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Networking. INFO/CSE 100, Fall 2006 Fluency in Information Technology http://courses.washington.edu/info100/. Lab 2 / Homework 2. Any questions?. Readings and References. Reading Fluency with Information Technology Chapter 3, Making the Connection. Today’s Objectives.

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networking
Networking

INFO/CSE 100, Fall 2006

Fluency in Information Technology

http://courses.washington.edu/info100/

networks @ university of washington

lab 2 homework 2
Lab 2 / Homework 2
  • Any questions?

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readings and references
Readings and References
  • Reading
    • Fluency with Information Technology
      • Chapter 3, Making the Connection

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today s objectives
Today’s Objectives
  • Learn Basics of networks / what they can do
  • Understand protocols
    • IP
    • Routing
    • HTTP & URL Structure
    • DNS

networks @ university of washington

networks
Networks…
  • Computers are useful alone, but are even more useful when connected (networked)
    • Access more information and software than is stored locally
    • Help users to communicate, exchange information .. Changing ideas about social interaction
    • Perform other services -- printing, audio, video
    • Immediate access to knowledge: for example, Google

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networking changes life
Networking Changes Life
  • The Internet is making fundamental changes … the FIT text gives 5 ways
    • Nowhere is remote -- access to information is no longer bound to a place
    • Connection with others -- email is great! But what about spam?!?
    • Revised human relationships -- too much time spent online could be bad
    • English is becoming a universal language
    • Enhanced freedom of speech, assembly

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network structure
Network Structure
  • Internet: all of the wires, fibers, switches, routers, etc… connecting named computers
    • Networks are physically structured differently based (mostly) on how far apart the computers are
      • Local area network (LAN)
        • A small area such as a room or building
      • Wide area networks (WAN)
        • Large area, e.g. distance is more than 1Km
      • What do you think a PAN might be?!?

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local area network
Local Area Network

Mac disk and printers available on the nearby Windows PC

Windows disk and printers available on the nearby Mac

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wide area network
Wide Area Network

instant messenger

world wide web

UW servers

Internet

router

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exercise
Exercise
  • Our class is the Internet - lets pass some data!

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transfer data
Transfer Data
  • Goal: get “data packet” to the named student
  • Rules: (to replicate internet)
    • only the person with the packet can ask questions of other students
    • you can talk to students who physically sit next to you (all 9 directions) (as your aren’t “connected” to the others)
    • must hand off packet to one of 9 students for them to repeat

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how did that work
How Did that work?
  • What didn’t work?
    • Imagine this more than 1,000,000,000,000 times per day!
  • What can make this process better?

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what is your ip address
What is your IP Address?
  • IP Address =ROW.COLUMN
  • Examples:
  • 10.1
  • 8.13
  • 2.3

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protocols are important
Protocols are Important!
  • To communicate, computers need to know how to set-up the info to be sent and to interpret the info received
    • Communication rules are a protocol
    • Example protocols:
      • Ethernet for physical connection in a LAN
      • TCP/IP -- transmission control protocol/internet protocol
      • HTTP -- hypertext transfer protocol (for the WWW)
      • FTP -- file transfer protocol (for transferring files)
    • Protocols often rely on or build on other protocols

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lan in the lab
LAN in the Lab
  • Ethernet is a popular LAN protocol

Connection to campus network infrastructure

Typical MGH or OUGL Lab

PC

PC

PC

PC

PC

PC

Ethernet Cable

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campus the world
Campus & The World
  • The campus sub-networks interconnect computers of the UW domain which connects to the Internet via a gateway
    • The protocol used is TCP/IP

Switch

MGH

Homer

Gate

way

Dante

Student

washington.edu

CS

Switch

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ip like using postcards
IP -- Like Using Postcards
  • Information is sent across the Internet using the Internet Protocol -- postcard analogy
    • Break message into fixed size units
    • Form IP Packets with destination address, sequence number, and content
    • Each makes its way separately to destination, possibly taking different routes
    • Reassembled at destination forming message
      • Taking separate routes lets packets by-pass congestion and out-of-service network devices

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ip con d
IP con’d

DEST ADDRESS | SIZE | # | DATA

Source

Destination

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a trip to switzerland
A Trip to Switzerland
  • A packet sent from UW to ETH (Swiss Federal Technical University took 21 hops

UW Gateway

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check internet hops
Check Internet Hops
  • There are numerous Trace Route utilities
    • Windows: tracert, OSX: Network Utility

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what the internet looks like
What the Internet “looks like”

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naming computers
Naming Computers
  • Computers connected to the Internet are part of a network domain
    • A hierarchical scheme that groups computers
  • .edu All educational computers
    • .washington.edu All computers at UW
  • dante.u.washington.edu A UW computer
      • .ischool.washington.edu iSchool computers
  • .cs.washington.edu CSE computers
  • www.ischool.washington.edu an iSchool computer

