VOICE OVER INTERNET PROTOCOL (VOIP)introduction

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VOICE OVER INTERNET PROTOCOL (VOIP) IS A TRANSMISSION TECHNOLOGY FOR DELIVERY OF VOICE COMMUNICATIONS OVER IP

NETWORKS.

WHAT IS VOICE Vibration of substance produce sound. in human beings it is done by vibration of vocal cord.

Sound in terms of electronics :The sound is the most important way of communication in human beings. so in electronics communication it is converted in to equivalent electrical form by help of electronic equipments.

Distant Sound communication Evolution of analog & digital telephone network Internet telephony

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Dedicated line with a constant connectionOriginally very expensiveEach call transmits at 64 kilobits per second

64 kbps x 2 directions = 128 kbps128 kbps = 16 kilobytes per secondDuring a 10 minute call, about 10 MBHighly inefficient

WIRED CONNECTION

DP-Distribution point Cabinet MDF –Main distribution frame

INTERNET TELEPHONEY When the transport is the public Internet or

the Internet backbone from a major carrier, it is generally called 'Internet telephony’.

VOIP

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HISTORY

• 1974 — The Institute of Electrical and Electronic Engineers (IEEE) published a paper titled "A Protocol for Packet Network Interconnection.

• 1981 — IPv4 is described in RFC 791. • 1995 — Vocal Tec releases the first commercial

Internet phone software. • 1996 — ITU-T begins development of standards

for the transmission and signaling of voice communications over Internet Protocol networks with the H.323 standard.

• 1999 — The Session Initiation Protocol (SIP) specification RFC 2543 is released.

• 2004 — Commercial VoIP service providers proliferate

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STRUCTURE AND WORKING OF VOIP

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HOW VOIP WORKS? VoIP protocols first converts your voice

or media into digital signal and travels over the internet. At receiver side it decode in its original format.

VoIP allows you to make a call from your desktops/laptops or from IP phones using internet. You can make a call from your traditional telephones using spceial type of phone adapter.

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1. PC to PC

• Need a pc with sound card

• IP telephony software

2. PC to phone

• Need a gateway that connects IP

network to phone network

( Router to PBX )

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(3) Phone to Phone

• Need more gateways that connect IP network to phone network

• Ip network could be Internet or dedicated intranet

VOIP GATEWAY PROTOCOLS AND CODECS

Codec ( coder – decoder ) :-

Software or hardware that converts analog signals to digital form and signals from digital to analog form

It also determines sound quality and bandwidth required to send the packet

If a user doesn’t able to hear anything, the application in user side

does not support codec with which data had been coded

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VOIP DEVICES ATA: Most useful device for VoIP is ATA(Analog

telephone Adaptor). It helps you to connect your standard phone to computer and lets you call.

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NETWORK GATEWAY

It is a network point that acts as an entrance to another network

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PBX

IP VoiceIP Network

PSTN

VOIP Gateway

Protocol conversion

Voice decompres

sion

PACKET SWITCHING VS. CIRCUIT SWITCHING

It is two different technologies for sending messages and data from one point to another.

Each has its advantages and disadvantages depending on what you are trying to do.

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CIRCUIT SWITCHING This channel remains open and in use throughout

the whole call and cannot be used by any other data or phone calls.

There are three phases in circuit switching:EstablishTransferDisconnect

The telephone message is sent all together; it is not broken up.

The message arrives in the same order that it was originally sent.

A circuit-switched network is excellent for data that needs a constant link from end-to-end, for example, real-time video.

Circuit switching can be analog or digital.21-08-2013 VISHNU M D

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CIRCUIT SWITCHING

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Circuit is dedicated to the call – no interference, no sharing

Guaranteed the full bandwidth for the duration of the call

Guaranteed quality of service

Inefficient – the equipment may be unused for a lot of the call; if no data is being sent, the dedicated line still remains open.

It takes a relatively long time to set up the circuit.

