[ns] regarding the ns tutorial

[Sumitha Bhandarkar <sumitha@ee.tamu.edu>]

the ns tutorial at the link

http://www-mash.cs.berkeley.edu/ns/tutorial/

says that it is very outdated. however it does not give a link to some
other site which may have the tutorial. the ns manual goes too much into
detail and is dificult for using as a quick reference. is there any other
manual which (like the manual at this link) lists all the objusts in ns
and a brief one-paragrah explanation about each object ? if yes pls let me
know. i am not currently on the ns-users mailing list, so pls reply to
this mail directly or send reply to 
sumitha@cs.tamu.edu

also, is there some simple way in which i can drop a packet  at some
regular intervals of simulations time say 2, 4, 6 and 10 seconds ? the
topology is simple and contains just two nodes and a link between and the
agent used is TCP with an FTP source.

thanks in advance. i appreciate it.
sumitha