MPLS VPNs or not?

Tue Aug 7 20:32:38 UTC 2001

Stepping back one notch from this discussion, there's a basic
architectural point here.

As Milo Medin is fond of saying, "with enough thrust anything will fly"
and sometimes they get enough thrust to semi-permanently embed themselves
into the networking infrastructure.

ATM is a case in point.  By about 1993, it was clearly losing steam, but
so much money had been put into it, that it was already part of the
infrastructure, and once in, it wasn't leaving soon.  (Side note,
the marginal cost of using an inferior technology that is already
installed is often lower than the cost of installing the better technology).

MPLS has a genealogy that leaves it suspect (it descends from a vendor
response to IP switching -- and IP switching turned out to be a fad) but
a lot of careful work has gone into trying to make MPLS a sturdy technology.
The issue is, has that work succeeded?

I'm actually not in a good place to say.  I know some of the things people
say about MPLS are clearly silly (the notion MPLS is faster to switch than
IP reflects a poor knowledge of router innards, or a poor router design).
Other statements have some credibility -- carriers have long wanted to do
overlay networks to better track resources (witness how UUNET ran their
backbone a few years ago) and MPLS apparently can help.

Craig