Re: draft-ietf-l3vpn-as4octet-ext-community-00.txt

[Yakov Rekhter <[e-mail]>]

Bruno,

> > > Yakov, Srihari, Dan,
> > >
> > > >From RFC 4893 (BGP Support for Four-octet AS Number Space): "Currently
> > > assigned 2-octet Autonomous System numbers are converted into 4-octet
> > > Autonomous System numbers by setting the two high-order octets of the
> > > 4-octet field to zero.  Such a 4-octet AS number is said to be mappable
> > > to a 2-octet AS number."
> > >
> > > So it seems that a 2-octet Autonomous System would have two ways to
> > > encode a Route Target or Route Origin:
> > > - using a two-Octet AS Specific Extended Community as defined in rfc4360
> > > (BGP Extended Communities Attribute)
> > > - using a four-octet AS specific extended community as described in
> > > draft-ietf-l3vpn-as4octet-ext-community-00.txt
> > >
> > > It looks to me this could create interop issue for BGP/MPLS VPN, even
> > > within a 2 octet AS.
> > >
> > > IINM, may I suggest that you add a sentence in the draft to handle such
> > > case? (e.g., mandating the use of *Two*-Octet AS Specific Extended
> > > Community, reserving the "mappable to a 2-octet" AS numbers, ...).
> > 
> > That seems reasonable. Could you propose the text.
> 
> Please find below a proposition. Feel free to reword it as you wish.
> 
> Thanks,
> Regards,
> Bruno
> 
> 
> 
> 3. Considerations for two-octet Autonomous Systems
> 
> As per [RFC4893], a two-octet Autonomous System number can be converted
> into a 4-octet Autonomous System number by setting the two high-order
> octets of the 4-octet field to zero.
> 
> As a consequence, a two-octet Autonomous System could use both two-octet
> and four-octet AS specific extended communities. This is undesirable as
> both communities would be treated as different even if they had the same
> Type, Sub-Type and Local Administrator values.
> 
> Therefore, for backward compatibility with existing deployments and to
> avoid inconsistencies between two-octet and four-octet specific extended
> communities, two-octet Autonomous Systems SHOULD use two-octet AS
> specific extended communities rather than four-octet AS specific
> extended communities.
> 
> 9. Normative References
> 
> [RFC4893] Vohra, Q., Chen, E., "BGP Support for Four-octet AS Number
> Space", RFC 8993, May 2007.

The text looks fine to me. In the absence of any objections within
the next week or so I'll integrate your text into the draft and will
issue a revised version.

Yakov.