cosc1078 introduction to information technology lecture 20 internet

Lecture 20: Internet Intro to IT

COSC1078 Introduction to Information Technology

Lecture 20

InternetJames Harland

[email protected]


Introduction

James Harland• Email: [email protected]• URL: www.cs.rmit.edu.au/~jah• Phone: 9925 2045• Office: 14.10.1 • Consultation: Mon 4.30-5.30, • Thu 11.30-12.30Who am I? And where do

you find me?


Introduction to IT1 Introduction 2 Images3 Audio4 Video WebLearnTest 1 5 Binary Representation Assignment 16 Data Storage7 Machine Processing8 Operating Systems WebLearn Test 29 Processes Assignment 210 Internet11 Internet Security WebLearn Test 312 Future of IT Assignment 3, Peer and Self Assessment


Overview Questions?

Assignment 3

Peer and Self Assessment

Internet

Questions?


Assignment 2 Some initial comments

Some people have submitted .docx files. This will be penalised.Some people have not included blogs on Blackboard. This will be penalised. Some people have worked individually without permission. Guess what will happen ….


Assignment 3 Reflect

Answer reflection questions from tutorialsSee last lecture for ideas

ResearchWrite about a particular IT topic of your choice (5-6 paragraphs)electronic voting, information security, 3D user interfaces, digital music, digital video, electronic commerce, natural language processing, DNA computing, quantum computing, cryptography, malware detection and removal, Moore's Law, green computing, …

Lecture 20: Internet SE Fundamentals

Self and Peer Assessment How well has each person contributed to the

group? Evaluated over the entire semester Assessed on process, not product Work out a grade for each person (CR, DI etc) Then convert this to a mark out of 20 Submit list of marks to tutor with justifications Repeat previous step until the tutor is satisfied See guidelines in Blackboard material


Communications Developments ????: Writing 1440: Printing press 1844: Telegraph 1877: Telephone 1919: Radio 1928: Television 1969: ARPANET (Advanced Research Projects Agency) 1970's: Internet Protocol (IP) 1984: Domain names (.com, .org, etc) 1991: World Wide Web

Lecture 20: Internet: Images Intro to IT

Number of Internet Hosts

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

0

100000

200000

300000

400000

500000

600000

Internet Originally designed to survive nuclear war Grew out of army research into missile

communication Key role in breaking down the Berlin Wall



Internet Dedicated channel:

two nodes exclusively use a single channel works like traditional telephone

Packet switching: break data down into packetssend packets from many users along linkcan exploit redundancies and variations in network


Protocols Transmission Control Protocol (TCP):

basic necessities for data transferconnection-oriented

Internet Protocol (IP): data-orientednecessary for packet-switched network

“Should run on two tin cans and a string”There is an implementation for carrier pigeons ...


Protocols


Application Protocols

Define messages sent and data formats used Generally known by user Examples include HTTP, HTTPS, FTP, etc.Often specified in resource identifiershttp://www.mysite.com:8080/info/mypage.htmlhttp://www.mysite.com:8080/info/mypage.htmlhttp://www.mysite.com:8080/info/mypage.htmlhttp://www.mysite.com:8080/info/mypage.html


World Wide Web (WWW) Combination of 4 different ideas: Hypertext: information format for moving

documents around Markup Language: codes embedded in text

indicating structure and presentation meaning Resource Identifiers (URI, URL, ...) Client-server model: client software requests

resources from servers Note WWW is not the Internet …


Internet Uses File transfer & remote services Email Instant messaging Web browsing Peer to peer (P2P) Telephony Streaming media “Web 2.0” ....

Lecture 19: Internet: Images Intro to IT

Internet Lisa?Hi Dad! Listen!Lisa?

Hi Dad! Listen!


Internet Structure

Application Application

Transport Transport

Network

Link

Network

Link

Mordor sucks!

2 dor1 Mor3 suc 4 ks!

1 2 3 49 5 6 2

143

22

13

4

2 3 1 49 5 6 2

2 dor1 Mor3 suc 4 ks!

Mordor sucks!


Internet Structure

1 Mor

1

6

6


Network Layer (Internet Protocol) Real intelligence is in the network layer Adds next destination to packet Not complete list of addresses Sends to next destination Retrieves final destination packets for this node Passes them to the transport layer Routing tables can be updated when

disconnections occur Hop counts used to stop endless looping


Transport layer Transmission Control Protocol (TCP) often used User Datagram Protocol (UDP) becoming more

common TCP

Establishes connection firstSend and wait for acknowledgementReliableCan adjust flow control to avoid congestionOften best for email (which is not real-time)Older


Transport layer UDP

Doesn’t establish connectionJust sends and forgetEfficientNo congestion adjustmentWorks well for DNS lookupOften used for Voice over Internet Protocol (VoIP) applications such as Skype


Internet addresses Unique 32-bit identifier (up to 4,294,967,296) Soon to become 128-bit identifier Managed by Internet Corporation for Assigned

Names and Numbers (ICANN) ISPs get “blocks” of addresses 32-bit string represented as N1.N2.N3.N4 where Ni

is in the range 0..255 17.12.25.0 means00010001 00001100 00011001 00000000


Internet addresses Dotted decimal notation is still not very kind to

humans … www.sludgefacethemovie.com -> ??.??.??.?? Translation done by name servers which look up

the Domain Name System (DNS) Domains such as rmit.edu.au can be structured by

the domain owner (eg goanna.cs.rmit.edu.au)


IPv4 vs IPv6 Internet Protocol version 4 (used since 1981) 32-bit addresses Can handle “only’’ 4,294,967,296 unique

addresses Exhausted in February 2011 IPv6 uses 128-bit addresses IPv6 can handle “only” 3.4×1038 addresses IPv5 didn’t change the IPv4 address space

and wasn’t successful for other reasons …


Conclusion

Work on Assignment 3

Name 5 people who are unaffected by the Internet …

cosc1078 introduction to information technology lecture 20 internet

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