VoIP Brief overview

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VoIP Brief overview

• Milo Stojanovic

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What is VoIP ?

• Voice over IP
• Internet Telephony, IP Telephony, Digital
  Phone
• Real-time voice communication

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Basic concept
Telephone
Adapter
Modem / Router
Internet
PC with software phone
Modem / Router
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Requirements

• IP-based network infrastructure
• QoS capabilities
• Packet loss, jitter, delay
• Software / Hardware
• VoIP carrier (DID) services
• Direct Inward Dialing, assigning numbers
• PSTN lt-gt VoIP

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Technologies Protocols

• Audio codecs (Speex, G.729, etc)
• Communication protocols
• Based on (S)RTP
• H.323
• SIP

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H.323

• Early availability of standards
• Originally created for multimedia applications
  distribution over LAN
• Flexible addressing mechanisms
• URI, email addresses, E.164 (PSTN),
• Voice, video and data conferencing
• Used by largest carriers in core backbones

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SIP

• Session Initiation Protocol
• Lightweight
• Text based human readable control messages
• Transport-independent
• TCP, UDP, ATM,
• Limited addressing (SIP-URIs only)
• Some video and no data conferencing support. No
  video packet loss recovery

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VoIP Pros

• Cost
• PSTN - 37 din/min (Serbia to US)
• VoIP 10 din/min (Serbia to US)
• PC-to-PC no expenses !
• Functionality
• Easy management and administration via PC
• Re-Routing calls
• No need for dual-network infrastructure

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VoIP Cons

• Reliability
• Power outage, IP connectivity, emergencies
• Vulnerability
• Malware, man in the middle, spam, etc
• Quality
• QoS, multipath routing, redundant packets
• Wasted bandwidth
• Packet headers wrapping, silence suppression

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Popular software solutions (1)

• Skype
• Freeware (closed source)
• Proprietary protocol
• Peer to peer (decentralized) model
• Supernodes
• Windows Live Messenger (MSN)
• SIP compatibility

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Popular software solutions (2)

• Ekiga
• Under GPL
• SIP
• Linux only
• Google Talk
• Freeware
• Based upon XMPP

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Evolution tendencies?

• VoIP as mainstream
• Make PSTN obsolete
• Mobile VoIP
• Voice over WiFi, over WiMax
• Future of cell phones?