Subject: Re: NATs *ARE* evil!

From: [email-masked] (Sean Doran)
Date: Fri, 22 Dec 2000 02:11:13 +0100 (CET)

| from label switching, so what I'm suggesting is that we take the bull by
| the horns once and for all and run MPLS over IP instead of under it... 

an mplsd-like tag fits neatly in the first half of an ipvsux destination 
address, although there are other places in the vsux header you can put 
tag bits if you're inclined to do so for stacking reasons or whatnot.

one nicety of stuffing the tag into the vsux header (or even *below*
the vsux header, as payload) is that you can forward through v6 networks
such as they exist, without them also simultaneously having to be MPLSd.
that is, you abstract a collection of vsux-but-not-mplsd routers
into a connection between two lsrs (with likely hit to reservation based
control plane).

in other words, a particularly useful mplsd label is one that causes the
next-hop lsr to generate a packet that is relevant within a non-mplsd
network with its own topological namespace.   that is, generate an IPvsux
or ordinary IP packet out an interface such that things on the other
side of the interface can route back to it.   that is, tag "xyzi" means
be a NAT and send packet out IP/IPvsux interface "i".

this has all the same problems of NAT where there is no end-to-end
namespace that is not TOPOLOGICAL in nature separate from but convertible
between a namespace populated with globally unique IDENTITY names.
(where that namespace can mean single hosts or service locations or whatever,
but not two or more of these things simultaneously! overloading bad.)

	Sean.

---

From: Fred Baker <[email-masked]>
Date: Thu, 21 Dec 2000 21:34:35 -0800

>tag bits if you're inclined to do so for stacking reasons or whatnot.

actually, I should think the flow label field might be pressed into service...

---

From: Keith Moore <[email-masked]>
Date: Fri, 22 Dec 2000 02:41:00 -0500

yeah, I really wish those who are trying to improve network routing
(an endeavor which I respect in principle) would consider that
applications really do need stable endpoint identifiers which 
are globally scoped, exchangable with other applications, and 
reliably usable from anywhere to reach the process listening 
to that endpoint.

Keith