Re: [spring] [Lsr] Adjacency SID and Passive Interface

Thanks everybody for your answer.

It is clear that Adj-SID is linked to the existence of an IS-IS adjacency with a neighbour, thus it is not usable for passive interface or inter-domain link.

Regards

Olivier

Le 10/05/2019 à 14:22, Ketan Talaulikar (ketant) a écrit :
> +1
>
> Hi Oliver,
>
> Technically Adj-SID refers to an IGP adjacency between two nodes as per RFC8402 semantics. I don't think a passive (stub) link falls under that category. It would be better to define a passive link separately (somewhat on lines of what was done for inter-AS TE) so that it does not get mixed up with the classical IGP links. I would think a new draft would be apt for such an extension.
>
> Thanks,
> Ketan
>
> -----Original Message-----
> From: Lsr <lsr-bounces@ietf.org> On Behalf Of Acee Lindem (acee)
> Sent: 10 May 2019 17:39
> To: Christian Franke <chris@opensourcerouting.org>; olivier.dugeon@orange.com; SPRING <spring@ietf.org>; LSR <lsr@ietf.org>
> Subject: Re: [Lsr] Adjacency SID and Passive Interface
>
> Hi Chris, Olivier, 
>
> On 5/10/19, 4:41 AM, "Lsr on behalf of Christian Franke" <lsr-bounces@ietf.org on behalf of chris@opensourcerouting.org> wrote:
>
>     On 5/10/19 9:58 AM, olivier.dugeon@orange.com wrote:
>     > In the current state of Segment Routing drafts, do you think it is possible to advertise
>     > Adjacency SID on such passive or inter-domain interfaces or do we need to specify this behaviour
>     > in a new draft ?
>     > 
>     > For me I don't see anything in the drafts that prohibits this kind of advertisement, but perhaps I'm wrong.
>     
>     My understanding is that the SID is specific to an adjacency and
>     advertised in IS-IS in either TLV 22, 222, 23, 223.
>     
>     As adjacencies will not be formed on a passive interface, an adjacency
>     SID should not be advertised for the passive interface.
>
> I agree with Chris. We shouldn't reuse the existing Adj-SID when there will never be an adjacency and the current semantics require this. If we need advertisement of SIDs for passive interfaces, it would definitely be a new draft that clearly articulates the use case and designates a new type of SID that has different semantics. Also note that while passive interfaces are very useful in order to include a stub network in the topologies, they are not part of the OSPF specifications. I haven't done an exhaustive search on IS-IS. 
>
> Thanks,
> Acee
>
>     
>     I might also be wrong here, though.
>     
>     All Best,
>     Chris
>     
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>
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