Re: [Idr] MP-BGP Extension and the Procedures for IPv4/IPv6 Mapping Advertisement

[Robert Raszuk <[e-mail]>]

Hi Acee,

Apologies if this has already been covered but it was clear from
> yesterday’s IDR meeting chat  that I’m not the only one who questions the
> necessity of this BGP extension.
>
> Why can you just use one of the IPv6 addresses ranges reserved for
> embedded IPv4 addresses as described in section 2.2.5 of RFC 4291?
>

You man 2.5.5 ?

Well the issue here is that this section describes a special address block
to be used for mapping and last time I checked is hardly routable
interdomain.

Moreover the goal of "IPv4-mapped IPv6 address" as explained even better in
RFC4038 is to provide a way to talk to IPv6 services itself for IPv4  only
sites/hosts. This proposal just aims to assist to interconnect IPv4 only
sites.

So authors here are proposing to signal arbitrary prefix within and overlay
between interesting (typically non directly connected ASNs) which of their
prefix should be used to reach remote IPv4 sites.

I think from this perspective the proposal is sound.

What is however questionable and what we have recently discussed with Ketan
- why not do encapsulation instead of double translation ... to accomplish
the very same.

Cheers,
R.

PS.

If you use these embedded IPv4 using the standard mappings there no reason
> to advertise explicit mappings. There is already precedence for doing this
> - https://datatracker.ietf.org/doc/rfc6992/
>

This is intradomain only.