bài thuyết trình về Voip

bài thuyết trình về Voip

Voice over IP

Habib Ullah 12-MS-CSc-12

 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.

Yesterday’s NetworksCircuit Switched Networks (Voice)

VoIP – How does it work?

 Converting the voice signal

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,

LT S

©Telcordia Technologies, Inc Slide 10

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

Applications (e.g., email, web pages)

Email Data (1000 bytes)

TCP Header (20 bytes)

IP Header

(20 bytes)

A Typical IP Datagram

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 500 readers to assess

whether they would consider using voice over IP:

Key Business Drivers for LAN-Based Telephony and VoIP

81% 59%

38%

26%

Save Money Better Utilization of Bandwidth

Support Multimedia Improve Network Management

Summary

Questions?