VOIP BASIC

Voice Over IP
Presented By

Dhara Patel
Jay Patel

21-Feb-2013
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Voice Over IP

Overview
VOIP uses the Internet Protocol (IP) to transmit voice
as packets over an IP network.
VOIP can be achieved on any data network that uses
IP, like the Internet, Intranets and Local Area Networks
(LAN).
The voice signal is digitized, compressed and
converted to IP packets and then transmitted over the IP
network.
VOIP services need only a regular phone connection,
while others allow you to make telephone calls using an
Internet connection instead.

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Voice Over IP

Definition of VOIP
VOIP is a technology that allows
telephone calls to be made over
computer networks like the Internet.

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Voice Over IP

Continue…
VoIP converts analog voice signals into
digital data packets and supports realtime, two-way transmission of
conversations using Internet Protocol
(IP).

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Voice Over IP

What is VOIP?
VoIP is actually a very simple technology.
But it is also powerful and as you will see it
can save you substantial money over
conventional phone calls via your usual
telephone operator (Telkom) that basically
does the same thing, but using their own
network to route your calls.

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Voice Over IP

Why VoIP?
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Can make and receive calls with / without a
computer
Can surf the net while making calls
Can make local / long distance calls
Supports both the Voice and Data
Integrates other media like Video, Electronic
White Board
Flexibility
Reliable Services

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Voice Over IP

How does VOIP work ?
 You place your call by dialing a telephone number to
any normal telephone number anywhere in the world.
 A connection between you and the dialed number is
then established.
 As you talk into your telephone handset your voice is
converted into digital data.
 This data is then transmitted across the connection that
you have already established by dialing the other parties
telephone number.

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Voice Over IP

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 The data is routed across the Internet using the same
standard computer language that the Internet uses - which
is called Internet Protocol (all computers connected to the
Internet understand and use this language to
communicate).

 The data that was your voice is reconstituted on the other
side into normal analogue sound that human beings
understand.

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Voice Over IP

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 VoIP calls can be made on the Internet using a VoIP
service provider and standard computer audio systems.
Alternatively, some service providers support VoIP
through ordinary telephones that use special adapters to
connect to a home computer network.

 Many VoIP implementations are based on the H.323
Protocol.

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Voice Over IP

Protocols :
 Voice over IP has been implemented in various ways
using both proprietary and open protocols and
standards. Examples of the network protocols used to
implement VoIP include:
H.323
Media Gateway Control Protocol (MGCP)
Session Initiation Protocol (SIP)
Real-time Transport Protocol (RTP)
Session Description Protocol (SDP)
Inter-Asterisk eXchange (IAX)
Jingle XMPP VoIP extensions

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Voice Over IP – RFC 3714

What is H.323 protocol?
The H.323 protocol was one of the first VoIP
protocols that found widespread implementation
for long-distance traffic, as well as local area
network services. However, since the development
of newer, less complex protocols such as MGCP
and SIP, H.323 deployments are increasingly
limited to carrying existing long-haul network
traffic. In particular, the Session Initiation Protocol
(SIP) has gained widespread VoIP market
penetration.

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Voice Over IP

H.323 Protocol
 An International Telecommunications Union (ITU)
standard that provides specification for computers,
equipment, and services for multimedia communication
over packet based networks that defines how real-time
audio, video and data information is transmitted.
 H.323 is commonly used in VoIP, Internet Telephony, and
IP-based videoconferencing. Users can connect with
other users over the Internet and use arying products
that support H.323. This standard is based on the
Internet Engineering Task Force (IETF) Real-Time
Protocol (RTP) and Real-Time Control Protocol (RTCP),
with additional protocols for call signaling , and data and
audiovisual communications.
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Voice Over IP

Process of VOIP
 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.
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Voice Over IP

Continue…
 Once the sound is recorded by the computer and
compressed into very small samples, the samples are
collected together into larger chunks and placed into
data packets for transmission over the IP network.

 This process is referred to packetization. Generally, a
single IP packet will contain 10 or more milliseconds of
audio, with 20 or 30 milliseconds being most common.

