Lecture-01-overview tcp-ip stack-part 1

  • 38 trang
  • file .pdf
Wireless Networking Concepts
Dr. Nguyen Tuan Nam
Outline
• Overview of network background and technology
– Important concepts in computer networking
– Security
• Introduction to wireless network
– Cellular network
– 802.11
– WEP
– WiMax
– WAP
– Bluetooth and security in Bluetooth
– J2ME
– MANET
WNC 2010 2
Prerequisites of this Course
• Computer Networking
WNC 2010 3
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
WNC 2010 4
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
WNC 2010 5
Project/Presentation
• Projects
WNC 2010 6
Overview
• TCP/IP layers
• Important properties of a network protocol
• Important concept in computer network
WNC 2010 7
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)
WNC 2010 9
Network Stacks/Layers
• OSI 7-layer model
– 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?
WNC 2010 10
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,
MAC and LLC (Phys Adr) ATM
Physical
Wire, Radio, Fiber Optic, Acoustic
Media, Signal, Bin Transmission
WNC 2010 11
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
WNC 2010 12
Illustration
. . . 0101011101010111010101010101 . . .
Physical signal (wave, voltage, light pulses)
WNC 2010 13
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
WNC 2010 14
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
WNC 2010 15
Illustration 2
MAC: flat address,
00FF00AA00BA specify nothing about
the network structures
Switch
00FF00AA00BB Hub 00FF00AA00BC
00FF00AA00BD
WNC 2010 16
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
WNC 2010 17
Quiz
• Can 2 adapters (computers) in a LAN
(local area network) have the same MAC
address?
00FF00AA00BA
Switch
00FF00AA00BB Hub 00FF00AA00BA
00FF00AA00BD
WNC 2010 18
Quiz
• Can a computer have 2 network adapters?
00FF00AA00BA
00FF00AA00BC
Switch Switch
Hub Hub
00FF00AA00BB 00FF00AA00BC
00FF00AA00B9
00FF00AA00BD
WNC 2010 19
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
WNC 2010 20