dnsfunnel(1)			   Vantages			  dnsfunnel(1)

NAME

       dnsfunnel - a DNS PMTU walking tool

SYNOPSIS

       dnsfunnel [@server] [OPTIONS] <zone>

DESCRIPTION

       dnsfunnel  is a simple tool that queries each of a zone's authoritative
       name servers to determine what the DNS PMTU limitation is.  The dnsfun-
       nel  tool  uses	a  binary search to determine the precise EDNS0 buffer
       size that can be specified before a DNS response is silently dropped by
       the network.

       The  formal  of	the  output is designed to resemble traceroute in that
       during a PMTU walk, each request size to each name server is  specified
       on its own line.  For example:

       129.82.138.19   4096B   0.000151
       129.82.138.19   2304B   0.000159
       129.82.138.19   1408B   0.000161
       129.82.138.19   960B    0.000092 (truncated)
	...

       The results of running dnsfunnel show what the minumum buffer size that
       can be specified is before a truncation bit is set (i.e. the server has
       more  data  to  send  but could not fit it in the advertized size), the
       maximum size that can be advertised before  a  network  drop,  and  the
       optimal size to specify in order to get the most data that can fit over
       the path:

	...
       PMTU walking summary:
       ================================================
       Name Server     Keys    Small   Largest Optimal
       IP	       fit?    Buffer  Buffer  Buffer
       ------------------------------------------------
       131.179.96.160  yes     2096    4096    2096
       129.82.138.19   yes     2117    4096    2117

OPTIONS

       The options are:

       @server
	      This options specifies what server you wish dnsfunnel  to  query
	      from.

       -t --timeout <number of seconds>
	      The number of seconds before timeout.

       -r --retries <log file>
	      The number of retries to an unresponsive server.

       -h --help
	      Display a helpful reminder of this information.

SEE ALSO

       vantaged, vantaged.conf, dnskey-grab.

AUTHORS

       dnsfunnel  was mainly developed by Eric Osterweil, with help from Bren-
       dan Sheridan, and Dave Oko

CONTACT

       tools@netsec.colostate.edu




UCLA/CSU NetSec 		 Jul 20, 2009			  dnsfunnel(1)