traceroute/Solaris ICMP issue

Neal Cardwell (cardwell@cs.washington.edu)
Wed, 16 Sep 1998 12:55:49 -0700 (PDT)

When Stefan and i heard from Vern Paxon at SIGCOMM that Solaris
rate-limits outgoing ICMP packets, this reminded me of something i thought
i rememberd from playing around with traceroutes: some end hosts seemed to
deterministically drop the second response. That is, you get seomething
like:

traceroute to WWW.LB.CS.CMU.EDU (128.2.209.79) from 128.255.56.4
....
5 garcia-72.psc.edu (128.182.72.16) 21 ms 20 ms 21 ms
6 140.173.6.78 (140.173.6.78) 21 ms 21 ms 21 ms
7 ALMOND.SRV.CS.CMU.EDU (128.2.209.79) 25 ms * 25 ms

where there is *always* an asterisk in the middle of the last line, even
with low loss rates along this path.

While setting up my Mom's ISP service, i noticed one of these cases, and
found a bunch more. It seems to be widespread, particularly among Solaris
machines. For example, all the Solaris machines in the department here
that i tried (about 8) exhibited this quirk, as did a bunch more:

now.cs.berkeley.edu (Solaris)
u1.cs.berkeley.edu (Solaris)
clump0.cs.berkeley.edu (Solaris)
www.inktomi.com (Solaris)
www.javasoft.com (Solaris)
www.infoseek.com
www.cs.stanford.edu
www.cs.cmu.edu
www.ee.cornell.edu
www.lcs.mit.edu
www.cs.princeton.edu

This may or may not be caused by Solaris ICMP quirks, but it seems that it
is fairly widespread, and, if we haven't accounted for this already, we'll
need to be very careful in the future when using traceroute results to
infer loss rates, so we don't think that (say) all the solaris hosts in
the world are seeing 33% loss rates.

neal