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Voice Over IP

Ways Of Using VoIP
PC to PC
PC to Phone
Phone to PC
Phone to Phone

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Voice Over IP

Diagrams

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Voice Over IP

Conceptual Model

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Voice Over IP

The phone works – why bother with VoIP
user perspective

carrier perspective

variable compression: tin can to
broadcast quality  no need for
dedicated lines

better codecs + silence suppression –
packet header overhead = maybe
reduced bandwidth

security through encryption

shared facilities simplify management,
redundancy

caller & talker identification

advanced services

better user interface (more than 12
keys, visual feedback, semantic rather
than stimulus)

cheaper bit switching

no local access fees (but dropping to
1c/min for PSTN)

fax as data rather than voiceband data
(14.4 kb/s)

adding video, application sharing is
easy
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Voice Over IP

Advantages of VOIP
Main advantage of VOIP is that the customer can make calls from
anywhere in the world where broadband internet connection is
available.
Greater Efficiency.
Another main advantage is the amount of money you end up saving
on your phone bills as compared to a traditional phone line.
Inexpensive and easy to use. Since it is simple, upgrading is
relatively simpler too.
You can integrate it with an existing phone connection.
With VOIP PC-to-PC, calls are free no matter the distance and PCto-Phone charges are nominal.
For a monthly fee you may make unlimited free calls within a
geographic area.

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Voice Over IP

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 You may purchase a number in a geography area of your choice,
which works out very cheap. If your relatives and friends live in
Virginia and you moved to California, you may purchase a Virginia
number and make local calls to your loved ones.
 You may access your VOIP account just like your email Id from any
where in the world as long as you have an internet phone. This
makes it easy for those who travel frequently to make calls
frequently to those back at home at local call rates, no matter where
they are.
 You may call or message or do both at the same time with VOIP
services.
 VOIP cost about half the cost of traditional phone services and it
seems that the taxes and surcharges are much lower. Also your bill
is easier to understand and it can be viewed via the Internet.
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Voice Over IP

Disadvantages
You must have high-speed internet access in order to
obtain VoIP phone service.
Loss of service during outages.

Without power VOIP phones are useless, so in case
of emergencies during power cuts it can be a major
disadvantage.
With VOIP emergency calls, it is hard to locate you
and send help in time.(Show video)
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Voice Over IP

Continue..
Some times during calls, there may be
periods of silence when data is lost while it
is being unscrambled.

Latency and traffic.
No standard protocol is applicable.

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Voice Over IP

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VoIP packet loss occurs when a large
amount of traffic on the network causes
dropped packets. This results in dropped
conversations, a delay in receiving the
voice communication, or extraneous noise
on the call.

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Voice Over IP

Threats / Risks
Many of the threats associated with VoIP are similar to the
threats inherent to any internet application. Internet users are
already familiar with the nuisance of email abuse in the form of
spam and phishing attempts. VoIP opens yet another pathway for
these annoyances, which can lead to spam over internet telephony
(SPIT), spoofing, and identity theft. Additionally, the confidentiality of
VoIP conversations themselves has come into question, depending
on service type or VoIP configuration.
 Spam over internet telephony (SPIT)
 Spoofing
 Confidentiality concerns
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Voice Over IP

How to Protect Against Risks
 Use and maintain anti-virus and anti-spyware programs.
 Be cautious about opening files attached to email messages or
instant messages.
 Verify the authenticity and security of downloaded files and new
software.
 Configure your web browser(s) securely.
 Use a firewall.
 Identify, back-up, and secure your personal or financial data.
 Create and use strong passwords.
 Patch and update your application software.
 If you are using a software VoIP application, consider using
encryption software for both your installation and for those you wish
to talk to.

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Voice Over IP

Continue…
 The disadvantages of VOIP could be annoying, but their effects are
relatively limited. The complaints of VOIP are usually tolerable if the
callers are using a free service. As the technology is advancing, we
will expect the VOIP quality will match the traditional telephone
technology.

These are some of advantages and
disadvantages of VOIP. All said and done,
we could say that the advantages of VOIP
outweigh the disadvantages of it.
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Voice Over IP

Name confusion
 Commonly used interchangeably:

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Internet telephony
Voice-over-IP (VoIP)
IP telephony (IPtel)

 Also: VoP (any of ATM, IP, MPLS)
 Some reserve Internet telephony for transmission across
the (public) Internet
 Transmission of telephone services over IP-based
packet switched networks
 Also includes video and other media, not just voice.

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VOIP BASIC

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