Download 802.11i: WiFi Protected Access

Introduction
Chapter 1
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
‫دیباچه‬
‫درخت چنار تنومند تنها روی تپه ایستاده بود‪ .‬صدها سال بود که آنجا بود و‬
‫گویی تا ابد نیز قرار بود بماند‪ .‬ریشه هایش همچون پنجه ای آهنین در اعماق‬
‫خاک فرو رفته بود؛ آنچنان که گویی کس ی را یارای برکندن آن نیست‪.‬‬
‫ا‬
‫یک شب صاعقه ای درخت را به دو نیم کرد؛ درخت از درون کامل تهی و‬
‫پوسیده بود‪.‬‬
‫آین راند (اطلس شانه باالانداخت)‬
Uses of Computer Networks
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Business Applications
Home Applications
Mobile Users
Social Issues
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Business Applications (1)
A network with two clients and one server
The server can also be a local printer
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Business Applications (2)
* The client-server model involves requests and replies
* Business Networks can be joined by VPNs
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Business Applications (3)
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Setting up a communication medium:
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Email Service
Phone Service: VoIP
Video Conference
Desktop Sharing: Interactive team working
Telemedicine
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Remote patient monitoring
e-commerce
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Electronic shopping, ticket booking, …
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Home Applications (1)
o
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o
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o
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Gaming
TV, Radio
Photo and Video editing
Music
Internet connection
Online news
Online digital library : ACM, IEEE, …
Ubiquitous computing: Smart homes, smart metering systems, …
o
o
o
a)
Power-line networks
Zigbee networks
RFID technology
Internet of Things (IoT)
Metcalfe’s law: the value of a network is proportional to the
square of the number of users
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Home Applications (2)
* In a peer-to-peer system there are no fixed clients and servers.
* BitTorrent is an example
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Home Applications (3)
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Instant Messaging: sms, mms, …
Multiperson messaging: Twitter, Viber, Telegram, …
Audio & video Sharing: YouTube, Facebook , Instagram, …
Colaborating content creation: Wikipedia

e-commerce:
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Mobile Users
Combinations of wireless networks and mobile computing
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Mobile Users (1)
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Smart Phones : 3G, 4G Mobile networks
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Global positioning system (GPS) + google map
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m-commerce (mobile commerce)
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Sensor Networks : traffic monitoring , …
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Vehicular networks
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Wearable computers : smart watches, …
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Social Issues
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Spreading wrong or offensive political or religious views
Censorship
Content pricing or Network neutrality
Digital Millennium Copyright Act
Employee-Employer issues
Content overhearing (e.g. by government)
Profiling users: internet cookies
misleading information
Spam
Electronic viruses
Phishing confidential information (e.g. bank acounts)
e-gambling
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Network Hardware
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Transmission technology
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broadcast: shared media e.g. wireless links
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point-to-point (unicast): multihop, routing
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Single target
Multicast
Broadcast
Scale
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Personal area networks
Local area networks
Metropolitan area networks
Wide are networks
internetwork (the Internet)
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Personal Area Network
Bluetooth PAN configuration
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Local Area Networks
(a) 802.11 (WiFi)
*Virtual LAN (VLAN)
*Static or Dynamic Medium Access
(b) Switched Ethernet. (802.3)
Centralized
Decentralized
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Home Networks
Requirements
1.
Easy to use devices
2.
Reliable work
3.
Low price
4.
Compatibility
5.
Security
Technologies
a)
Wireless
b)
Wired
c)
Power-line
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Metropolitan Area Networks
A metropolitan area network based on cable TV
* WiMAX (802.16) is another example
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Wide Area Networks (1)
WAN that connects three branch offices in Australia
* The transmission lines may be: telephone wires, optical fibers, or
wireless (e.g. Satellite) links
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Wide Area Networks (2)
WAN using a virtual private network (VPN).
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Wide Area Networks (3)
WAN using an ISP network.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Network Software
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Network architechture: multiple layers abstracted from each other
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Protocol stack: agreement between same layer parties
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Protocol replacement: must be done without changing the service
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Protocol Hierarchies (1)
Layer1 peer
Layers, protocols, and interfaces.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Protocol Hierarchies (2)
The philosopher-translator-secretary architecture
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Protocol Hierarchies (3)
Example information flow supporting virtual
communication in layer 5.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Design issues for the layers
•Reliability:
Error detection
Error correction
Routing
• Addressing
•Internetworking: Packet shaping
•Scalability
•Resource Allocation
•Flow or Congestion Control
•Quality of Service (QoS)
•Security
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Connection-Oriented Versus
Connectionless Service
Telephone like
Mail like
Six different types of service.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Service Primitives (1)
Six service primitives that provide a simple
connection-oriented service
* Primitives run as system calls on an operating system
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Service Primitives (2)
A simple client-server interaction using
acknowledged datagrams.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Relationship of Services to
Protocols
The protocol peers are like objects in a program.
