CSCD58 W INTER 2018 W EEK 1 - I NTRODUCTION /O VERVIEW P ART A Brian - - PowerPoint PPT Presentation

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CSCD58 WINTER 2018

WEEK 1 - INTRODUCTION/OVERVIEW PART A Brian Harrington

University of Toronto Scarborough

January 9, 2018

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WELCOME TO CSCD58

• Welcome to CSCD58
• Introductory course in Computer Networks
• No assumed prior knowledge of/exposure to networks
• Covering principles and technologies underlying networks

including the internet

• Shared focus on principles and practicals

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ADMIN STUFF

• Website:
• www.utsc.utoronto.ca/~bharrington/cscd58
• Assignments, lecture notes, tutorial handouts, etc. posted

here

• Check regularly for announcements
• Piazza Forum
• Course Info Sheet with all the technical policy details
• Textbook:
• James F. Kurose, Keith W. Ross, Computer

Networking, a top-down approach, 6th Edition, Addison Wesley, 2013, ISBN-10: 0-13-285620-4

• 4th - 5th editions can also be used (but you are responsible

for transposing any assigned reading indices)

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ADMIN STUFF

• My Details:
• Brian Harrington
• brian.harrington@utsc.utoronto.ca
• IC 342
• Office hours: Thursdays 1-3 (or by appointment)
• Assessment:
• 2 Programming Assignments (25%)
• 2 Problem Sets (15%)
• Midterm (20%)
• Final (40%)

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INTRODUCTION

• The Internet (and other large networks) are complex
• Our goal: break down (arguably) the most complicated

systems ever developed by humans into something you can understand

• Within 12 weeks
• Where to begin:
• Look at multiple levels of abstraction
• Start at the top (most abstract) and work our way down (low

level details)

• At each stage, see how the pieces fit together

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INTRODUCTION

• By the end of this course, you should be able to:
• Have a complete picture of the networks behaviour when

you send an e-mail, or click on a web-page.

• Appreciate the limitations and opportunities of various

types of network design/implementation

• Given an infinite amount of time, re-build the internet from

scratch following a major disaster/nuclear holocaust/zombie invasion

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INTRODUCTION

• So where to first?
• Let’s try to get a “big picture” view of networks
• We’ll go into (much) greater detail later in the course
• After the break... what is this “Internet” thing the kids are

talking about?

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BREAK

http://www.opte.org/the-internet/

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CIRCUIT SWITCHING

• Phone/Television networks
• Set number of links between each point in the network
• “Call” sets up an end-to-end path using 1 link for each hop
• Reliable, set path, dedicated resources
• Call set-up required, capacity limit

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CIRCUIT SWITCHING

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CIRCUIT SWITCHING

• Two ways of multiplexing: Frequency Division Multiplexing

(FDM) and Time Division Multiplexing (TDM)

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PACKET SWITCHING

• 1961: Kleinrock, 1964: Baran
• Instead of dividing resources, divide data
• Each “packet” of data uses full link bandwidth
• Only move one hop at a time, each packet sent separately
• No need to divide bandwidth, much more flexible resource

allocation

• Resource contention, congestion, reliability issues, routing
• verhead

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HISTORY: ARPAET AND EARLY PACKET SWITCHING

• 1967-1969: ARPANet built on packet-switching protocols
• 1972: First public demonstration
• NCP (Network Control Protocol) - First host-host protocol
• First e-mail program
• 15 Nodes

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HISTORY: CERF & KAHN

• Throughout 70s, lots of smaller proprietary networks pop

up

• 1974: Cerf & Kahn - Architecture for interconnecting

networks

• Each Network must be autonomous
• Best Effort Communications (failure = re-send)
• Connections (later: “routers”) are black-boxes, no

information retained

• No global control

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HISTORY: 1980S - NEW PROTOCOLS

• 1982: SMTP E-mail protocol
• 1983: TCP/IP
• 1983: DNS
• 1985: FTP
• 1986: TCP Congestion Protocol

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HISTORY: 1990S - WORLD WIDE WEB

• 1989: HTML, HTTP
• 1993: Mosaic - First Web Browser
• Late 90s: Internet starts to go from niche toy to

mainstream service

• Proliferation of commercial ISPs, traffic starts to grow

exponentially

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HISTORY: 2000S - BOOM, BUST AND ECHO

• Late 1990s - Early 2000s: “Dot-Com Era”
• 2000-2001 - Bubble Bursts
• Lycos: Bought in 2000 for $12.5 billion, sold in 2004 for $95

million

• Geocities: Purchased in 1999 for $3.57 billion, abandoned

in 2009

• Investment during dot-com era = 100s of millions of

connected devices, much faster backbone, billions of users now online

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HISTORY: 2010S - INTERNET EVERYWHERE AND ???

• Now: Live in a world where most of us are connected to

everyone else 24/7/365.

• Future: ???
• “When I was young:"
• Grandparents: We had to walk to our neighbour’s house if

we wanted to talk to them

• Parents: We had one newspaper available to us, and one

set of encyclopaedias in our school

• Future: We actually had to take a device out of our pockets

and look at it if we wanted to know a piece of information. Cars were actually piloted by humans. Our refrigerator didn’t even warn us if we were running low on milk, and we would actually have to go to the store to get more.