During a crisis or disaster, the network may become unstable or unavailable.

It was primarily developed for voice traffic rather than data traffic.

advantage Disadvantage

PACKET SWITCHING

In packet-based networks, the message gets broken into small data packets.

These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuits become available.

This does not necessarily mean that they seek out the shortest route.

Each packet may go a different route from the others.

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PACKET SWITCHING

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PACKET SWITCHING

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Each packet is sent with a ‘header address’ which tells it where its final destination is, so it knows where to go.

The header address also describes the sequence for reassembly at the destination computer so that the packets are put back into the correct order.

One packet also contains details of how many packets should be arriving so that the recipient computer knows if one packet has failed to turn up.

If a packet fails to arrive, the recipient computer sends a message back to the computer which originally sent the data, asking for the missing packet to be resent.

PACKET SWITCHING

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Security Bandwidth used to full potential Devices of different speeds can

communicate Not affected by line failure

(redirects signal) Availability – no waiting for a

direct connection to become available

During a crisis or disaster, when the public telephone network might stop working, e-mails and texts can still be sent via packet switching

Under heavy use there can be a delay

Data packets can get lost or become corrupted

Protocols are needed for a reliable transfer

Not so good for some types data streams (e.g. real-time video streams can lose frames due to the way packets arrive out of sequence)

Advantage Disadvantage

IP - The Internet Protocol

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WHİCH PROTOCOLS ARE REQUİRED FOR VOIP………?

UDP (User Datagram Protocol) RTP (Real-Time Transport Protocol) SIP( Session Initiation Protocol) H323

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UDP PROTOCOL

Available in transport layer Enable the transmission of information

between the correct processes (or applications) on host computers.

UDP protocol is commonly used in transport layer as an alternative to TCP protocol.

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INDUSTRY PROTOCOL STANDARDS

H.323 Protocol Suite

H323 ARCHİTECTURE

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SIP PROTOCOL

SIP is a application layer control simple signalling protocol for VoIP implementations

SIP: not only for VoIP, but in general for multimedia communication

eg: audio / video conferencing, server-based or p2p

provides the market with fast operation, flexibility, scalability and multiservice support.

format similar to HTTP creates, modifies and terminates sessions which are

internet multimedia conferences, Internet telephone calls and multimedia

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SIP WORKS AS FOLLOWS

Callers and callees are identified by SIP addresses

a caller first locates the appropriate server and then sends a SIP request

a SIP request may be redirected or may trigger a chain of new SIP requests by proxies

Users can register their location(s) with SIP servers

SIP messages can be transmitted either over TCP or UDP

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METHODS COMMAND:

- Invite: Initiate Call

- Ack: Confirm Final Response

-Bye: Terminate and Transfer Call

- Cancel: Cancel Searches and ‘Ringing’

-Options: Features Support by Other Side

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VoIP has become a powerful force in telecommunications due to several reasons. 

cheaper than PSTN service providers compatible with web-based applications enabling the user to change, adjust , or listen to these features over the Internet. Long distance is usually provided free of charge. 

FeaturesCall Waiting

Caller Id

Call Forwarding

Voice Mail

Call Transfer

VOIP PROVIDERS

Eg:

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Providers

Skype

Vonage

Speakeasy

Galaxy Voice

Packet 8

VOIP

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Factors that Affect Call Quality in VoIP Latency: Changing in delivery

time between voice packets Jitter: Changing in delivery

order of voice packets Packet Loss: Echo and jitter

occurs because of packet loss. Echo: waving of voice

Viruses, worms, and hackers

advantage disadvantage

Offer Features For Free stuff

Saves Money And Cost Efficient Integration

With Audio, Data And Video Applications

Ability To Choose Your Own Area Codes

Flexibility

REFERENCES

http://www.en.wikipedia.org/voip Data communications & Networking(4th edition-

BehrousA.forouzan) http:// www.iee.com Electronics for you vol.37

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