Tom BehrensAdam Muniz

OverviewWhat is VoIPSIPSessionsH.323ExamplesProblems

What is VoIPVoice Over IPInternet as Telephone

NetworkConverts Analog

Audio to Digital AudioEliminates Circuit

Switched NetworkCommunicates over

Packet-Switched Internet

SIP & H.323 Protocols

SIP – Session Initiation ProtocolDesigned by IETFApplication LayerEstablished, Manages, and Terminates a

Multimedia SessionTwo-Party, Multiparty, Multicast SessionsIndependent of the Transport Layer

Runs on UDP, TCP, or SCTPSIP Messages

INVITE, ACK, BYE, OPTIONS, CANCEL, & REGISTER

SIP Addressessip:addressTelephoneEmailIP

Simple Session using SIPEstablishing a Connection

Three-Way HandshakeINVITE, Reply Message, ACK

CommunicatingUse Two Temporary Ports

Terminating a ConnectionBYE

Simple Session using SIP

Tracking the CalleeCallee is at a Different LocationRegistrar Server knows Callee Location

Email AddressINVITE -> Proxy ServerProxy Server Sends INVITE to Callee

Tracking the Callee

H.323Allows Telephones on the Public Telephone

Network to talk to ComputersGateway

Connects the Internet to the Telephone Network

Translates MessagesGatekeeper

Registrar Server on a LAN

H.323

H.323 OperationTerminal sends a broadcast message to the

GatekeeperGatekeeper responds with its IP addressTerminal and Gatekeeper negotiate bandwidthTerminal, Gatekeeper, Gateway, and

Telephone negotiate compression methodTerminal, Gatekeeper, Gateway, and

Telephone exchange audioTerminal, Gatekeeper, Gateway, and

Telephone terminate communication

H.323 Operation

ExamplesSkypeVonageCisco Systems Telephones

ProblemsNo Power or No Internet, No PhonePoor Internet connection leads to a poor

phone connectionSecurity Threats

Identity/Service TheftViruses, malware, spamming, and phishing

attacks