With all the excitement around SIP and its ability to transform the way we communicate with one another, you may be surprised that the SIP standards body defines only 19 different telephone features. That’s right, only 19. In fact, they have a name, SIPPING-19, and they are the only telephone features that a SIP soft switch is required to support. Specifically, they are:
Call Hold
Music on Hold
Consultative Hold
Find Me
Transfer Instant Message
Transfer Attended
Transfer Unattended
Call Park
Call Pickup
Automatic Redial
Click to Dial
Message Waiting Indicator
Call Forward Unconditional
Call Forward Busy
Call Forward No Answer
3-Way Conf Party Added
3-Way Conf Party Joins
Incoming Call Screening
Outgoing Call Screening
Now, after being spoiled by the over 700 features on an Avaya H.323 telephone brings to your enterprise you might be asking yourself, “Why in the world would I ever convert to SIP?” In other words, “Why should I upgrade my telephones in order for them to act like 30-year-old technology?” Fear not because not only does an Avaya SIP telephone support the entire SIPPING-19 feature set, it also supports nearly every telephony feature currently supported by your H.323 telephone.
How is that possible? Does that mean that an Avaya SIP telephone uses something other than SIP to support the remaining 680-plus features? Absolutely not and allow me to explain why.
Solution Building
In a previous article I wrote about SUBSCRIBE, NOTIFY, and PUBLISH and how they can be used to build complex SIP solutions. That’s exactly how Avaya supports telephone features beyond the basic 19. The next time you configure an Avaya SIP telephone in System Manager pay attention to the section that lists the event packages that the telephone supports. Specifically, note the one entitled avaya-cm-feature-status. This event package is the secret sauce that allows an Avaya telephone to do more than every other SIP telephone on the market today.
When an Avaya telephone boots, it sends a SIP SUBSCRIBE message for every one of its configured event packages. These event packages direct the Avaya system to empower the Avaya telephone with a particular set of functions. When an Avaya Communication Manager receives a subscription for avaya-cm-feature-status, it knows that this telephone is running Avaya SIP firmware and is able to receive NOTIFY messages that will direct it to perform one of the many extended Avaya telephone features. For example, this is how an Avaya phone supports bridged call appearances, hunt groups, and loudspeaker paging all of which are not part of SIPPING-19.
If you were to put a packet analyzer tool such as Wireshark between a Communication Manager and an Avaya SIP telephone, you would see NOTIFY messages that instruct the telephone’s firmware as to how to process the specific feature in terms of screen display, lamps, and media path. This allows Avaya to remain in full compliance with the SIP specification without having to wait for the IETF to define these extended features.
You Have a Choice
So, when it comes to choosing which handset your enterprise will deploy, the question of SIP over H.323 isn’t one of what features are or are not supported. Rather, it becomes an architectural discussion of Aura, evolution servers, feature servers, and the transformational power of SIP and enterprise cloud computing.
As for me, I like that freedom.
For some deeper follow-ups, please check out these articles:
Tao, Zen, and Tomorrow 
Great read! Can an 9600 seriers SIP phone use all SIP 19 features without a feature server(CM)?
Thank you. Although I have never done this myself, I’ve heard that you can connect a 96xx SIP phone to a non Avaya call server and get basic (i.e. SIPPING-19) functionality. You will need something in the middle, though, because the phone expects to successfully register before it will work.
Yes, a non-AST Avaya 9620 phone is capable of setting up a conference call. The two phones were loaded with SIP firmware. They were NOT registered to Session Manager and therefore clearly no Communication Manager. They created the call by entering the IP address of the first phone. They hit the soft conference button and made a second call to the third phone. Hitting the conference button again established the conference call using SIPPING-19 feature. I am told that a traceSM indicated the audio (RTP packets) went from the first phone to both of the other phones. In other words, I believe that means if the first phone were to disconnect, the entire conference call would drop. This experiment was done in a classroom environment, not a production one.
Thanks, John! I am happy to hear that someone was able to set this up. However, if you are not using Session Manager how are you using traceSM? Don’t you have to have the SIP messages go through Session Manger for traceSM to see them?
Oops. That is correct; to have useful information in traceSM you would need to have the SIP messages routing through Session Manager. Sorry, I was not standing behind the engineers when they set up their phones. So the phones must have been registered to SM. But they were quite clear that CM was not involved. Sorry.
Andrew is the same true for the IP Office as the CM in terms of SIP phones connected to an IP Office can do more than the SIP 19 features?
Avaya SIP phones on IP Office can do more than SIPPING-19, but they don’t use Session Manager to accomplish that. Unfortunately, I am not an IP Office expert, so that’s about as far as I can go on that. Sorry.
Can we configure our Avaya phones to drop PPM and only support SIPPING 19?
I believe you can, but I would have to think about how to do it. Why do you want this?
I am new and not good in this field but I have been able to do some miracles on cisco ip phones to change them to sip firmware. I am looking for a simple step by step document on how I can turn avaya 9611G and 9630G IP phones to sip firmware so that I can use them on freepbx
Hi Andrew – In this explanation “If you were to put a packet analyzer tool such as Wireshark between a Communication Manager and an Avaya SIP telephone, you would see NOTIFY messages that instruct the telephone’s firmware” My question is SIP Phone subscribe to event packages on CM, and CM will update with notify. Where would publish be sent in order to update changes occurred on subscribed feature set ? Who is the broker in this case ?