[77654] in North American Network Operators' Group
Rapidly-variable routing on the time scale of seconds to minutes?
daemon@ATHENA.MIT.EDU (Charles Shen)
Mon Jan 31 04:21:03 2005
From: "Charles Shen" <charles@cs.columbia.edu>
To: <nanog@merit.edu>
Date: Mon, 31 Jan 2005 04:20:31 -0500
Errors-To: owner-nanog-outgoing@merit.edu
We did a "traceroute" end-to-end routing measurement in 2004 and found =
about
5-10% of measuremnts exhibiting rapidly-variable routing on the time =
scale
of a single traceroute (seconds to minutes). In other words, the packets
belonging to a single traceroute took multiple paths.=20
Vern Paxson mentioned in 1997 one mechanism that can lead to this "route
fluttering" behavior as "route splitting", which is explicity allowed in
RFC1812 - Requirements for IP version 4 Routers.=20
Route change in such a short scale for packets in the same flow could be
troublesome. But the occurrence of such behavior does not seem to have
reduced over the past years at least from our measurements. Does anyone =
know
how to explain this behavior? Thanks!
An example traceroute record containing the fluttering is shown below =
(see
the 5th hop)
Fri Apr 09 09:35:35 2004
1 cisfhfb.fh-friedberg.de (212.201.24.1) 1.095 ms 0.402 ms 0.321 ms
2 ar-frankfurt2.g-win.dfn.de (188.1.42.9) 120.105 ms 198.766 ms =
200.040
ms
3 cr-frankfurt1-ge5-0.g-win.dfn.de (188.1.80.1) 2.093 ms 2.142 ms =
2.087
ms
4 so-6-0-0.ar2.FRA2.gblx.net (208.48.23.141) 2.461 ms 2.349 ms =
2.333 ms
5 pos5-0-2488M.cr2.FRA2.gblx.net (67.17.65.53) 2.448 ms
pos6-0-2488M.cr1.FRA2.gblx.net (67.17.65.77) 2.368 ms 2.281 ms
6 so3-0-0-2488M.ar2.FRA3.gblx.net (67.17.65.82) 2.676 ms 2.750 ms
so2-0-0-2488M.ar2.FRA3.gblx.net (67.17.65.58) 2.569 ms
7 ge-7-2.Frankfurt1.Level3.net (195.122.136.245) 10.971 ms 10.967 ms
10.882 ms
8 ae-0-55.mp1.Frankfurt1.Level3.net (195.122.136.97) 11.488 ms =
11.417 ms
11.353 ms
9 so-0-0-0.mp1.London2.Level3.net (212.187.128.61) 27.203 ms 27.042 =
ms
27.048 ms
10 so-1-0-0.bbr1.Washington1.Level3.net (212.187.128.138) 91.004 ms
91.006 ms 90.977 ms
11 ge-0-0-0.mpls1.Honolulu2.Level3.net (4.68.128.13) 212.254 ms =
212.321
ms 212.351 ms
12 so-7-0.hsa1.Honolulu2.Level3.net (4.68.112.90) 212.407 ms 212.250 =
ms
212.365 ms
13 s1.lavanet.bbnplanet.net (4.24.134.18) 212.609 ms 212.372 ms =
213.270
ms
14 malasada.lava.net (64.65.64.17) 212.260 ms 212.460 ms 212.226 ms
Best regards,
Charles=20
