Its Functions It Structures Introduction and Overview of Network and Telecommunications Image you are setting up a wireless network at home How much do you have to think about the whole structure of the Internet ID: 597118
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Slide1
How Do You Describe What the Internet Is?
Its Functions
It StructuresSlide2
Introduction and Overview of Network and TelecommunicationsSlide3
Image you are setting up a wireless network at home.Slide4
How much do you have to think about the whole structure of the Internet?Slide5
How
much do you have to be worried about the
compatibility of the gears you need to buy?Slide6
Internet Model
Modularized Internet
The whole Internet is broken into thousands of small networksSlide7
For A Single Network Connected to the Internet
A modularized network
Several independent and interconnected layers
!
An analogy: think about a post system
Sending a letter to another country
Programs
,t
ools
(Browser, Email App)
Transport protocol software
Routers, Internet Protocol software
Network interface cards, switches
Cable, fiber optics,
wifi
signalsSlide8
A More General Model: OSI
OSI
Open Systems Interconnection
Developed by the ISO
International Organization for Standardization
Seven layersSlide9
A More General Model: OSISlide10
Layering
Dividing
a task into pieces at different layers and then
solving
each piece independently
Establishing a well defined
interface
between layers.Slide11
Modularization Is Useful.
Help to manage complex systems
Houses, cars, roads, etc.
Different contractors/professionals to deal with different parts of work.
Education
Different grades
Healthcare systems
Hospitals, testing labs, pharmacies, insurance companies (?), etc.
As long as modules are well coordinated!Slide12
OK, We Know the Internet Model and Structure
.
How Does the Internet Really Work, Say Sending Information Around?Slide13
A Simple Example
http://zhang.ist.psu.edu/helloworld.html
What is really happening behind the wall?Slide14
An Analogy
The Internet works like a post system.
Documents/information: mails
Each computer/phone: houses with address
The Internet: delivering documents based on computer/phone addresses through mailmen. Slide15
It is more complicated.
Two ends could be
quite far away!Slide16
Many "mailmen" have to
be involved.Slide17
When you type in a URL on your mobile phone to visit a web page, what really happens between your phone and the server you try to visit? Can you sketch a diagram to illustrate through what a path your phone gets information?Slide18
Cellular Tower
Server
Internet Gateway
(Phone Company)
Internet Gateway
(Map Service Company)
Internet Gateway
(Cable Company)
Wireless Router
Cable Modem
Maps Server
Map DataSlide19
It is more complicated.
Documents could be huge!Slide20
Can Post Offices Deliver This?Slide21
We need to find a way to handle all kinds of documents, any type and any size.
But How?Slide22
Recall the Video
Warriors
of the NetSlide23
An example
<HTML><BODY>Hello World!</BODY></HTML> Slide24
<HTML><BODY>Hello
World
!</BODY></HTML>
TCP
</BODY></HTML>
<HTML><BODY>
Hello World!
</BODY></HTML>
Packets
TCP
</BODY></HTML>
IP
TCP
</BODY></HTML>
IP
MAC
TCP
</BODY></HTML>
IP
MAC
TCP
</BODY></HTML>
IP
TCP
</BODY></HTML>
</BODY></HTML>
LAN
<HTML><BODY>Hello World! </BODY></HTML>
}
sender
}
receiverSlide25
Some Key Points
Data is transmitted as
packets
.
Small data pieces.
Packets are handled by equipments at
different layer
.
Data are wrapped up at each layer.
Each layer has its
own protocols to follow.Different ways to wrap up.
New information, or header, is added or removed before sending to the next layer. Slide26
Why Using Packets?Slide27
The Internet
Diversification of the use of the Internet
Resource sharing
Communication
Entertainment
Contents
Text
multimediaSlide28
Imagine This Scenario
Your roommate is watching a 2-hour long, HD movie.
You are submitting a homework assignment with a deadline in 5 minutes.
What is the best way to use the network by you two?Slide29
Do You Like This Truck Ahead of You?Slide30Slide31
The Network Is Shared by Many Computers!Slide32
Connections between Computers
n(n-1)/2
Overhead Telephone and Telegraph Wires in Broadway, 1890
From
Book of Old New York. Henry Collins Brown
. 1913Slide33Slide34
Switch Model: Reducing the Mess
Analogy
Airport hubsSlide35
Switch Model: Reducing the Mess
Analogy
Airport hubsSlide36Slide37Slide38Slide39
Challenges
Packets
Size
Timing
Sequence
Fair opportunity
Destinations
Identification of each computer
TCP/IPSlide40
TCP: Transmission Control Protocol
IP: Internet Protocol
TCP/IP
Tolerating heterogeneous network data
Implementation at both software and hardware levels
Led to the InternetSlide41
Friday
Work on your first group assignment.