2. 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.
3. 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.
5. 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 user's contact addresses
• Location server – providing of user location details
• Redirect server – return callee's addresses to caller
• Application server – providing advanced services for users
10. 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.
11. 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
15. 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
16. 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).
