Session Initiation Protocol is a signaling communications protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP) networks.

1. SIP
SESSION INITIATION PROTOCOL
CSC 255
Sailee Choudhary

2. AGENDA
 Introduction to SIP
 Network elements needed in SIP
 SIP Message types
 SIP Session establishment and termination
 SIP call redirection
 SIP call proxying

3. INTRODUCTION
 SIP is the core protocol for initiating, managing and
terminating sessions in the Internet
 It is an application layer protocol designed to be
independent of the underlying transport layer.
 SIP sessions involve one or more participants and
can use unicast or multicast communication.

4. NETWORK ELEMENTS
 User Agent:
1.User Agent Client (UAC)
2.User Agent Server (UAS)
 Proxy Server
 Registrar
 Redirect Server
 Session border controller
 Gateways

5. SIP MESSAGE TYPES
Requests – sent from client to server
 INVITE : Used to establish a media session
between user agents.
 ACK : Confirms reliable message exchanges.
 BYE : Terminates a session between two users in a
conference.
 CANCEL : Terminates a pending request.
 OPTIONS : Requests information about the
capabilities of a caller, without setting up a call.
 REGISTER : Used by a UAC to indicate its current
IP address and the URLs for which it would like to
receive calls.

6. SIP MESSAGE TYPES
Responses – sent from server to the client
 Success: The action was successfully received,
understood, and accepted.
 Redirection : Further action needs to be taken to
complete the request.
 Client Error: The request contains bad syntax or
cannot be fulfilled at the server.
 Server Error: The server failed to fulfill an
apparently valid request.
 Global failure : The request cannot be fulfilled at
any server.

7. REQUEST AND RESPONSE HEADER FOR ALL
TYPES OF MESSAGES

8. SIP MESSAGE EXAMPLE

9. SIP SESSION ESTABLISHMENT AND CALL
TERMINATION

10. SIP CALL REDIRECTION

11. CALL PROXYING

12. Thank you