Subject: [Idr] partial bit set for AS4_PATH

From: Thomas Mangin <[email-masked]>
Date: Sat, 26 Jul 2014 09:20:07 +0100

Hello,

I have found recently that an implementation of BGP is encoding the AS4_PATH attribute, setting the PARTIAL flag [1]
I do not see anything in RFC 4893 about setting this flag.

How an implementation should handle this case .. Is it an error or not ?
Perhaps idr-draft-error-handling should have some wording about AS4_PATH ?

Thank you,

Thomas

[1] https://github.com/Exa-Networks/exabgp/issues/150

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From: "Saikat Ray (sairay)" <[email-masked]>
Date: Sat, 26 Jul 2014 10:58:39 +0000

If there is a BGP speaker in the middle that doesn't understand AS4_PATH,
you would get the attribute with the Partial bit set to 1.

>From 4271:

"  If a
   path with an unrecognized transitive optional attribute is accepted
   and passed to other BGP peers, then the unrecognized transitive
   optional attribute of that path MUST be passed, along with the path,
   to other BGP peers with the Partial bit in the Attribute Flags octet
   set to 1.  If a path with a recognized, transitive optional attribute
   is accepted and passed along to other BGP peers and the Partial bit
   in the Attribute Flags octet is set to 1 by some previous AS, it MUST
   NOT be set back to 0 by the current AS.  Unrecognized non-transitive
   optional attributes MUST be quietly ignored and not passed along to
   other BGP peers.
"

On 7/26/14, 1:20 AM, "Thomas Mangin" <[email-masked]>
wrote:

>Hello,
>
>I have found recently that an implementation of BGP is encoding the
>AS4_PATH attribute, setting the PARTIAL flag [1]

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From: Thomas Mangin <[email-masked]>
Date: Sat, 26 Jul 2014 15:22:35 +0100

Saikat,

Thank you - I should have seen this - sorry for the noise on-list.

Thomas