NAME

     sc_tracediff — display traceroute paths where the path has changed.

SYNOPSIS

     sc_tracediff [-a] [-m method] [-n] file1.warts file2.warts

DESCRIPTION

     The sc_tracediff utility displays pairs of traceroutes to a destination where the path has
     changed.  It takes two warts files as input and displays paths where a hop differs by its
     address.  The options are as follows:

     -a      dump all traceroute pairs regardless of whether they have changed.

     -m method
             specifies the method used to match pairs of traceroutes together.  If dst is
             specified, traceroutes are matched if the destination IP address of both traces are
             the same.  If userid is specified, traceroutes are matched if the userid field of
             both traces are the same.  If dstuserid is specified, traceroutes are matched if the
             destination IP address and userid fields are the same.  By default, the destination
             IP address is used.

     -n      names should be reported instead of IP addresses, where possible.

     sc_tracediff can be useful in network monitoring to identify when a forward IP path has
     changed.  In this scenario, it is recommended that Paris traceroute is used with the same
     UDP source and destination ports for each execution of scamper so that only paths that have
     changed are identified, not merely alternate paths visible due to per-flow load-balancing.
     By default scamper uses a source port based on the process ID, which will change with each
     execution of scamper.

EXAMPLES

     The command:

        scamper -O warts -o file1.warts -c 'trace -P udp-paris -s 31337' -f list.txt

     collects the forward IP paths towards a set of IP addresses found in list.txt using 31337 as
     the UDP source port value.  If the above command is adjusted to subsequently collect
     file2.warts, then we can identify paths that have subsequently changed with the command:

        sc_tracediff file1.warts file2.warts

     If Paris traceroute with ICMP probes is preferred, then the following invocation of scamper
     is appropriate:

        scamper -O warts -o file1.warts -c 'trace -P icmp-paris -d 31337' -f list.txt

     In this case, scamper uses 31337 as the ICMP checksum value in each probe.

SEE ALSO

     scamper(1),

     B. Augustin, X. Cuvellier, B. Orgogozo, F. Viger, T. Friedman, M. Latapy, C. Magnien, and R.
     Teixeira, Avoiding traceroute anomalies with Paris traceroute, Proc. ACM/SIGCOMM Internet
     Measurement Conference 2006.

AUTHOR

     sc_tracediff was written by Matthew Luckie <mjl@luckie.org.nz>.