draft-ietf-idr-bgp4-cap-neg-05.txt   rfc2842.txt 
Network Working Group Ravi Chandra
Internet Draft Siara Systems
Expiration Date: August 2000 John G. Scudder
cisco Systems
Capabilities Negotiation with BGP-4
draft-ietf-idr-bgp4-cap-neg-05.txt
1. Status of this Memo Network Working Group R. Chandra
Request for Comments: 2842 Redback Networks Inc.
Category: Standards Track J. Scudder
cisco Systems
May 2000
This document is an Internet-Draft and is in full conformance with Capabilities Advertisement with BGP-4
all provisions of Section 10 of RFC2026 except that the right to
produce derivative works is not granted.
Internet-Drafts are working documents of the Internet Engineering Status of this Memo
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 This document specifies an Internet standards track protocol for the
and may be updated, replaced, or obsoleted by other documents at any Internet community, and requests discussion and suggestions for
time. It is inappropriate to use Internet-Drafts as reference improvements. Please refer to the current edition of the "Internet
material or to cite them other than as ``work in progress.'' Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
The list of current Internet-Drafts can be accessed at Copyright Notice
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at Copyright (C) The Internet Society (2000). All Rights Reserved.
http://www.ietf.org/shadow.html.
2. Abstract Abstract
Currently BGP-4 [BGP-4] requires that when a BGP speaker receives an Currently BGP-4 [BGP-4] requires that when a BGP speaker receives an
OPEN message with one or more unrecognized Optional Parameters, the OPEN message with one or more unrecognized Optional Parameters, the
speaker must terminate BGP peering. This complicates introduction of speaker must terminate BGP peering. This complicates introduction of
new capabilities in BGP. new capabilities in BGP.
This document defines new Optional Parameter, called Capabilities, This document defines new Optional Parameter, called Capabilities,
that is expected to facilitate introduction of new capabilities in that is expected to facilitate introduction of new capabilities in
BGP by providing graceful capability negotiation without requiring BGP by providing graceful capability advertisement without requiring
that BGP peering be terminated. that BGP peering be terminated.
3. Overview of Operations 1. Overview of Operations
When a BGP speaker that supports capabilities negotiation sends an When a BGP speaker that supports capabilities advertisement sends an
OPEN message to its BGP peer, the message may include an Optional OPEN message to its BGP peer, the message may include an Optional
Parameter, called Capabilities. The parameter lists the capabilities Parameter, called Capabilities. The parameter lists the capabilities
supported by the speaker. supported by the speaker.
A BGP speaker determines the capabilities supported by its peer by A BGP speaker determines the capabilities supported by its peer by
examining the list of capabilities present in the Capabilities examining the list of capabilities present in the Capabilities
Optional Parameter carried by the OPEN message that the speaker Optional Parameter carried by the OPEN message that the speaker
receives from the peer. receives from the peer.
A BGP speaker that supports a particular capability may use this A BGP speaker that supports a particular capability may use this
capability with its peer after the speaker determines (as described capability with its peer after the speaker determines (as described
above) that the peer supports this capability. above) that the peer supports this capability.
A BGP speaker determines that its peer doesn't support capabilities A BGP speaker determines that its peer doesn't support capabilities
negotiation, if in response to an OPEN message that carries the advertisement, if in response to an OPEN message that carries the
Capabilities Optional Parameter, the speaker receives a NOTIFICATION Capabilities Optional Parameter, the speaker receives a NOTIFICATION
message with the Error Subcode set to Unsupported Optional Parameter. message with the Error Subcode set to Unsupported Optional Parameter.
In this case the speaker should attempt to re-establish a BGP In this case the speaker should attempt to re-establish a BGP
connection with the peer without sending to the peer the Capabilities connection with the peer without sending to the peer the Capabilities
Optional Parameter. Optional Parameter.
If a BGP speaker that supports a certain capability determines that If a BGP speaker that supports a certain capability determines that
its peer doesn't support this capability, the speaker may send a its peer doesn't support this capability, the speaker may send a
NOTIFICATION message to the peer, and terminate peering. The Error NOTIFICATION message to the peer, and terminate peering. The Error
Subcode in the message is set to Unsupported Capability. The message Subcode in the message is set to Unsupported Capability. The message
should contain the capability (capabilities) that causes the speaker should contain the capability (capabilities) that causes the speaker
to send the message. The decision to send the message and terminate to send the message. The decision to send the message and terminate
peering is local to the speaker. Such peering should not be re- peering is local to the speaker. Such peering should not be re-
established automatically. established automatically.
