presentation on voip

8/11/2019 Presentation on VoIP

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PRESENT TION ON VOIP

Ashirwad Tomar 220/11 IIIrd IT

Gaurav Priyadarshi 229/11 IIIrd

IT

ComputerNetworks

Computer Science and

Engineering Deptt

HBTI Kanpur

Prepared By:


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VoIP


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VoIP: Voice over Internet

Protocol

IS a methodology or group of technology for

delivery of voice communication and

multimedia messages over IP networks like

internet.Also known as internet telephony

Internet telephony is provisioning of

communication services (SMS, fax, voice, etc.)over internet rather than public switched

telephone network (PSTN).


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VoIP : How stuff Works..

Steps and principals of transmission are same

as PSTN i.e. signaling, channel setup,

digitalization of analog voice signal, encoding,

instead of transmitted over a circuit switchednetwork information is packetized and

transmitted as IP packets over Packet

switched networks.


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Circuit Switched Network

Dial tone : connection to service provider

Number Dialing:

1800-123-44331

Ringin

gTring..

Tring..

CallPicks

HIHello

bye Bye

Switching CircuitsConnection Terminated


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10 mins talk time

Data rate in one way = 64 kbps

Data rate in to and fro transaction = 128 kbps

Data used in 10 min = 128x10x60 = 76800kb= 75 MB

Efficient time of talk = 3 mins

Efficient data required = 128x3x60 = 23024kb= 22.5MB

Data wasted = 52.5 MB


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VoIP: Packet Switching

Data networks do not use circuit switching.

Your Internet connection would be a lot slower

if it maintained a constant connection to the

web pages you were viewing at any giventime. Instead, data networks simply send and

retrieve data as you need it. And, instead of

routing the data over a dedicated line, the data

packets flow through a chaotic network along

thousands of possible paths. This is

called packet switching.


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VoIP: Packet Switching

DATA DATA

REASSEMBLED

Routing system


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VoIP: Mechanics

You pick up the receiver, which sends a signal to the ATA.

The ATA receives the signal and sends a dial tone. This letsyou know that you have a connection to the Internet.

You dial the phone number of the party you wish to talk to.The tones are converted by the ATA into digital data andtemporarily stored.

The phone number data is sent in the form of a request toyour VoIP company's call processor. The call processorchecks it to ensure that it's in a valid format.

The call processor determines to whom to map the phone

number. In mapping, the phone number is translated to an IPaddress. The soft switchconnects the two devices on eitherend of the call. On the other end, a signal is sent to yourfriend's ATA, telling it to ask the connected phone to ring.


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VoIP: Mechanics (cont..)

Once your friend picks up the phone, a session is establishedbetween your computer and your friend's computer. This means thateach system knows to expect packets of data from the othersystem. In the middle, the normal Internet infrastructure handles thecall as if it were e-mail or a Web page. Each system must use thesame protocol to communicate. The systems implement two

channels, one for each direction, as part of the session. You talk for a period of time. During the conversation, your system

and your friend's system transmit packets back and forth whenthere is data to be sent. The ATAs at each end translate thesepackets as they are received and convert them to the analog audiosignal that you hear. Your ATA also keeps the circuit open between

itself and your analog phone while it forwards packets to and fromthe IP host at the other end.

You finish talking and hang up the receiver.

When you hang up, the circuit is closed between your phone andthe ATA.

The ATA sends a signal to the soft switch connecting the call,terminating the session.


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VoIP: Advantages

Cost Efficient

Data Efficient


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VoIP: Disadvantages

VoIP is dependent on wall power

VoIP is susceptible to worms, viruses and

hacking

Other systems in your home may be integrated

into the phone line. (like digital recorders,

security systems, etc.)


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VoIP: Important Terminologies

Codecs

Soft switching and Protocols


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VoIP: Codecs

A codec, which stands for coder-decoder, converts an

audio signal into compressed digital form for transmission

and then back into an uncompressed audio signal for

replay. It's the essence of VoIP.

Codecs accomplish the conversion by sampling the audiosignal several thousand times per second.

Codecs use advanced algorithms to help sample, sort,

compress and packetize audio data. The CS-ACELP

algorithm(CS-ACELP = conjugate-structure algebraic-code-excited linear prediction) is one of the most prevalent

algorithms in VoIP. CS-ACELP organizes and streamlines

the available bandwidth. Annex Bis an aspect of CS-

ACELP that creates the transmission rule, which basically

states "if no one is talking, don't send any data."


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VoIP: Soft Switches and

Protocols The soft switch contains a database of users and phone

numbers. If it doesn't have the information it needs, it hands

off the request downstream to other soft switches until it finds

one that can answer the request. Once it finds the user, it

locates the current IP address of the device associated withthat user in a similar series of requests. It sends back all the

relevant information to the softphone or IP phone, allowing

the exchange of data between the two endpoints.

Protocols: They help different hardware and software

components (Soft switches, routers, ATAs, etc) of VoIP tocommunicate.

There are several protocols currently used for VoIP. These

protocols define ways in which devices like codecs connect to

each other and to the network using VoIP. They also includespecifications for audio codecs.


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THANK YOU

We can say VoIP over conventional Telephony is nothing but:

Clever re-invention of WHEEL

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