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Voice Over IP (VoIP)
1. Voice over IPVoice over IP
Habib UllahHabib Ullah
12-MS-CSc-1212-MS-CSc-12
2. Contents
Abstract
What isVoIP
HowVoIP works
VoIP Architecture
Components
Pros & Cons
Summary
3. 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.
4. 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 telephony.
5. PSTN vs. INTERNET
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.
6. PBX
Yesterday’s Networks
Circuit Switched Networks (Voice)
CO
PBX
CO
CO
Packet Switched Networks (Data)
Router
Router
Router
Router
Router
• Separated networks
• Separated applications/services
8. VoIP – How does it work?
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
9. VoIP – How does it work?
The 1-2-3s of VoIP
1. Compression – voice is compressed
typically with one of the following codecs, G7.11
64k, G7.29AB 8k, G723.1 6.3k
2. Encapsulation – the digitized voice is
wrapped in an IP packet
3. Routing – the voice packet is routed thru
the network to its final destination
12. VoIP Network Model
SIP
RTP, RTCP, RTSP
Transport Layer (UDP, TCP)
Network Layer (IP, IP Multicast)
Data Link Layer
Physical Layer
13. PURC
IP Protocol LayeringIP Protocol Layering
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
16. VoIP Gateway
A VoIP gateway is a gateway device that uses Internet
Protocols to transmit and receive voice communications
(VoIP).
17. 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.
18. Do Companies Want VoIP?
76% Will!76% Will!
Unsure
4%
Not at all
likely
4%
Not very
likely
16%
Likely
28%
Very likely
32%
Extremely
likely
16%
Network World asked 500 readers to assess
whether they would consider using voice over IP:
19. Key Business Drivers for LAN-Based Telephony and VoIP
81%81%
59%59%
38%38%
26%26%
0 50 100
Save MoneySave Money
Better Utilization of BandwidthBetter Utilization of Bandwidth
Support MultimediaSupport Multimedia
Improve Network ManagementImprove Network Management
20. Security Risks
AsVoIP uses the Internet, for example, it is vulnerable to
the same type as security risks
Hacking
Denial of service
Eavesdropping
MOS- Mean Opinion Score, a measure of voice quality score, each codecs has its own bandwidth requirements, VoIP normal delay is 100ms, so 3.5 is a good quality achievement