Network Working Group P. Pillay-Esnault
Request for Comments: 4136 Cisco Systems
Category: Informational July 2005
Network Working Group P. Pillay-Esnault
Request for Comments: 4136 Cisco Systems
Category: Informational July 2005
OSPF Refresh and Flooding Reduction in Stable Topologies
稳定拓扑中的OSPF刷新和洪泛减少
Status of This Memo
关于下段备忘
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 (2005).
版权所有（C）互联网协会（2005年）。
Abstract
摘要
This document describes an extension to the OSPF protocol to reduce periodic flooding of Link State Advertisements (LSAs) in stable topologies.
本文档描述了OSPF协议的扩展，以减少稳定拓扑中链路状态播发（LSA）的周期性泛滥。
Current OSPF behavior requires that all LSAs, except DoNotAge LSAs, to be refreshed every 30 minutes. This document proposes to generalize the use of DoNotAge LSAs in order to reduce protocol traffic in stable topologies.
当前OSPF行为要求所有LSA（DoNotAge LSA除外）每30分钟刷新一次。本文建议推广DoNotAge LSA的使用，以减少稳定拓扑中的协议流量。
The explosive growth of IP-based networks has placed focus on the scalability of Interior Gateway Protocols such as OSPF. Networks using OSPF are growing every day and will continue to expand to accommodate the demand for connections to the Internet or intranets.
基于IP的网络的爆炸性增长将焦点放在内部网关协议（如OSPF）的可扩展性上。使用OSPF的网络每天都在增长，并将继续扩展，以满足连接到Internet或内部网的需求。
Internet Service Providers and users that have large networks have noticed non-negligible protocol traffic, even when their network topologies were stable.
互联网服务提供商和拥有大型网络的用户已经注意到不可忽略的协议流量，即使他们的网络拓扑是稳定的。
OSPF requires every LSA to be refreshed every 1800 seconds or else they will expire when they reach 3600 seconds [1].
OSPF要求每个LSA每1800秒刷新一次，否则它们将在达到3600秒时过期[1]。
This document proposes to overcome the LSA expiration by generalizing the use of DoNotAge LSAs. This technique will facilitate OSPF scaling by reducing OSPF traffic overhead in stable topologies.
本文档建议通过推广使用DoNotAge LSA来克服LSA过期问题。该技术将通过减少稳定拓扑中的OSPF通信开销来促进OSPF扩展。
This enhancement relies on the implementation of the DoNotAge bit and the Indication-LSA. The details of the implementation of the DoNotAge bit and the Indication-LSA are specified in "Extending OSPF to Support Demand Circuits" [2].
此增强依赖于DoNotAge位和指示LSA的实现。“扩展OSPF以支持需求电路”[2]中规定了DoNotAge位和指示LSA的实现细节。
Flooding-reduction-capable routers will continue to send hellos to their neighbors and keep aging their self-originated LSAs in their database. However, these routers will flood their self-originated LSAs with the DoNotAge bit set. Thus, self-originated LSAs do not have to be re-flooded every 30 minutes and the re-flooding interval can be extended to the configured forced-flooding interval. As in normal OSPF operation, any change in the contents of the LSA will cause a reoriginated LSA to be flooded with the DoNotAge bit set. This will reduce protocol traffic overhead while allowing changes to be flooded immediately.
具有洪水减少能力的路由器将继续向其邻居发送HELOS，并在其数据库中不断老化其自主生成的LSA。然而，这些路由器将使用DoNotAge位集淹没其自源LSA。因此，自创LSA不必每30分钟重新注水一次，并且可以将重新注水间隔延长到配置的强制注水间隔。与正常OSPF操作一样，LSA内容的任何更改都将导致重新定序的LSA充满DoNotAge位集。这将减少协议通信开销，同时允许立即淹没更改。
Flooding-reduction-capable routers will flood received non-self-originated LSAs with the DoNotAge bit set on all normal or flooding-reduction-only interfaces within the LSA's flooding scope. If an interface is configured as both flooding-reduction-capable and Demand-Circuit, then the flooding is done if and only if the contents of the LSA have changed. This allows LSA flooding for unchanged LSAs to be periodically forced by the originating router.
