out of the black bags of wizards...

  • To: apops at teckla dot apnic dot net
  • Subject: out of the black bags of wizards...
  • From: David R Conrad <davidc at apnic dot net>
  • Date: Wed, 23 Apr 1997 08:42:22 +0900
  • Sender: owner-apops@apnic.net
    • For those who don't know, Van was the guy who came up with
      traceroute, vat, and TCP slow-start...
      ------- Forwarded Message
      Date:    Mon, 21 Apr 1997 06:19:16 -0700
      From:    Van Jacobson <van at ee dot lbl dot gov>
      To:      ietf at ietf dot org
      cc:      rem-conf at es dot net
      Subject: pathchar - a new tool for characterizing Internet paths
      For the past 6 years, I've been working on a tool to figure out
      more about an Internet path that just what routers you go through.
      I've developed a tool called `pathchar' (for `path characteristics')
      that tells you the bandwidth, distance from previous hop, average
      queue, and drop rate for every hop on the path (*not* just the
      bottleneck hop).  This is a typical output:
          % pathchar ka9q.ampr.org
           mtu limitted to 1500 bytes at local host
           doing 32 probes at each of 64 to 1500 by 32
           0 localhost
           |   8.7 Mb/s,   292 us (1.97 ms)
           1 ir40gw.lbl.gov (
           |    29 Mb/s,   132 us (2.64 ms)
           2 er1gw.lbl.gov (
           |    91 Mb/s,   189 us (3.15 ms)
           3 lbl-lc1-1.es.net (
           |    25 Mb/s,   6.92 ms (17.5 ms)
           4 gac-atms.es.net (
           |    11 Mb/s,   424 us (19.4 ms)
           5 CERFNETGWY.GAT.COM (
           |   7.0 Mb/s,   1.20 ms (23.5 ms)
           6 sdsc-ga.cerf.net (
           |   ?? b/s,   -263 us (22.8 ms)
           7 mobydick-fddi.cerf.net (
           |    46 Mb/s,   -51 us (22.9 ms)
           8 qualcomm-sdsc-ds3.cerf.net (
           |   9.0 Mb/s,   17 us (24.3 ms)
           9 krypton-e2.qualcomm.com (
           |   5.5 Mb/s,   1.04 ms (28.6 ms)
          10 ascend-max.qualcomm.com (
           |   56.7 Kb/s,   6.19 ms (253 ms)
          11 karnp50.qualcomm.com (
           |    10 Mb/s,   -50 us (253 ms),  +q 3.32 ms (6.58 KB) *2
          12 unix.ka9q.ampr.org (
          rtt 32 ms (253 ms), bottleneck 56.7 Kb/s, pipe 4706 bytes
      The lines starting with `|' are the characteristics of the link
      between the hops listed above & below.  The first number is the
      link bandwidth, the 2nd is the one-way prop time (i.e., for a
      zero length packet) & the number in parens is the round trip
      time you would get if there were no queues and you sent a
      path-mtu sized packet from the source to this hop (i.e., the
      unloaded data rtt).  If there's a queue larger than 1 packet,
      its size in both time & bytes is printed.  If the drop rate is
      more than 1%, it's printed.
      Note that it successfully found the LBL FDDI dmz (hops 2-3) &
      SDSC-Qualcomm T3 (hops 7-8) even though I was running it behind
      a 10Mb/s ethernet.  And that the long hop from San Francisco to
      San Diego is clearly visible (3-4).  (Also note that I was
      running this at 1am this morning so the normal cerfnet queues
      were missing & only Phil's P50 ISDN box showed a queue.)
      We're hoping to release pathchar sometime in the next two weeks.
      I'm giving a talk on it today at 4pm PDT for MSRI Math Awareness
      Week and the talk should be mboned.  I've put the viewgraphs
      from the talk (which are the only existing documentation) at
      If you really deperately want to play with a very flakey, alpha
      version of pathchar, there are binaries for freebsd, linux and
      solaris in the same directory (but you are totally on your own
      when running this -- we'll answer questions once the beta release
      goes out but right now we're putting all our energy into getting
      it out).
       - Van
      ------- End of Forwarded Message
      To unsubscribe: send "unsubscribe" to apops-request at apnic dot net