Re: document coming around one more time

[Tom Reddington <treddington@bell-labs.com>]

Wai,

I took out the two references to vulnerability that occurred in this
paragraph. I think people think of vulnerabilities as being inherent design
flaws or misconfigurations  in a system. A fault may occur because of a
vulnerability but it may also occur because the design specifications of a
system are exceeded. So, a cable that is left lying on the top of a road is
considered vulnerable but a cable that is buried 3 feet down is not considered
vulnerable. In both cases a fault may occur when the back hoe moves.

The word "vulnerability" is somewhat interpretive.

tom

Try this for a definition

Shared risk group (SRG) is a set of network elements that are collectively
impacted by a specific fault or fault type. For example, a shared risk link
group (SRLG) is the union of all the links on those fibers that are routed in
the same physical conduit in a fiber-span network. This concept includes,
besides shared conduit, other types of compromise such as shared fiber cable,
shared right of way, shared optical ring, shared office without power sharing,
etc. The span of an SRG, such as the length of the sharing for compromised
outside plant, needs to be considered on a per fault basis.