regarding e-mails

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

2012-04-02 Katherine Deibel, Fluency in Information Technology 1

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


Connecting with NetworksFluency with Information Technology


Katherine Deibel

INFO100 and CSE100

Katherine Deibel

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.


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


Basic Types of Networks


Network Type Differentiating FactorsPeer-to-Peer • No computer running server softwareServer-Based Networks • Computer running server software

manages network traffic

Local Area Network (LAN) • Limited geographical areaWide 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 proximityMetropolitan Area Network (MAN)

• Clusters of buildings in close proximity separated from other clusters

• Third-party service provider

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)


LAN in the Lab EtherNet is a popular LAN protocol

▪ Recall, it’s a “party” protocol


Connection to campus network infrastructure

PC PC PC PC PC PCEther Net Cable

Typical MGH or OUGL Lab

Campus & The World The campus subnetworks interconnect

computers of the UW domain which connects to Internet via a gateway


All communication by TCP/IP

Homer

Dante

Student CS

MGH

Gateway

washington.edu

Internet

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


http://www.youtube.com/watch?v=PBWhzz_Gn10

http://www.youtube.com/watch?v=PBWhzz_Gn10

History of the Internet 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


http://vimeo.com/2696386

http://vimeo.com/2696386

Design Goals for the Internet Diversity of systems in place


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

Design Goals for the Internet Diversity of systems in place

Solution: Accept the diversity


Site C:Uses carrier pigeons

Site B:Morse Code

Site A:Pig Latin

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


Internet Protocol


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 CodeIP IP IP

Hourglass Analogy


Turtle Cobra

Crocodile

SquirrelEchidna

Mole

Reptiles

Mammals

DNA

Hourglass Analogy


AOL Comcast

ClearWire

UWUBC

UM

ISPs

University Networks

IP connects them all

Hourglass Analogy


? ?

?

??

?

?

?

?

Talk with your neighbor for a minute and come up with other examples of hourglass analogies.

Design Goals for the Internet Diversity of systems in place Maintain communication in times of

disasters, breakdowns, etc.


Design Goals for the Internet Diversity of systems in place Maintain communication in times of

disasters, breakdowns, etc.Solution: Postcard analogy


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


Tracing these Virtual Routes


You can find such “trace route” sites through Google

tracert 128.227.205.2

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▪ june.cs.washington.edu A CSE computer


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


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)


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


Internet vs World Wide Web 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

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"


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


What we did not cover 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

For Wednesday Check the calendar for due dates Read Chapters 5 & 6 Continue GoPosting


regarding e-mails

Documents