voice over internet
TRANSCRIPT
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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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