1. VOIP TECHNOLOGY-
THE NEXT STEP IN GLOBAL COMMUNICATIONS
Mohammad Ali Khan
Jakir Hossain
Jannatul Ferdaus Happy
Dept. of Computer Science & Engineering
Faculty of Engineering
University of Development Alternative (UODA)

2. Talk Overview
 Introduction
 Using VoIP
 VoIP- Packet Switching
 Major concerns of VoIP
 CODECS
 VoIP: Soft Switches and Protocols
 VoIP: Quality of service

3. What is VOIP?
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 analog PSTN
(Public Switched Telephone Network) lines.
Call anyone in the world at unbelievably low ratesCall anyone in the world at unbelievably low rates

4. Why
VoIP?
 Can make and receive calls with / without a computer
 Can surf the net while making calls
 Can make local / long distance calls
 Can make and receive call to / from PSTN
 Cost effective
 Digital features not commonly available on PSTN lines such as :
 v o i c e m a i l ,
 c a l l e r I D ,
 c o n f e r e n c e a n d s o o n.

5. Flavors of VoIP
 ATA
 Connects a standard phone to a computer or an Internet
connection for use with VoIP.
 The ATA is an analog-to-digital converter.
 IP Phones
 connect directly to a router and have all the hardware and
software necessary right onboard to handle the IP call.
 Computer-to-computer
 There are several companies offering free or very low-cost
software that you can use for this type of VoIP.
 All you need is the software, a microphone, speakers, a sound
card and an Internet connection

6. How does VoIP
work?
VoIP converts the
voice signal from
your telephone
into a digital
signal that
travels over the
Internet. If you
are calling a
regular phone
number, the signal
is then converted
back at the other
end. Internet
Voice can allow
you to make a
call directly
from a personal
computer. If you
make a call using
a phone with an

7.  The users voice (or fax) is converted into a digital signal, compressed, and
broken down into a series of packets.
 The packets are then transported over private or public IP networks and
reassembled and decoded on the receiving side.
 At the receiving end, the re-assembled packets arrive as a normal
sounding voice call.
 Packet switching is very efficient. It lets the network route the packets along
the least congested and cheapest lines. It also frees up the two computers
communicating with each other so that they can accept information from
other computers, as well.
PACKET
SWITCHING

8. CHALLENGES
 Some VoIP service providers may have limitations to their 911 service.
 Some VoIP services don’t work during power outages
 VoIP is susceptible to worms, viruses and hacking.
 Because VoIP uses an Internet connection, it's susceptible to all the
hiccups normally associated with home broadband services. All of these
factors affect call quality:
 Latency
 Jitter
 Packet loss
 Phone conversations can become distorted, garbled or lost because of
transmission errors.

9. o I P – C O D E
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 sample the audio signal several
thousand times per second.
Summary of available codecs:
VoIP software processes and routes the calls.
8 kbpsG.729
16 kbpsG.728
32 kbpsG.721
64 kbpsG.711

10. Soft Switches and Protocols
 Soft Switches- where to send data?
 It 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.
 VoIP-Protocols:-
 H.323 -
 ITU-Standard initially a multimedia conferencing protocol.
 Defines all aspects of call transmission, from call establishment to
capabilities exchange to network resource availability.
 SIP -
 IETF’s standard for establishing VOIP connections.
 Defines how sessions are to be set up and torn down.

11. Q o s - i n V o I P
 Quality of Service is essential for the success of VoIP.
 The human ear is extremely sensitive to even minor changes in an audio
signal.
 Loss of quality occurs when the voice packets are transferred over the
inherently unreliable packet-based networks.

12.  Some methods to enhance the QoS achieved in VoIP are:
 Classification of Service: Using the TOS bits in the IP header to set a
priority for the voice packet.
 Tagging the packets with labels and using the labels to decide the route.
Voice packets can be routed over less congested networks.
 Reserving resources to meet requirements for bandwidth, delay, jitter, etc.
along a particular path through a series of routers.
Q o s - i n V o I P

13. CREDITS
 http://communication.howstuffworks.com/ip-telephony.htm
 http://www.fcc.gov/voip/
 http://www.discover-voip.info/branded-voip/branded-voip.html
 http://www.packetizer.com/ipmc/papers/understanding_voip/hype_vs_realit
y.html