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domains
Domains
  • .edu, .com, .mil, .gov., .org, .net domains are some of the “top level domains” in the USA
    • Recently added TLD names include:
      • .biz, .info, .name, .pro, .aero, .coop, .museum, .tv
  • Each country has a TLD name: .ca (Canada), .es (Spain), .de (Germany), .au (Australia), .uk (England), .us (USA)
  • The FIT book contains the complete list of country domains

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naming computers con d
Naming Computers con’d
  • Computers are named by IP address, four numbers in the range 0-255 called an octet
    • dante.u.washington.edu: 140.142.14.67
    • live.xbox.com: 65.59.234.169
      • Remembering IP address would be brutal for humans, so we use domain names
      • Computers find the IP address for a domain name from the Domain Name System (DNS)
        • An IP address-book for the computer

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logical vs physical
Logical vs. Physical
  • There are 2 ways to view the Internet
    • Humans see a hierarchy of domains relating computers
      • Logical network
    • Computers see groups of four-number IP addresses
      • Physical network
    • Both are ideal for the “users” needs
  • Domain Name System (DNS) relates the logical network to the physical network by translating domains to IP addresses

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anatomy of it all
Anatomy of it All
  • Domain name:

dante . u . washington . edu

  • IP address:

140.142.14.67

Third-level

Second-level

Top-level

Fourth-level

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your dns name as your name
Your DNS Name as your name
  • IP Address =ROW.COLUMN
  • Examples:
  • 10.1 = Ima Student
  • 8.13 = Will Getana
  • 2.3 = Bob Upndown

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client server structure
Client/Server Structure
  • Many internet applications rely on theclient / server model to provide services
    • Example services: email server, web server, sftp server
    • UW servers: dante, students, www
    • Frequently, a “server” is actually many computers acting as one, e.g. dante is a group of more than 50 servers called a cluster or a farm
  • Protocol governs the communication
    • Client packages a request and sends it to a server;
    • Server does the service and sends a reply

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world wide web
World Wide Web
  • World Wide Web (WWW) is a collection of web servers on the Internet
  • Subset of Internet computers
    • WWW is not the same as the Internet!
  • They give access to information using the HTTP protocol
    • The “server” is a web site computer and the “client” is a web browser (like Internet Explorer)
    • Many Web server’s domain names begin with www by tradition, but any name is OK
    • Often multiple servers map to the same site:moma.org and www.moma.org

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history of the www
History of the WWW
  • Web beginnings
    • 1989: Tim Berners-Lee
      • URLs, http, first browser (HTTP 1.0)
    • 1993: NCSA Mosaic
      • HTTP 1.1 supported images
      • Then Netscape, then Mozilla
    • 1994: World Wide Web Consortium
      • http://w3.org/
      • Standards organization for Web protocols and formats
    • 1994-5: Web crawlers and search engines
      • WebCrawler, Lycos, AltaVista, Yahoo
      • Developed at UW CSE School

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world wide web1
World Wide Web
  • URL -- uniform resource locator
      • Web page addresses
  • HTTP -- hypertext transfer protocol
      • Client-server communication rules
  • HTML -- hypertext markup language
      • A specifal format for making the pages universally readable by all clients

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dissecting a url
Dissecting a URL
  • Web addresses are URLs (uniform resource locator)
    • A server address and a path to a particular file
  • http://courses.washington.edu/info100/classwork/calendar/index.html

protocol = http://

Web server = courses

domain = washington.edu

path = /info100/classwork/calendar/ dirs(folders)

file = index

file extension = .html hypertext markup language

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client server interaction

Server

Client

Server

Server

Client

Client

request

Server

Client

Server

Client

reply

Server

Server

Client

Client

Server

Client

Client/Server Interaction
  • For Web pages, the client requests a page the server returns it: there’s no permanent connection, just a short conversation
    • Details of the conversation are specified by HTTP

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simple http request
Simple HTTP Request

request

protocol

method

GET /pub/WWW/TheProject.html HTTP/1.1

Host: www.w3.org

host

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a typical browser request
A Typical Browser Request

GET/pub/WWW/TheProject.htmlHTTP/1.1

Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-powerpoint, application/vnd.ms-excel, application/msword, application/x-shockwave-flash, */*

Accept-Language: en-us

Accept-Encoding: gzip, dflate

User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; APC)

Host: www.w3.org

Connection: Keep-Alive

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server response
Server Response

HTTP/1.1 200 OK

Date: Monday, 23 May 2005 22:38:34 GMT

Server: Apache/1.3.27 (Unix) (Red-Hat/Linux)

Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT

Etag: "3f80f-1b6-3e1cv03b"

Accept-Ranges: bytes

Content-Length: 438

Connection: close

Content-Type: text/html

<html>

<head><title>A Sample Page</title></head>

<body>

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summary
Summary
  • Networking is changing the world
    • Internet: named computers using TCP/IP
    • WWW: servers providing access to information via the HTTP protocol
    • Principles
      • Local network of domain names
      • Physical network of IP address
      • Protocols rule: LAN, TCP/IP, HTTP
      • Domain Name System connects the two
      • Client/Server, relationship on WWW

networks @ university of washington