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From: "Patrick W. Gilmore" <patrick@ianai.net> In-Reply-To: <B0EE3AA4-1DF6-4B8B-B75C-54EC1A70B227@pch.net> Date: Fri, 25 Mar 2011 13:51:02 -0400 To: NANOG list <nanog@nanog.org> Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org On Mar 25, 2011, at 1:44 PM, Bill Woodcock wrote: > On Mar 24, 2011, at 4:27 PM, Ravi Ramaswamy wrote: >>=20 >> 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? >=20 > 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. >=20 > Ironically, it's quite easy for any one ISP to answer internally, but = these numbers are closely held as trade-secrets. >=20 > One thing you can do is look at the total volume of publicly-reported = traffic across IXP switch fabrics: >=20 > = https://prefix.pch.net/applications/ixpdir/summary/growth-region/?sort1=3D= bandwidth&sort2=3D_current&order=3Ddesc=20 >=20 > = https://prefix.pch.net/applications/ixpdir/?show_active_only=3D0&sort=3Dtr= affic&order=3Ddesc >=20 > =85where 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.) --=20 TTFN, patrick
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