The services are like object functions.
The protocols are like object definitions.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Reference Models
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OSI reference model: Valid model from ISO but unused protocols
Open System Interconnection (1983 developed, 1995 revised)
Networked Apps. like HTTP
Data structuring
Multiple sessions on a connection
Establish e2e connection
Routing+ congestion+
Connection+ address
Error+ Framing+ mac
Bit Transmission
TCP/IP Model
Base of ARPANET (Introduced 1974, Standardized 1989)
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TCP/IP Protocols
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The preferred reference model
Used in this class
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Example networks - Internet
a)
Telephone based network
b) proposed distributed system for
ARPANET
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(Advanced Research Projects Agency)
The original ARPANET design
56 Kbps
IMP :Interface Message Processor
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TCP/IP developed in 1974
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NSFNET
* National Science Foundation TCP/IP network that was connected to ARPANET in
the Carnegie-Mellon.
* NSF encouraged MERIT, MCI, and IBM to form a nonprofit corporation, ANS
(Advanced Networks and Services), as the first step along the
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road to commercialization.
Internet architecture
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DSLAM (Digital Subscriber Line Access Multiplexer)
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CMTS (Cable Modem Termination System)
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POP (Point of Presence)
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IXPs (Internet eXchange Points)
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Example networks- Mobile network
1)
First generation: analog voice transmission - AMPS(Advanced
Mobile Phone System)- 1982
2)
Second generation: digital voice and SMS- GSM(Global System for
Mobile communications)- 1991
3)
Third generation: broadband data- UMTS(Universal Mobile
Telecommunications System) + WCDMA(Wideband Code
DivisionMultipleAccess)- 2001
4)
Forth generation: higher bandwidth – WiMAX (802.16) + LTE
(Long Term Evolution)- 2011
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Cellular network and frequency reuse
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UMTS 3G architecture
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RNC(Radio Network Controller)
MSC(Mobile Switching Center)
MGW(Media Gateway)
SGSN(Serving GPRS Support Node)
HSS(Home SubscriberServer)
- GMSC(Gateway Mobile Switching Center)
- PSTN(Public Switched Telephone Network)
41 Node)
- GGSN(Gateway GPRS Support
Mobility and Handover
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Network example- Wireless LAN
a) WLAN with access point
b) 802.11 in ad hoc mode
*IEEE 802.11 or WiFi
*ISM (Industrial, Scientific, and Medical)band = 902-92843MHz, 2.42.5 GHz, 5.725-5.825 GHz
Multipath fading in WLANs
a)
b)
c)
d)
802.11 : 1-2 Mbps
802.11b : 11 Mbps by spread spectrum
802.11a,g: 54 Mbps by OFDM (Orthogonal Frequency Division Multiplexing)
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802.11n (2009) : 450 Mbps by using multiple antennas
CSMA (Carrier Sense Multiple Access)
Hidden terminal problem
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WLAN Security
a)
WEP (Wired Equivalent Privacy)
b)
802.11i: WiFi Protected Access (WPA, WPA2)
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Network example- RFID
UHF: 902-928 MHz
Passive
Radio Frequency IDentification (RFID)
HF : 13.56 MHz
Active
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Network example- Sensor Networks
Multihop topology of a sensor network
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Network standardization
a)
ITU (International Telecommunication Union): 200 governments
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ITU-T: telecommunications
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ITU-R: radio communications
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ITU-D: developement
b)
ISO (International Standards Organization): 157 members e.g. ANSI (U.S.), BSI
(Great Britain),…
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CD (Committee Draft) DIS (Draft International Standard) IS
(International Standard)
c)
NIST (National Institute of Standards and Technology)
d)
IEEE (Institute of Electrical and Electronics Engineers)
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IEEE 802 standards
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Internet standardization
1) IAB (Internet Activities Board)
IRTF (Internet Research
Task Force)
IETF (Internet Engineering
Task Force)
www.ietf.org
RFCs (Request For Comments)
2) World Wide Web Consortium (W3C): 300 member
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Metrics for network speed
Metrics for memory size
Kilo = 2e10 = 1024
Mega = 2e20 = 1,048,576
Giga = 2e30 = 1,073,741,824
Tera = 2e40 = 1,099,511,627,776
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