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1. Session Initiation Protocol
(SIP)
SARATH P.R

2. Agenda
 Why
do we need SIP ?
 The protocol
 Sip components & services
 Internet Telephony with SIP
 Conclusion

3. Introduction
 SIP
is the core protocol for initiating,
managing and terminating sessions in the
Internet
 These sessions may be text, voice, video or
a combination of these
 SIP sessions involve one or more
participants and can use unicast or multicast
communication.

4. SIP entities
 User
Agent
User Agent Client
User Agent Server
 Proxy
Server
 Redirect server
 Registrar

5. SIP message types
SIP is modeled on HTTP
–
Use same syntax and semantics as HTTP
 Request
– Method (INVITE, ACK, BYE, etc.)
– Header (Accept, Contact, etc.)
 Answer
– Status code (200 OK, 180 Ringing, etc.)
– Header (Content-type, Content-encoding, etc.)

6. SIP Message Types
Requests – sent from client to server







INVITE
ACK
BYE
CANCEL
OPTIONS
REGISTER
INFO

7. SIP methods







INVITE initiate call
ACK confirm final response
BYE terminate (and transfer) call
CANCEL cancel searches and “ringing”
OPTIONS features support by other side
REGISTER register with location service
INFO mid-call information (ISUP)

8. SIP Message Types (Contd.)
Responses – sent from server to the client






Success
Redirection
Forwarding
Request failure
Server failure
Global failure

9. Sip message types
SIP Methods
INVITE
SIP Answers
Initiate a call by inviting a user to take part in a session.
ACK
Confirm that the client received a final response
to a request INVITES.
BYE
Indicate the end of the call.
CANCEL
Cancel a request.
REGISTER
OPTIONS
To register the User Agent.
Used to know the capacities of the server.
1xx - Informational Messages.
2xx - Successful Responses.
3xx - Redirection Responses.
4xx - Request Failure Responses.
5xx - Server Failure Responses.
6xx - Global Failure Responses.

10. Message parts
 Start
line
 Headers
 Body content

11. SIP End-devices

12. SIP components and services
SIP Servers and services
Registrar
Redirect
Location
Database
Locate
Where this name is
or tel. number…
Proxy
SIP Server
Register
I am here
SIP User
Agents
Redirect
Here is the address
Proxy INVITES
I will call it
for you.
INVITE
I want to speak
with another agent.
SIP User
Agents
GW SIP

13. SIP Addresses













SIP gives you a globally reachable address.
􀁠 Callees bind to this address using SIP REGISTER method.
􀁠 Callers use this address to establish real-time communication with callees.
􀁠 URLs used as address data format; examples:
􀁠sip:jiri@iptel.org
􀁠sip:voicemail@iptel.org?subject=callme
􀁠sip:sales@hotel.xy; geo.position:=48.54_-123.84_120
􀁠 must include host, may include user name, port number, parameters
(e.g., transport), etc.
􀁠 may be embedded in Webpages, email signatures, printed on your
business card, etc.
􀁠 address space unlimited
􀁠 non-SIP URLs can be used as well (mailto:, http:, ...)

14. SIP Session Establishment and Call
Termination
From the RADVISION whitepaper on SIP

15. SIP Call Redirection
From the RADVISION whitepaper on
SIP

16. Call Proxying
From the RADVISION whitepaper on SIP

17. References
 Computer
Telephony – June 2000
 http://www.radvision.com
 www.cs.columbia.edu/hgs/
 www.networkcomputing.com
 www.wikipedia.com

18. CONCLUSION
 Sip
is working behind session in internet
 It makes voip easier
 In future we can expect more in sip

19. Questions
?

20. Thank you