Last week I presented a webinar on adding mobile SIP devices to your communications network. I give webinars on a fairly regular basis and will admit that some topics require more research than others. However, this one was a bit of a no-brainer for me since I’ve been using mobile SIP technology for many years now. I can’t say for sure, but I am pretty sure that I installed my first SIP soft phone on my PC back in 2001. I was working for Nortel at the time and was part of the team that developed the MCS 5200 carrier-grade SIP soft switch. Despite the fact that this was very early in the life of SIP, our soft phone was very feature rich. Not only did it do the standard telephony stuff like conference and transfer, but we had a full array of collaboration applications including a shared whiteboard, file transfer, screen share, network clipboard, and even a SIP-based chess game. Today I have three SIP soft clients on my iPhone and run two different desktop clients on my PC.
However, my webinar reinforced the fact that not everyone has had the same experiences with SIP mobility that I’ve had. I received a number of questions during and after the webinar that clearly showed confusion about what is possible and what is required to add SIP Mobility. Here is a subset of the questions and my answers.
Q. Do I need a Session Border Controller for SIP phones?
A. Do you need one? No. Do you want one? Absolutely. Allowing remote SIP phones to connect to your network without a SBC in the middle would be like connecting to the Internet without a firewall. There are a lot of nasty people out there and you need to protect yourself against toll fraud, denial of service attacks, and spying.
Q. Do I need to add a phone twinning feature like Avaya’s EC-500 to support SIP phones?
A. No. EC-500 is a feature that will simultaneously ring a desk phone and a cell phone. The key word here is “cell.” A SIP client uses your smart phone’s date network. It does not use the cellular network and therefore the twinning feature is unnecessary. In fact, using something like EC-500 with a SIP soft client will confuse the user as he or she will receive two calls at the same time – one on the EC-500 cell link and one on the SIP data link.
Q. Doesn’t WebRTC eliminate the need for SIP?
A. No, and I recently blogged about this very subject. WebRTC deals strictly with media and a signaling protocol like SIP is still needed. For more information, please see my article, WebRTC and SIP.
There were more questions, but I would like to direct you to a replay of the webinar (Adding Mobile SIP Technology to Your Communications System) for a deeper dive into SIP mobility. If you have questions of your own, feel free to reach out to me and I will do my best to answer them.