ATM Wide-Area Networks
salo at msc.edu
Tue Jul 30 21:03:32 UTC 1996
>From: Sean Doran <smd at icp.net>
>To: pferguso at cisco.com, salo at msc.edu
>Subject: Re: sell shell accounts?
>Cc: nanog at merit.edu
>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.
| ________ _______________________ ________
| | Router | loop A | | loop C | Router |
| | A |=========| Wide-Area ATM Service |========| C |
| |________| |_______________________| |________|
| | <=== This Thing Here
| | Router |
| | B |
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