Re: [OSPF] draft-ietf-spring-conflict-resolution/draft-ietf-ospf-segment-routing-extensions: If you please provide your inputs on the issue.

[Peter Psenak <[e-mail]>]

Mahendra,

On 23/02/18 05:48 , Mahendra Singh Negi wrote:
> Dear Authors,
>
> Amidst implementing conflict resolution for OSPF SR (
> https://tools.ietf.org/html/draft-ietf-spring-conflict-resolution-05) we
> came across this issue.
>
> **
>
> **
>
> *Topology:*
>
> *Issue:*
>
> 1.Prefix conflict occurs at RT1 and RT2.
>
> 2.Both RT1 and RT2 resolve the conflict and download corresponding Label
> for SID:1 (SID:1 wins conflict resolution).
>
> 3.Both RT1 and RT2 advertise inter-area Extended Prefix Opaque LSA for
> prefix 10.10.10.10 in area a1 with SID:1.
>
> Reference:
> https://tools.ietf.org/html/draft-ietf-ospf-segment-routing-extensions-24#section-7.2
>
>
> &
>
> https://tools.ietf.org/html/draft-ietf-ospf-segment-routing-extensions-24#section-5
>
>
>    (If an OSPF router advertises multiple Prefix-SIDs for the same
> prefix, topology and algorithm, all of them MUST be ignored.)

which router advertises multiple Prefix-SIDs for the same prefix in your 
example?
>
> 4.Now at RT1, user *changes the  SID configuration value to 4*, and
> still SID 1 wins the conflict resolution as in area a1 RT2 has not
> flushed or updated SID:1, and SID:1 is forever in LSDB.

I don't understand the above. Why would that happen?

Peter



>
> *How to fix the issue?*
>
> a)think ABRs should advertise all the SIDs to leaking areas and MUST
> condition mentioned highlighted in yellow above be relaxed(i.e. update
> inter-area segment routing section accordingly) and let each node run
> conflict-resolution.
>
> b) On SID configuration change, RT1 Flushes the SID:1 and waits for
> SID:1 flushing out from the LSDB and then originates with new SID:4.(How
> long to wait is decided locally).
>
> I prefer (a), if you please provide your opinion on this.We are under
> development, highly appreciate prompt  responses.
>
> Regards,
>
> Mahendra
>