Your SlideShare is downloading. ×
  • Like
INFT132 093 02 Internet Concepts
Upcoming SlideShare
Loading in...5

Thanks for flagging this SlideShare!

Oops! An error has occurred.


Now you can save presentations on your phone or tablet

Available for both IPhone and Android

Text the download link to your phone

Standard text messaging rates apply

INFT132 093 02 Internet Concepts


Internet Concepts

Internet Concepts

Published in Education , Technology , Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads


Total Views
On SlideShare
From Embeds
Number of Embeds



Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

    No notes for slide


  • 1. INFT11/71-132 Web Applications Internet Concepts Dr Michael Rees School of Information Technology
  • 2. The Internet • The Internet is a global, wide area network (WAN) of computers • Composed of millions of smaller local area networks (LANs) all connected together • All computers support Internet Protocol (IP) • Each computer must have a unique IP address: a unique 32 bit value made up of 4 numbers (each 0-255) • Example IP Address: – Binary: 11101110.00010001.10011111.00000100 – Decimal: © 2009 Michael Rees Web Applications 2
  • 3. Internet Protocol • Transfer data from source device to destination device (computers today but any device in future – the Internet of Things) • IP source software creates a packet representing the data: – About 1500 characters – Header: source and destination IP addresses, length of data, and so on – Data itself – Checksum used to test data integrity and correct transmission • If destination is on another LAN, packet is sent to a gateway or router that connects one network to another © 2009 Michael Rees Web Applications 3
  • 4. Packet switched network • TCP (Transfer Control Protocol) breaks data into packets at the sending end and reassembled at the receiving end • Packets pass from a source computer, possibly through several intermediate computers to the destination computer • Computers acting as routers examine the packets and decide the onward path each packet should travel © 2009 Michael Rees Web Applications 4
  • 5. Transmission Control Protocol • TCP overcomes the limitations of IP: – No guarantee of packet delivery (packets can be dropped) – Communication is one-way (source to destination) • TCP adds concept of a connection on top of IP: – Provides guarantee that packets are delivered – Provide two-way (full duplex) communication © 2009 Michael Rees Web Applications 5
  • 6. TCP Handshake Can I talk to you? Establish connection { OK. Can I talk to you? OK Here’s a packet Send packet with acknowledgment { Source Got it Destination Here’s a packet Resend packet if no (or delayed) acknowledgment { Here’s a resent packet Got it © 2009 Michael Rees Web Applications 6
  • 7. TCP Ports • TCP also adds concept of a port • TCP header contains port number representing an application program on the destination computer • Some port numbers have standard meanings • Other port numbers are available first-come-first served to any application © 2009 Michael Rees Web Applications 7
  • 8. TCP Ports • Port numbers identify particular services on an Internet host computer • Examples: – port 25 used for SMTP (mail transfers) – port 23 used for TELNET (remote host connection) – port 80 used for HTTP (web page transfers) © 2009 Michael Rees Web Applications 8
  • 9. User Datagram Protocol - UDP • Like TCP in that: – Builds on IP – Provides port concept • Unlike TCP in that: – No connection concept – No transmission guarantee • Advantage of UDP vs. TCP: – Lightweight, so faster for one-time messages © 2009 Michael Rees Web Applications 9
  • 10. Domain Name Service - DNS • DNS RFC • DNS is the “phone book” for the Internet – Map between host names and IP addresses – DNS often uses UDP for communication • Host names – Labels separated by dots: • – Final label is a top-level domain • Generic: .com, .org, .tv, .name • Country-code: .au, .us, .il © 2009 Michael Rees Web Applications 10
  • 11. Domain Name System • Allows human-readable domain names to map to IP addresses (try: nslookup • Used in Universal Resource Locator (URL): domain file protocol folder server is a Fully Qualified Domain Name - FQDN © 2009 Michael Rees Web Applications 11
  • 12. So, who runs the Internet? • ISOC (The Internet Society) – Is a non profit central organization for the groups that are responsible for the standards for internet structure – • ICANN (Internet Corporation for Assigned Names and Numbers) – • W3C (World Wide Web Consortium) – develops standards for the web – © 2009 Michael Rees Web Applications 12