Re: (ngtrans) Re: draft-ietf-ngtrans-isatap-scenario-00.txt

[Pekka Savola <[e-mail]>]

On Fri, 28 Jun 2002, Fred L. Templin wrote:
> > That is an alternative approach, yes. (However, if there are many of these
> > compartments and each of them acts as one ISATAP site, the routers should
> > be meshed in some fashion, perhaps with ISATAP :-) -- this may soon get
> > more complex though.)
>
> Glad to know that you see this as an alternative approach. This
> area clearly needs more study so the thoughts are appreciated.

Agreed -- this can become very complex.  It seems that ISATAP has a 
property (a good one) that the created IPv6 topology will be flat.

Two practical requirements for this kind of approach is that different
compartments have different subdomains, are using the subdomain first
in their DNS resolver search path and the ISATAP name is added (pointing 
to the local ISATAP router) in each subdomain where this behaviour is 
requested.  (Alternatively, some form of manual configuration is always 
possible.)

> > IMO the ability that one /64 can be used to configure very many nodes is 
> > rather irrelevant.  (Or, it may be more relevant in some scenarios, e.g. 
> > if ISP only gives you a /64 -- but this needs to be a separate item if 
> > deemed so.)
> 
> I believe this point is *very* relevant from the standpoint of prefix
> aggregation in IPv6 border routing protocols. If each of N hosts in
> a site were to assign their own /64 prefix independently of the others,
> as many as N different prefixes for the site might be advertised in
> IPv6 border routing protocols instead of just one. 

To where?  To upstream there would only be one aggregated prefix, to 
ISATAP routers and other components in the same all of them.

My point is that if there's no shortage of /64's, I don't think there's 
much loss to use a couple of them.

But I mostly agree; however, I thikn 4.2. should be reworded a bit to make 
it clearer we're talking about prefix aggregation.  (When talking about 
border gateway aggregation, one often regards this as access aggregation, 
like 500 T1-line customers in, Gigabit Ethernet out.)

> > I think, from the perspective of ISATAP, a crucial special case is when 
> > two routers advertise the same prefix.
> 
> I believe the behavior in this case would be identical to the case of
> multiple native IPv6 routers advertising the same prefix, i.e., the
> behavior would be identical to RFC 2461. 

Yes.

> Did you have any specific
> concerns about this case?

Not really.  Only a notion that this scenario may come up more often with
ISATAP (esp. in larger organizations).

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords