On Jul 16, 2009, at 7:05 PM, Wayne E. Bouchard wrote:
On Thu, Jul 16, 2009 at 06:32:32PM -0400, Deepak Jain wrote:
As for trying to determine where your inbound traffic is coming from by looking at natural bgp, this is absolutely impossible to do correctly. First off, your inbound is someone else's outbound, and the person sending the traffic outbound is in complete and total control. The vast majority of the traffic on the Internet is being picked by local- prefs based on policies like "what does this make/cost me monetarily" or "which major networks can I grab in a simple as-path regexp to balance some traffic". But even if you ignore all of that, the "natural" path selection is based on criteria which is specific to the other network or even to a specific session which you can't possibly know about remotely (e.g. their router id).
I would actually disagree with that and go one step further. Look at content providers. They're not concerned about best path. They're not even concerned about shortest path. Since bandwidth consuming services are what they provide, they're interested in cheapest path as much as they are the shortest path.
s/content providers/some content providers, some eyeball networks, some corporate networks, and some of just about every type of network/ OTOH: Some content providers measure latency, packet loss, and throughput and react accordingly to ensure the end users get adequate performance, no matter the path or cost. Interestingly, in either case, the 'natural' BGP selection is a poor predictor of inbound traffic. But then we already knew that. :) -- TTFN, patrick