Introduction to VoIP Communications

Multimedia Systems

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• A PBX could be setup if any one of you is interested

come and see me on Wednesday and I can give you the tutorial to setup the VoIP Exchange

Introduction

• Before knowing about Voice Over IP Communications following terms are necessary to understand;

1. What is VoIP2. Getting Started with VoIP3. Reasons for switching to VoIP4. VoIP Pitfalls5. VoIP or internet telephony6. 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 connectionII. Choose the type of serviceIII. Choose a VoIP ProviderIV. Get yours VoIP equipmentV. Get a Phone numberVI. 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 ComparisonTechnology 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. 0.0.0.02. 00000000.00000000.00000000.000000003. 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.