network tuning and performance troubleshooting

[Bob McIsaac]

   Josh Carroll wrote:

     Problem: Browser status 'looking up address' for 10 seconds for any
      web page clicked. Slashdot takes almost a minute to load. But FTP
     performance is good and running a shoutcast stream is no problem.
     Sending mail via my ISP is slow.

     How about a large transfer over http with fetch or wget? Does it
     perform as well as an ftp connection? It could be a DNS problem.
     Try a
     dig of slashdot.org and see what the query time is:
     dig A slashdot.org | grep 'Query time'
     Run that a few times and see how fast it's resolving. It should be
     on
     the order of a 100ms or less, at least after the first query.
     Josh

   $ dig A slashdot.org | grep 'Query time'
   ;; Query time: 95 msec
   $ dig A slashdot.org | grep 'Query time'
   ;; Query time: 15 msec
   $ dig A slashdot.org | grep 'Query time'
   ;; Query time: 7 msec
   $ dig A slashdot.org | grep 'Query time'
   ;; Query time: 11 msec
   $ fetch  -v [1]http://www.freebsd.org/ports/growth/status.png
   looking up [2]www.freebsd.org
   connecting to [3]www.freebsd.org:80
   requesting [4]http://www.freebsd.org/ports/growth/status.png
   local size / mtime: 4725 / 1163039436
   remote size / mtime: 4725 / 1163039436
   status.png                                    100% of 4725  B   53
   kBps
   $ fetch -v [5]http://www.kde.org/screenshots/images/3.5/01-welcome.png
   looking up [6]www.kde.org
   connecting to [7]www.kde.org:80
   requesting [8]http://www.kde.org/screenshots/images/3.5/01-welcome.png
   remote size / mtime: 185546 / 1145367871
   01-welcome.png                                100% of  181 kB  177
   kBps
   $
   The numbers above seem sensible for 'dig' but fetch is not reporting
   the looking/connecting time which is seconds more than the
   download time.
   On google.maps the screen is divided into a grid and it takes a few
   seconds
   to fill in each one.  I always thought it was a single image.

References

   1. http://www.freebsd.org/ports/growth/status.png
   2. http://www.freebsd.org/
   3. http://www.freebsd.org/
   4. http://www.freebsd.org/ports/growth/status.png
   5. http://www.kde.org/screenshots/images/3.5/01-welcome.png
   6. http://www.kde.org/
   7. http://www.kde.org/
   8. http://www.kde.org/screenshots/images/3.5/01-welcome.png