What is SIP?

sip the session initiation protocol a protocol to initiate a session but what is a session and why do we need a protocol to get one started well we're talking about a communication session in fact an IP communication session using IP devices and an IP network at its heart sip is a signaling protocol to set up an IP communication session now when we think about it virtually all communications begin with signaling even a face-to-face conversation davia wants to talk to Nathan tent by calling over hey Nathe a sound wave carried through the air recognising the invitation to talk Nathe signals back to accept what's up with Dave's invitation signal answered with Nathan's acceptance signal both parties are ready to converse they begin a dialogue and exchange of media in this case more sound waves traveling through the air conversation complete Dave issues another signal this time to end the session and just to be polite Nathan signals back confirming he knows the session is ending signaling in an IP world follows the same principles instead of signaling with an audio way through the air IP devices signal with IP packets over the IP network now there's lots of different types of IP packet each with their own function and content the important thing is that both sender and receiver understand the packet construct and what to do with its data in IP communications there are two types of IP packets there's signaling packets and immediate packets back is to establish or set up the session and media packets to then convey the audio the video the whiteboarding data and so on with a voice session the analog wave on one side is encoded into ones and zeros that are put into media packets and then sent out over the IP network on the other side the ones and zeros are unpacked and decoded the wave reconstructed and played back to the user n coding and decoding also applies to video images from the camera are encoded the binary digits packaged in media packets and sent out over the IP network at the other side again the data is decoded the image reconstructed and then displayed to the user now every second of conversation has many many media packets audio and perhaps video packets that convey the real-time conversation simple enough but for this media exchange to take place we're assuming two important things have already been sorted that both parties know each other's location they know where to send their media packets and that both parties are using the same codecs for encoding and decoding the media so here's the big question how do we locate or find the other users IP address and how do we decide which codecs to use we need a process some descriptions and rules that help us locate each other and agree on codecs what we need is a protocol and that's where sip comes in the session initiation protocol it's essentially a rulebook that describes how to locate the other party and which codec to use for encoding and decoding media it also defines how to construct and send IP signaling packets to set up the call and what to do to then manage the call so now if Dave wants to use his sip phone to call Nathe on his sip phone Dave's phone follows all the steps defined by sip to construct a special IP signaling packet a sip packet populated with all the data needed to set up the call and send it out over the IP network on the other side Nathe sip phone understanding the rules of sip recognises the packet as an invitation to talk and knows to alert Nathe by playing the phone's ringing sound more signaling packets are exchanged we'll talk about those later then with signalling complete and codecs determined the phone's get busy exchanging media packets that digitally convey the conversation then sometime later one of the parties signals the end of the call and both stop sending Media the call is terminated simple now understanding the essence of sip is really quite easy it's just signaling to set up and manage IP communication sessions understanding its full potential however and knowing enough to fully implement real-life sip solutions and to support real IP communications networks is something else there's much to learn many complexities to unravel and understand but worry not that's why we're here that's the purpose of this course by the time we're done you'll be a sip expert it will all make good sip sense

Channel: sipsense.com

Views: 346,037

Rating: 4.9382558 out of 5

Keywords: SIP, Session Initiation Protocol (Internet Protocol), voip, Telecommunications (Industry), ip telephony, SIP training, training, what is sip

Id: erICfPV8-Lg

Length: 5min 9sec (309 seconds)

Published: Fri Nov 21 2014