Introduction - Department of Computer Engineering
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Transcript Introduction - Department of Computer Engineering
INT-201:
Computer Network and
Communication System
Module1: Introduction
อ.ดร. ภัทร ลีลาพฤทธิ์
Computer Networking: A
Top Down Approach ,
4th edition.
Jim Kurose, Keith Ross
Addison-Wesley, July
2007.
Dr. Pattara Leelaprute
Computer Engineering Department
Kasetsart University
[email protected]
http://www.cpe.ku.ac.th/~pattara/int201
Introduction
1-1
Outline
Introduction to Computer
Operating System
What is Internet?
Network structure
The Network Core
Introduction
1-2
Definition of Computer
Devices for performing computations
at high speeds with great accuracy
A machine that can be programmed to
manipulate symbols
Physical components are known as
“Hardware”
Introduction
1-3
Where to find Computer?
Home
Business
School
Where else?
Hospital, automobiles, aircraft,
electronic appliance, mobile phone, etc…
Introduction
1-4
Computer Systems
Hardware (HW)
Actual
physical machines (equipment)
that make up the computer (e.g. monitor,
keyboard)
Software (SW)
Programs
written for a specific
application are often called software
(e.g. Window XP, Linux, Microsoft word)
Introduction
1-5
Computer Categories
Personal Computer
Desktop Computer
Notebook
PDA – Personal Digital Assistant
Supercomputer Mainframe
High Computation Power
Server
Workstation
Introduction
1-6
Server & Workstation
Introduction
1-7
Computer Components
Input Devices
Output Devices
Computing & Processing Unit
Introduction
1-8
Computer Components (details)
Input Devices
CPU
Secondary
Memory
(DVD,
FDD,
HDD)
Main
Memory
Output Devices
HD
*CPU= Central Processing Unit
Introduction
1-9
Computer Components (pictures)
Hard disc
CPU
Introduction
1-10
Computer Memory
Can be divided into 2 Categories
RAM (Random Access Memory)
ROM (Read Only Memory)
Memory in Computer
Main Memory
Secondary Memory
Introduction
1-11
Main Memory VS Secondary Memory
Main Memory
Much
Secondary Memory
faster
More expensive
Volatile (Temporary)
Slower
Less
expensive
Permanent
Introduction
1-12
1. Main Memory
Memory Cell -> Byte -> bit
1 Byte = 8 bits
Introduction
1-13
2. Secondary Memory
Floppy disk
Hard disk
CD-ROM, CD-R, CD-RW
DVD-ROM, DVD-R, DVD-RW
Blu-ray disc
Etc…
Introduction
1-14
Data Representation
Data in computer is represented in “bit”
bit = binary digit
• 0 or 1
Byte = 8 bits
1 byte can represent many kids of data
• 1 byte = 011000012
• the above 1 byte means, 97 or “a” in ASCII code
• ASCII =American Standard Code for Information Interchange.
• the meaning of 1 byte depends on the program
• Photos, Voice, Video, etc
1 Kbyte = 210 = 1024 bytes (KB)
1 Mbyte = 220 = 1,048,576 bytes (MB)
1 Gbyte = 230 = 1,073,741,824 bytes (GB)
1 Tbyte = 240 = 1,099,511,627,776 bytes (TB)
Introduction
1-15
ASCII code
8bit code for character
representation
(7 bits plus parity)
0-127 represents the
letter of alphabet,
numbers and symbols
Introduction
1-16
Binary and Decimal
How to convert binary to decimal?
1 0 0 1 1
2
2 5 5 1
10
1 0 0 1 1
1 0 0 1 1
= ?
= ?2x103 + 5x102 + 5x101 + 1x100
2
= 1x24 + 0x23 + 0x22 + 1x21 + 1x20
2
= 24 + 21 + 1 = 16+2+1 = 19
How to convert decimal to binary ?
Introduction
1-17
Boolean Expression
And
Or
Not
0
0
1
1
and
and
and
and
0
1
0
1
0
0
1
1
or
or
or
or
=
=
=
=
0
1
0
1
=
=
=
=
0
0
0
1
0
1
1
1
not 0 = 1
not 1 = 0
Introduction
1-18
Type of Application
Local application
Program, such as a word processor, that is
stored on the hard disk of the computer.
