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Regarding e-mails
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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Office Hours
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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Connecting with NetworksFluency with Information Technology
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Katherine Deibel
INFO100 and CSE100
Katherine Deibel
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Networks...
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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Network Structure
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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Basic Types of Networks
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Network Type Differentiating FactorsPeer-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) • Across town or across the globe• Third-party service provider• More bandwidth = more expense• Connects to LANs with a router
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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Protocols
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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LAN in the Lab
EtherNet is a popular LAN protocol▪ Recall, it’s a “party” protocol
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Connection to campus network infrastructure
PC PC PC PC PC PCEther Net Cable
Typical MGH or OUGL Lab
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Campus & The World
The campus subnetworks interconnect computers of the UW domain which connects to Internet via a gateway
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All communication by TCP/IP All communication by TCP/IP
Homer
Dante
Student CS
MGH
Gateway
washington.edu
Internet
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What is TCP/IP
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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History of the Internet
Again, a video: History of the Internethttp://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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Design Goals for the Internet
Diversity of systems in place
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Site C:Uses carrier pigeons
Site B:Morse Code
Site A:Pig Latin
Not feasible to rebuild every site with the same
type of connectivity
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Design Goals for the Internet
Diversity of systems in placeSolution: Accept the diversity
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Site C:Uses carrier pigeons
Site B:Morse Code
Site A:Pig Latin
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Internet Protocol
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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Internet Protocol
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A
Pig Latin
Network A convert Pig Latin into IP Packets and sends out on Internet
IP
B
Network B converts IP into Morse Code
Morse Code
IP IP IP
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Hourglass Analogy
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TurtleCobra
Crocodile
Squirrel
Echidna
Mole
Reptiles
Mammals
DNA
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Hourglass Analogy
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AOLComcast
ClearWire
UWUBC
UM
ISPs
University Networks
IP connects them all
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Hourglass Analogy
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??
?
?
?
?
?
?
?
Talk with your neighbor for a minute and come up with other examples of hourglass analogies.
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Design Goals for the Internet
Diversity of systems in place Maintain communication in times of
disasters, breakdowns, etc.
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Design Goals for the Internet
Diversity of systems in place Maintain communication in times of
disasters, breakdowns, etc.Solution: Postcard analogy
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Postcard Analogy
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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Tracing these Virtual Routes
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You can find such “trace route” sites through GoogleYou can find such “trace route” sites through Google
tracert 128.227.205.2
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Naming Computers—Take 1
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
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Naming Computers—Take 2
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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Top-Level Domains (TLDs)
.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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Logical vs Physical
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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Internet vs World Wide Web
Many people misuse the terms “Internet” and “World Wide Web”
Let’s get them right
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Internet:
All of the wires, fibers, switches, routers etc. connecting named computers
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
World Wide Web:
That part of the Internet that stores and serves Web pages—web servers, client computers
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internet or Internet?
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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Summary
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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What we did not cover
Net neutrality SOPA Digital divide Government control of Internet access Web 2.0 VPNs Wireless pirating Etc.
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These topics could be interesting fodder for GoPost discussions
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For Wednesday
Check the calendar for due dates Read Chapters 5 & 6 Continue GoPosting
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