Networking At UW, The Internet And Beyond

Various computers will be used in this class, so a quick introduction to their arrangement and networking is useful. Along the way we answer the pressing question: What is the difference between the Internet and the World Wide Web

Accomplishments To Date …

You have a UWNetID that gives you access to the UW’s computers, but also access to the World Wide Web … your account is on Dante

You have sent email, set up folders, set up an address book

You have visited home pages for UW, CSE100, other sites

You have tried out a search engine

Other things you should find out about …

Printing is possible for most computer applications … how do you use the printers at OUGL or MGH labs?

In Pine, it is possible to “postpone” a mail message that you are writing -- that is, set it aside to use Pine in other ways and then return to it. Try out “postpone” in your next mail.

Computers of the Realm...

We will discuss how computers really work later, but for now think of them as having many forms

Embedded -- processor, ROM, channels to sensor/actuators; m-wave oven

Laptop -- processor, RAM, floppy disk, hard disk, LCD; mobility

Desk Top -- processor, RAM, floppy, hard disk, CD, monitor; educational and office work

Server -- processors (4-32), RAM, many hard disks, CD; services

Supercomputer -- processors (16-1K), RAM, hard disks; big science

Class Computers

FIT100 uses

Laptop for lectures

Desktop in Collabs, OUGL, MGH

Dante server

An unconnected computer can only access the data stored locally on its hard disk, run the software stored locally, read and write floppy disks, etc.

The UW computers are connected, i.e. networked, together allowing us to send email and access the World Wide Web

Networks ...

Networks connect computers, making them much more useful because

Access more information and software

Help users communicate, share information

Perform services for one another

UW’s networks ship ~1/2 trillion bytes of data per day

Half this information goes to or comes from the Internet

How are these networks arranged?

Ethernet … It’s Like Conversation

Think of a dozen students sitting around the dorm telling stories …

Everyone listens while one person tells his/her story

When the story is finished, there is a pause

A person with a story to tell starts talking, listening all the while

If no one else started talking too, the person continues

If others started talking, he/she stops and waits briefly before trying again

In Ethernet, only the computers actually communicating listen to the transmission … the others simply wait for the break

UW Networks Connect To Internet

The subnetworks of campus interconnect the computers of the UW domain (.washington.edu), which is connected to the Internet via a Gateway

How Are Computers Named Logically

The logical way to name computers is using domains

All educational institutions    .edu

U Dub                 .washington.edu

CSE               .cs.washington.edu

Me           boris.cs.washington.edu

This scheme is hierarchical

Easier to remember names

Names are associated with like units

No limit to size or organizational depth

How Are Computers Named Physically

The physical way to name computers is using an Internet protocol address, or IP address

boris.cs.washington.edu’s IP address is: 128.95.2.227

cs.washington.edu’s IP address: 128.95.1.4

washington.edu’s IP address: 140.142.15.163

The domain name system (DNS) associates human readable names with the physical IP addresses for use by the computers and routers of the Internet

Logical Network … Physical Network

An important concept ...

In computing it is common to separate the logical idea of something -- the way you think about it -- from the physical implementation -- how it’s actually built

This is called a physical / logical separation

In networking, the domain names make up our logical network, a hierarchical arrangement of names that tell us associations: cs.washington.edu

The computers actually use physical addresses

The DNS enables the separation by making the correspondence between the two

How Is Information Sent?

Sending information over the Internet works like this:

Imagine sending the novel you wrote from Tahiti where you live to New York City where your publisher is using only postcards

The Internet Protocol

How is the information sent?

Information -- email, web pages, phone calls, everything sent over the internet -- is broken up into small units, called packets

Packets contain an IP address, a sequence number and some actual information, a part of the whole message

This scheme is called the Transmission Control Protocol and Internet Protocol, or TCP/IP

The packets are sent independently, usually taking different routes, and reassembled at the destination to reconstruct the original message

World Wide Web

The world wide web is composed of those computers, called web servers, capable of sending information to your browser, e.g. Netscape or IE

In most domains the computer that is the web server is called “www”, e.g. www.washington.edu

But, a web server can have any name … your pages will be served by students.washington.edu

The actual pages will be stored somewhere else, e.g. Dante

There are different ways to connect to these servers

Hyper-text transfer protocol, http for web pages

File transfer protocol, ftp for files of information

Web Pages

Web pages are just text files containing instructions to your browser on how to lay out the web page

Web pages can be created with a text editor

Web pages can be created with special tools, eg Adobe Page Mill

The Web page instructions are written in a special language, hyper-text mark-up language, HTML

