How to send/recv priority data!

[Zhu Ming <zhum@sentosa.sas.ntu.ac.sg>]

Hello,

Send/Recv message among nodes, and the messages are priority messages...
 

If I set up the link----a priority link--- as following:

 $ns duplex-link $n1 $n2 1.5Mb 10ms RED

and then set up Agent TCP or UDP and attch-agent to send/recv data in the 
link.

set tcp [new Agent/TCP]
$ns attach-agent ...

But I want to send/recv  high-priority data in the network, meantime, put 
the background traffic in low-priority.
How can I deal with them? Can I control the priority of sending/recving 
data in the TCL script file? Or I must modify the send() function in 
UDP/TCP agent?

Thank you very much,
Zhu Ming.