The application runs only on that computer.
Network application
Program that is designed to run over a network,
such as the Internet.
A network application has two components, one
that runs on the local computer and one that
runs on a remote computer.
ex., Email
Introduction
1-19
Outline
Introduction to Computer
Operating System
What is Internet?
Network structure
The Network Core
Introduction
1-20
Operating System (OS)
Software component of a computer system
Responsible for the management and
coordination of activities and the sharing of
the resources of the computer.
All computerized devices, such as servers,
desktops, laptops require an OS
ex. Microsoft Windows, MAC OS X, Linux,
Unix
Ex., RAM, Hard disk, CPU
Introduction
1-21
Operating System (OS)
What does OS do?
Program execution
Memory management
Multitasking
Disk access and file systems
Device drivers (printer, monitor)
Input/Output
Networking
Let’s think about WORD application.
Write a report and print it out.
• OS collaborates keyboard, monitor, hard disk, and printer.
Introduction
1-22
User Interface (for OS)
Command line interface (CLI)
Graphical user interface (GUI)
CLI
Introduction
1-23
Quiz
((1 and 0) or (1 and 1)) = ?
What is I/O device ?
What is RAM and ROM ?
1 byte = xxx bits
1 Mbyte = xxx byte
10000102 = ?
Introduction
1-24
Outline
Introduction to Computer
Operating System
What is Internet?
Network structure
The Network Core
Introduction
1-25
What’s the Internet: overview
PC
millions of connected
computing devices:
hosts = end systems
wireless
laptop
running network
cellular
handheld
apps
communication links
fiber, copper,
access
points
radio, satellite
wired
links
transmission
rate = bandwidth
routers: forward
router
packets (chunks of
data)
Mobile network
server
Global ISP
Home network
Regional ISP
Institutional network
Introduction
1-26
“Cool” internet appliances
Web-enabled toaster +
weather forecaster
IP picture frame
http://www.ceiva.com/
World’s smallest web server
http://www-ccs.cs.umass.edu/~shri/iPic.html
Internet phones
Introduction
1-27
What’s the Internet: “nuts and bolts” view
protocols control sending,
Mobile network
receiving of msgs
e.g., TCP, IP, HTTP, Skype,
Ethernet
Internet: “network of
networks”
loosely hierarchical
public Internet versus
private intranet
Global ISP
Home network
Regional ISP
Institutional network
Internet standards
RFC: Request for comments
IETF: Internet Engineering
Task Force
Introduction
1-28
What’s the Internet: a service view
communication
infrastructure enables
distributed applications:
Web, VoIP, email, games,
e-commerce, file sharing
communication services
provided to apps:
reliable data delivery
from source to
destination
“best effort” (unreliable)
data delivery
Introduction
1-29
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 format,
order of msgs sent and
received among network
entities, and actions
taken on msg
transmission, receipt
Introduction
1-30
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
<file>
time
Q: Other human protocols?
Introduction
1-31
Outline
Introduction to Computer
Operating System
What is Internet?
Network structure
The Network Core
Introduction
1-32
Network structure:
network edge:
applications and
hosts (send-receive msg)
access networks,
physical media:
wired, wireless
communication links
network core:
interconnected
routers
network of
networks
Introduction
1-33
The network edge:
end systems (hosts):
run application programs
e.g. Web, email
at “edge of network”
peer-peer
client/server model
client host requests, receives
service from always-on server
client/server
e.g. Web browser/server;
email client/server
peer-peer model:
minimal (or no) use of
dedicated servers
e.g. Skype, BitTorrenth
Introduction
1-34
Network edge: reliable data transfer
service
Goal: data transfer
between end systems
handshaking: setup
(prepare for) data
transfer ahead of time
Hello, hello back human
protocol
set up “state” in two
communicating hosts
TCP - Transmission
Control Protocol
Internet’s reliable data
transfer service
TCP service [RFC 793]
reliable, in-order byte-
stream data transfer
loss: acknowledgements
and retransmissions
flow control:
sender won’t overwhelm
receiver
congestion control:
senders “slow down sending
rate” when network
congested
Introduction
1-35
Network edge: best effort (unreliable)
data transfer service
Goal: data transfer
between end systems
same as before!