It is possible to see the HTML that is producing the page you are looking at by selecting “source” from the View menu in your browser

HTML From CSE100 Home Page


	Various computers will be used in this class, so a quick introduction to their arrangement and networking is useful. Along the way we answer the pressing question: What is the difference between the Internet and the World Wide Web


	You have a UWNetID that gives you access to the UW’s computers, but also access to the World Wide Web … your account is on Dante
		You have sent email, set up folders, set up an address book
		You have visited home pages for UW, CSE100, other sites
		You have tried out a search engine
	Other things you should find out about …
		Printing is possible for most computer applications … how do you use the printers at OUGL or MGH labs?
		In Pine, it is possible to “postpone” a mail message that you are writing -- that is, set it aside to use Pine in other ways and then return to it. Try out “postpone” in your next mail.


	We will discuss how computers really work later, but for now think of them as having many forms
		Embedded -- processor, ROM, channels to sensor/actuators; m-wave oven
		Laptop -- processor, RAM, floppy disk, hard disk, LCD; mobility
		Desk Top -- processor, RAM, floppy, hard disk, CD, monitor; educational and office work
		Server -- processors (4-32), RAM, many hard disks, CD; services
		Supercomputer -- processors (16-1K), RAM, hard disks; big science


	FIT100 uses
			Laptop for lectures
			Desktop in Collabs, OUGL, MGH
			Dante server
	An unconnected computer can only access the data stored locally on its hard disk, run the software stored locally, read and write floppy disks, etc.
	The UW computers are connected, i.e. networked, together allowing us to send email and access the World Wide Web


	Networks connect computers, making them much more useful because
			Access more information and software
			Help users communicate, share information
			Perform services for one another
	UW’s networks ship ~1/2 trillion bytes of data per day
			Half this information goes to or comes from the Internet
	How are these networks arranged?


Think of a dozen students sitting around the dorm telling stories …
	Everyone listens while one person tells his/her story
	When the story is finished, there is a pause
	A person with a story to tell starts talking, listening all the while
		If no one else started talking too, the person continues
		If others started talking, he/she stops and waits briefly before trying again
In Ethernet, only the computers actually communicating listen to the transmission … the others simply wait for the break


	The subnetworks of campus interconnect the computers of the UW domain (.washington.edu), which is connected to the Internet via a Gateway


The logical way to name computers is using domains
		All educational institutions .edu
		U Dub .washington.edu
		CSE .cs.washington.edu
		Me boris.cs.washington.edu
This scheme is hierarchical
	Easier to remember names
	Names are associated with like units
	No limit to size or organizational depth


	The physical way to name computers is using an Internet protocol address, or IP address
			boris.cs.washington.edu’s IP address is: 128.95.2.227
			cs.washington.edu’s IP address: 128.95.1.4
			washington.edu’s IP address: 140.142.15.163
	The domain name system (DNS) associates human readable names with the physical IP addresses for use by the computers and routers of the Internet


	An important concept ...
	In computing it is common to separate the logical idea of something -- the way you think about it -- from the physical implementation -- how it’s actually built
	This is called a physical / logical separation
	In networking, the domain names make up our logical network, a hierarchical arrangement of names that tell us associations: cs.washington.edu
	The computers actually use physical addresses
	The DNS enables the separation by making the correspondence between the two


	Sending information over the Internet works like this:
	Imagine sending the novel you wrote from Tahiti where you live to New York City where your publisher is using only postcards


	How is the information sent?
		Information -- email, web pages, phone calls, everything sent over the internet -- is broken up into small units, called packets
		Packets contain an IP address, a sequence number and some actual information, a part of the whole message
		This scheme is called the Transmission Control Protocol and Internet Protocol, or TCP/IP
		The packets are sent independently, usually taking different routes, and reassembled at the destination to reconstruct the original message


	The world wide web is composed of those computers, called web servers, capable of sending information to your browser, e.g. Netscape or IE
	In most domains the computer that is the web server is called “www”, e.g. www.washington.edu
			But, a web server can have any name … your pages will be served by students.washington.edu
			The actual pages will be stored somewhere else, e.g. Dante
	There are different ways to connect to these servers
			Hyper-text transfer protocol, http for web pages
			File transfer protocol, ftp for files of information


	Web pages are just text files containing instructions to your browser on how to lay out the web page
			Web pages can be created with a text editor
			Web pages can be created with special tools, eg Adobe Page Mill
	The Web page instructions are written in a special language, hyper-text mark-up language, HTML
	It is possible to see the HTML that is producing the page you are looking at by selecting “source” from the View menu in your browser