转发时不受支持的错误，应导致生成错误代码为“路由错误”且错误值为“错误显式路由对象”的PathErr消息。
If an ERO is used to specify outgoing interface information at the egress and label recording is indicated for the LSP, the egress should include the specified interface information and the specified label or labels in the corresponding RRO (Route Record Object).
如果ERO用于指定出口处的输出接口信息，并且为LSP指示了标签记录，则出口应包括指定的接口信息以及相应RRO（路由记录对象）中的指定标签。
This document clarifies procedures defined in [RFC3473] but does not define any new procedures. As such, no new security considerations are introduced.
本文件澄清了[RFC3473]中定义的程序，但未定义任何新程序。因此，没有引入新的安全注意事项。
Valuable comments and input were received from Adrian Farrel, Alan Kullberg, and Dimitri Papadimitriou.
Adrian Farrel、Alan Kullberg和Dimitri Papadimitriou提出了宝贵的意见和建议。
[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。
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003.
[RFC3471]Berger，L.“通用多协议标签交换（GMPLS）信令功能描述”，RFC 3471，2003年1月。
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3473]Berger，L.“通用多协议标签交换（GMPLS）信令资源预留协议流量工程（RSVP-TE）扩展”，RFC 3473，2003年1月。
Author's Address
作者地址
Lou Berger Movaz Networks, Inc. 7926 Jones Branch Drive Suite 615 McLean VA, 22102
Lou Berger Movaz Networks，Inc.地址：弗吉尼亚州麦克莱恩市琼斯支路615号7926室，邮编：22102
Phone: +1 703 847-1801
EMail: lberger@movaz.com
Phone: +1 703 847-1801
EMail: lberger@movaz.com
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