UDP - User Datagram
Protocol [RFC 768]:
connectionless
unreliable data
transfer
no flow control
no congestion control
App’s using TCP:
HTTP (Web), FTP (file
transfer), Telnet
(remote login), SMTP
(email)
App’s using UDP:
streaming media,
teleconferencing, DNS,
Internet telephony
Introduction
1-36
Access networks and physical media
Q: How to connect end
systems to edge router?
residential access nets
institutional access
networks (school,
company)
mobile access networks
Keep in mind:
bandwidth (bits per
second) of access
network?
shared or dedicated?
Introduction
1-37
Residential access: point to point access
Dialup via modem
up to 56Kbps direct access to
router (often less)
Can’t surf and phone at same
time: can’t be “always on”
DSL: digital subscriber line
deployment: telephone company (typically)
up to 1 Mbps upstream (today typically < 256 kbps)
up to 8 Mbps downstream (today typically < 1 Mbps)
dedicated physical line to telephone central office
Introduction
1-38
Residential access: cable modems
HFC: hybrid fiber coax
asymmetric: up to 30Mbps downstream, 2
Mbps upstream
network of cable and fiber attaches homes to
ISP router
homes share access to router
deployment: available via cable TV companies
Introduction
1-39
Residential access: cable modems
Diagram: http://www.cabledatacomnews.com/cmic/diagram.html
Introduction
1-40
Company access: local area networks
company/univ local area
network (LAN) connects
end system to edge router
Ethernet:
10 Mbs, 100Mbps,
1Gbps, 10Gbps Ethernet
modern configuration:
end systems connect
into Ethernet switch
LANs: chapter 5
Introduction
1-41
Wireless access networks
shared wireless access
network connects end system
to router
via base station aka “access
point”
wireless LANs:
802.11b/g (WiFi): 11 or 54 Mbps
wider-area wireless access
provided by telco operator
~1Mbps over cellular system
(EVDO, HSDPA)
next up (?): WiMAX (10’s Mbps)
over wide area
router
base
station
mobile
hosts
Introduction
1-42
Home networks
Typical home network components:
DSL or cable modem
router/firewall/NAT
Ethernet
wireless access
point
to/from
cable
headend
cable
modem
router/
firewall
Ethernet
wireless
laptops
wireless
access
point
Introduction
1-43
Physical Media
Bit: propagates between
transmitter/rcvr pairs
physical link: what lies
between transmitter &
receiver
guided media:
signals propagate in solid
media: copper, fiber, coax
Twisted Pair (TP)
two insulated copper
wires
Category 3: traditional
phone wires, 10 Mbps
Ethernet
Category 5:
100Mbps Ethernet
unguided media:
signals propagate freely,
e.g., radio
Introduction
1-44
Physical Media: coax, fiber
Coaxial cable:
Fiber optic cable:
conductors
bidirectional
baseband:
pulses, each pulse a bit
high-speed operation:
two concentric copper
single channel on cable
legacy Ethernet
broadband:
multiple channels on
cable
HFC
glass fiber carrying light
high-speed point-to-point
transmission (e.g., 10’s100’s Gps)
low error rate: repeaters
spaced far apart ; immune
to electromagnetic noise
Introduction
1-45
Physical media: radio
signal carried in
electromagnetic
spectrum
no physical “wire”
bidirectional
propagation
environment effects:
reflection
obstruction by objects
interference
Radio link types:
terrestrial microwave
e.g. up to 45 Mbps channels
LAN (e.g., Wifi)
11Mbps, 54 Mbps
wide-area (e.g., cellular)
3G cellular: ~ 1 Mbps
satellite
Kbps to 45Mbps channel (or
multiple smaller channels)
270 msec end-end delay
geosynchronous versus low
altitude
Introduction
1-46
Outline
Introduction to Computer
Operating System
What is Internet?
