Protocol Convergence - 7 : Session Initiation Protocol (SIP)
Full playlist of #Protocol #Convergence identifies existing and emerging protocols that support converged communications. Covers Ethernet, #DHCP, IP, SIP, H.323, #Megaco, and more.
• 52 : Protocol Convergence - Fundament...
SIP stands for Session Initiation Protocol. The SIP protocol, as the name indicates, is designed to establish a "session," or a connection, between two IP devices. Most people associate "sessions" with IP phone calls, but the SIP protocol itself does not care what type of traffic goes across the connection. It can support data, and video, as well as voice traffic.
The two main functions of SIP are to set up connections and to establish PRESENCE. Presence is simply the ability to locate the called party to allow you to set up a communication channel. Today, with legacy phone communications, you may need to call several numbers to locate someone. You might have to dial a home number, an office number, or maybe a cell phone number before you reach the person you're calling.
Now, however, the SIP protocol is actually able to track you down - kind of like a bloodhound. Let's say someone tries to call you, and it rings at your home. If you're not there, depending on the configuration, the protocol may also try to reach you at multiple other phones, like at work, school, and even on your cell phone. If the phones ring at all these places, when you pick up, SIP knows your location, and is ready to set up the connection. The idea here is that the calling party only needs to dial one number, one time. It's the intelligent communication system's job to locate you.
SIP phones also have the ability to have one phone call another phone using any type of central application or database. In addition, if your phone knows or can determine the address of the other phone, no other switching devices or special applications are required to establish the call. With this ability, direct phone-to-phone connectivity is possible.