HTTP/1.1 200 OK Date: Tue, 09 Apr 2002 03:10:03 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Mon, 27 Apr 1998 14:29:00 GMT ETag: "2edbb7-18c2-3544962c" Accept-Ranges: bytes Content-Length: 6338 Connection: close Content-Type: text/plain Network Working Group Ravi Chandra Internet Draft Cisco Systems Expiration Date: October 1998 John G. Scudder Internet Engineering Group, LLC Capabilities Negotiation with BGP-4 draft-ietf-idr-bgp4-cap-neg-01.txt 1. Status of this Memo This document is an Internet-Draft. 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.'' To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). 2. Abstract Currently BGP-4 [BGP-4] requires that when a BGP speaker receives an OPEN message with one or more unrecognized Optional Parameters, the speaker must terminate BGP peering. This complicates introduction of new capabilities in BGP. This document defines new Optional Parameter, called Capabilities, that is expected to facilitate introduction of new capabilities in BGP by providing graceful capability negotiation without requiring that BGP peering be terminated. The proposed parameter is backward compatible - a router that supports the parameter can maintain BGP peering with a router that doesn't support the parameter. Chandra, Scudder [Page 1] Internet Draft draft-ietf-idr-bgp4-cap-neg-01.txt April 1998 3. Overview of Operations When a BGP speaker that supports capabilities negotiation sends an OPEN message to its BGP peer, the message may include an Optional Parameter, called Capabilities. The parameter lists the capabilities supported by the speaker. A BGP speaker may use a particular capability when peering with another speaker only if both speakers support that capability. A BGP speaker determines the capabilities supported by its peer by examining the list of capabilities present in the Capabilities Optional Parameter carried by the OPEN message that the speaker receives from the peer. A BGP speaker determines that its peer doesn't support capabilities negotiation, if in response to an OPEN message that carries the Capabilities Optional Parameter, the speaker receives a NOTIFICATION message with the Error Subcode set to Unsupported Optional Parameter. If a BGP speaker that supports a certain capability determines that its peer doesn't support this capability, the speaker may send a NOTIFICATION message to the peer, and terminate peering. The Error Subcode in the message is set to Unsupported Capability. The message should contain the capability (capabilities) that causes the speaker to send the message. The decision to send the message is local to the speaker. 4. Capabilities Optional Parameter (Parameter Type 2): This is an Optional Parameter that is used by a BGP speaker to convey to its BGP peer the list of capabilities supported by the speaker. The parameter contains one or more triples , where each triple is encoded as shown below: +------------------------------+ | Capability Code (1 octet) | +------------------------------+ | Capability Length (1 octet) | +------------------------------+ | Capability Value (variable) | +------------------------------+ Chandra, Scudder [Page 2] Internet Draft draft-ietf-idr-bgp4-cap-neg-01.txt April 1998 The use and meaning of these fields are as follows: Capability Code: Capability Code is a one octet field that unambiguously identifies individual capabilities. Capability Length: Capability Length is a one octet field that contains the length of the Capability Value field in octets. Capability Value: Capability Value is a variable length field that is interpreted according to the value of the Capability Code field. A particular capability, as identified by its Capability Code, may occur more than once within the Optional Parameter. This document reserves Capability Codes 128-255 for vendor-specific applications. This document reserves value 0. Capability Codes (other than those reserved for vendor specific use) are assigned only by the IETF consensus process and IESG approval. 5. Extensions to Error Handling This document defines new Error Subcode - Unsupported Capability. The value of this Subcode is 7. The Data field in the NOTIFICATION message lists the set of capabilities that cause the speaker to send the message. Each such capability is encoded the same way as it was encoded in the received OPEN message. Chandra, Scudder [Page 3] Internet Draft draft-ietf-idr-bgp4-cap-neg-01.txt April 1998 6. Security Considerations This extension to BGP does not change the underlying security issues. 7. Acknowledgements To be supplied. 8. References [BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP- 4)", RFC 1771, March 1995. 9. Author Information Ravi Chandra Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 e-mail: rchandra@cisco.com John G. Scudder Internet Engineering Group, LLC 122 S. Main, Suite 280 Ann Arbor, MI 48104 e-mail: jgs@ieng.com Chandra, Scudder [Page 4]