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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