On Jul 24, 2008, at 5:12 PM, Norberto Meijome wrote:
I'm interested in knowing the application level RTT for a HTTP application - ie, not from SYN , SYN/ACK ... FIN , FIN/ACK , but from the POST (http.request
in wireshark) by an  app on my side to the response by the server
(http.response). I have no access to either app's code.

Try something like this on the webserver or client machine:

# tcpdump -ttt -q -n -A tcp port 80
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on fxp0, link-type EN10MB (Ethernet), capture size 96 bytes
000000 IP > tcp 488
[EMAIL PROTECTED]/.%....|.g...A.P.4`...&8...."c.....
9".,....GET /server-status HTTP/1.1
001348 IP > tcp 1448
[EMAIL PROTECTED]@....g.....|.P.A..&8.4b.....J......
....9".,HTTP/1.1 200 OK

...which indicates a delay of 1.348 ms from the HTTP GET to the HTTP 200 response. This is using the following "delta timestamp" mode;

-ttt Print a delta (in micro-seconds) between current and previous
              line on each dump line.)

If you use tcpdump -w to save the packets captured to a file for analysis, you can feed it to net/tcpflow port to reconstruct this into individual flows, which will make it easier to figure out if your traffic starts getting interleaved.


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