Course Overview - Classes - Oregon State University

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Course Overview Spring 2014 ECE/CS 372 Introduction to Computer Networks Lecture 1 School of Electrical Engineering and Computer Science Oregon State University

Credit for lecture slides to Professor Bechir Hamdaoui Adapted from Jim Kurose & Keith Ross (original copyright)

Chapter 1, slide:

1

Lecture/Office/Lab Hours  Course website 



http://classes.engr.oregonstate.edu/eecs/spring2014/cs372-001/

Please write down this URL—all course material and information will be provided thru this site

 Lectures 

Tuesday, Thursday 12:00-1:20pm, 212 Kearney Hall

 Instructor 

Stephen Redfield ([email protected])



Office hours: TR 1:30-2:30pm @ Kelley Engineering Center Rm 2077

Chapter 1, slide:

2

Lecture/Office/Lab Hours  Tamara AlShammari  Location: KEC 2063  Lab hours: to help you with your labs  Hours TBD

Information can be found in course’s website

 MohammadJavad NoroozOliaee (MJ)  Location: KEC 2063  Office hours: to help you with your assignments  Hours TBD Information can be found in course’s website

Chapter 1, slide:

3

Prerequisite/Textbook

Prerequisite:

 CS or ECE 271 or an equivalent course  Basic mathematical/probability skills

Textbook  Textbook is Required Computer Networking: A Top-Down Approach Featuring the Internet, 6th Edition, Games F. Kurose, Keith W. Ross

Chapter 1, slide:

4

Grading Policy  Assignments: 15%   

Each student must hand in one copy 5 assignments: approx. 1 every two weeks Check, Check Minus, X Grading

 Labs: 20%  

Each student must hand in one copy 4 labs: approx. 1 every two weeks

 Bonus pop quizzes: extra 2 to 10% 

You need to get it completely right to receive an extra 1%

 One midterm exam: 30%  Final exam: 35%

Chapter 1, slide:

5

Lectures & assignments Objective  Deep understanding of basic and fundamental networking concepts, architectures, and philosophies  IMPORTANT: this course is not about setting up your

router at home, or writing a twitter program!!

Approach: how to do well in this course  Easy: attend ALL lectures and do ALL assignments  Do your assignments individually (Don’t use Solutions)  Do NOT miss any Bonus Quiz (i.e., do not miss class)  Some HW problems will be solved in class: this gives you the opportunity to clarify things further Chapter 1, slide:

6

Labs Objective  Understand how Internet protocols work  Force network protocols to perform certain actions  Observe and analyze protocols’ behavior Approach  Software tool: Wireshark  

Install on your Laptop Do this EARLY so you can avoid problems with Lab 1

 Allows you to sniff and analyze traffic

sent/received from/by your end system: real measurement of Internet traffic  Lab 1 is posted and is due next Tuesday Chapter 1, slide:

7

Break  Online Course Available  We’ll start after a 10-min break

Chapter 1, slide:

8

Chapter 1: Introduction Our goal:  learn basic network

terminologies  more depth, detail later in course  approach:  use Internet as example

Acknowledgement: slides drawn heavily from Kurose & Ross

Chapter 1, slide:

9

Chapter 1: roadmap 1 What is the Internet? 2 Network edge 3 Network core 4 Internet structure and ISPs 5 Protocol layers, service models 6 Delay & loss in packet-switched networks

Chapter 1, slide: 10

What’s the Internet: a “service” view  communication infrastructure

enables distributed apps:  

Enables apps to communicate Web, email, games, ecommerce, file sharing

 communication services

provided to apps: 

Offers services

Chapter 1, slide: 11

What’s the Internet: “nuts and bolts” view  hosts or end systems:

millions of connected computing devices  

e.g., Laptops, workstations running network apps

router server

mobile

local ISP

 routers & switches:  forward packets (chunks of data)

 communication links  e.g., fiber, copper, radio, satellite

workstation

regional ISP

company network Chapter 1, slide: 12

What’s the Internet: “nuts and bolts” view  Internet standards  IETF (Internet Eng. Task Force) • RFC: Request for comments 

router

workstation

server

mobile

local ISP

IEEE: for links/hardware E.g., Ethernet

regional ISP

 network protocols  control sending/receiving of messages  e.g., TCP, IP, HTTP, FTP, PPP company network

Chapter 1, slide: 13

What’s a protocol? a human protocol and a computer network protocol: Hi

TCP connection request

Hi

TCP connection response

Got the time?

