Re: Alternative to NetFlow for Measuring Traffic flows

[Richard A Steenbergen <ras () e-gerbil net>]

On Mon, Dec 16, 2002 at 11:41:12PM -0500, alex () yuriev com wrote:
> > 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 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.

-- 
Richard A Steenbergen <ras () e-gerbil net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)