[ns] Why TCP's t_seqno does not decreasing?

[yschoi]

Hi.

I want to plot seqno. vs time(figure likes W. R. Stevens, TCP/IP Illustrated
Vol. 1, Figure 21.6.)

I used Polly Huang's red.tcl example(http://nile.wpi.edu/NS/Example/red.tcl)
and simply add following code

-snip-
set tcpxxx [open xxx.dat w]
$tcp1 attach $tcpxxx
$tcp1 trace cwnd_
$tcp1 trace t_seqno_
-snip-

As far as I understand, t_seqno_ is "next pkt to send"

So when tcp restransmission, t_seqno_ motion down.

But results are strange for me.

Although there are some pkt losses(and ECN is not enabled), t_seqno_ does
not decrease. it simply monotonously increases.

What am I missing?

Thanks a lot in advance,
And with best regards...

--
Young S.Choi