Khalid Khursheed 09-MBA-27 voip • Real-time interactive audio/video application. • Voice over ip,internet telephony. • Idea- use internet as a telephone IDEA network with some additional capabilities. • Instead of circuit switched packet switched is used. • Two protocols-SIP,H.323 How it works. • VoIP services convert your voice into a digital signal that travels over the Internet • If you are calling a regular phone number, the signal is converted to a regular telephone signal. • VoIP can allow you to make a call directly from a computer, a special VoIP phone, or a traditional phone connected to a special adapter. Devices required • A broadband (high speed Internet) connection is required. This can be through a cable modem, or high speed services such as DSL or a local area network. • A computer, adaptor, or specialized phone is required. Some VoIP services only work over your computer or a special VoIP phone, while other services allow you to use a traditional phone connected to a VoIP adapter SIP • Session initiation protocol • An application layer that manages and terminates a multimedia session call. • It can be used to create two party,multiparty or multicast sessions. • SIP is designed to be independent of the underlying transport layer. • SIP is a text based protocol as is HTTP.,uses messages. SIP messages INVITE ACK BYE OPTIONS REGISTER CANCEL SIP messages • Each message has a header and a body. • Header consist of several lines describe structure of message,callers capability. • INVITE-caller initiates a session with invite message. • ACK-After callee answers call,caller sends an ACK message for confirmation. SIP message • BYE-it terminates a session. • OPTIONS-message queries a machine about its capabilities. • CANCEL-this message cancels an already started initialization process. • REGISTER-this message makes a connection when the callee is not availabe. SIP formats Sip:email@example.com Sip:firstname.lastname@example.org Sip:bob@408-864-8900 Ip address E-mail address phone no. Simple sessions Simple session using SIP consists of three modules: Establishing Communicating terminating Simple session Establishing a session-requires three way handshake. Caller sends an INVITE message. If callee is willing to start session,she sends a reply ,message. To confirm that a reply code has been received the caller sends an ACK message. Continued.. • Communicating-after session has been established ,the caller and callee can communicate by using two temporary ports. • Terminating the session-the session can be terminated with a BYE message sent by either party.