Network Resilience - is it just a pretty picture?
TIPPINST --Some times when things go very wrong with a network you may ask your self, "why are we completely cut off?". "Where is our fall back that this nice drawing/map depicts?". Then you discover that the sales people for the ISP know how to draw pretty diagrams, but the engineers never got to implement them.
I have seen this occur at least half a dozen times in the past 10 years, and every time no one can answer or explain, why the pretty picture/ topology did not deliver. The problem with testing your resilience is that no ISP wants to completely cut off a link to demonstrate something to you, as they are afraid they will affect other customers while the links and routes are being recalculated etc.
As part of our networking course in Multimedia and Software development here in Tipperary Institute we examine the whole issue of poison reverse, hold down timers etc and how they facilitate resilience. The only time our students will ever see this in real life will be when something bad happens. It is only then will discover the real resilence of their network.
The reason is simply, your looking at the wrong "pretty picture". You need to look at the one the engineers have not the one the sales people have.