2013Dr. Ali Rodan 1 Handout 1 Fundamentals of the Internet

2013 Dr. Ali Rodan1

Handout 1

Fundamentals of the Internet

2013 Dr. Ali Rodan2

The Internet

A "network of networks" that consists of millions of smaller domestic, academic, business, and government networks.

– Worldwide, publicly accessible

Mixing computing and communications technologies. Carrying information and services, such as

electronic mailelectronic mail, online chatonline chat, file transferfile transfer, and the interlinked Web pages and other documents of the World Wide WebWorld Wide Web.

2013 Dr. Ali Rodan3

Packets and Routing

Data is transmitted on the internet by packet switching using the standard Internet Protocol (IP)

Packet – a unit of information carriage Packet switching – process of moving

packets from one node (computer device) to another

2013 Dr. Ali Rodan4

Internet, Packets and Routing

At the sender, data is broken into packets and sent to the nearest node (router)

At each router, it sends the packet to another router that is closer to the final destination

At the receiver, packets are reassembled to get the original data

A simple analogy: mailing system

2013 Dr. Ali Rodan5

TCP/IP and Domain Names

Basic task of IP – moving packets as quickly as possible from one router to another

Yet, it doesn’t check whether packets are delivered successfully, thus need TCP

TCP (Transmission Control Protocol) – disassemble/reassemble packets, error checking, ACK packets

2013 Dr. Ali Rodan6


We need some sort of address in order to identify different nodes, as if every house has a mailing address in order to receive mail from others

The one used by Internet Protocol is called IP address

Every host on the Internet has a unique IP address, made up of four numbers. E.g.. 192.56.215.131, each number is between 0 and 255

2013 Dr. Ali Rodan7


The numbers in an IP address is hard to remember, while names are easier

Domain Name System – a mapping between the human-readable name (domain name) of a host and its IP address

A domain name consists of two or more parts, e.g. cs.ju.edu.jo

The rightmost label conveys the top-level domain, e.g. jo

2013 Dr. Ali Rodan8


Each label to the left specifies a subdomain, in our example, subdomain is ju (University of Jordan), and sub-subdomain is cs (computer science).

A top-level domain contains of multiple subdomains, each subdomain can contain multiple sub-subdomain, so on.

The database contains the mapping between a domain name and an IP address is stored on a DNS server.

2013 Dr. Ali Rodan9

The World Wide Web

Introduced in 1990 by Tim Berners-Lee A system of interlinked, hypertext documents

accessed via the Internet. – With a web browser, a user views web pages that

may contain text, images, and other multimedia and navigates between them using hyperlinks.

– Hypertext refers to text on a computer that will lead the user to other, related information on demand

2013 Dr. Ali Rodan10

World Wide Web

hypertext documents are WebPages (documents on the WWW) created using a special kind of document formatting or “markup” language called HyperText Markup Language (HTML).

HTML is sent or received over the network using HyperText Transfer Protocol (HTTP).


What is Web Browser ?

A Web browser is a software that enables a user to display and interact with the Web’s rich multimedia content such as text, images, and other information.

The Web could be the World Wide Web, a local area network, or a web page on your own machine.

Microsoft Internet Explorer or Netscape Navigator– The appearance of a Web page may differ between

browsers.


Client-Server Model

A web browser (client) lets a user request a resource.

A web server takes the client request and gives something back to the client.

Clients and servers know HTML.

Client

Request

Response


Scripting Languages

Scripting languages, which can be embedded within HTML, commonly are used to add functionality to a Web page.

Scripting languages came about largely because of the development of the Internet as a communications tool. JavaScript, ASP, JSP, PHP, Perl and Python are examples of scripting languages.


URLs and Client-Server Model

Each document/resource on the WWW needs to have an identifier in order to be accessed by others.

A Uniform Resource Identifier (URI), is a compact string of characters used to identify or name a resource.

A Uniform Resource Locator (URL) is a URI which provides means of obtaining the resource by describing its network “location”.


URL & Hyperlinks

URL (Uniform/Universal Resource Locator)– Web page address – typing in Address field

HTTP (HyperText Transfer Protocol)– Protocol for transferring data over the Internet

HTTPS (Secure HyperText Transfer Protocol)– Protocol for transferring encrypted data over the Internet.

Hyperlinks– Graphical or textual elements

Click to link to another Web page Loads new page into browser window


URLs and Client-Server Model

Two things are given by the URL– Exact location of the document– The method or protocol by which to retrieve and display

the document Example,

http://www2.ju.edu.jo/sites/academic/a.rodan/default.aspx• http:// – specifies the protocol• www2.ju.edu.jo – specifies the host name / domain name• sites/academic/a.rodan/default.aspx –

specifies the path of the document on the host


Goal of This Course

HTML – Focuses on writing HTML files.

JavaScript– Teaches programming language and

programming language principles.

Client-side applications– Teaches how to create Internet-based and Web-

based applications.


Online Resources

http://www.w3.org/– The World Wide Web Consortium (W3C).

http://www.w3schools.com/– Full Web Building Tutorials - All Free


Putting it All Together

Documents

2013Dr. Ali Rodan 1 Handout 1 Fundamentals of the Internet