bgp flap dampening

[Sean Doran <smd () cesium clock org>]

I should point out that there are now a couple of large
networks playing around with code derived from the 
paper Curtis Villamizar presented at the NANOG meeting
at NCAR.

Initial testing with route-dampening seems to hold out
some promise.  Probably the main question now will be 
how aggressively to attack the issues of flapping prefixes.

With the current default values, and given that it's 
not exactly peak usage time, there are some 100 prefixes
from essentially all over the Internet being dampened.

        Sean.