[ns] changing more TCP defaults in NS

[Sally Floyd <floyd@aciri.org>]

I recently added a minrto_ variable to TCP, to set a minimum value for
the TCP RTO (retransmit timeout).  I just changed the default value
for minrto_ from 0 to 1 second.  To reproduce the earlier behavior,
just set minrto_ to 0 in tcl/lib/ns-default.tcl.

I would also like to change the following defaults for one-way TCP:
Agent/TCP set syn_ true
Agent/TCP set delay_growth_ true

This would result in the first TCP packet being 40 bytes.
In addition, if the TCP initial window is larger than one packet, then 
the initial window only applies after the first packet exchange. 
This is intended to partially model the SYN and SYN/ACK in TCP.

(The next most pressing thing on the list would be to change one-way
TCP to take into account the size of the packet header...)

- Sally
http://www.aciri.org/floyd/