From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: "stephane.litkowski@orange.com" <stephane.litkowski@orange.com>,
 "isis-wg@ietf.org" <isis-wg@ietf.org>
Thread-Topic: draft-ginsberg-isis-prefix-attributes &
 draft-ietf-isis-segment-routing-extensions
Thread-Index: AdB7eZRWVBiAPkUSTViDyaxVyA+rAQAARjeA
Date: Mon, 20 Apr 2015 15:04:56 +0000
Message-ID: <F3ADE4747C9E124B89F0ED2180CC814F57466B29@xmb-aln-x02.cisco.com>
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Archived-At: <http://mailarchive.ietf.org/arch/msg/isis-wg/poYipPOBGrY1I-vJ0a7NlJ7pjjc>
Subject: Re: [Isis-wg] draft-ginsberg-isis-prefix-attributes &
 draft-ietf-isis-segment-routing-extensions
Precedence: list

Stephane -

We have stated publicly that the plan is to deprecate the N flag in the pre=
fix-SID sub-TLV. The only issue is timing as we have early deployments of S=
R. So we need to:

1)Get prefix-attributes as a WG document
2)Get early allocation of codepoints for prefix-attributes so folks can imp=
lement it
3)Allow a transition period for early SR deployments to add prefix-attribut=
es support
4)Deprecate the redundant flag in SR

During the transition implementations will send both flags and accept eithe=
r one.

We won't reuse the flag in SR until we are certain there are no legacy depl=
oyments. (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-isi=
s-
> segment-routing-extensions
>=20
> Hi,
>=20
> 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.
>=20
> 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 ...)
>=20
> N-Flag was introduced in Prefix SID SubTLV because the information was no=
t
> 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.
>=20
> For sure, we need to take care about backward compatibility as some SR
> codes already used N-Flag in Prefix SID for FRR.
>=20
> Thoughts ?
>=20
>=20
> Best Regards,
>=20
> Stephane
>=20
>=20
>=20
> __________________________________________________________
> __________________________________________________________
> _____
>=20
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>=20
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