Transcript Introduction to VoIP Communications

Introduction to VoIP
Communications
Telecom Management Week 4
Aim of the Lecture
• In this lecture we aim to cover the following
concepts;
• Difference between circuit and packet
switching
• Standardization
• Protocols and
• VoIP Communications
Introduction
• Before knowing about Voice Over IP
Communications following terms are necessary
to understand;
1. What is VoIP
2. Getting Started with VoIP
3. Reasons for switching to VoIP
4. VoIP Pitfalls
5. VoIP or internet telephony
6. Features of VoIP
What is VoIP?
• Stands for Voice over Internet Protocol.
• It is also referred as IP Telephony or internet
Telephony.
• It is another way of making telephone calls.
• The calls are relatively cheaper or completely
free.
• You don’t need to have a telephone
equipment.
VoIP Usage
• There are many ways of using VoIP
Technology.
• It all depends on where and how you will be
making the calls.
• It could be at home, at work or in corporate
network.
• The way you call varies with the service you
use.
VoIP Services
• In US/ Europe you have Residential VoIP
Providers that has migrated the traditional phone
services to VoIP Telephony.
• Device Based providers are also called no
monthly bill service. The service is restricted to
US only.
• The most vulgarized service used world wide is
software based providers.
• For Apple I phone you have mobile services that
provide VoIP Telephony.
Getting Started
• Once you are aware of the benefits you are very
likely to migrate on VoIP.
Following steps you have to consider;
I. Have a good internet connection
II. Choose the type of service
III. Choose a VoIP Provider
IV. Get yours VoIP equipment
V. Get a Phone number
VI. Setup your VoIP
A Good Internet Connection
• With VoIP yours voice will be transmitted over
IP.
• There is a need of good internet connection.
• A question here is that what bandwidth is
adequate?
• Do you understand what is meant by
bandwidth?
Technology Comparison
Technology
Speed
Use in VoIP
Dial Up Modem
Up to 56 Kbps
Not suitable
ISDN
Up to 128 Kbps
Suitable for fixed and
dedicated services
ADSL
Up to several Mbps
One of the best WAN
technologies but no
mobility
Wireless Technologies
Up to several Mbps
Some are suitable but some
have limitations over
distance and signal quality
LAN
Up to Gbps
Limited to the length
Cable
1 to 6 Mbps
No mobility is offered
Limitations of VoIP Telephony
•
•
•
•
Voice Quality (QoS)
Bandwidth Dependency
Emergency Calls
Security
The major issue of VoIP over PSTN is that the data
has to be compressed and transmitted and than
de compressed and delivered in a very short
interval of time. Difficult if you have a slow
internet connection or hardware. This very
phenomenon is referred as “ECHO”
Some other limitations
• Highly dependant on bandwidth
• Connection down, poor connection, shared
connection effect the quality.
• You need power for ATA, Router or any other
hardware that you install.
• Emergency calls 911 are not bound by the
regulations.
• Security issues like identity theft, viruses, call
tempering etc. are the issues.
Features of VoIP
• VoIP does provide some fancy features that
includes;
• Caller ID
• Voice mail
• Call blocking
• Call waiting
• Call forwarding etc.
How VoIP works?
• The IP behind the Voice
• How does VoIP allow calls between IP
Network and PSTN
• Voice compression in VoIP
• IP Routing
• Circuit Switching & Packet Switching
• Factors Affecting the VoIP quality
IP (The Internet Protocol)
• You must have asked yourself what is IP in
VoIP means.
• IP Does stands for Internet Protocol
• How IP Actually works, two aspects are
involved;
Routing & The Protocol
Understanding IP
• Simply a protocol reflects that a set of rules
governing how things will work in a certain
technology.
• So there are some kind of standardization.
• When put into a telecommunication network
context, a protocol is the set of rules
governing how packets are transmitted over a
network.
Understanding IP (Continued)
• The IP Protocol standardize the way machines
over the internet or any IP Network forward or
route their packets based on their IP.
• An IP Is a unique address used to locate and
identify a device over a network.
• The device can be an electronic device, a
computer, a server a router or even an IP Phone.
• It is the addressing used for the transmission of
data packets over a networking working with the
IP Protocol.
Scenario
Suppose a person ‘X’, using a Machine ‘Y’
is involved in some hacking of a Bank
Name ‘A’ at Location ‘B’.
