
If not your UW e-mail address, be
sure to include your name (or even
your UW netID) in the message

Sign your e-mails with your name
(and preferably in English)

Also e-mail your TA to ensure we
reply promptly
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


Now posted on the website
You can attend any TA’s office hours
My hours are
 after class on Fridays
 by appointment
 when I’m in my office with the door open
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INFO100 and CSE100
Fluency with Information Technology
Katherine Deibel
Katherine Deibel
2012-04-02
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
Computers are useful alone, but are
better 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, Web,
email, texting, mobile, etc.
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
Different networks depending on
distance between computers:
 Local area network (LAN)
▪ Small area: room or building
▪ Either wired or wireless
 Wide area networks (WAN)
▪ Large area: more than 1 km
▪ Fiber-optic, copper transmission lines, satellite
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Network Type
Differentiating Factors
Peer-to-Peer
• No computer running server software
Server-Based Networks
• Computer running server software
manages network traffic
Local Area Network (LAN)
• Limited geographical area
Wide Area Network (WAN)
•
•
•
•
Campus Network
• Buildings in close proximity
Metropolitan Area Network
(MAN)
• Clusters of buildings in close proximity
separated from other clusters
• Third-party service provider
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Across town or across the globe
Third-party service provider
More bandwidth = more expense
Connects to LANs with a router
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

To communicate computers need to
know how to set up the data to be sent
and interpret the data received
Example protocols
 EtherNet—for physical connection in a LAN
 TCP/IP: transmission control protocol /
internet protocol (Internet)
 HTTP: hypertext transfer protocol (Web)
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
EtherNet is a popular LAN protocol
▪ Recall, it’s a “party” protocol
Connection to
campus
network
infrastructure
PC
PC
Typical MGH or OUGL Lab
PC
PC
PC
PC
Ether Net
Cable
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
The campus subnetworks interconnect
computers of the UW domain which
connects to Internet via a gateway
washington.edu
MGH
Homer
Internet
Dante
Student
CS
Gateway
All communication by TCP/IP
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
Transfer Control Protocol / Internet Protocol
The primary protocol for data transmission
on the Internet
 Video: Warriors of the Net

 http://www.youtube.com/watch?v=PBWhzz_Gn10
 Linked to on the Calendar page
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

Again, a video: History of the Internet
http://vimeo.com/2696386
The basic story:
 Computer systems at multiple locations
 Desire to share data and eliminate
duplicate work
 Two major design challenges
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
Diversity of systems in place
Site B:
Morse Code
Site A:
Pig Latin
Not feasible to rebuild
every site with the same
type of connectivity
Site C:
Uses carrier
pigeons
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
Diversity of systems in place
Solution: Accept the diversity
Site B:
Morse Code
Site A:
Pig Latin
Site C:
Uses carrier
pigeons
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

Within a local network, any protocol
is allowed
To send messages outside a local
network, it must be converted into
the IP protocol
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Network A convert Pig Latin
into IP Packets and sends
out on Internet
A
Pig Latin
B
IP
IP
IP
IP
Morse
Code
Network B converts IP
into Morse Code
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Turtle
Cobra
Reptiles
Crocodile
DNA
Echidna
Squirrel
Mole
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Mammals
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AOL
Comcast
ISPs
ClearWire
IP connects them all
UBC
UW
UM
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University
Networks
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?
?
?
?
?
Talk with your neighbor
for a minute and come
up with other examples
of hourglass analogies.
?
?
?
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?
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

Diversity of systems in place
Maintain communication in times of
disasters, breakdowns, etc.
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

Diversity of systems in place
Maintain communication in times of
disasters, breakdowns, etc.
Solution: Postcard analogy
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


Break messages into parts
Send each message separately
Delivery:
 Each card moves forward to a server
that knows how to get to the destination
 Cards can take multiple paths
 Cards arrive out of order
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tracert 128.227.205.2
You can find such “trace route” sites through Google
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
People give computers domain names
 Hierarchical scheme
 Domains begin with a “dot” and get “larger”
going right
▪ .edu
All educational computers, a TLD
▪ .washington.edu
All computers at UW
▪ dante.washington.edu A UW computer
▪ .ischool.washington.edu
iSchool computers
▪ .cs.washington.edu CSE computers
▪ june.cs.washington.edu
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A CSE computer
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
Computers are named by IP address,
four numbers in the range 0-255
▪ cse.washington.edu: 128.95.1.4
▪ ischool.washington.edu: 128.208.100.150
 Remembering IP addresses would be
brutal for humans, so we use domains
 Computers find the IP address for a
domain name from the Domain Name
System—an IP address-book computer
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
.edu .com .mil .gov .org .net domains
are “top level domains” for the US
 Recently, new TLD names added
 Each country has a top level domain name:
▪ .ca (Canada)
▪ .es (Spain)
▪ .de (Germany)
▪ .au (Australia)
▪ .at (Austria)
▪ .us (US)
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
View the Internet in two ways:
 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 “user's” needs

The Domain Name System (DNS)
relates the logical network to the
physical network by translating
domains to IP addresses
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
Many people misuse the terms “Internet”
and “World Wide Web”

Let’s get them right
Internet:
All of the wires, fibers, switches, routers etc.
connecting named computers
World Wide Web:
That part of the Internet that stores and serves
Web pages—web servers, client computers
2012-04-02
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
The terms "internet" and "Internet"
refer to different things
 "Internet" is the complete collection of
internetworked computers
 "internet" refers to any collection of
networked computers

Most of the time, you probably mean
the "Internet"
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
Networking is changing the world
 Internet: named computers using TCP/IP
 WWW: servers providing Web pages
 Principles
▪ Logical network of domain names
▪ Physical network of IP addresses
▪ Protocols rule: LAN, TCP/IP, http...
▪ Domain Name System connects the two
▪ Client/Server, fleeting relationship on WWW
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
Net neutrality

SOPA

Digital divide

Government control of Internet access

Web 2.0

VPNs

Wireless pirating

Etc.
These topics could be interesting
fodder for GoPost discussions
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


Check the calendar for due dates
Read Chapters 5 & 6
Continue GoPosting
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