ATM Wide-Area Networks

From: Sean Doran <>
Subject: Re: sell shell accounts?
Date: Wed, 24 Jul 1996 01:43:30 +0100

o Given that each link is rather expensive, it behooves the
  NSP to try to avoid needlessly moving a packet back and
  forth across a DS-3 local loop just because my ATM
  provider can't provide me with any more PVCs.
  (Which was my major point, by the way.)

Interestingly enough, the NSPs I observe moving large amounts
of traffic around are set up in such a way that their routers
are generally colocated with carrier transmission gear, and
so there *is* no local loop to speak of, as an added cost to
an outside supplier.

Hopefully, my thinking is clearer than my writing...

What I originally called "local loop B," now relabeled "This Thing Here,"
is probably comprised of:

o a port on the ATM switch/service

o a connection between the router and the switch, (usually a
  wide-area link, given that most wide-area ATM services
  backhaul traffic to a few ATM switches)

o a port on the router

A short-cut VC would avoid needlessly passing packets back and forth
across "This Thing Here." That would seem to be a good thing in
most circumstances, inasmuch as some or all of the components of
"This Thing Here" cost something and may potentially become a bottleneck.