New modem affecting iChat?

Question

Hi,
I've recently installed a new modem (Thomson ST780WL) - it's one of them VOIP ones. I'm in The Netherlands and I used to be able to iChat to a friend in the UK who has an Orange Livebox, but since I've had the new modem I get the "insufficient bandwidth" error when trying to start an audio chat with him. I'm guessing the two are related. It doesn't work regardless of who initiates the call. The firewall is on at my modem. We've both checked our Quicktime settings. He's running 10.3.9 on an iBook G4. I have plenty of bandwidth and so does he.
I haven't resorted to any port forwarding in my modem yet, because -
1. I didn't fiddle with my previous modem (Speedtouch) and that worked OK with the firewall on.
2. I can audio chat with the apple test sites (or at least I hear some audio).
3. My friend says he can start an audio chat with the apple test sites (although I haven't watched him doing it so he may just mean that he can see the green light).
The only significant thing I've done to my new modem is unbind SIP from port 5060
connection unbind application=SIP port=5060
or something like that.
I did this because Gizmo, which is my fallback option when iChat doesn't work, wouldn't work with the new modem. It did after that. BTW, in my experience, iChat never works with student halls in the UK, whereas Gizmo does.
So I guess my questions are :-
1. If I can audio chat with an apple test site, and so can he, wouldn't that mean we should be able to talk to each other? I realise that there's a difference here - when we're testing with apple, in both cases we are the ones initiating the call, whereas when we talk to each other, one of us is accepting the call.
2. Is port forwarding the solution?
I can post my error log if you like.
Thanks.

Answer 1

I am not sure I can split the info down to any smaller chunks than it is already in the link I supplied in my first post.
I will try.
Certain manufacturers force their modems to make sure SIP is always on port 5060.
The International standard for SIP did say that SIP should have the option of one of 4 ports (5060-5063)
The forcing (Binding) of SIP to port 5060 limits it to this one port.
At this point two things are somewhat of concern.
1) Because this is forced/bound by a NAT action it adds data to the NAT info that is being sent out in the packets from your end so that return info knows where to send it once it arrives back at you modem (or router). The way this is done and the NAT Data at the head of the packets seems to be the problem.
2) If you have a VoIP phone or device (which uses SIP as part of the VoIP protocol) then you have a problem as all SIP data is using one port and in this situation it should use two (one for Each device or application).
I had a Thomson-Alcatel Speedtouch as I said.
It certainly had the SIP binding in version 3 firmware.
It could be unbound by the telnet command using Terminal on a Mac or the Command Line Interface on a PC.
The Version 4 firmware (up to 4.2.9) could also be unbound fully.
Side bar.
Version 4.3 firmware is an attempt to create version 5 firmware for version 4 and earlier devices that can not run Version 5 itself and has the same issues.
At version 5 things changed.
You performed the Unbinding and got a message that it was done. The success rate of Video and Audio chats went up but the errors that did come up still had the same Symptoms and error logs.
Some testing by a Poster who posts here as ibosie with Thomson-Alcatel came to the knowledge that the unbinding is not fully implemented in version 5 firmware onwards.
I hope this is clearer for you.
7:32 PM Wednesday; February 6, 2008