Created by, Nancy Harris, James Madison University, VA FLUENCY WITH INFORMATION TECNOLOGY Skills,...

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

chapter3

Copyright © 2003 Pearson Education, Inc. Slide 1-3

Internet - Age

>What has the internet meant to you?

> How do you use it?


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—E-mail


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 e-mails, listservs, close captioned

broadcast

> Point-to-point – One sender and one receiver of the message.—IM, individual e-mail, snail mail.


Figure 3.1. A diagram of the Internet.


Figure 3.2. Computers connected to the Internet are given IP addresses.

IP – Internet Protocol Address4 byte addresses


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.


Figure 3.3a. Two diagrams of domain hierarchy.


Figure 3.3b. Two diagrams of domain hierarchy.


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 www.jmu.edu, that is translated into an IP address and the jmu.edu network is accessed.

http://www.jmu.edu/


Figure 3.4. Hosts like Spiff make requests to a local DNS server.


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.


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)


Figure 3.6. The Internet makes use of whatever routes are available to deliver packets.


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?”


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.


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.


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.”


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.


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.


Web addresses

> http://users.cs.jmu.edu/harrisnl/index.html

> 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.

http://users.cs.jmu.edu/harrisnl/index.html

http://users.cs.jmu.edu/harrisnl/index.html


Figure 3.10. A hierarchy diagram showing the path between xerox-alto.jpg and the desktop.


Figure 3.11. The pathname hierarchy ending in pioneer.html.


Organizations

> ICANN – Internet Corporation for Assigned Names and Numbers – controls assignment of domain names and IP addresses and policies. www.icann.org> IANA – Internet Assigned Numbers

Authority www.iana.org> Internic – provides a database to check out

domain names. However, I have often found it to be too busy to serve. http://www.internic.net/whois.html

http://www.icann.org/

http://www.iana.org/

Created by, Nancy Harris, James Madison University, VA FLUENCY WITH INFORMATION TECNOLOGY Skills,...

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