[asterisk-users] Difference between SCCP and Cisco Call Manager traffic?

[shawnl at up.net]

I'm wondering about the difference between Cisco Call Manager and
SCCP(2) network traffic.  I'm working on getting a Cisco 7960 phone to
speak through a NAT to an asterisk box, without having to do a bunch of port
forwarding on the NAT device.

Without the nat, everything works fine.  

If the phone is behind a cisco pix that is doing the natting, it works
fine (fixup protocol).  

If the phone is behind a more generic nat device, such as a linux box
running ipfilter.  Then it can dial out, but there is no audio.  The
interesting part is that this same phone, behind the same NAT works just
fine if it is talking to a Cisco Call Manager box instead of an
asterisk server.  So, I'm wondering what the difference in the protocols is
(I no longer have access to the call manager box, so I can't look @ the 
traffic).  In a perfect world, I'd like to have the phone pretty much just
work wherever it's plugged in as long as it can see the asterisk server.


Any ideas ?


Thanks 


Shawn