Tom Behrens Adam Muniz

Overview What is VoIP SIP Sessions H.323 Examples Problems

What is VoIP Voice Over IP Internet as Telephone Network Converts Analog Audio to Digital Audio Eliminates Circuit Switched Network Communicates over Packet-Switched Internet SIP & H.323 Protocols

SIP – Session Initiation Protocol Designed by IETF Application Layer Established, Manages, and Terminates a Multimedia Session Two-Party, Multiparty, Multicast Sessions Independent of the Transport Layer Runs on UDP, TCP, or SCTP SIP Messages INVITE, ACK, BYE, OPTIONS, CANCEL, & REGISTER

SIP Addresses sip:address Telephone IP

Simple Session using SIP Establishing a Connection Three-Way Handshake INVITE, Reply Message, ACK Communicating Use Two Temporary Ports Terminating a Connection BYE

Simple Session using SIP

Tracking the Callee Callee is at a Different Location Registrar Server knows Callee Location Address INVITE -> Proxy Server Proxy Server Sends INVITE to Callee

Tracking the Callee

H.323 Allows Telephones on the Public Telephone Network to talk to Computers Gateway Connects the Internet to the Telephone Network Translates Messages Gatekeeper Registrar Server on a LAN

H.323

H.323 Operation Terminal sends a broadcast message to the Gatekeeper Gatekeeper responds with its IP address Terminal and Gatekeeper negotiate bandwidth Terminal, Gatekeeper, Gateway, and Telephone negotiate compression method Terminal, Gatekeeper, Gateway, and Telephone exchange audio Terminal, Gatekeeper, Gateway, and Telephone terminate communication

H.323 Operation

Examples Skype Vonage Cisco Systems Telephones

Problems No Power or No Internet, No Phone Poor Internet connection leads to a poor phone connection Security Threats Identity/Service Theft Viruses, malware, spamming, and phishing attacks