Network structure
The Network Core
Introduction
1-47
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”
Introduction
1-48
Network Core: Circuit Switching
End-end resources
reserved for “call”
link bandwidth, switch
capacity
dedicated resources:
no sharing
circuit-like
(guaranteed)
performance
call setup required
Introduction
1-49
Network Core: Circuit Switching
network resources
(e.g., bandwidth)
divided into “pieces”
pieces allocated to calls
dividing link bandwidth
into “pieces”
frequency division
time division
resource piece idle if
not used by owning call
(no sharing)
Introduction
1-50
Circuit Switching: FDM and TDM
Example:
FDM
4 users
frequency
time
TDM
frequency
time
Introduction
1-51
Network Core: Packet Switching
each end-end data stream
divided into packets
user A, B packets share
network resources
each packet uses full link
bandwidth
resources used as needed
Bandwidth division into “pieces”
Dedicated allocation
Resource reservation
resource contention:
aggregate resource
demand can exceed
amount available
congestion: packets
queue, wait for link use
store and forward:
packets move one hop
at a time
Node receives complete
packet before forwarding
Introduction
1-52
Packet Switching: 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,
bandwidth shared on demand statistical multiplexing.
TDM: each host gets same slot in revolving TDM frame.
Introduction
1-53
Packet-switching: store-and-forward
L
R
takes L/R seconds to
R
transmit (push out)
packet of L bits on to
link at R bps
store and forward:
entire packet must
arrive at router before
it can be transmitted
on next link
delay = 3L/R (assuming
zero propagation delay)
R
Example:
L = 7.5 Mbits
R = 1.5 Mbps
transmission delay = 15
sec
more on delay shortly …
Introduction
1-54
Packet switching versus circuit switching
Packet switching allows more users to use network!
1 Mb/s link
each user:
100 kb/s when “active”
active 10% of time
circuit-switching:
10 users
packet switching:
with 35 users,
probability > 10 active
at same time is less
than .0004
N users
1 Mbps link
Q: how did we get value 0.0004?
Introduction
1-55
Packet switching versus circuit switching
Is packet switching a “slam dunk winner?”
great for bursty data
resource sharing
simpler, no call setup
excessive congestion: packet delay and loss
protocols needed for reliable data transfer,
congestion control
Q: How to provide circuit-like behavior?
bandwidth guarantees needed for audio/video apps
still an unsolved problem (chapter 7)
Q: human analogies of reserved resources (circuit
switching) versus on-demand allocation (packet-switching)?
Introduction
1-56
Summary
Introduction to Computer
Operating System
What is Internet?
Network structure
The Network Core
Introduction
1-57
Tips (useful links)
http://en.wikipedia.org
http://th.wikipedia.org/wiki/
http://longdo.com
http://cisco.netacad.net
Introduction
1-58
Tips (Programming Languages)
Program
A set of instructions for a computer to
follow, written in specific programming
language
Types of programming language
High-Level Language
Machine Language
Assembly Language
Introduction
1-59
Tips (Programming Languages)
High-level Language
Nearly like human word
SUM := A * 2 + ALPHA/3;
Assembly Language
Some key words are understandable
MULL3 A, #2, R
ADDL3R6, R7, SUM
Machine Language
Only “0” and “1”
00011000011
00011001111
10011000111
Computer itself understands only Machine language
Introduction
1-60
Tips (Programming Languages)
High-Level Languages
Procedural Language
Fortran
Cobol
Basic
C
Pascal
Object-Oriented Language
C++
C#
Java
Functional Language
Lisp
Logic Language
Prolog
Introduction
1-61
Homework
What is Blu-ray disc? (~1000 characters)
Give 3 names of the application, describe
what does it do and its type. (~1000 characters)
Describe why the service in the Internet is called
best effort service? (~1000 characters)
Describe how to represent the picture that has the
size of X*Y pixel, and has 8 tone level (0~7) for each
R,G,B color by using binary. In addition, calculate
the number of bit needed for that X*Y picture.
• Please write your name, student ID, hand in date on the top.
• Deadline is 11th June 2008 (next class).
Introduction
1-62