VOICE OVER INTERNET

8/7/2019 VOICE OVER INTERNET

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VOICE OVER INTERNETVOICE OVER INTERNETPROTOCOL(VoIP)PROTOCOL(VoIP)

DebanjanDebanjan KonarKonar

Dept of Computer sc &Dept of Computer sc &

EnggEngg..MtechMtech in MSSin MSS

Roll No.Roll No.--1414


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CONTENTSCONTENTSIntroductionIntroduction

What is VoIPWhat is VoIP

Why VoIPWhy VoIP

VoIPTechnologyVoIPTechnology

How VoIPworksHow VoIPworks

VoIPChallengesVoIPChallenges

VoIPCodecVoIPCodec


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INTRODUCTIONINTRODUCTION

Broadband is a faster way for us to gain access to theBroadband is a faster way for us to gain access to the

Internet.Internet.

Due to increase in broadband, many new applicationsDue to increase in broadband, many new applications

have been created with enormous benefits to the user.have been created with enormous benefits to the user.

The most prominent example is the development ofThe most prominent example is the development of

VoIP.VoIP.


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WHAT IS VoIP ?WHAT IS VoIP ?

VoIP is a protocol optimized for the transmission ofVoIP is a protocol optimized for the transmission of

voice through the Internetvoice through the Internet

VoIP allows high quality twoVoIP allows high quality two--way voice transmissionway voice transmission

over broadband connections.over broadband connections.

VoIP system carry telephony signals as digital audio,VoIP system carry telephony signals as digital audio,encapsulated in data packet stream over IP.encapsulated in data packet stream over IP.


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WHAT IS VoIP ?WHAT IS VoIP ?


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WHYVOIP ?WHYVOIP ?

VoIP typically include TollVoIP typically include Toll--bypass allows longbypass allows long--distance calls to be placed without incurring the usualdistance calls to be placed without incurring the usual

toll charges.toll charges.

Through network consolidation, voice, video, andThrough network consolidation, voice, video, and

data can be carried over a single network .data can be carried over a single network .

With service convergence, enhanced functionality canWith service convergence, enhanced functionality canbe implemented.be implemented.


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VOIP CALLS IN IP NETWORKVOIP CALLS IN IP NETWORK


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THE VoIP TECHNOLOGYTHE VoIP TECHNOLOGY

VoIP is a family of technology that enable voiceVoIP is a family of technology that enable voice

communications using IP networks .communications using IP networks .

VoIP is a core technology that drives things like voiceVoIP is a core technology that drives things like voice

chat software.chat software.

VoIP is the fabulous secret ingredient inVoIP is the fabulous secret ingredient inVonage,skype,googleVonage,skype,google--talk, Cisco .talk, Cisco .


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THE VoIP COMPONENTSTHE VoIP COMPONENTS


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HOWVoIPWORKSHOWVoIPWORKS

VoIP converts the user voice signal into digital signalVoIP converts the user voice signal into digital signal,compressed packets.,compressed packets.

Voice samples are encapsulated inVoice samples are encapsulated in RTP and beforeRTP and before

being transmitted in an IP frame.being transmitted in an IP frame.

At the receiving end reassembled and decodedAt the receiving end reassembled and decoded

packets arrives normal sounding voice call .packets arrives normal sounding voice call .


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HOWVoIPWORKS(SIP)HOWVoIPWORKS(SIP)


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VOIP CHALLENGESVOIP CHALLENGES

Available bandwidthAvailable bandwidth

Network latencyNetwork latency

Packet LossPacket Loss

JitterJitter

EchoEcho

SecuritySecurity

ReliabilityReliability


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QUALITYOF VOICEQUALITYOF VOICE

For voice communications over IP the delay needsFor voice communications over IP the delay needs

to be less than a threshold value.to be less than a threshold value.

To ensure good quality of voice theseTo ensure good quality of voice these are requiredare required

Echo CancellationEcho Cancellation

Packet PrioritizationPacket Prioritization

Forward Error Correction.Forward Error Correction.


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DELAYDELAY


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FRAME LOSSFRAME LOSS

VoIP frames traverse an IP network, which isVoIP frames traverse an IP network, which is

unreliable due to network congestion or dataunreliable due to network congestion or data

corruption.corruption.