具有泛洪抑制能力的路由器将泛洪接收到的非自创LSA，并在LSA泛洪范围内的所有正常或仅泛洪抑制接口上设置DoNotAge位。如果一个接口被配置为具有泛洪抑制能力和需求电路，则当且仅当LSA的内容发生变化时，才会进行泛洪。这允许原始路由器周期性地强制对未更改的LSA进行LSA泛洪。
Routers supporting the demand circuit extensions [2] will be able to correctly process DoNotAge LSAs flooded by routers supporting the flooding reduction capability described herein. These routers will also suppress flooding DoNotAge LSAs on interfaces configured as demand circuits. However, they will also flood DoNotAge LSAs on interfaces that are not configured as demand circuits.
支持需求电路扩展[2]的路由器将能够正确处理由支持本文所述的泛洪减少能力的路由器泛洪的DoNotAge lsa。这些路由器还将抑制配置为需求电路的接口上的泛洪DoNotAge LSA。但是，它们也会在未配置为需求电路的接口上使用DoNotAge LSA。
When there are routers in the OSPF routing domain, stub area, or NSSA area, that do not support the demand circuit extensions [2] then the use of these flooding reduction capabilities will be subject to the demand circuit interoperability constraints articulated in section 2.5 of "Extending OSPF to Support Demand Circuits" [2]. This implies that detection of an LSA, with the DC bit clear, will result in the re-origination of self-originated DoNotAge LSAs with the DoNotAge clear and purging of non-self-originated DoNotAge LSAs.
当OSPF路由域、存根区域或NSSA区域中存在不支持需求电路扩展的路由器[2]时，这些泛洪抑制能力的使用将受到“扩展OSPF以支持需求电路”[2]第2.5节中阐述的需求电路互操作性约束的约束。这意味着在DC位清除的情况下检测LSA将导致使用DoNotAge clear重新生成自源DoNotAge LSA，并清除非自源DoNotAge LSA。
This memo does not create any new security issues for the OSPF protocol. Security considerations for the base OSPF protocol are covered in [1].
此备忘录不会给OSPF协议带来任何新的安全问题。[1]中介绍了基本OSPF协议的安全注意事项。
The author would like to thank Jean-Michel Esnault, Barry Friedman, Thomas Kramer, Acee Lindem, Peter Psenak, Henk Smit, and Alex Zinin for their helpful comments on this work.
作者要感谢Jean-Michel Esnault、Barry Friedman、Thomas Kramer、Acee Lindem、Peter Psenak、Henk Smit和Alex Zinin对这项工作的有益评论。
[1] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[1] Moy，J.，“OSPF版本2”，STD 54，RFC 23281998年4月。
[2] Moy, J., "Extending OSPF to Support Demand Circuits", RFC 1793, April 1995.
[2] Moy，J.，“扩展OSPF以支持需求电路”，RFC 1793，1995年4月。
A. Configurable Parameters
A.可配置参数
This memo defines new configuration parameters for the flooding reduction feature. The feature must be enabled by configuration on a router and is, by default, off.
此备忘录定义了洪水减少功能的新配置参数。该功能必须通过路由器上的配置启用，并且默认情况下处于关闭状态。
flooding-reduction <all | list of interfaces> Indicates that the router has the flooding reduction feature enabled. By default, this parameter applies to all interfaces running under the OSPF instance to which it applies. The feature can be enabled on a subset of explicitly specified interfaces.
泛洪减少<所有|接口列表>表示路由器启用了泛洪减少功能。默认情况下，此参数适用于在其应用的OSPF实例下运行的所有接口。可以在显式指定接口的子集上启用该功能。
flooding-interval <n minutes> Indicates the interval in minutes for the periodic flooding of self-originated LSAs. By default, this value is 30 minutes as per [1]. The minimum value is also 30 minutes. A value of infinity will prevent re-flooding of self-originated LSAs that have not changed.
泛洪间隔<n分钟>表示自发LSA周期性泛洪的间隔（分钟）。根据[1]，默认情况下，此值为30分钟。最小值也是30分钟。值为无穷大将防止未更改的自创LSA再次泛滥。
Author's Address
作者地址
Padma Pillay-Esnault Cisco Systems 170 W. Tasman Drive San Jose, CA 95134
帕德玛·皮莱·埃斯纳尔特思科系统有限公司加利福尼亚州圣何塞塔斯曼大道西170号，邮编95134
EMail: ppe@cisco.com
EMail: ppe@cisco.com
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