4. Capabilities Optional Parameter (Parameter Type 2): 2. Capabilities Optional Parameter (Parameter Type 2):
This is an Optional Parameter that is used by a BGP speaker to convey 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. to its BGP peer the list of capabilities supported by the speaker.
The parameter contains one or more triples <Capability Code, The parameter contains one or more triples <Capability Code,
Capability Length, Capability Value>, where each triple is encoded as Capability Length, Capability Value>, where each triple is encoded as
shown below: shown below:
+------------------------------+ +------------------------------+
| Capability Code (1 octet) | | Capability Code (1 octet) |
skipping to change at page 3, line 30 skipping to change at page 3, line 13
of the Capability Value field in octets. of the Capability Value field in octets.
Capability Value: Capability Value:
Capability Value is a variable length field that is interpreted Capability Value is a variable length field that is interpreted
according to the value of the Capability Code field. according to the value of the Capability Code field.
A particular capability, as identified by its Capability Code, may A particular capability, as identified by its Capability Code, may
occur more than once within the Optional Parameter. occur more than once within the Optional Parameter.
5. Extensions to Error Handling 3. Extensions to Error Handling
This document defines new Error Subcode - Unsupported Capability. This document defines new Error Subcode - Unsupported Capability.
The value of this Subcode is 7. The Data field in the NOTIFICATION 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 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 the message. Each such capability is encoded the same way as it was
encoded in the received OPEN message. encoded in the received OPEN message.
6. IANA Considerations 4. IANA Considerations
As specified in this document, the Capability optional parameter Section 4 defines a Capability Optional Parameter along with an
contains the Capability Code field. Capability Code value 0 is Capability Code field. IANA is expected to create and maintain the
registry for Capability Code values. Capability Code value 0 is
reserved. Capability Code values 1 through 63 are to be assigned by reserved. Capability Code values 1 through 63 are to be assigned by
IANA using the "IETF Consensus" policy defined in RFC2434. Capability IANA using the "IETF Consensus" policy defined in RFC2434. Capability
Code values 64 through 127 are to be assigned by IANA, using the Code values 64 through 127 are to be assigned by IANA, using the
"First Come First Served" policy defined in RFC2434. Capability Code "First Come First Served" policy defined in RFC2434. Capability Code
values 128 through 255 are vendor-specific, and values in this range values 128 through 255 are for "Private Use" as defined in RFC2434.
are not to be assigned by IANA.
7. Security Considerations 5. Security Considerations
This extension to BGP does not change the underlying security issues This extension to BGP does not change the underlying security issues
inherent in the existing BGP [Heffernan]. inherent in the existing BGP [Heffernan].
8. Acknowledgements 6. Acknowledgements
The authors would like to thank members of the IDR Working Group for The authors would like to thank members of the IDR Working Group for
their review and comments. their review and comments.
9. References 7. References
[BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP- [BGP-4] Rekhter, Y. and T. Li, "A Border Gateway Protocol 4
4)", RFC 1771, March 1995. (BGP-4)", RFC 1771, March 1995.
[Heffernan] Heffernan, A., "Protection of BGP Sessions via the TCP [Heffernan] Heffernan, A., "Protection of BGP Sessions via the TCP
MD5 Signature Option", RFC2385, August 1998. MD5 Signature Option", RFC 2385, August 1998.
10. Author Information 8. Authors' Addresses
Ravi Chandra Ravi Chandra
Siara Systems Incorporated Redback Networks Inc.
1195 Borregas Avenue 350, Holger Way
Sunnyvale, CA 94089 San Jose, CA 95134
e-mail: rchandra@siara.com
EMail: rchandra@redback.com
John G. Scudder John G. Scudder
Cisco Systems, Inc. Cisco Systems, Inc.
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
e-mail: jgs@cisco.com
EMail: jgs@cisco.com
9. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
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The limited permissions granted above are perpetual and will not be
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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