[comp.protocols.tcp-ip] fales warning of Possible ARPA segmentation

jseeger@BBN.COM (12/24/88)

Gene, et. al.,

Bob Pyle who studies ARPANET performance all the time and KNOWS this
network well, sent me the following message in response to my forwarding
him yours of Wednesday, 21 December 1988 12:34:29 EST.  He starts with
a copy of your message.  His words follow at the end.

------- Forwarded Message

To: gswallow@BBN.COM, jwiggins@BBN.COM, hinden@BBN.COM, jseeger@BBN.COM
Subject: Don't panic, it's not true
Date: Thu, 22 Dec 88 09:40:05 -0500
From: Robert Pyle BBNCC 20/672 x3518 <rpyle@BBN.COM>


- ------- Forwarded Message (edited down in size)

Date: Wednesday, 21 December 1988 12:34:29 EST
From: Gene.Hastings@boole.ece.cmu.edu
Reply-To: hastings@morgul.psc.edu
Subject: Possible ARPA segmentation next week? Danger, Will Robinson!

Arpanet PSN #14 (CMU) will be without power 2400 Tuesday 27 December until
2000 Thursday 29 December. 

My understanding of the current ARPA topology is that CMU is in the middle
of the only cross-country land line, and that only the Wideband satellite
link will connect the coasts, meaning that there will be high delays from
coast to coast.

Gene

- ------- End of Forwarded Message


Not so.  The terrestrial path from RCC5 -> UROCH -> WISC -> SAC and
westwards from there will exist (barring additional outages).  What
the CMU outage *will* do is break the DCEC - CMU - PURDU path, which
is about the busiest part of ARPANET, mostly due to EGP-extra-hop
traffic to and from PURDU.  Next week should see the lowest traffic
all year, and the Butterfly mailbridges are presumably already
handling some traffic that used to be forwarded via PURDU, so I see no
cause for alarm.

Most coast-to-coast traffic already uses the various satellite lines
anyway.  Even some east-coast traffic currently takes routes like
MIT-SRI-DCEC or BBN-ISI-DCEC via two satellite hops in preference to
the multihop terrestrial path.

			--Bob


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