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Re: Statistical Games Providers Play (RE: availability and resiliency)
From: Vijay Gill <vijay () umbc edu>
Date: Sun, 1 Oct 2000 00:52:38 -0400


On 30 Sep 2000, Sean Donelan wrote:

If you look at network backbones, almost everyone uses the same
vendors, supplying essentially the same equipment, and nearly the same
network design.  So why would different providers have different
availability numbers?  Is it just an accident of the statistical
series, some providers had their failures earlier but everyone will
end up the same in Year Infinity? Or are there real differences,
besides price, between providers?

There appear to be two major and some minor variants in backbone
engineering and architecture. The major ones being the UUNET design and
the Sprint/Qwest design for circuit layout and aggregation/hierarchy.  
There are a lot more variants regarding the routing architecture (IGP
setup, bgp setup, et al), and depending on various failure modes, some are
better than others for a subset of failures and vice versa.

The hierarchical UUNET design for example, is fairly dense in terms of
volume, with a small time diameter per region for a network of that size,
which allows for some local optimizations. And if you get two circuits
into two regions, some failures in one region can be isolated and
compartmentalized, without a major spillover into the neighboring regions,
which would not be the case in a large flat network.

As always, with good engineering, comparable reliability can be
established, given appropriate amounts of money being thrown at the
problem.

/vijay




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