SIP VoIP

SIP or Session Initiation Protocol is the IETF protocol for VOIP sessions, like instant messaging, video, online games and various other services. Session Initiation Protocol or SIP VoIP is an application-layer control protocol for creating, modifying, and terminating sessions with one or more participants. These sessions include Internet telephone calls, multimedia distribution and conferences.

Following are the features of SIP:

• SIP the text based protocol uses UTF-8 encoding.

• Port 5060 is required for UDP and TCP. It can use other transports also.

• SIP has the features of common telephone like media transfer, conference and hold.

• It is a flexible protocol and more features can be added to keep downward interoperability.

• Most companies provide the features like standard caller ID, call waiting, three ways calling, call forwarding, voicemail, email voicemail, free subscriber phone calls.

SIP VoIP can easily be regarded as the enabler protocol for phones over Internet Protocol services. In enabling the IP telephony following are the main requirements of the SIP VoIP:

• SIP ensures that the name translations and user locations of the called party be mapped out. It also ensures the details of the session call.

• The feature negotiation allows the group call to agree on the features supported by � recognizing that all parties cannot support features of same level. SIP supports any type of MIME but it does not support any video.

• When a call is going a participant can bring others into the call and also can cancel connection to other users. User can also be transferred or placed on hold.

• Options for change of call features are also available.

• The Internet SIP mechanism also enables media negotiation.