Discovering AS Path confederation...

Chris Rapier rapier at
Wed Jul 25 20:55:07 UTC 2001

I was wondering if anyone knew how to do as path confederation

Let me explain...

I'm plotting observed traffic against BGP reported AS paths to get a
logical view of traffic flow in a smallish network (I2). However, it was
pointed out to me (by Bradley Huffaker) that the BGP reported path does
not always correspond to the ASes a packet actually traverses. He
provided me with some skitter data and routing table archives and I was
able to confirm this on both his data and my own data. 

My contention is that the vast majority of this seeming divergence is
the result of AS confederation and not any specific failure of the
protocol (or implementation) as a whole. However, in light of what I am
trying to do for my research, its important that I have more than a gut
feeling to back up this claim. 

What I was thinking of doing was to collect a large number of traces and
their corresponding traversed ASes and run statistical analysis on it to
infer the confederations. If these confederations are mostly stable then
I can say the observed divergence corresponds to this previously seen
path. E.g.... I run a trace and find it traverses 701 702 8414 2912 7262
101 while the route table indicates its path should be 701 7262 101. If
I know that 701 is confederating 8414 and 2912 then I know that the
actual path corresponds to the routing table. However, I first need to
determine that UUnet if actually doing that. 

At this point I'm stuck on that step and could use any pointers or
insights people might have. Obviously, the best thing would be a paper
that has already done exactly this so I can move on but I'll take
anything. :) 

Chris Rapier

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