Copyright 2007 Jim Martin1 Internet and the WWW Dr. Jim Martin

Copyright 2007 Jim Martin2 History of the Internet Goal: To function if part of network were disabled Became functional September 1969 ARPANET Networking project by Pentagon’s Advanced Research Projects Agency (ARPA) Goal: To allow scientists at different locations to share information

Copyright 2007 Jim Martin3 History of the Internet Today More than 400 million host nodes 1984 More than 1,000 host nodes 1969 Four host nodes

Copyright 2007 Jim Martin4 Who controls the Internet? World Wide Web Consortium (W3C)  Oversees research, sets standards and guidelines  Tim Berners-Lee, director Internet2 (I2)  Internet-related research and development project  Develops and tests advanced Internet technologies  No one c — c it is a public, cooperative, and independent network  Several organizations set standards

Copyright 2007 Jim Martin5 Internet names and addresses The Internet Protocol (IP) defines many of the rules that make the Internet work. IP requires all computers on the Internet have an IP address. A 32 bit (4 bytes) quantity Every computer must have a different IP address. You might here about an IP address shortage… There are only 4,294,967,296 unique IP addresses (according to there are just over 6.6 billion people- so everyone can not have their own IP address) To find the IP address of a Windows machine, Go to start, control panel, network and Internet connections, network connections and click the right Button on the Local Area network connection and Select status. You will see this panel of information. The default gateway is the IP address of a machine Nearby that helps your machine connect to the Internet.

Copyright 2007 Jim Martin6 Internet names and addresses The Internet Protocol (IP) defines many of the rules that make the Internet work. All computers on the Internet have an IP address What is a IP address? Number that uniquely identifies each computer or device connected to Internet Some computers have a domain name that is mapped to the computers IP address Domain Name: Address in dotted decimal format: Address in binary:

Copyright 2007 Jim Martin7 Internet names and addresses Names are organized in a hierarchy Clemson’s Internet Names Educational Institution -.edu Clemson University – clemson.edu Clemson’s Web Server – Computer Science – cs.clemson.edu Other Top-Level Domains.com – commercial.org – non profit organization.gov – government sites

Copyright 2007 Jim Martin8 Web browsers and servers Internet Internet Explorer, FireFox BellSouth HTTP GET COMMAND: "GET /~jmarty/index.html HTTP/1.0" Returns the web object. File size ranges From 20 bytes to gigabytes

Copyright 2007 Jim Martin9 Web browsers and servers Internet Internet Explorer, FireFox BellSouth Data sent between computers is packaged in packets. TCP/IP refers to the set of protocols that defines the rules for sending and receiving packets

Copyright 2007 Jim Martin10 Web browsers and servers Internet Internet Explorer, FireFox BellSouth HTTP GET COMMAND: "GET /~jmarty/index.html HTTP/1.0" Returns the web object. File size ranges From 20 bytes to gigabytes The time from when the browser Sends the message until when all The data is received is the response time.

Copyright 2007 Jim Martin11 Where do the delays come from? Transmission time: time to transmit the message over a link. T-t : message size in bits / link speed (bits) bits per second Propagation delay : Time for the bit to propagate over the physical medium. Electro-Magnetic energy travels at the speed of light. E.g., propagation delay from NY to LA is about.003 seconds.

Copyright 2007 Jim Martin12 Ping program Ping is an Internet program that tests if a machine is alive. Also lets us test the round trip time (RTT) and the loss rate between two machines. All computers have the ping program. However not all computers will reply. Ping request msg Ping reply msg

Copyright 2007 Jim Martin13 Ping: RTT calculation Two computers connected by a bps link. The one – way propagation delay over the link is.003 seconds. What RTT would you expect if a 64 byte message is sent and echoed back? RTT= 2 * transmission delay + 2 * propagation delay = 2 * ( (64 * 8) / 64000) + 2 * (.003) = 2 * (.008) + 2 * (.003) =.022 seconds

Copyright 2007 Jim Martin14 Assessing application performance When downloading a file throughput is used to assess performance: Throughput: how much data is sent in a given time. Download a 10,000 byte file in.060 seconds Throughput = 10,000 * 8 /.060 = 1.33 megabits per second (1.33 Mbps)