[LARTC] Server and router on the same box

[o7sh at actcom.net.il]

Hello list.
I'm trying to set up traffic shaping on a (web) server which is also a 
router(NAT) for my LAN.
It is connected to the LAN via Ethernet and also has PPP Internet connection 
on another interface.
I need traffic shaping to make sure that the upstream is fully available to 
the web-server when it's active so when a LAN client is bulk downloading the 
web-server clients won't wait for hours. Its kind giving high priority to the 
upstream and lowering the downstream.
it will be nice that when the web-server is not using any upstream, LAN 
clients will enjoy full bandwidth.
I've found lots of information on how to ensure downloading while uploading. 
but not on the reverse way.
Any idea for such a setup ?
Thanks.