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Bad packet duplication in Germany

  • From: Mark Handley < >
  • Date: Fri, 03 May 96 13:24:46 +0100
  • Cc: 
A tcpdump I had running just caught this packet duplication:
13:18:19.362971 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 42, id 40581)
13:18:19.368508 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 41, id 40581)
13:18:19.379626 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 40, id 40581)
13:18:19.399898 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 39, id 40581)
13:18:19.406711 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 38, id 40581)
13:18:19.417609 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 37, id 40581)
13:18:19.436923 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 36, id 40581)
13:18:19.447283 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 35, id 40581)
13:18:19.461495 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 34, id 40581)
13:18:19.473894 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 33, id 40581)
13:18:19.485550 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 32, id 40581)
13:18:19.499816 faui45r.informatik.uni-erlangen.de.47276 > 224.2.127.255.9876: udp 184 (ttl 31, id 40581)

Clearly there's a ttl 1 loop somewhere either in Erlangen or between
there and Stuttgart, then the ttl falls below the threshold 32 on the
link to me:

Mtrace from 131.188.34.54 to 128.16.64.19 via group 224.2.0.1
Querying full reverse path... 
  0  shrew.cs.ucl.ac.uk (128.16.64.19)
 -1  lea.cs.ucl.ac.uk (128.16.64.24)  DVMRP  thresh^ 1  Output pruned
 -2  mbone-atm.rus.uni-stuttgart.de (129.69.200.36)  DVMRP  thresh^ 32  
 -3  ? (188.1.78.28)  DVMRP  thresh^ 32  
 -4  ds9.gate.uni-erlangen.de (131.188.6.3)  PIM  thresh^ 24  
 -5  sashimi.gate.uni-erlangen.de (131.188.6.9)  PIM  thresh^ 8  Wrong interface
Round trip time 206 ms

What this is doing to the German Mbone I hate to think.

Mark
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