What is SIP(Session Initiation Protocol) ? • A signaling protocol for setting up multimedia sessions between endpoints . • SIP is end-to-end, client-server session signaling protocol similar to HTTP. • SIP designed in line with other Internet protocols by the IETF.
SIP Basic Functionality Supports 5 facets of communication:• User location: determination of the end system to be used for communication;• User capabilities: determination of the media and media parameters to be used;• User availability: determination of the willingness of the called party to engage in communications;• Call setup: "ringing", establishment of call parameters at both called and calling party;• Call handling: including transfer and termination of calls.
SIP Entities• User Agent (UA) User Agent Client (UAC) – initiates a SIP request User Agent Server (UAS) – handles and eventually sends a response to a request• Proxy server – routing of SIP requests• Registar server – registration of users contact addresses• Location server – providing of user location details• Redirect server – return callees addresses to caller• Application server – providing advanced services for users
The response types• 1xx - Provisional response• 2xx - Successful response• 3xx - Redirect response• 4xx - Client error• 5xx - Server error• 6xx - Global error
Via Field in Header• The Request headers include a Via field• The Via field indicates the path taken by the request so far.• Every proxy adds a Via Header with its address to make sure that responses within a transaction take the same path (to avoid loops, or to make sure that same firewall will be hit on the way back)• This prevents request looping and ensures replies take the same path as the requests.
SIP Transaction • User agent A contacts DNS server to map domain name in SIP request to IP address. • User agent A sends a INVITE message to proxy server that uses location server to find the location of user agent B. • Call is established between A and B. Then media session begins. • Finally, B terminates the call by sending a BYE request
Instant Messaging and SIMPLE• Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions.• Instant messaging (IM) ,the most common and popular methods of communicating over IP networks.• IM applications:-■ AIM, America Online Instant Messenger■ Google talk■ Yahoo Messenger■ MSN Messenger
WHAT IS VOIP• Voice over IP (VoIP) is any technology that facilitates the voice communication and video conferencing uses live images and sound, over an IP network, such as the Internet.• The two (or more) endpoints - often referred to as terminals or clients - could be any device with a microphone and speaker, such as a normal PC computer or something resembling a traditional phone.• Session Initiation Protocol (SIP) is standard used in Voice over IP (VoIP).