In the simplest case, the terminal leaves a gap in theIn the simplest case, the terminal leaves a gap in the

voice stream if a voice sample is missing.voice stream if a voice sample is missing.

If too many frames are lost, the speech will soundIf too many frames are lost, the speech will sound

choppy with syllables or words missing.choppy with syllables or words missing.


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FRAME LOSSFRAME LOSS

CODEC I(0% LOSS) I(2% RANDOM

FRAME LOSS)

I(5% RANDOM

FRAME LOSS)

G.711 withoutPLC 0 35 55

G.711 with

PLC 0 7 15

G.729A 11 9 26

G.723.1 (6.3 kbps) 15 24 32

Based on the previous voice samples, the decoder willpredict what the missing frames should be. This technique

is known as Packet Loss Concealment(PLC).


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PACKET LOSS AND JITTERPACKET LOSS AND JITTER


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VOIP CODECVOIP CODEC

A codec converts an audio signal into compressedA codec converts an audio signal into compresseddigital form for transmission and then back into andigital form for transmission and then back into an

uncompressed audio signal for replay.uncompressed audio signal for replay.

Phone No is converted into IP address. SimplePhone No is converted into IP address. Simple

format for addressing:format for addressing:

@


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VOIP CODECVOIP CODEC

CODING STANDARD ALGORITHM DATA RATE

G.711 PLC(Pulse Code

Modulation)

64 kbps

G.726 ADPCM(AdaptiveDifferentialPulse Code

Modulation)

16, 24, 32, 40 kbps

G.728 LD-CELP(Low Delay Code

ExcitedLinearPrediction)

16 kbps

G.729 CS-ACE LP(ConjugateStructure Algebraic CELP)

8 kbps

G.723.1 M P-MLQ(Multi-Pulse

Maximum Likelihood

Quantization)

6.3 kbps


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REFERENCESREFERENCES

1.Managing VoIP Quality of Experience on Your Network1.Managing VoIP Quality of Experience on Your Network

Jeff Hicks, VoIP Architect,Jeff Hicks, VoIP Architect, NetQoSNetQoS, Inc., Inc.

2. Voice over IP : Protocols and Standards2. Voice over IP : Protocols and Standards

file:///H:/edonkey/docs/programming/SYNGRESSfile:///H:/edonkey/docs/programming/SYNGRESS

3. ITU3. ITU--T Recommendation G.723.1 (1996), Speech coders:T Recommendation G.723.1 (1996), Speech coders:

4. IETF RFC 2543 (3/1999), H4. IETF RFC 2543 (3/1999), H SchulzrinneSchulzrinne, J Rosenberg, "The IETF Internet, J Rosenberg, "The IETF Internet

Telephony Architecture and Protocols", IEEE Network, May/June 1999 pp. 18Telephony Architecture and Protocols", IEEE Network, May/June 1999 pp. 18--23235.http://207.127.135.8/5.http://207.127.135.8/nini/private/1999/may//private/1999/may/schulzrinne.htmlschulzrinne.html

6. Configuring Cisco Voice Over IP6. Configuring Cisco Voice Over IP--Angus MaAngus Ma

7.[7.[TechguideTechguide] "Voice over IP", 24 pages,] "Voice over IP", 24 pages,http://www.techguide.com/comm/sec_html/voiceip.shtmlhttp://www.techguide.com/comm/sec_html/voiceip.shtml

8. Configuring Cisco Voice Over IP8. Configuring Cisco Voice Over IP--http://www.cis.ohiohttp://www.cis.ohio

state.edu/~state.edu/~jainjain/cis788/cis788--99/99/voip_protocolsvoip_protocols/index.html/index.html http://communication.howstuffworks.com/iphttp://communication.howstuffworks.com/ip--telephony.htmtelephony.htm

http://www.fcc.gov/voip/http://www.fcc.gov/voip/

http://www.discoverhttp://www.discover--voip.info/brandedvoip.info/branded--voip/brandedvoip/branded--voip.htmlvoip.html

http://www.packetizer.com/ipmc/papers/understanding_voip/hype_vs_reality.htmlhttp://www.packetizer.com/ipmc/papers/understanding_voip/hype_vs_reality.html


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VOICE OVER INTERNET

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