Mô tả:
Wireless Networking Concepts
Dr. Nguyen Tuan Nam
Outline
• Overview of network background and technology
– Important concepts in computer networking
– Security
• Introduction to wireless network
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Cellular network
802.11
WEP
WiMax
WAP
Bluetooth and security in Bluetooth
J2ME
MANET
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Prerequisites of this Course
• Computer Networking
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Assignments & Grading
• 2 exams
– Midterm 20%
– Final exam (40%)
• Projects (30%)
– Individual
– Coding/Presentation
• Quiz
– 10%
• Students responsible for going to class & take notes
• Extra credit for advanced projects and class participation
• Fun & creative
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Exams (closed notes, closed books)
• Questions mostly discussed in class, so don’t
skip lecture J
• Midterm
– Basic concepts from Computer Networking course
– Plus all topics discussed from today until that day
• Final exam
– All lectures
– Lab material given by your TAs
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Project/Presentation
• Projects
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Overview
• TCP/IP layers
• Important properties of a network protocol
• Important concept in computer network
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TCP/IP Layers
Dr. Nguyen Tuan Nam
Quiz 1
• What happen when you open a website
like www.yahoo.com ??
• Hints: (DNS look up, TCP connection, what
happen in each layer)
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Network Stacks/Layers
• OSI 7-layer model
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Physical
Data link
Network
Transport
Session
Presentation
Application
• TCP/IP stack
– 5 layers
• Each layer:
– Only uses functions of the layer below
– Export functionality to layer above
– Why divides it into layers?
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The 5 Layers
Application
HTTP, FTP, SSH
Network aware program
Transport
TCP, UDP
End-end connections & Reliability
Network
IP
Path Determination (Logic Adr)
Data Link
Ethernet, Wi Fi 802.11, Bluetooth,
ATM
MAC and LLC (Phys Adr)
Physical
Media, Signal, Bin Transmission
Wire, Radio, Fiber Optic, Acoustic
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Physical Layer
• Most complex layer
• Define the means of transmitting raw bits
– Bit stream converted to physical signal
• Main responsibilities:
– Definition of Hardware Spec: shapes and properties of
electrical connectors
– Encoding and signaling
– Data transmission and reception
– Topology and physical network design
• Pretty much about hardware
• Example: repeater
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Illustration
. . . 0101011101010111010101010101 . . .
Physical signal (wave, voltage, light pulses)
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Data Link Layer
• Put data into frames
– Ethernet frames
– Local delivery of frames between devices on the same LAN
– Start/end of the frame
• Time based
• Character counting
• Bit pattern
– Frame header contains info about the frame
– Hop-to-hop frame delivery
• Physical Address:
– MAC address
– Identify which computer in the subnet
– Source and Destination Addresses
• Collision Avoidance/Detection
– Frame collision
– Can be reliable/unreliable transmission
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Illustration
Frame 3
Frame 2
Frame 1
010…0111
0101…110
101…0101
00FF00AA00BD
00FF00AA00BE
| Start | MAC addresses | Content | End |
MAC address: _ unique address, uniquely identify an adapter in LAN
6 bytes in hexadecimal
First 3 bytes: manufacture, Last 3 bytes: serial number
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Illustration 2
00FF00AA00BA
MAC: flat address,
specify nothing about
the network structures
Switch
00FF00AA00BB
Hub
00FF00AA00BC
00FF00AA00BD
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Quiz
• Do 2 adapters (computers) in a LAN (local
area network) need to have the same MAC
address prefix?
00FF00AA00BA
00FF00
Switch
00FF00AA00BB
Hub
00FF00AA00BC
00FF00AA00BD
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Quiz
• Can 2 adapters (computers) in a LAN
(local area network) have the same MAC
address?
00FF00AA00BA
Switch
00FF00AA00BB
Hub
00FF00AA00BA
00FF00AA00BD
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Quiz
• Can a computer have 2 network adapters?
00FF00AA00BA
Switch
00FF00AA00BB
00FF00AA00BC
Hub
00FF00AA00BC
Switch
Hub
00FF00AA00B9
00FF00AA00BD
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Switch/Bridge vs Hub
• Hub:
– Repeater
– Take incoming data packet in 1port
– Copies it to all other ports
– No filtering or redirection of data
• Switch/Bridge:
– Layer 2
– Only forward packet to the correct adapter
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