Internet and the World Wide Web
Network: A group of interconnected computers
Internet: A global system of interconnected computer networks that use the standardized Internet Protocol Suite
(TCP/IP) to serve billions of users worldwide.
o TCP/IP: A standard transmission control protocol with rules for the format and transmission of data.
o The Internet is hardware of networks, while the World Wide Web is software that runs on the Internet.
One can connect to the internet through:
o Internet service provider by modem (ISP)
o Internet ready cable
o Digital subscriber line (DSL)
How does the internet work?
o Circuit switching: Transfer the complete data without splitting it. How a phone line works.
o Packet switching:
Packet: Small group of consisting of:
Header (64 bytes): Destination and source
Body (512 bytes): Actual message content
On the internet, data is sent through transferring packets through different IP addresses.
o TCP (Transmission Control Protocol)
At the sending end:
Take a large chunk of data and break it into small packets.
IP is responsible for sending the packets out on to the internet.
At the receiving end:
Detect lost packets, error packets because of network congestion, traffic load balancing, etc.
Request packets to be resent from the source.
Rearrange and reassemble the packets back into the original document.
o IP (Internet Protocol)
Picks a route for a packet, stopping at router devices which pick the next best machine to send it
Need to be able to identify all the machines on the internet, and thus each machine has a unique IP.
4 numbers that range from 0 to 255. <000.001.002.225>
Can be also written in binary, hexadecimal, or decimal, but dotted quad is most popular
Not based on geography.
Domain name: Text name corresponding the numeric IP address of the computer on the internet
A DNS (Domain Name System) maps the domain name to the correct IP address
o URL (Uniform Resource Locator)
Website address; Established by Tim Berners-Lee
An address of a web document on a computer that every website has http://www.uwo.ca/its/courses/spring.html
http://: Hypertext Transfer protocol. Rules that define how data is exchanged.
www: Indicates file is on the World Wide Web
uwo.ca: Domain name. Name of the site.
spring.html: Webpage file
o Subdomains: Used to organize your web server
Maximum of 127 labels, each with maximum of 63 characters
Whole domain cannot exceed 255 chars, including TLD
.com: Top Level Domain
mycar. 2 ndlevel doma