[ns] Need help simulating model

[Brenda Lindsay Williams]

Hi I'm trying to simulate a core network and carry out measurements based on
VoIP QoS parameters...
I wanna connect 3-4 WAN models to a core network which consists of
routers...
Can someone pls give me an idea of how to go about this using NS-2...
what would my tcl scripts look like?
how many nodes do i need for each WAN and how can I interconnect them to
depict a proper WAN model?
how can I use tcl scripts to configure a core network which consists of
routers and manage traffic?
Please someeone help.
Thanks

Regards,

Brenda