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Presented by
SYEDA SAMIRA
MOHSIN ARIF
FAHAD AFTAB
Data Communication
&
Networking
Abstract
Voice over Internet
Protocol
(VoIP) is a technology that
enables one to make and
receive phone calls through
the Internet instead of using
the traditional analogy
PSTN (Public Switched
Telephone Network) lines.
Definition
Voice over IP (VoIP) is a methodology and
group of technologies for the delivery
of voice communications over IP networks,
such as the Internet
Category of Hardware and Software
Transmission medium for telephone calls
Rather than by traditional circuit
transmissions of the [email protected] 6
What Is VOIP
VoIP is packetisation and transport of
classic public switched telephone system
audio over an IP network.
It allows 2-way voice transmission over
broadband connection.
It is also called IP telephony, internet
telephony, voice over broadband, broadband
PSTN
Voice network use circuit
switching.
Dedicated path between
calling and called party.
Bandwidth 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 needed.
Cost is not based on
distance and time.
PSTN vs. INTERNET
Why VoIP
IP telephony is economic, High costs for
traditional telephone switching equipment
Cheapest
Quality
DVBS (Digital Video Broadcasting Satellite)
How VoIP works
Converting the voice signal ADC (analog to digital) DAC (digital to analog)
Voice (source) - - ADC - - - Internet - - - DAC - - Voice (dest)
Transmission of voice traffic in packets
How VoIP works
Compression – voice is compressed
typically with one of the following codecs,
G7.11 64k, G7.29AB 8k, G723.1 6.3k
Encapsulation – the digitized voice is
wrapped in an IP packet
Routing – the voice packet is routed
through the network to its final [email protected] 11
IP Network
Multimedia PC
Multimedia PC
Initially, PC to PC
voice calls over the
Internet
PSTN
(DC)
Gateway
PSTN
(NY)Gateway
Public Switched
Telephone Network
Gateways allow PCs
to also reach phones
…or phones to reach
phones
VoIP Architecture
Challenges
Voice transmission delay Call setup, call establishment, call
termination, etc. Backward compatibility with existing
PSTN (Public Switched Telephone Network)
Related issues
Voice over Frame Relay
Voice over ATM (Asynchronous Transfer Mode)
Security
As VoIP uses the Internet, for example, it is
vulnerable to the same type as security risks
Hacking
Denial of service
Eavesdropping
Protocol
SIP
RTP, RTCP, RTSP
Transport Layer (UDP, TCP)
Network Layer (IP, IP Multicast)
Data Link Layer
Physical Layer
Physical Transport (e.g, Cable Modem)
IP (Internet Protocol)
TCP UDP
Applications (e.g., email, web pages)
Email Data (1000 bytes)TCP Header (20 bytes)
IP Header (20 bytes)
A Typical IP Datagram
IP Protocol layering
Gateway
A VoIP gateway is a gateway device that uses Internet Protocols to transmit and receive voice communications (VoIP).
Codecs
Codecs are used to convert an analog
voice signal to digitally encoded version.
Codecs vary in the sound quality, the
bandwidth required, the computational
requirements, etc.
Do Companies Want VoIP?
Extremely likely16%
Very likely32%
Likely28%
Not very likely16%
Not at all likely4%
Unsure4%
76% Will!
Do Companies Want VoIP?
81%
59%
38%
26%
0 50 100
Save Money
Better Utilization of Bandwidth
Support Multimedia
Improve Network Management
Conclusion
Voice over IP (VoIP) is a methodology and group of
technologies for the delivery of voice communications over IP
networks, such as the Internet
ECONOMICAL
Transmission medium for telephone calls
It is also called IP telephony, internet telephony, voice over
broadband, broadband telephony.Converting the voice signal
ADC (analog to digital) DAC (digital to analog) As VoIP uses the Internet, for example, it is vulnerable to
the same type as security risks
