gaurav bhatt 6167 wireless

8/9/2019 Gaurav Bhatt 6167 Wireless

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Made by Gaurav Bhatt

ECE 8th

Semester


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Contents in the slide

Definition of wireless LAN

Its history

Architecture of WLAN Common topology

Security features


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What is a Wireless Lan

n/w

Wireless LAN is atype of local area

network thatuseshigh

frequency radiorather than

wires to

communicatebetween nodes.


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History of wireless LAN

The first radio network technology was developed atUniversity of Hawaii in a research project callALOHANET. The ALOHANET system allows computerwith 7 sites, which spread out in four islands withoutusing any wired transmission links.

four islands


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History of wireless LAN

In 1980 the hobbyists in Canada and US haddeveloped the equipment call TNCs (terminal nodecontroller).


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Common TopologiesThe wireless LAN connects to a wired LAN

The access point bridges wireless LAN traffic into the wired LAN. The

access point (AP) can also act as a repeater for wireless nodes,effectively doubling the maximum possible distance between nodes.


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System Architecture

Two basic systemarchitectures

1. Ad hoc

2. Infrastructure based


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Ad hoc wireless LANs

A group of stations using the sameradio frequency Basic Service Set

The physical size of the network isdetermined by the maximum reliablepropagation range of the radio signals.Referred to as ad hoc networks
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Infrastructure based

Wireless LANs Stations and Access

Points

Distribution systemconnects cells viaaccess points to forma single network

Extends wireless areacoverage


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802.11 Wireless LAN

Provides network connectivity over wireless

media

An Access Point (AP) is installed to act asBridge between Wireless and WiredNetwork

The AP is connected to wired network and

Network

connectivity

to the

legacywired LAN

Desktop

with PCI 802.11 LAN card

Laptop

with PCMCIA 802.11 LAN cardAccess Point


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Access Points

Stations select an AP and associate with it Support roaming

Provide other functions time synchronization

power management support

point coordination function

Traffic typically (but not always) flows

through AP direct communication possible


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802.11b Security Features

Wired Equivalent Privacy (WEP) A protocol toprotect link-level data during wirelesstransmission between clients and accesspoints.

Services: Authentication: provides access control to the

network by denying access to client stations that failto authenticate properly.

Confidentiality: intends to prevent informationcompromise from casual eavesdropping

Integrity: prevents messages from being modifiedwhile in transit between the wireless client and the

access point.


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Authentication

Means: Based on cryptography

Non-cryptographic

Both are identity-based verificationmechanisms (SSID Service Set Identifier ofthe wireless network).


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Privacy

Cryptographic techniques

WEP Uses RC4 symmetric key, streamcipher algorithm. The stream is XORed with

the data to be transmitted

Key sizes: 40 bits to 128 bits


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Data Integrity

Data integrity is ensured by a simpleencrypted version of CRC (Cyclic RedundantCheck)

Also vulnerable to some attacks


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Security Problems

Use of static WEP keys (keys are in use for avery long time).

WEP does not provide key management.

Cryptographic keys are short.

No user authentication occurs only devicesare authenticated. A stolen device can accessthe network.

Identity based systems are vulnerable.

Packet integrity is poor.


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gaurav bhatt 6167 wireless

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