Re: [Idr] BGP: Vendor Specific Capabilities

  John,

       I have one more more doubt which needs clarification :

          In response to an open message with capabilities, a peer that supports no capabilities 

                1) MUST send NOTIFICATION message with unsupported optional parameter.

                                 OR

                 2) SHOULD send NOTIFICATION message with unsupported optional parameter.

        Say for example, as a BGP speaker X support some capability and its  peer Y has the basic implementation of BGP without any optional capabilities. So in that case:

             - Will the peer Y always (MUST) send NOTIFICATION message to the speaker X with unsupported optional parameter? 

             - Or if a peer Y doesn't send any notification and closes the connection then should the speaker X send a new open message without any optional capabilities or should speaker X wait for the peer's open message and adjust accordingly?

        I don't see this defined clearly in any of the RFCs which I have read. Could you please clarify this or point me to the section of RFC which states this?

thanks,
Sundeep

-----Original Message-----
From: ext John G. Scudder [mailto:jgs@bgp.nu]
Sent: Tue 4/22/2008 3:25 PM
To: Mudgal Sundeep (Nokia-S&S/MtView)
Cc: idr@ietf.org
Subject: Re: [Idr] BGP:  Vendor Specific Capabilities

Continue the connection.  In general one can think of the semantics of  
a BGP capability as being "I am able to do X" rather than "I insist on  
doing X".  If a pair of peers exchanges X, then that capability will  
typically be used.  If the peers do not exchange X, then it won't be.   
So, if your peer sends you X, and you don't support X, there's no  
problem.  You simply won't send X, so the peer won't attempt to use X  
on that peering.

--John

On Apr 22, 2008, at 2:39 PM, sundeep.mudgal@nokia.com wrote:

> So when you say "ignore", does it mean that peer continues with the  
> connection or drop the connection without sending any notification?
>
>
> -----Original Message-----
> From: ext John G. Scudder [mailto:jgs@bgp.nu]
> Sent: Tue 4/22/2008 12:59 PM
> To: Mudgal Sundeep (Nokia-S&S/MtView)
> Cc: idr@ietf.org
> Subject: Re: [Idr] BGP:  Vendor Specific Capabilities
>
> It should be ignored.  Per RFC 3392, the unsupported capability
> message is a way to complain if your peer doesn't support a capability
> that you insist on having support for.  An example would be if the
> peer doesn't support MP-BGP and you are trying to establish a v6
> peering.  Here is the pertinent text from RFC 3392:
>
> "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 (see Section
> "Extensions to Error Handling" for more details). 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 and terminate peering is
> local to the speaker. If terminated, such peering SHOULD NOT be re-
> established automatically."
>
> I apologize for the confusing name of the notification message.
> Probably something like "Required Capability Missing" would have been
> better. :-(
>
> Correct behavior with respect to any unknown capability from your peer
> (whether vendor-specific or otherwise) is generally to ignore it.
>
> --John
>
> On Apr 22, 2008, at 11:35 AM, <sundeep.mudgal@nokia.com> <sundeep.mudgal@nokia.com
>  > wrote:
>
> >
> > Hi,
> >
> >         Could you please confirm whether vendor-specific
> > capabilities should be ignored or responded to with the unsupported
> > capability message?
> >
> > Thanks,
> > Sandeep Mudgal
> >
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>