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SEMINAR TOPIC

PRESENTED BY:

RAJAN KUMAR

8th SEM(ENTC-A)

REGD.

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OUTLINEINTRODUCTION

WHAT IS VOIP?

HISTORY

PSTN Vs. VOIP

MODES OF OPERATION OF VOIP

BASIC PRINCIPLES OF VOIP

HOW VOIP WORKS?

ADVANTAGES

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INTRODUCTIONØThe traditional method used for

transmitting voice is PSTN.

ØNow more and more communication is done in digital format and transported via data networks such as internet.

ØAs data traffic is much faster than telephone traffic, so we prefer to send voice over data networks.

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WHAT IS VOIP?

ØVoice Over Internet protocol (VoIP) is a protocol used for the transmission of voice and fax phone calls through the Internet or other packet-switched networks.

ØIt is also called IP telephony, Internet telephony, voice over broadband, broadband telephony.

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HISTORY OF VOIP

• The commercial Voipsoftware was introduced in 1995 by Vocaltec.

ØDesigned for home PCØUses H.323 Protocol

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PUBLIC SWITCHED TELEPHONE NETWORK

• POTS (Analog Telephony) It stands for Plain Old Telephone

Service.ØDedicated link between partnersØReserved bandwidth

• ISDN (Digital Telephony) It stands for Integrated Services Digital

Network.

ØOn each link a channel is reserved

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Analog Telephony

Digital Telephony

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PSTN vs. INTERNET PSTN

• Voice networks use circuit switching.

• Dedicated path between calling and Called party.

• Bandwidth is 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 is needed.

• Cost is not dependent on time and distance.

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CIRCUIT SWITCHING

PACKET SWITCHING

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MODES OF OPERATION

vPC to PCvPC to PhonevPhone to Phone

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qAudio CodecsqData Transport (RTP, RTCP)qAddressingqSignaling (SIP, H.323) 

VOIP: BASIC TECHNIQUESVOIP: BASIC TECHNIQUES

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vHere analog signal is converted into digital data. Three popular audio codecs :-

G.711

G.723.1

G.729

vImplemented using voice coders: Since voice contains lot of data, it is compressed by Vocoders without compromising the reliability and quality of voice signal.

AUDIO CODECS:AUDIO CODECS:

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• Translation of analog signal to digital signal

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RTP• It stands for Realtime Transport

Protocol.• Application layer protocol for

transmitting real time data (audio, video, ...)

• Includes payload type identification, sequence numbering, time stamping, delivery monitoring.

DATA TRANSPORT (RTP, RTCP)DATA TRANSPORT (RTP, RTCP)

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RTCP• It stands for Realtime Transport Control Protocol.

• Main functions:–support for multi-point communication

–Periodic transmission of control packets to all participants in the session.

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• Here phone no. is converted to an IP address.

• Simple format addresing: <user | phone number>@<domain |

hostname | IP address>

ADDRESSINGADDRESSING

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• Signaling in VOIP is needed for :ØLocating partners.ØAgreeing on port numbers for RTP /

RTCP sessions.Øagreeing on coding / decoding procedures.

• Types of Signaling Protocols:H.323SIP

SIGNALINGSIGNALING

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H.323• Recommendation published by

ITU in 1996.

• It is designed to act above transport layer and is mainly used for transmission of voice, data and video conferencing over packet networks.

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SIP• SIP stands for Session Initiation

Protocol.• Developed by IETF since 1999.

• It is an text-based application-layer control protocol for creating, modifying and terminating sessions with one or more participants.

• Sessions include Internet Multimedia conferences or Internet

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How VoIP Works?

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ADVANTAGES:• Cheaper call rates• Simplification• High efficiency• Calling person need not

necessary to receive call.• Better Voice Quality Using

Wideband Codecs• Adding new features and

applications over time is easy.• Integration of voice, data, fax, video

is possible.

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LIMITATIONS

qPacket DelayqPacket Loss (no guarantee of delivering

packets)qJitter (variable delay)

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APPLICATONS• Real time applications:

Ø Telephony ( two-way)Ø Radio-TV Broadcast (one-way)

• Non-real time applications:Ø e_mail

OTHERS:• Integration of data,voice and fax• Video telephony• Enhanced teleconferencing• Used in Amateur Radio

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COMMERCIAL APPLICATIONS1: VONAGE

• founded in January 2001• about 130,000 customers

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2: AT&T AT&T is rapidly evolving

from a company that handles mostly long-distance voice calls to a company that provides data and voice communications over any distance.

3: INODE4:TELEKOM AUSTRIA

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CONCLUSION●Like everything else, as the technology

changes so at first only a few companies like Cisco and Lucent offered VoIP services, but the large telecommunications carriers – such as AT&T and Sprint -- are catching on .

●VoIP is predominately used for personal instead of enterprise-wide use.

● The availability of high-quality audio using wideband codecs, video conferencing, and document sharing enables more effective and pleasant communication.

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• ELECTRONICS FOR YOU(VOLUME-37)• VoipFundamentals By Jonathan Davidson• www.bestneo.com• www.google.com• www.wikipedia.com• www.howstuffworks.com• www.cisco.com• www.seminartopics.com• www.quintum.com • www.tech-faq.com

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THANK U…

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QUERIES?