Re: [Isis-wg] draft-ginsberg-isis-prefix-attributes & draft-ietf-isis-segment-routing-extensions

Stephane -

We have stated publicly that the plan is to deprecate the N flag in the prefix-SID sub-TLV. The only issue is timing as we have early deployments of SR. So we need to:

1)Get prefix-attributes as a WG document
2)Get early allocation of codepoints for prefix-attributes so folks can implement it
3)Allow a transition period for early SR deployments to add prefix-attributes support
4)Deprecate the redundant flag in SR

During the transition implementations will send both flags and accept either one.

We won't reuse the flag in SR until we are certain there are no legacy deployments. (A long time...)

   Les

> -----Original Message-----
> From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of
> stephane.litkowski@orange.com
> Sent: Monday, April 20, 2015 7:58 AM
> To: isis-wg@ietf.org
> Subject: [Isis-wg] draft-ginsberg-isis-prefix-attributes & draft-ietf-isis-
> segment-routing-extensions
> 
> Hi,
> 
> Introducing the IPv4/IPv6 extended reachability attribute flags, we are
> introducing some redundancy with some informations contained in Prefix-
> SID SubTLV, especially the N-Flag representing that the prefix belongs to the
> node itself.
> 
> I'm not sure this is a good idea to keep both flags or if we do, we need to
> define the relationship between them (are they independent or not ...)
> 
> N-Flag was introduced in Prefix SID SubTLV because the information was not
> existing at this time.
> Now we defined new attributes for the prefix containing this information, so
> the PrefixSID information is redundant and not useful anymore.
> 
> For sure, we need to take care about backward compatibility as some SR
> codes already used N-Flag in Prefix SID for FRR.
> 
> Thoughts ?
> 
> 
> Best Regards,
> 
> Stephane
> 
> 
> 
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