1. VoIP Tom Behrens Adam Muniz

2. Overview • What is VoIP • SIP • Sessions • H.323 • Examples • Problems

3. 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

4. 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

5. SIP Addresses • sip:address • Telephone • Email • IP

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

7. Simple Session using SIP

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

9. Tracking the Callee

10. 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

11. H.323

12. 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

13. H.323 Operation

14. Examples • Skype • Vonage • Cisco Systems Telephones

15. 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