1. Web Programming– UFCFB3-30-1 Lecture 2
Instructor : Mazhar H Malik
Global College of Engineering and Technology

2. Previous Lecture The World Wide Web environment.
Describe the history and development of the WWW.
WWW vs Internet vs Networking.
Describe WWW contents.
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3. Today’s Lecture LAN and WAN, TCP and UDP Packet vs Circuit Switching
Protocols
Internet Protocol Suit
Web forms
Scripts and Applets
FTP
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4. Lecture 2 - The Internet as a Network LO 1
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5. Networks Advantages: Disadvantages: Enable people to work together
Reduce costs from sharing networked hardware and software
Increase productivity by sharing data
Provide access to a wide range of services and specialized peripheral devices
Disadvantages:
Unavailable resources when network malfunctions
More vulnerable to unauthorized access than stand alone computers
Susceptible to an increased number of worms, Trojan horses, and blended threats

6. Local Area Network (LAN)
Network of computers located in a single location, like a home, school, or office building
Can share connection with other LANS and with the internet

7. Characteristics of a LAN?
Local area network
Relatively limited in size
Computers connected in small areas
Same office
True peer-to-peer
Can support limited number of nodes

8. Wide Area Network (WAN)
Network over a large area like a city, a country, or multiple countries
Connects multiple LANs together
Generally utilizes different and much more expensive networking equipment than LANs
The internet is
the most
popular WAN

9. Suggested reading - Chapter 2, Discovering Computers 2007
Key words
Node
Any device connected to a network
Your computer at home, one in the lab, one out there on the internet
Has a unique network address
Client
Any node that requests and uses resources available from other nodes.
Usually from another computer, often a computer called a server
Server
A node that shares resources with other nodes
File server, print server, mail server or web server
Client-server relationship
Can be file server, printer server, communications server, Web server, Database server depending on the resources being shared.
Suggested reading - Chapter 2, Discovering Computers 2007
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10. TCP and UDP
TCP or Transmission Control Protocol and UDP or User Datagram Protocol.
TCP is connection oriented – once a connection is established, data can be sent bidirectional.
UDP is a simpler, connectionless Internet protocol. Multiple messages are sent as packets in chunks using UDP.
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11. e.g User Name and Password e.g Audio, Video and Gaming Traffic
TCP
UDP
Connection Oriented
Connection Less
Reliable
Not Reliable
Slow
Fast
e.g User Name and Password
e.g Audio, Video and Gaming Traffic
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12. Packet switched network
Packets (units of information) are routed between nodes over data links shared with other traffic
Contrasts with circuit switching, which sets up a dedicated connection between the two nodes for their exclusive use for the duration of the communication
Packet switching…
Makes best use of the capacity in a network
Improves time it takes for data to pass across the network
Increases the stability of the network
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13. Packet switching Files to be transmitted are divided into packets
Labelled with to, from, and # of #
Sent across the network…may take different routes
Put together at the destination
Missing packets are re-sent
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14. Circuit and Packet Switching
(1) circuit switching (example: telephone networks)
• a sequence of links (communication path) between two communicating nodes is determined ahead of the actual communication
• data is sent as a stream of bits through the network.
packet switching (example: the Internet)
data is sent through network in short blocks – packets
network links are dynamically shared by many packets; each packet uses full link bandwidth
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15. Circuit switching Steps
(1) circuit establishment
• before any data is transmitted, an end-to-end circuit must be established, i.e. network resources on path/ links between end-devices must be reserved
(2) data transfer
• data transmission and signaling may each be digital or analog .
(3) circuit disconnect
• after some period of data transfer, the connection is terminated, by action of one of two stations, and dedicated resources are released.
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16. Protocols The standards that specify how the network functions
The set of rules for communication over the network
The language or the grammar that allows computers to “talk” to each other
The Internet uses many protocols
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17. Internet protocol suite
Designed to be independent of the underlying physical medium
Any communications network, wired or wireless, that can carry two-way digital data can carry Internet traffic
Thus, Internet packets flow through wired networks like copper wire, coaxial cable, and fibre optic, and through wireless networks like Wi-Fi. Together, all these networks, sharing the same protocols, form the Internet
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18. TCP/IP IP - Internet Protocol TCP - Transmission Control Protocol
Handles the packets
TCP - Transmission Control Protocol
Handles the sending (routing) of the packets from sender to receiver via nodes on the network
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19. Internet addresses IP address Unique to each device connected
4 groups of numbers, each separated by a full-stop.
Each of the four numbers is
A word equivalent (URL - uniform resource locator) is easier to remember =
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20. Connectivity
This can be a hard word to define in computer science terms
Generally it means the ease and ability of devices to connect and share digital data
Includes computers, phones, PDA’s, etc, wired and wireless
Refer to the picture on the title slide
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21.
Create, send, receive, forward, store, print and delete electronic messages
Can attach files e.g. graphic, video, Word document or spreadsheet
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23. Forms on web pages Web page users often fill in a form, e.g.
Feedback
eCommerce - a shopping cart is an extended form
Subscribe, enrol at university etc
Design is important
Easy and clear to use
People will use it
People will use it correctly and give the information you want
Conforms to technical standards
Will display and function reliably
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24. Submit button. Needs a reset button too
Parts of a web form
A drop-down list
Radio buttons; can only select one
Check boxes; can select more than one
Text box - usually a set size
Note that this example form is not very well designed!
Submit button. Needs a reset button too
Text box displays * instead of text; usually for passwords
Text box; large field
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25. How a form is processed
User completes the form and clicks Submit (or Send? or Finished? or OK? What is the best word?)
A script* or applet* runs
Transmits the data to the server, and if needed, sends data back to the client e.g. “Thank you, your order is being processed”
Usually the data goes to a database, or is ed
* See next slide
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26. Scripts and Applets
A script or an applet is a mini computer program that runs on the client’s computer
It is usually downloaded with the web page, in the background. When needed (e.g. by clicking on “Submit”) it runs
An applet usually runs faster than a script
Scripts and applets communicate with the web server using the common gateway interface (CGI) communication standard
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27. FTP File Transfer Protocol
Used to transfer data from one computer to another over the Internet, or through a network
Example - create a website on your machine; use FTP to copy the site to the web server; now everyone can use the site
Then use FTP to update the files as you maintain the site
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28. Revision and Questions?
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