PSU VoIPThe Cisco 7906 with the current SIP firmware load (8.3.4 SR1) connected to an Asterisk system performs very much like it does connected to CallManager via SCCP. Cisco has been pushing for feature parity between SIP and SCCP protocols on their IP phones (see this white paper) since they began to really embrace SIP a couple years ago. Because SCCP implements most of its functionality on the PBX end, and SIP puts most of the functionality at the endpoint, Cisco's SIP firmware has to implement some of the CallManager functionality and look-and-feel on the endpoint device.
Biggest drawback when using SIP is the need to setup a client-side dialplan in order to effect PSTN-like (or CallManager-like) dialing: the PBX knows when you're done dialing a number and immediately begins to process it. With the SIP firmware you have to either set up a client-side dialplan or press a "Dial" softkey after entering a number (like you do on a cell phone). Cisco's SIP firmware implements KPML (RFC 4730) to make this smoother, but Asterisk does not.
The interface is nearly identical. There's a DND key on the SIP phone by default. Hold, call waiting, conference (using the phone's built-in conference bridge), and attended transfer all work. Unattended transfer does not--I'm unclear as to why not.
I would guess that Cisco's higher-end phones show more disparity between the SCCP and SIP interface and functionality but on the 7906, Cisco's current low-end single line phone model, they've just about reached their goal of feature parity.
I just found your blog googling for a guide to change a cisco 7906's firmware to SIP. Are you planning to release a mini-guide?
I already got the SIP firmware files. But I got no idea, how to upload it.
Best Regards
I'll try to put together a mini-guide. My guide will basically be a summary of notes I found on http://voip-info.org, a wonderful resource for all things Asterisk. Start with this page and go from there. Here's another one specific to 7941/7961 but the instructions for loading are basically the same. The critical steps are to set up DHCP and TFTP correctly. Once this infrastructure is in place, the phone gets the files it needs automatically.
Thank you for the feedback! It was really useful.
I finally managed to change the firmware of the 7906. Now, I just need to read the xml config format and I should be donne. I just write here to say Thank you.
any chance you could email me the config you used please? :)
Hi Bill,
I love your 7906 with SIP working... I have a few of these phones and they are breaking my heart, can't get them to upgrade to SIP and can't get SCCP working either on my Asterisk machine (v1.4.21). Any chance you could put together the steps you did in a Mini howto? I've followed the links you mention in you article but they are very confusing, no one seems to have the answers! All the other guides are for different Cisco models, you seem to be the only guy with a working SIP 7906 on the net!
Regards,
Mark