1. Accessing the World Wide Web from Home Many students access the World Wide Web from home Here is how it works, in terms of standards

2. 2 Accessing the WWW from Home n A Common and Important Situation – Must be understood – Good way of introducing networking concepts

3. 3 The Internet n The Internet is a Worldwide Group of Networks – Not a single network – Individual networks on the Internet are called subnets

4. 4 The Internet n Messages are Broken into Small Packets for Transmission, as Noted Earlier – More efficient than sending long messages Message Packets

5. 5 The Internet n Routers – Connect the Internet’s individual networks (subnets) – Cooperate to give an end-to-end route for each packet Routers Route

6. 6 The Internet n Hosts – Any computer attached to the Internet is a host – Webservers are host – Desktop and notebook PCs are hosts too Host

7. 7 The Internet n Network deliver messages based on network addresses – The Internet has two addressing systems for hosts n IP addresses n Host names Host

8. 8 The Internet n Host IP addresses – Strings of 32 ones and zeros – Usually represented by four number segments separated by dots: dotted decimal notation – For example, 128.171.17.13 – Official addresses for hosts 127.18.47.145 127.47.17.47

9. 9 The Internet n Dotted Decimal Notation – IP addresses are really strings of 32 bits (1s and 0s) n 10000000101010100001000100001101 – To convert this to dotted decimal notation, first, divide them into four bytes (also called octets) n 10000000 10101010 00010001 00001101 – Both octets and bytes are collections of eight bits

10. 10 The Internet n Dotted Decimal Notation – Convert each binary (Base 2) octet into decimal (Base 10) n 10000000 is 128 n 10101011 is 171 n 00010001 is 17 n 00001101 is 13

11. 11 The Internet Value (2 N ) BitDecimal 1281 6400 321 1600 800 400 212 111 163 Position (N) 7 6 5 4 3 2 1 0 Binary 10100011 = Decimal 163 Note: Starts with 0

12. 12 The Internet n Why dotted decimal notation? – Strings of 32 bits are very difficult to memorize – Dotted decimal representations of IP addresses are (somewhat) easier to remember – So dotted decimal notation is merely a mnemonic device for representing IP addresses

13. 13 The Internet n Host Names – The other network addressing system on the Internet – Easy to remember n www.microsoft.com n voyager.cba.hawaii.edu n Two or more text “labels” separated by dots n No relationship between segments and labels CNN.COM

14. 14 The Internet n Host Names – Like nicknames n Not official addresses n Each host must have an IP address n But only some hosts have host names n If you give it a host name, your browser must look up IP address of host (Chapter 3 discusses how) CNN.COM