Network Working Group Justin Fletcher Internet Draft Proficient Networks Expiration Date: July 2003 Inactive Path Advertisement in BGP-4 draft-fletcher-bgp-inactive-path-00.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Abstract This document defines BGP capabilities and a path attribute to permit advertisement of routes other than those selected during the BGP decision process. These extensions would provide additional routing information for research, monitoring and policy decisions. 1. Introduction BGP [BGP-4] as currently defined advertises only routes to BGP peers selected through the decision process. These advertised routes, known as the active path, provide an incomplete view of a BGP peer's knowledge of network adjacency; additional routes may be present in the Adj-RIBs-In which have not been selected by the decision process, otherwise known as the inactive path. Advertisement of a peer's complete set of active and inactive paths will provide additional information for route servers, research, monitoring and policy Fletcher [Page 1] Internet Draft Inactive Path Advertisement in BGP-4 January 2003 decisions. The INACTIVE_PATH Path Attribute and Inactive Path Capabilities are defined to identify advertised routes on an inactive path and routers capable of processing such routes. A potential application in a production network would be for a provider to selectively advertise as inactive paths a customer's CIDR ranges back to them. This would allow the customer to see advertised routes after provider processing for troubleshooting purposes. Outbound filtering may be applied to constrain the visibility of specific attributes. 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]. 2. Path Attribute INACTIVE_PATH is an optional non-transitive attribute of length 0; the type code for this attribute is specified in the "IANA Considerations" section of this document. It is used by a BGP speaker to inform other BGP speakers that the advertised route is not advertised as a result of the BGP decision process. As such, it MUST NOT be considered in the listener's decision process and MUST NOT be re-advertised. 3. Inactive Path Capabilities The Inactive Path Capabilities are two new BGP capabilities [BGP- CAP]. The Capability Code for both of these Capabilities are specified in the "IANA Considerations" section of this document. The Capability Length field of both Capabilities is set to 0. By advertising the Inactive Path Send Capability to a peer in the OPEN, a BGP speaker informs the peer that the speaker is capable of sending UPDATE messages containing routes with the INACTIVE_PATH attribute set. By advertising the Inactive Path Receive Capability to a peer in the OPEN, a BGP speaker informs the peer that the speaker is capable of processing UPDATE messages containing routes with the INACTIVE_PATH attribute set. Fletcher [Page 2] Internet Draft Inactive Path Advertisement in BGP-4 January 2003 4. Configuration When Inactive Path Capabilities are supported, a configuration option MUST be provided specifying whether inactive path routes are to be advertised or received on a per-peer basis. The default configuration for this option MUST be to advertise or receive only active path routes. 5. Route Advertisement Routes are selected for advertisement through the BGP decision process. When is option is enabled, the routes that were not selected through the decision process are processed into the associated Adj-RIBs-Out with the INACTIVE_PATH attribute set including applicable filtering and route processing performed by the BGP peer. Outbound filters are then applied and the resultant Adj- RIBs-Out are advertised to the BGP peers. Routes containing the INACTIVE_PATH attribute set MUST NOT be sent unless the speaker has sent the Inactive Path Send Capability and the listener has sent the Inactive Path Receive Capability in the corresponding OPEN messages. References [BGP-4] Y. Rekhter, and T. Li, "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, March 1995. [BGP-CAP] R. Chandra, J. Scudder, "Capabilities Advertisement with BGP-4", RFC 2842, May 2000. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Security Considerations These extensions to BGP do not change the underlying security issues. IANA Considerations This document uses a BGP Capability Code to indicate that a BGP speaker supports the Inactive Path Capability and a Attribute Type to indicate an advertised inactive path. The Capability Code and Attribute Type must be assigned by IANA per RFC 2842. Fletcher [Page 3] Internet Draft Inactive Path Advertisement in BGP-4 January 2003 Acknowledgments The author would like to thank Robert Bays and Bruce Pinsky for providing invaluable insight and expertise. Author Information Justin Fletcher Proficient Networks 300 California Suite 500 San Francisco, CA 94104 e-mail: jfletcher@proficient.net Fletcher [Page 4]