On Mar 25, 2011, at 1:44 PM, Bill Woodcock wrote: > On Mar 24, 2011, at 4:27 PM, Ravi Ramaswamy wrote: >>
>> I am using 2.5 Tbps as the peak volume of peering traffic over all peering >> points for a Tier 1 ISP, for some modeling purposes. Is that a reasonable >> estimate? > > That's actually a very difficult research question for the academic > community, and one that they've been struggling with since they lost their > overview of the NSFNET backbone in ~1992. > > Ironically, it's quite easy for any one ISP to answer internally, but these > numbers are closely held as trade-secrets. > > One thing you can do is look at the total volume of publicly-reported traffic > across IXP switch fabrics: > > > https://prefix.pch.net/applications/ixpdir/summary/growth-region/?sort1=bandwidth&sort2=_current&order=desc > > > > https://prefix.pch.net/applications/ixpdir/?show_active_only=0&sort=traffic&order=desc > > …where you see about 8.3Tbps of overall reported traffic. Then you could do > various analyses comparing IXPs where crossconnects are prevalent (Equinix > Ashburn, say) to ones where they are not, and looking at which ISPs peer at > each. You could also try to find out from ISPs which IXPs they use > crossconnects at, and which they don't. That may be easier information for > you to get than how much traffic they're doing individually. IXP vs. private interconnect (be it peering or customer/transit) ratios varies dramatically with geography, scale, and even the proclivities of the various network architects. The question is whether "some data" is better than "no data". Honestly, I'm not sure. I see lots of things with 'some data' that are actually worse than guesses. But where I cannot eventually find the actual answer, I am left wanting to prefer the "some data" ones, probably because "data" sounds good. > It might also be interesting to look at some of the IXPs that publish > per-participant traffic figures, to see if you can develop characteristic > statistical distributions for amount-each-participant-contributes-to-the-IXP, > though you should be cautioned that the curve might be much heavier-tailed > for a large exchange than a small one. Even that is dangerous. For instance, some participants move traffic away from such IXPs. (That is not a guess, I know first hand that this happens - especially as I am one of those people.) -- TTFN, patrick
