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bài thuyết trình về Voip
Voice over IP Voice over IP Habib Ullah Habib Ullah 12-MS-CSc-12 12-MS-CSc-12 Contents Abstract What is VoIP How VoIP works VoIP Architecture Components Pros & Cons Summary Abstract Voice over Internet Protocol (VoIP) is a technology that enables one to make and receive phone calls through the Internet instead of using the traditional analogy PSTN (Public Switched Telephone Network) lines. What is VoIP? VoIP is packetisation and transport of classic public switched telephone system audio over an IP network. It allows 2-way voice transmission over broadband connection. It is also called IP telephony, internet telephony, voice over broadband, broadband telephony. PSTN vs. INTERNET PSTN Voice network use circuit switching. Dedicated path between calling and called party. Bandwidth reserved in advance. Cost is based on distance and time. INTERNET Data network use packet switching. No dedicated path between sender and receiver. It acquires and releases bandwidth, as it needed. Cost is not based on distance and time. PBX Yesterday’s Networks Circuit Switched Networks (Voice) CO PBX CO CO Packet Switched Networks (Data) Router Router Router Router Router • Separated networks • Separated applications/services PBX IP Phone Converged Network PSTN CO Gateway Router Router Router Router • Converged network • Separated or integrated applications PBX IP Phone VoIP – How does it work? Converting the voice signal ADC (analog to digital) DAC (digital to analog) Voice (source) - - ADC - - - Internet - - - DAC - - Voice (dest) Transmission of voice traffic in packets VoIP – How does it work? The 1-2-3s of VoIP 1. Compression – voice is compressed typically with one of the following codecs, G7.11 64k, G7.29AB 8k, G723.1 6.3k 2. Encapsulation – the digitized voice is wrapped in an IP packet 3. Routing – the voice packet is routed thru the network to its final destination LT S ©Telcordia Technologies, Inc. Slide 10 IP Network Multimedia PC Multimedia PC Initially, PC to PC voice calls over the Internet VoIP Architecture? PSTN (DC) Gateway PSTN (NY) Gateway Public Switched Telephone Network Gateways allow PCs to also reach phones …or phones to reach phones [...]... VoIP Protocols VoIP Gateway VoIP Codecs VoIP Network Model SIP RTP, RTCP, RTSP Transport Layer (UDP, TCP) Network Layer (IP, IP Multicast) Data Link Layer Physical Layer IP Protocol Layering Applications (e.g., email, web pages) TCP UDP IP (Internet Protocol) Physical Transport (e.g, Cable Modem) A Typical IP Datagram IP Header (20 bytes) PURC 2004 TCP Header (20 bytes) Email Data (1000 bytes) VoIP. .. Email Data (1000 bytes) VoIP SIP VoIP Gateway A VoIP gateway is a gateway device that uses Internet Protocols to transmit and receive voice communications (VoIP) VoIP Codecs Codecs are used to convert an analog voice signal to digitally encoded version Codecs vary in the sound quality, the bandwidth required, the computational requirements, etc Do Companies Want VoIP? 76% Will! Network World asked... World asked 500 readers to assess whether they would consider using voice over IP: Key Business Drivers for LAN-Based Telephony and VoIP 26% Improve Network Management 38% Support Multimedia 59% Better Utilization of Bandwidth 81% Save Money 0 50 100 Security Risks As VoIP uses the Internet, for example, it is vulnerable to the same type as security risks Hacking Denial of service Eavesdropping