RE: IPv6 addresses for EP or why are exhanges so special ?
- Date: Wed, 16 May 2001 12:20:29 +0100
>
>
> > I have tried to follow this discussion, and stumbeled over a
> > fundamental question when trying to reason about this:
> >
> > * why are exchange points so special?
>
> My take on this is that "they are not".
>
> But before plunging on, I would find it useful to distinguish
> between the two portions that have been discussed so far:
>
> o Addresses for the exchange point medium itself (usually a
> layer-two network of some sort)
>
> o Addresses for a "service network", probably used by the
> organization which runs the exchange point and which can
> provide additional common services of interest to the
> connected networks.
>
> I'll also mention that my experience on the matter is based on
> IPv4, so if there are additional quirks that are specific to IPv6
> that I don't know about, you'll have to excuse me.
>
> For the exchange point medium itself, if the medium is a "multiple-
> access broadcast network" it *is* actually a benefit to use the
> "natural" way to number such networks, i.e. use a single IP subnet,
> as in that case you can use BGP in the "standard configuration".
> Starting to muddle with secondary IP addresses and run "multiple
> subnet on the same layer-two medium" when you in reality don't have
> to, just causes extra complications, and should therefore be
> avoided. If your exchange point is implemented using a "multiple-
> access non-broadcast network" of some sort, the multiple point-to-
> point links, each with their own subnet out of a connected peer's
> address block makes sense.
>
I'm of the same opinion.
> Some have said that the IP network used to number the exchange
> itself does not have to be announced on the global level. However,
> it would appear that practices vary quite widely on this point for
> IPv4, and many are announced globally. You mention the possible use
> of link-local addresses; I wonder if that won't make it difficult to
> handle such things as ICMP; it'll probably be met with similar
> issues as folks who use RFC 1918 addresses in today's network (e.g.
> breaking Path MTU discovery because RFC 1918-originated datagrams
> are often summarily dropped on the floor).
>
I fear that as well. Of course, however, it's a question of being smallest
MTU on path - but for avoiding such potential problems...
> I may have misunderstood something fundamental, but I also don't
> quite know what's so bad with using IP(v4) addresses out of a
> provider's block to number the exchange point medium.
>
>
> As for the "service network", it will of course need global
> connectivity, and thus has to get transit service from one or more
> ISPs. What I don't understand is why this service network needs to
> be so special up and above other normal customers when it comes to
> IP address assignment?
>
Depending on how transit / co-location is provided, yes. Hrm,... maybe I'm
wrong, maybe I'm right... but couldn't suitable PI disjunct to IX infra
space (and/or close segment) be a choice as well?
Thoughts?
Kind regards
Michael
>
> Creating these "special cases" as exceptions to the rules just opens
> up the floor for other folks who will stand up and say "My Cause is
> Extremely Worthy too, so I want some too under those conditions!!".
>
>
> Best regards,
>
> - Håvard
>
