PRESENTED BY:

Namra Afzal (1528)

Shahreen Gul (1544)

Rabiah Sharafat (1453)1

OUTLINEINTRODUCTION

WHAT IS VOIP?

HISTORY

PSTN Vs. VOIP

MODES OF OPERATION OF VOIP

BASIC PRINCIPLES OF VOIP

HOW VOIP WORKS?

ADVANTAGES

LIMITATIONS

APPLICATIONS

CONCLUSION

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INTRODUCTIONThe traditional method used for transmitting

voice is PSTN.(public switched telephone network)

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

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

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WHAT IS VOIP?

Voice Over Internet protocol (VoIP) is the technology of digitizing sound, compressing it, breaking it up into data packets, and sending it over an IP network.

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

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VoIP Diagram

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HISTORY OF VOIP

•The commercial Voip software was introduced in 1995 by Vocaltec.

Designed for home PC

Uses H.323 Protocol

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PSTN Vs. VoIPPSTNRefers to the international telephone system• Telephone service carried by the PSTN is often called

(POTS).• POTS (Analog Telephony)

It stands for Plain Old Telephone Service.

Dedicated link between partnersReserved bandwidth

VoIPUses packet-switched telephony Voice info travels in countless individual

network packets

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Analog Telephony Digital Telephony

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PSTN vs. VoIP PSTN

• Voice networks use circuit switching.

• Dedicated path between calling and Called party.

• Bandwidth is reserved in advance.Each line is 64kbps

• Cost is based on distance and time.

• Features such as call waiting, Caller ID and so on are usually available at an extra cost

VoIP

• VoIP uses 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.

• Features such as call waiting, Caller ID and so on are usually included free with service 9

PSTN

• Can be upgraded or expanded with new equipment

• Long distance is usually per minute or bundled minute subscription

• Hardwired landline phones (those without an adapter) usually remain active during power outage

VoIP

• Upgrades usually requires only bandwidth and software upgrades

• Long distance is often included in regular monthly price

• Lose power, lose phone service without power backup in place

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PSTN

• When placing an emergency call it can be traced to your location

VoIP

• Emergency calls cannot always be traced to a specific geographic location

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CIRCUIT SWITCHING PACKET SWITCHING

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MODES OF OPERATION

•PC to PC

•PC to Phone

•Phone to Phone

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Basic Principles of VoIPAudio Codecs,Video Codecs

Data Transport (RTP, RTCP)

Addressing

Signaling (SIP, H.323)

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Audio Codecs Are used to convert analog signal into digital data.

The most common codecs for VoIP are

Codec Bandwidth/kbps

G.711 64

G.722 48/56/64

G.723.1 5.3/6.3

Stands for coder-decoder

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

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Translation of analog signal to digital signal

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Video Codecs

• Video Codecs: common examples include H.261 (for 64kbps and above), H.263 (for 64kbps and below), and MPEG 4.

• The encoded information is then encapsulated within an IP packet and these packets are then transported across the network to their destination.

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Data Transport (RTP,RTCP) RTP

•It stands for Realtime Transport Protocol.

•Application layer protocol for transmitting real time data (audio, video, ...)

•Includes sequence numbering, time stamping, delivery monitoring.

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RTCP• It stands for Realtime Transport Control

Protocol.•While RTP carries the media streams

(e.g., audio and video), RTCP is used to monitor transmission statistics and quality of service (QoS) and aids synchronization of multiple streams.

•Main functions:• support for multi-point communication• Periodic transmission of packets to all

participants in the session.23

ADDRESSING•Here phone no. is converted to an IP

address.

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VoIP SIGNALING PROTOCOLS• Signaling in VOIP is needed for :

to establish a point to point connection and to keep it open for the duration of the call.

agreeing on coding / decoding procedures.

• Types of Signaling Protocols:

o H.323

o SIP 25

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.

• SIP is the core protocol for initiating, managing and terminating communication sessions (i.e audio & video call) over the Internet

• These sessions may be text, voice, video or a combination of these

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• SIP sessions involve one or more participants and can use unicast or multicast communication.

• Sessions include Internet Multimedia conferences or Internet Telephone calls.

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How VoIP Works?

•VoIP converts the voice signal from your telephone into a digital signal that can travel over the Internet.

•Depending on the type of VoIP service, you can make a VoIP call from a computer, a special VoIP phone, or a traditional phone with or without an adapter. 29

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

Packet Delay

Packet Loss (no guarantee of delivering packets)

Jitter (variable delay)

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APPLICATONSReal time applications:

• Telephony ( two-way)

• Radio-TV Broadcast (one-way)

Non-real time applications:

• Email

OTHERS:

• Integration of data, voice and fax

•Video telephony

•Enhanced teleconferencing 34

COMMERCIAL APPLICATIONS1: VONAGE

• founded in January 2001

• about 130,000 customers

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2: AT&TAT&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: INODE

4: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)

• Voip Fundamentals 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

• http://www.sipnology.com/en/company/19-voip-born 38

REFERENCES:

• http://compnetworking.about.com/od/voipvoiceoverip/g/bldef_pstn.htm

• http://www.voip-facts.net/signalling-protocol-h-323/

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THANK YOU