Re: Arpanet outage


CERF@A.ISI.EDU
16 Dec 1986 08:04-EST


Dan,

the physical diversity problem is real and not easy to solve. First, any
particular supplier of long-haul service may not have a great deal of
physical diversity available. One would have to go to different vendors
to achieve it. The procurement of communication services by DoD does not
always (ever?) rate physical diversity at a high enough level of priority
to justify paying different amounts of money for the "same" service to
achieve diversity. I had a similar problem at MCI and had to specifically
work with the voice network engineering and operations staff to make them
understand how critical physical diversity was to a packet network.

With fiber, this is particualrly a problem because the economics of fiber
make it very attractive to dig a trench and put lots of fiber in the one
trench rather than digging many different trenches.

Vint



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