Transcript VoIP - Alumni

Tom Behrens
Adam Muniz
Overview
 What is VoIP
 SIP
 Sessions
 H.323
 Examples
 Problems
What is VoIP
 Voice Over IP
 Internet as Telephone
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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
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sip:address
Telephone
Email
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
 Email 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