Alternative to NetFlow for Measuring Traffic flows

William B. Norton wbn at
Tue Dec 17 01:46:10 UTC 2002

Hi all -

Here is the problem: Everyone wants to know how much traffic would 
ultimately be  passed in peering relationships at an IX before signing 
up/building into an IX.

I heard an interesting solution recently to estimating the traffic volume 
destined to an AS in the absence of NetFlow or the like. The ability to 
measure traffic via sampling has been difficult for a variety of reasons 
(lack of staff resources, capabilities of the interface cards, expensive 
SW, etc.) and I found from talking to Peering Coordinators that less than 1 
in 20 ISPs actually do the traffic  measurements. In the absence of data, 
ISPs are often left to intuition, guessing that a particular AS would be a 
good peering candidate.

Here is the Solution:

Assuming that:
1) You are multi-homed
2) You have some ideas of who you would want to peer with
3) <more assumptions here I'm sure>

1) You adjust routing to prefer one transit provider or the other for the AS
2) Shift traffic to the particular AS from one transit provider to the 
other, noting the change in the loads on the transit providers.

If you do this at peak time you can get a rough estimate of the peak 
traffic to this AS, and therefore a rough order of magnitude estimate of 
the amount of traffic that would go to this AS in a peering relationship. 
(Rough Estimate means determining if the traffic volume is likely to be 2 
Mbps vs. 20 Mbps vs. 200Mbps)

Interesting idea. Comments?

The other approach some ISPs use is to set up a "trial" peering session, 
usually using a private cross connect to measure the traffic volume and 
relative traffic ratios. Then both side can get an idea of the traffic 
before engaging in a contractual Settlement-Free Peering relationship.


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