Alternative to NetFlow for Measuring Traffic flows

alex at alex at
Tue Dec 17 14:06:40 UTC 2002

> > > Also, that method has the same "knowing the routes" problem as netflow. 
> > > Whereever you are getting your list of ASN's route ASN.*"'s routes, there 
> > > is pretty much no way they are accurate (for an ASN of ANY size).
> > 
> > The vast majority of the routes will be an intersection of routes
> > announced by the AS to other AS (including looking glasses).
> Assume you are provider A, and you are considering peering with provider
> B. Assume Provider B has customer Z, who buys transit from Provider B and
> Provider C. Assume you already peer with provider C.
> You have no way to know if customer Z will be part of your routes to 
> Provider B, or if you will prefer them over provider C, without having the 
> route list.

This is a standard problem resolved in the set theory. Pick your set.
Measure. Pick your set again, measure. Repeat N times. Decide which set of
results you accept as more likely. Use them.


> This is a very common situation if you have any decent amount of peering,
> and/or if you are considering peering with a provider who has any
> reasonable number of multihomed customers. As we've already proved in
> previous nanog emails, the top 20 route-announcing providers added
> together have enough routes to cover the internet around 8 times over. 
> Even looking glasses may not contain all the paths available.
> Projecting actual IP traffic onto actual IP routes is the only way to do 
> it.


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