clink

clink (Characterize Links) is a utility I wrote that does the same thing
as pathchar -- it estimates the latency and bandwidth of Internet links by
sending UDP packets from a single source and measuring round-trip
times. The basic mechanism is similar to ping and traceroute, except that
clink generally has to send many more packets. 

The interface of clink is based on the interface of pathchar, and the
underlying mechanism is based on Jacobson's description of pathchar. No
pathchar source code is included in clink. 

Here is the documentation for clink. (see clink.doc)

clink is based on trout, which is a simple version of traceroute written
by Allen Downey, but which is heavily based on the version of traceroute
Richard Stevens presents in his book UNIX Network Programming: Volume 1,
Second Edition. 

In Summer 1998, I wrote the data processing part of clink, which became
one of the source code files below (process.c). I used the alpha version
of pathchar to collect data, and wrote a paper describing my experiences,
and proposing some improvements to pathchar's data processing. 

In Summer 1999, I wrote the data collection part of clink, which is the
source code file called collect.c, and assembled the pieces into this
distribution. I am currently working on (1) implementing the improvements
I suggested in my SIGCOMM paper, and (2) testing additional
improvements. 

So far, the primary differences between pathchar and clink are: 

1) clink uses the even-odd technique described in the SIGCOMM paper to
generate interval estimates for bandwidth. 

2) when clink encounters a routing instability, it collects data for ALL
the paths it encounters, until one of the paths generates enough data to
yield an estimate. 

The source code for clink is available here in a tar file (82 KB) or at
gzipped tar file (23 KB). The next major addition to clink will be
adaptive data collection as described in the SIGCOMM paper. 

The clink homepage is located at:

	http://allendowney.com/research/clink/

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