History of the Internet. Mid 1960’s During the Cold War – need for bomb proof communications system. Government Agency and few Universities Emergency military communications system operated by Department of Defense’s Advanced Reserarch Project Agency (ARPA) – ARPANET
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What is the Internet?
Network of Networks
Computers communicate over the internet using TCP/IP
(Transmission Control Protcol / Internet Protocol)
Client / Server Architecture
Funding the Internet
Funded through Agencies ( National Science Foundation, Government agencies pay for some high speed backbones)
We are going to look at the following Architectures
How Computers send data across the Internet
The basic idea of communication via the internet is to have two remote sites or computers connected together via a network or transmission line
The Heart of the Internet work is the Domain Name System (DNS), the way in which computers can contact each other and do things such as e-mail or display web pages. If a user wants to contact a specific location – e.g. visit Web pages they type in the address (URL) –
while numbers are convenient for machines, they are not for human beings, therefore humans use names for addresses and TCP/IP uses it DNS (Domain Name System) application (Name Servers) to provide name-to-address translation.
The DNS translates the plain english address into a series of numbers called an IP address,
An IP address marks the location on the internet similar to a house number and street address. All computers connected to the Internet must have an IP address.
Two types of IP address exist
Dynamic IP Addresses
.edu for educational institution, usually a university
.com for a commercial business
.gov for a government department or agency
.mil for a military unit
.org for a non-profit organisation
Following introduced to reduce the load on .com domain not all are in
use yet as they officially registered.
.areo for aviation industry .info for general use
.biz for business .coop for cooperatives
.museum for museums .name for individuals
.pro for professionals
In total there are more than 250 top-level domain names
The IP address is a 32 bit number but is now being expanded to 128 bit number to allow for more IP addresses to be accommodated.
Since networks vary in size, there are four different address formats or classes to consider when applying to NIC for a network number:
Class A addresses are for large networks with many devices.
Class B addresses are for medium-sized networks.
Class C addresses are for small networks (fewer than 256 devices).
An IP address is expressed as four decimal numbers (octets), each representing eight bits, separated by periods. The first few bits of each IP address indicate which of the address class formats it is using. The address structures look like this:
Each of the decimal digits represents a string of four binary digits. Thus, the above IP address really is this string of 0s and 1s:
0Network (7 bits values 1-126)Local address (24 bits, 3 remaining octets used to identify host)
10Network (14 bits first octet 128-191 + second octet used to identify network)Local address (16 bits, 2 octets used to identify host)
110Network (21 bits, first octet 192-223, 1st , 2nd and 3rd octet identify network)Local address (8 bits, 1 octet identifies host)
URLs uniquely identify each file on the web by specifying its name, what server it is on, and where it resides in the server’s directory structure and how the page can be accessed.
Much of the power of browsers is that they are multiprotocol. That is, they can retrieve and render information from a variety of servers and sources.
Routers are traffic cops of the Internet. They ensure that data gets to its final destination via the most efficient route.
Two broad type of routing protocols exist