[X4U] Software Update-low level how does it work?

[Russell McGaha]

Folks;
	First, PLEASE excuse the x-post for those of you who get both lists.
	Second, I've got some clients on a Government installation that are 
having troubles getting Software Update to do it's stuff.  Their 
networking department can 'see' packets going out to '17.250.248.95' 
(resolves to swscan.apple.com), but a reply NEVER comes back, yet 
anywhere EXCEPT on their network Software Update just 'does it's thing' 
[I've left an update waiting on my powerbook, just to check things].
	Does anyone know, what ports, protocols, etc. Software updates uses, 
or just how it works?  Supposedly they are NOT blocking any ports or 
going thru a proxy server that requires a username/password [the only 
article I found at Apple that closely matches what's happening, 
references this as a problem].

THANKS for ANY help;
Russell

P.S. The error Software Update gives is "unable to connect to the 
Internet, please check your network connection and try again"; all 
other browsing works fine.