What will be the steps required to trace
the person to prevent the hacking.
IP Addressing
• Will try to start from the basics so at the end
of the lecture every one of you will get
familiarize of the concept.
I. IP Address is unique.
II. Structure of IP Address.
III. The Network and Host Part of the IP Address.
IV. IP Addresses and domain names.
Unique Address for Each Machine
• An IP address must be unique over a network.
• You never ever get two machines with the
same IP Address.
• Over a LAN as well there must be no two
machines assigned with the similar IP Address.
• Incase if two machines are assigned a same IP
Address mistakenly what will happen?
Hint: IP Conflict
IP Structure
• All IP Addresses are made up of four parts
separated by dots.
• Given below are the three Addresses, identify
which of them are IP Addresses?
1. 0.0.0.0
2. 00000000.00000000.00000000.00000000
3. 192.178.1.1
A Common Interview Question
Have you seen this IP Address;
127.0.0.1
At the moment don’t confuse yourself, it is an
IP address assigned to any standalone
machine.
So if your machine is not connected to any
network the address will be 127.0.0.1.
This is also called the local host address.
Network ID and Host ID
• There are two parts of an IP, The network part
and the machine part.
• Let us make an analogy to yours house’s address.
• It is made of the country part, then the city part,
then the street part.
• All the people living in the locality will have the
same country part and city part.
• Only the house number and street number will
be different.
Scenario
• For IP, all machines on the same network will
have the same network part. The right side
varies upon the machines.
• For example right now I am using the LAN, the
routers IP Address is 10.15.30.1. my IP
Address is 10.15.30.5 and my fellows IP
Address is 10.15.30.6.
• Can you identify the Network ID and the
Machine/ Host ID?
IP Addresses
• Total number of bits in IPv4 are 32, 8 bits for each
quadrant.
• So can you guess how many total IP Addresses does
exist? 2 ^ 32 = 4.3 billion approximately.
• Unfortunately many of these are wasted. During the
early days big companies bought large chunks of IP
Addresses, that was never ever used till now.
• The current version till now was IPv4. A version IPv5
was developed just for the research purposes. The
newer version is v6, that can store up to 128 bits.
How IP Addresses are Assigned?
• As you have come to know that there must be
no inconsistencies and duplication for the
addresses.
• I am sure that majority of you will not know
that there is a regulatory company called
ICANN (International Company for the
Assignment of Names and Numbers).
Names to IP Addresses
• If you have a network harboring server, you need
to have one or more IP Addresses. You need one
for the server, which will use the server to be
identified over the internet and one or more for
the machines over the network.
• The network admin will set the IP for the
machines.
• If you have a website it has to be having a domain
name. which simply is the access you type in the
main page.
IP Address Naming
• Examples are google.com, facebook.com
• Just to the fact that IP Addresses must be
unique the names has to be unique.
• You can’t have two or more than two websites
with the similar name and address.
• When a user types the address of a site on a
browser, the name is converted, or rather
matched to IP Address at a DNS. Which is used
for the translation of IP Addresses.
Understanding DNS
• The Internet and many other larger private IP
Networks rely on the DNS System to help direct
traffic.
• Traffic means the network packets.
• The DNS maintains a distributed data base of
network names and addresses.
• It provides methods for computers to remotely
query the database.
• Some people call DNS the phonebook of the
internet.
DNS and www.
• All public websites runs on servers connected to the
internet with the public IP Addresses.
• The web servers at about.com for example have
addresses like 207.241..148.80.
• Although people can type http:// 207.241..148.80 into
the browser to visit sites.
• But they use about.com because it is easy and
convenient.
• When someone types a site’s name to their browser,
DNS Looks up the corresponding IP address and allows
the network connection between the browser and
server.
Understanding DNS
• DNS uses a client/ server model/ architecture.
• DNS servers are the computers designated to
store DNS database records (names and
addresses)
• While clients includes PC’s, phones and other
devices.
Buying IP Addresses
• If you want to get one or a set of IP addresses,
you have to buy these from IANA (Internet
Assigned Numbers Authority). But you do not
necessarily need to do so directly. Say you want
to create a web site and name it
somethingelse.com, you can go to any of the
hosting companies, where they ask you to choose
a
name
(and
they
check
whether
somethingelse.com is unique) and you pay for
their hosting services. They also assign an IP
address to your site. They check all this with
IANA.