ECE CS 372 introduction to computer networks lecture 1 chapter 1

Course Overview
Spring 2012
ECE/CS 372 Introduction to Computer Networks
Lecture 1
School of Electrical Engineering and Computer Science
Oregon State University

Chapter 1, slide:

1


Lecture/Office/Lab Hours
 Course website


/>rks.htm



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

 Lectures


Everyday 1-1:50pm

 Instructor


Yousef Qassim ()



Office hours: TR 2:30-3:20pm @KEC lounge

Chapter 1, slide:

2


Lecture/Office/Lab Hours
 Lab Assistant
 Location: Dearborn 205
 Lab hours: to help you with your labs
205 DEAR

Information can be found in course’s website

 Lab
 Location: Dearborn 205
 Access code: will be written on board

Chapter 1, slide:

3


Prerequisite/Textbook

Prerequisite:

 CS or ECE 271 or an equivalent course
 Basic Linux familiarity

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

 Labs: 15%



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

 One midterm exam: 30%
 Final exam: 40%

Chapter 1, slide:

5


Topics To Be Covered
 Architecture of the Internet, and network protocols
 Delay analysis
 Packet-switching and circuit-switching
 Congestion and flow control: TCP
 Routing algorithms: IP and datagram
 Data link layers and Ethernet: ARP, CSMA/CD
 Medium access control and local area networks

Chapter 1, slide:

6


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
 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:

7


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

already installed in Lab DEAR 205
To run, type: sudo wireshark then enter your eecs psswd

 Allows you to sniff and analyze traffic

sent/received from/by your end system: real
measurement of Internet traffic
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
infrastructure
enables distributed apps:

 communication



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
 millions of connected

computing devices: called
hosts or end systems








e.g., fiber, copper, radio,
satellite

mobile

local ISP

regional ISP

forward packets (chunks
of data)

communication links

workstation

server

routers & switches:




e.g., Laptops, workstations

running network apps

router

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
server



mobile

local ISP

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

network protocols


workstation

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 />

2:00

<file>
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 Network access and physical media
5 Internet structure and ISPs
6 Protocol layers, service models
7 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