Created by, Nancy Harris, James Madison University, VA FLUENCY WITH INFORMATION TECNOLOGY Skills, Concepts, and Capabilities

Created by, Nancy Harris, James Madison University, VA MAKING THE CONNECTION The Basics of Networking chapter 3

Copyright © 2003 Pearson Education, Inc. Slide 1-3 Internet - Age > What has the internet meant to you? > How do you use it?

Copyright © 2003 Pearson Education, Inc. Slide 1-4 Terms > Synchronous vs asynchronous communication — Synchronous means that the two communicators must be “together” in time. — Phone calls. Both parties must be connected to talk. — Chat rooms, IM are virtually synchronous (but are technically asynchronous) — TV/Radio (if you are personally listening or have a device to capture the program) — Asynchronous – occur at different times, one sends a message and at some other point it is “read”. — Snail mail —

Copyright © 2003 Pearson Education, Inc. Slide 1-5 More terms > Broadcast – Anyone listening can get the message. — Radio/television – anyone with a receiver can get the message. > Multicast – Many “listeners” are sent a message but the intended recipients are a limited population — Batch s, listservs, close captioned broadcast > Point-to-point – One sender and one receiver of the message. — IM, individual , snail mail.

Copyright © 2003 Pearson Education, Inc. Slide 1-6 Figure 3.1. A diagram of the Internet.

Copyright © 2003 Pearson Education, Inc. Slide 1-7 Figure 3.2. Computers connected to the Internet are given IP addresses. IP – Internet Protocol Address 4 byte addresses

Copyright © 2003 Pearson Education, Inc. Slide 1-8 IP Addresses vs Domain Names > IP addresses are cumbersome to use. > Instead we usually refer to a specific machine by a Domain Name. > A domain is a related group of networked computers. > ie. cs.jmu.edu is the CS department computers. > It is a part of the jmu.edu domain which includes all of the various department computers.

Copyright © 2003 Pearson Education, Inc. Slide 1-9 Figure 3.3a. Two diagrams of domain hierarchy.

Copyright © 2003 Pearson Education, Inc. Slide 1-10 Figure 3.3b. Two diagrams of domain hierarchy.

Copyright © 2003 Pearson Education, Inc. Slide 1-11 DNS – Domain Name System > How does a domain name (letters) get equated to the actual address (numbers). > A Domain Name System server tracks the Domain name and its equivalent IP and does the translation. > When I request through my browser the page that is translated into an IP address and the jmu.edu network is accessed.

Copyright © 2003 Pearson Education, Inc. Slide 1-12 Figure 3.4. Hosts like Spiff make requests to a local DNS server.

Copyright © 2003 Pearson Education, Inc. Slide 1-13 Top level domains > Originally —.com —.org —.net —.mil —.gov —.edu > These have expanded to allow countries to have their own designations, including us. > There are some other top-level domains now as well.

Copyright © 2003 Pearson Education, Inc. Slide 1-14 Figure 3.5. The TCP/IP postcard analogy. A packet of information (data, a request) is sent to the senders computer which sends a request to the appropriate IP address. This request is routed via the route that is best available at the time until it finally lands at the destination machine. That machine then sends a message (response) to the sender. This message may or may not follow the same routing (probably not)

Copyright © 2003 Pearson Education, Inc. Slide 1-15 Figure 3.6. The Internet makes use of whatever routes are available to deliver packets.

Copyright © 2003 Pearson Education, Inc. Slide 1-16 Figure 3.7. A ping from the author’s machine to eth.ch. A ping is a request to see if another machine is available. It is basically like saying “Are you there?”

Copyright © 2003 Pearson Education, Inc. Slide 1-17 Internet vs www > World Wide Web is a subset of the internet. > www computers serve up web pages to users of the internet. > Not all computers connected to the internet are “web enabled”. > So those with the address of www are available for serving web pages. > My web page is located at users.cs.jmu.edu/harrisnl – it is not necessarily intended to serve web pages, but many of us use it for that purpose. It is available on the internet for downloading files, etc.

Copyright © 2003 Pearson Education, Inc. Slide 1-18 And when we do get to a web page > We know that what we are seeing is the result of some code such as html.

Copyright © 2003 Pearson Education, Inc. Slide 1-19 Figure 3.8. Robert Metalfe’s original drawing of the Ethernet design; the unlabeled boxes, computers, “tap” onto the wire that Metcalfe has labeled “The Ether.”

Copyright © 2003 Pearson Education, Inc. Slide 1-20 Figure 3.9. A Web page and the HTML source that produced it. Notice that an additional image file, alto.jpg, is also required to display the page.

Copyright © 2003 Pearson Education, Inc. Slide 1-21 Figure 3.9 (continued). A Web page and the HTML source that produced it. Notice that an additional image file, alto.jpg, is also required to display the page.

Copyright © 2003 Pearson Education, Inc. Slide 1-22 Web addresses > > Protocol – http – tells the computers how to handle the file at the “end” of the address. > Domain name of the server (IP address) > Path name (absolute) to the particular file that we want to open.

Copyright © 2003 Pearson Education, Inc. Slide 1-23 Figure A hierarchy diagram showing the path between xerox-alto.jpg and the desktop.

Copyright © 2003 Pearson Education, Inc. Slide 1-24 Figure The pathname hierarchy ending in pioneer.html.

Copyright © 2003 Pearson Education, Inc. Slide 1-25 Organizations > ICANN – Internet Corporation for Assigned Names and Numbers – controls assignment of domain names and IP addresses and policies. > IANA – Internet Assigned Numbers Authority > Internic – provides a database to check out domain names. However, I have often found it to be too busy to serve.