Subject: Re: Why is IPv6 a must?

From: [email-masked] (Sean Doran)
Date: Mon, 12 Nov 2001 23:27:36 +0100 (CET)

Perry Metzger writes:

| You seem to dismiss link state offhand, but it
| isn't clear that link state couldn't help out a lot here. (Neither is
| it clear that it could but it appears to be an interesting area for
| some experiments.)

Actually, I'm a fan of link state (ask Sue Hares or Dave Ward & company),
but unfortunately there are lots of links in the Internet, so you
have to hide them.  If you don't, your graph-sort takes forever.

This link-hiding implies lots of levels [Kleinrock & Kamoun], which means 
that either you have the same problem as Geoff in his most recent message
(i.e., you have to do a lookup and keep the result along with the
packet, or lots of lookups, or both), or you need a way to encode
per-level information in the address such that it looks something
like [<L1-address>.<L2-address>.<L3-address>...<LN-address>].  

The problem is that 128 bits or about 64 bits, depending on what
semantics you put onto the addresses, is not very much room to
encode *anything near* the number of levels K&K hierarchical network
optimality calls for in the Internet, let alone the sort of disjoint
hierarchies and confederations thereof that one would want in a
more policy-rich Internet.   But, a variable-length field means
new syntax means it's not IPv6 or IPv4 at all.

	Sean.

---

From: "Perry E. Metzger" <[email-masked]>
Date: 12 Nov 2001 17:48:01 -0500

[email-masked] (Sean Doran) writes:
> optimality calls for in the Internet,

Who says you need to use the IP addresses for that purpose? There is
plenty of precedent -- for a a long time we've had this notion of the
routing protocols adding labels on that had nothing to do per se with
the IP address. See the "AS" notion, for example, in which we label
various clouds with AS numbers, which are never seen by end users. It
would be straightforward enough to build a labeling scheme that was
used inside the routing protocol that stayed inside the routing
protocol. You could happily label the nodes of the routing cloud with
whatever numbering/labeling scheme you like.

If you find yourself wanting to add information like that to the
packets to help them wind their way through the network rather than
simply having the routers keep that information in hand, v6 will
happily let you tag on an option with such information as you enter a
routing cloud that needs it, or one could use encapsulation
mechanisms, putting the data "around" the packet.

In other words, v6 has neither helped nor hurt the routing problem --
it is orthogonal.

--
Perry E. Metzger		[email-masked]
--
NetBSD Development, Support & CDs. http://www.wasabisystems.com/