Re: about Wedgelayer 3.5 / Fat IP approaches

[Brian E Carpenter <brc@zurich.ibm.com>]

marcelo bagnulo braun wrote:
> El 29/06/2004, a las 13:49, Brian E Carpenter escribió:
>
> > Eik Nordmark wrote:
> >
> > > > what about cgas?
> > > > They are locators, so you can use them for refferals to non multi6 
> > > > apps and hosts, they allow to map from id to locators using reverse 
> > > > dns, and they are crypto in nature
> > > > seems a good candidate to me :-)
> > >
> > > A downside of CGA approaches is that they would, on a global basis,
> > > cast the /64 subnet prefix boundary in stone forever.
> > > This is different than SeND which only assumes the /64 on a single link,
> > > and one can envision SeND evolving to handle different subnet prefix 
> > > lengths
> > > over time.
> > > Different people probably have very different level of concern for
> > > "/64 forever in stone" ranging from it being a good simplification
> > > to a fatal repeat of the 8 bit IPv4 network number + 24 bit host number
> > > (before Class B and C was invented).
> >
> >
> > Good point. The /64 boundary is only "architectural" in one place, 
> > stateless
> > autoconfig, and even that is a changeable decision.
> >
> > CGAs have other downsides for multihoming, too.
>
> such as?


<chair hat off>

I really don't want to start a discussion here about cryptographic
strength, but my objection to CGAs in the multi6 context is that they
include the /48 prefix in the hash, and that is variable in multi6,
which means that the host ID changes when you change prefix. I think
that's an unfortunate property because it eliminates some possible
tricks in the ID/locator split.

   Brian