draft-ietf-idr-bgp4-cap-neg-01.txt   draft-ietf-idr-bgp4-cap-neg-02.txt 
Network Working Group Ravi Chandra Network Working Group Ravi Chandra
Internet Draft Cisco Systems Internet Draft Cisco Systems
Expiration Date: October 1998 John G. Scudder Expiration Date: February 1999 John G. Scudder
Internet Engineering Group, LLC Internet Engineering Group, LLC
Capabilities Negotiation with BGP-4 Capabilities Negotiation with BGP-4
draft-ietf-idr-bgp4-cap-neg-01.txt draft-ietf-idr-bgp4-cap-neg-02.txt
1. Status of this Memo 1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
skipping to change at page 1, line 42 skipping to change at page 2, line 5
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 negotiation without requiring
that BGP peering be terminated. 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.
3. Overview of Operations 3. Overview of Operations
When a BGP speaker that supports capabilities negotiation sends an When a BGP speaker that supports capabilities negotiation 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 may use a particular capability when peering with A BGP speaker determines the capabilities supported by its peer by
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 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
capability with its peer after the speaker determines (as described
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 negotiation, 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
connection with the peer without sending to the peer the Capabilities
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 is local to to send the message. The decision to send the message and terminate
the speaker. peering is local to the speaker. Such peering should not be re-
established automatically.
4. Capabilities Optional Parameter (Parameter Type 2): 4. 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:
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/