RTT Stats

RTT (Round-Trip Time) statistics are generated when the -r option is specified along with the -l option (Section 4.1). The following fields of output are produced along with the output generated by the -l option.

surya:/home/mani/tcptrace-manual> tcptrace -lr indica.dmp.gz

1 arg remaining, starting with 'indica.dmp.gz'
Ostermann's tcptrace -- version 6.4.5 -- Fri Jun 13, 2003

153 packets seen, 153 TCP packets traced
elapsed wallclock time: 0:00:00.128422, 1191 pkts/sec analyzed
trace file elapsed time: 0:00:19.092645
TCP connection info:
1 TCP connection traced:
TCP connection 1:
	host a:        192.168.0.70:32791
	host b:        webco.ent.ohiou.edu:23
	complete conn: yes
	first packet:  Thu Aug 29 18:54:54.782937 2002
	last packet:   Thu Aug 29 18:55:13.875583 2002
	elapsed time:  0:00:19.092645
	total packets: 153
	filename:      indica.dmp.gz
   a->b:			      b->a:
     total packets:            91           total packets:            62      
           . . .                                  . . .
           . . .                                  . . .
     throughput:               10 Bps       throughput:               94 Bps  

     RTT samples:              48           RTT samples:              47      
     RTT min:                74.1 ms        RTT min:                 0.1 ms   
     RTT max:               204.0 ms        RTT max:                38.8 ms   
     RTT avg:               108.6 ms        RTT avg:                 8.1 ms   
     RTT stdev:              44.2 ms        RTT stdev:              14.7 ms   

     RTT from 3WHS:          75.0 ms        RTT from 3WHS:           0.1 ms   

     RTT full_sz smpls:         1           RTT full_sz smpls:         1      
     RTT full_sz min:        79.5 ms        RTT full_sz min:         0.1 ms   
     RTT full_sz max:        79.5 ms        RTT full_sz max:         0.1 ms   
     RTT full_sz avg:        79.5 ms        RTT full_sz avg:         0.1 ms   
     RTT full_sz stdev:       0.0 ms        RTT full_sz stdev:       0.0 ms   

     post-loss acks:            0           post-loss acks:            0
     
	  For the following 5 RTT statistics, only ACKs for
	  multiply-transmitted segments (ambiguous ACKs) were
	  considered.  Times are taken from the last instance
	  of a segment.
     ambiguous acks:            1           ambiguous acks:            0      
     RTT min (last):         76.3 ms        RTT min (last):          0.0 ms   
     RTT max (last):         76.3 ms        RTT max (last):          0.0 ms   
     RTT avg (last):         76.3 ms        RTT avg (last):          0.0 ms   
     RTT sdv (last):          0.0 ms        RTT sdv (last):          0.0 ms   
     segs cum acked:            0           segs cum acked:            0      
     duplicate acks:            0           duplicate acks:            0      
     triple dupacks:            0           triple dupacks:            0      
     max # retrans:             1           max # retrans:             0      
     min retr time:         380.2 ms        min retr time:           0.0 ms   
     max retr time:         380.2 ms        max retr time:           0.0 ms   
     avg retr time:         380.2 ms        avg retr time:           0.0 ms   
     sdv retr time:           0.0 ms        sdv retr time:           0.0 ms

The raw RTT samples found can also be dumped into data files with the -Z option as in

tcptrace -Z file.dmp

This generates files of the form a2b_rttraw.dat and b2a_rttraw.dat (for both directions of the first TCP connection traced), c2d_rttraw.dat and d2c_rttraw.dat (for the second TCP connection traced) etc. in the working directory. Each of the datafiles contain lines of the form :

seq#    rtt
where seq# is the sequence number of the first byte of the segment being acknowledged (by the ack packet that contributed this RTT sample) and rtt is the RTT value in milli-seconds of the sample. Note that only valid RTT samples (as counted in the RTT Samples field listed above) are dumped.


Super-User 2003-08-29