randy, On Sat, Sep 10, 2005 at 05:49:59PM +0700, Randy Bush wrote:
this report repeatedly uses the term "outage." how is that determined/measured?
i think this is covered in the report several times, but i'm sorry if it wasn't clear. this is based on work that we've done for a while (some of which was presented at nanog30: http://nanog.org/mtg-0402/ogielski.html). the general idea is: take a large peerset sending you full routes, keep every update forever, and take a reasonably long (at least a month or two) time horizon. calculate a consensus view for each prefix as to whether that prefix is reachable by some set of those peers. an outaged prefix is one that used to be reachable that not no longer is. in other words, one that has been withdrawn from the full table by some sufficiently large number of peers. we exclude single-peer outages and outages that only affect a few peers through some reasonable thresholding. make sense? that's the general idea. the implementation is obviously a *lot* more complicated. t. (i'm sure the question of covering prefixes will come up shortly and i'll address it when/if it does). :-) -- _____________________________________________________________________ todd underwood director of operations & security renesys - interdomain intelligence todd@renesys.com www.renesys.com