NAME

     sc_tbitpmtud — scamper driver to test systems for responsiveness to ICMP packet too big messages

SYNOPSIS

     sc_tbitpmtud [-r] [-a address-file] [-c completed-file] [-l limit-per-file] [-m maximum-transmission-unit]
                  [-o output-file] [-p scamper-port] [-t log-file] [-w window]

     sc_tbitpmtud [-d dump-id] [-A ip2as-file] [-m maximum-transmission-unit] [file ...]

DESCRIPTION

     The sc_tbitpmtud utility provides the ability to connect to a running scamper(1) instance and use that
     instance to test end systems for their ability to perform Path MTU Discovery, with the output written to a
     file in warts format.  sc_tbitpmtud first tests a given system for responsiveness to ICMP echo packets, and
     then tests the given system's TCP stack response to ICMP packet too big messages.

     The options are as follows:

     -?      prints a list of command line options and a synopsis of each.

     -a address-file
             specifies the name of the input file which consists of a sequence of systems to test, one system
             per line.

     -A ip2as-file
             specifies the name of a file which consists of a mapping of prefixes to ASes, one prefix per line.

     -c completed-file
             specifies the name of a file to record IP addresses that have been tested.

     -d dump-id
             specifies the dump ID to use to analyze the collected data.  Currently, ID values 1 (mssresults)
             and 2 (asnresults) are valid, which report PMTUD behaviour according to the server's MSS or the
             server's origin ASN.

     -l limit-per-file
             specifies the number of tbit objects to record per warts file, before opening a new file and
             placing new objects.

     -m maximum transmission unit
             specifies the pseudo maximum transmission unit to use.  The available choices are 0, 256, 576,
             1280, 1480.  If 0 is chosen, sc_tbitpmtud will test each website with all available MTU choices in
             decreasing size.  The default MTU value tested is 1280.

     -o output-file
             specifies the name of the file to be written.  The output file will use the warts format.

     -p scamper-port
             specifies the port on the local host where scamper(1) is accepting control socket connections.

     -r      shuffle the order in which websites are tested.

     -t log-file
             specifies the name of a file to log progress output from sc_tbitpmtud generated at run time.

     -w window-size
             specifies the maximum number of tests to conduct in parallel.  The window size value depends on the
             value of the -F parameter passed to the scamper(1) instance.

EXAMPLES

     Use of this driver requires a scamper(1) instance listening on a port for commands with a configured
     firewall.  The following invocation uses ipfw(8) firewall rules 1 to 100, with a corresponding window size
     of 100, and an unrestricted packets per second rate, as follows:

           scamper -P 31337 -F ipfw:1-100 -w 100 -p 0

     To test a set of web servers specified in a file named webservers.txt and formatted as follows:

        1,example.com 5063 192.0.2.1 http://www.example.com/
        1,example.com 5063 2001:DB8::1 http://www.example.com/
        1,example.com 5063 2001:DB8::2 https://www.example.com/

     the following command will test all servers for responsiveness to ICMP packet too big messages and record
     raw data into webservers_00.warts, webservers_01.warts, etc:

           sc_tbitpmtud -a webservers.txt -p 31337 -o webservers

     The webservers.txt file is required to be formatted as above.  The format is: numeric ID to pass to tbit, a
     label for the webserver, the size of the object to be fetched, the IP address to contact, and the URL to
     use.

     To characterize PMTUD behaviour according to the server's advertised MSS value:

           sc_tbitpmtud -d mssresults webservers_*.warts

     Given files with IPv4 prefixes in prefix2as4.txt and IPv6 prefixes in prefix2as6.txt formatted as follows:

        2001:DB8::     48     64496
        2001:DB8:1::   48     64497
        192.0.2.0      24     64498

     the following command will characterize PMTUD behaviour according to the origin ASN of the server:

           sc_tbitpmtud -d asnresults -A prefix2as4.txt -A prefix2as6.txt webservers_*.warts

SEE ALSO

     scamper(1), sc_wartsdump(1), sc_warts2json(1), warts(5),

     M. Luckie and B. Stasiewicz, Measuring Path MTU Discovery Behaviour, Proc. ACM/SIGCOMM Internet Measurement
     Conference 2010.

     A. Medina, M. Allman, and S. Floyd, Measuring Interactions between Transport Protocols and Middleboxes,
     Proc. ACM/SIGCOMM Internet Measurement Conference 2004.

AUTHORS

     sc_tbitpmtud was written by Matthew Luckie <mjl@luckie.org.nz>.  Ben Stasiewicz contributed an initial
     implementation of the Path MTU Discovery TBIT test to scamper, building on the work of Medina et al.