Re: [mpls] [Technical Errata Reported] RFC3107 (4499)

[Eric C Rosen <[e-mail]>]

Nice bit of detective work figuring out where the 0x800000 value came from.

However, I don't think the erratum can be accepted, given its potential 
for causing interoperability issues.

To the best of my knowledge, section 4 ("Advertising Multiple Routes to 
a Destination") is not widely implemented (to say the least), so the 
issue of "which route to the prefix did you intend to withdraw?" doesn't 
really come up.

On 10/13/2015 6:05 PM, RFC Errata System wrote:
> The following errata report has been submitted for RFC3107,
> "Carrying Label Information in BGP-4".
>
> --------------------------------------
> You may review the report below and at:
> http://www.rfc-editor.org/errata_search.php?rfc=3107&eid=4499
>
> --------------------------------------
> Type: Technical
> Reported by: Alexander Okonnikov <[e-mail]>
>
> Section: 3
>
> Original Text
> -------------
>     A BGP speaker can withdraw a previously advertised route (as well as
>     the binding between this route and a label) by either (a) advertising
>     a new route (and a label) with the same NLRI as the previously
>     advertised route, or (b) listing the NLRI of the previously
>     advertised route in the Withdrawn Routes field of an Update message.
>     The label information carried (as part of NLRI) in the Withdrawn
>     Routes field should be set to 0x800000.  (Of course, terminating the
>     BGP session also withdraws all the previously advertised routes.)
>
>
> Corrected Text
> --------------
>     A BGP speaker can withdraw a previously advertised route (as well as
>     the binding between this route and a label) by either (a) advertising
>     a new route (and a label) with the same NLRI as the previously
>     advertised route, or (b) listing the NLRI of the previously
>     advertised route in the Withdrawn Routes field of
>     an MR_UNREACH_NLRI attribute of an Update message.
>     The label information carried (as part of NLRI) in the Withdrawn
>     Routes field should be set to 0x000001.  (Of course, terminating the
>     BGP session also withdraws all the previously advertised routes.)
>
>
> Notes
> -----
> 1. Labeled routes are withdrawn by virtue of MR_UNREACH_NLRI attribute.
> 2. Label value should be set to 0x00000 with BoS=1.  Value 0x800000 was carried from draft, where BoS was high-order bit.
>
> Instructions:
> -------------
> This erratum is currently posted as "Reported". If necessary, please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party (IESG)
> can log in to change the status and edit the report, if necessary.
>
> --------------------------------------
> RFC3107 (draft-ietf-mpls-bgp4-mpls-04)
> --------------------------------------
> Title               : Carrying Label Information in BGP-4
> Publication Date    : May 2001
> Author(s)           : Y. Rekhter, E. Rosen
> Category            : PROPOSED STANDARD
> Source              : Multiprotocol Label Switching
> Area                : Routing
> Stream              : IETF
> Verifying Party     : IESG
>
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