Get http://www.awl.com/kurose-ross

2:00



time

Chapter 1, slide: 14

What’s a protocol? human protocols:  “What’s the time?”  “I have a question”  introductions … specific msgs sent … specific actions taken when msgs received, or other events

network protocols:  machines rather than humans  all communication activity in Internet governed by protocols protocols define (1) format, order of msgs sent and received among network entities, and (2) actions taken on msg transmission, receipt Chapter 1, slide: 15

Chapter 1: roadmap 1 What is the Internet? 2 Network edge 3 Network core 4 Internet structure and ISPs 5 Protocol layers, service models 6 Delay & loss in packet-switched networks

Chapter 1, slide: 16

A closer look at network structure:  network edge:

applications and hosts  network core: routers  network of networks 

 access networks,

physical media: communication links Chapter 1, slide: 17

The network edge: service models  end systems (hosts):   

run application programs e.g. Web, email at “edge of network”

 client/server model  

client host requests, receives service from always-on server e.g. Web browser/server; email client/server

 peer-to-peer model:  

minimal (or no) use of dedicated servers e.g. Skype, BitTorrent, KaZaA Chapter 1, slide: 18

Chapter 1: roadmap 1 What is the Internet? 2 Network edge 3 Network core 4 Internet structure and ISPs 5 Protocol layers, service models 6 Delay & loss in packet-switched networks

Chapter 1, slide: 19

The Network Core  mesh of interconnected

routers

 the fundamental question:

how is data transferred through net?  circuit switching: dedicated circuit per call: telephone net  packet-switching: data sent thru net in discrete “chunks” Chapter 1, slide: 20

Network Core: Circuit Switching End-end resources reserved for “call”  dedicated resources: no

sharing  call setup required  circuit-like (guaranteed) performance  same path for all chunks

Chapter 1, slide: 21

Network Core: Circuit Switching network resources (e.g., bandwidth) divided into “pieces”  allocated pieces per call  no sharing

resource piece idle if not used by owning call

Chapter 1, slide: 22

Network Core: Circuit Switching  Two ways of dividing bandwidth into “pieces”

frequency division  time division 

Chapter 1, slide: 23

Circuit Switching: FDM and TDM Example:

Freq. Division Multiplx. (FDM)

4 users

frequency time Time Division Multiplx. (TDM)

frequency

time

Chapter 1, slide: 24

Network Core: Packet Switching 100 Mb/s Ethernet

A

B

C 1.5 Mb/s

each end-to-end data stream is divided into packets  no dedication/reservation: all streams share resources  no setup is required  resources used as needed  each packet uses full link bandwidth  aggregate resource demand can exceed capacity  no guarantee Chapter 1, slide: 25

Network Core: statistical multiplexing 100 Mb/s Ethernet

A

B

statistical multiplexing

C

1.5 Mb/s queue of packets waiting for output link

D

E

Sequence of A & B packets does not have fixed pattern, shared on demand  statistical multiplexing. Whereas in TDM, each host gets same slot (periodically) Chapter 1, slide: 26

Packet switching versus circuit switching A

Circuit switching

B B: has no packets to send

A

2 Mb/s

• 2 circuits (use TDM) • A reserves 1 circuit • B reserves 1 circuit

Utilization = 50% only = 1 Mb/s

Packet switching

B

2 Mb/s

• statistical multiplex. • B uses full link since A is not using it

Utilization = 100% = 2 Mb/s Chapter 1, slide: 27

Packet switching versus circuit switching Packet-switching  Resources

sharing

 Congestion

may lead to it

 Overhead

less overhead; no connection setup

 Guarantee

Best-effort no guarantee

Circuit-switching dedicated admission control more overhead; reserve resources 1st

provide guarantee good for multimedia

Chapter 1, slide: 28

Numerical example  How long does it take to send a file of

640,000 bits from host A to host B over a circuit-switched network?

The link’s transmission rate = 0.64 Mbps  Each link uses TDM with 10 slots/sec  0.5 sec to establish end-to-end circuit Let’s work it out! You have few minutes! 

 Solution:  Bandwidth of circuit (in kbps)= .64x1000/10 = 64 kbps  Time to send: 640 kbits/64 kbps + 0.5s = 10.5s Chapter 1, slide: 29

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Course Overview - Classes - Oregon State University

Course Overview Spring 2014 ECE/CS 372 Introduction to Computer Networks Lecture 1 School of Electrical Engineering and Computer Science Oregon State ...

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