2. ABSTRACT
SIP provides for the seamless transmission of voice, fax, and data
across IP and traditional telephone networks.
The IETF defines SIP as “a text- based protocol, similar to HTTP
and SMTP, for initiating interactive communication sessions between
users. Such sessions include voice, video, chat, interactive games,
and virtual reality.”
The Session Initiation Protocol (SIP) is an Internet Engineering Task
Force (IETF) standard protocol for initiating an interactive user
session that involves multimedia elements such as video, voice, chat,
gaming, and virtual reality.
3. INTRODUCTION
SIP is a request-response protocol, dealing with requests from clients
and responses from servers. Participants are identified by SIP URLs.
Requests can be sent through any transport protocol, such as UDP,
SCTP, or TCP.
The protocol can also invite participants to unicast or
multicast sessions that do not necessarily involve the initiator.
Because the SIP supports name mapping and redirection services, it
makes it possible for users to initiate and receive communications
and services from any location, and for networks to identify the users
wherever they are.
4. APPLICATIONS
It has given rise to generation of new types of smart phone. With the
help of the technology now smart phones also support the video
conferencing.
setting up voice-over-IP calls
setting up multimedia conferences
event notification (subscribe/notify) à IM and presence
text and general messaging
signaling transport
5. FUNCTIONALITY
As the name implies the session initiation protocol is about initiation
interactive communications sessions between users. SIP also handles
termination and modifications of sessions as well.
Locating the user – supports personals mobility
Inviting the user for session
Delivering the session description
Terminate the session
7. WORKING PROCESS
User Agents:
User agent is an application which contains both a user agent client
and user agent server. A user agent client (UAC) is a client
application that initiates the SIP request. A user agent server (UAS)
is a server application that contacts the user when a SIP request is
received.
proxy server:
The Proxy Servers are application layer routers that forward SIP
request & responses.
8. Continution
Redirect server:
A redirect server is a server that accepts a SIP Requests & then return
the location of another SIP user agent & server where the user might
be found.
Registrar server:
A registrar is a server that accepts REGISTER requests. A registrarer
is typically co-located with a proxy or redirect server and offer
location services.
9. ADVANTAGES
SIP is scalable, easy to implement, and requires less setup time than
its predecessor protocols.
SIP can be used to modify any session in progress, a normal
telephone call session can be converted into a multi-party
videoconference.
Users can join in the session no matter what kind of terminal he is
using or where he is located. The other person may be logged on to
Internet through a PC, or may be traveling with a cell phone.
10. DISADVANTAGES
One SIP challenge is that SIP message contain information that
Client and/or server will like to keep private but SIP header as well
as message in the open and distributed architecture of VOIP systems
makes it difficult to keep this information confidential.
When a SIP user is registering with SIP Registrar server the attacker
can hijack the registration.
Two main reasons for this attack are: SIP messages being sent in
clear and no SIP message authentication built into the protocol
11. CONCLUSION
SIP is now a days used for internet conferences, internet
multimedia, internet telephony calls at distance learning with
compatible session like voice, chat , traditional telephony
networks, voice, fax, interactive games etc.
SIP become a standard IETF protocol for signaling in third –
generation mobile networking SIP runs on top of several
different transport protocols.
