Wireless Technology is an alternative to Wired Technology which is commonly used for connecting devices in wireless mode.
Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE 802.11 communications standard for Wireless Local Area Networks (WLANs).
Wi-Fi Network connect computers to each other to the internet and to the wired network.
4 The Wi-Fi Technology
Wi-Fi Networks use Radio Technologies to transmit receive data at high speed
5 IEEE 802.11b
Appear in late 1999
Operates at 2.4GHz radio spectrum
11 Mbps (theoretical speed) - within 30 m Range
4-6 Mbps (actual speed)
100 -150 feet range
Most popular Least Expensive
Interference from mobile phones and Bluetooth devices which can reduce the transmission speed.
6 IEEE 802.11a
Introduced in 2001
Operates at 5 GHz (less popular)
54 Mbps (theoretical speed)
15-20 Mbps (Actual speed)
50-75 feet range
Not compatible with 802.11b
7 IEEE 802.11g
Introduced in 2003
Combine the feature of both standards (ab)
100-150 feet range
54 Mbps Speed
2.4 GHz radio frequencies
Compatible with b
8 802.11 Physical Layer
There are three sublayers in physical layer
Direct Sequence Spread Spectrum (DSSS)
Frequency Hoping Spread Spectrum (FHSS)
Diffused Infrared (DFIR) - Wide angle
Direct sequence signaling technique divides the 2.4 GHz band into 11 22-MHz channels. Adjacent channels overlap one another partially with three of the 11 being completely non-overlapping. Data is sent across one of these 22 MHz channels without hopping to other channels.
10 IEEE 802.11 Data Link Layer
The data link layer consists of two sublayers
Logical Link Control (LLC)
Media Access Control (MAC).
802.11 uses the same 802.2 LLC and 48-bit addressing as other 802 LANs allowing for very simple bridging from wireless to IEEE wired networks but the MAC is unique to WLANs.
11 802.11 Media Access Control
Carrier Sense Medium Access with collision avoidance protocol (CSMA/CA)
Listen before talking
Avoid collision by explicit Acknowledgement (ACK)
Problem additional overhead of ACK packets so slow performance
Request to Send/Clear to Send (RTS/CTS) protocol
Solution for hidden node problem
Problem Adds additional overhead by temporarily reserving the medium so used for large size packets only retransmission would be expensive
12 802.11 Media Access Control(cont.)
MAC supports power conservation to extend the battery life of portable devices
Power utilization modes
Continuous Aware Mode
Radio is always on and drawing power
Power Save Polling Mode
Radio is dozing with access point queuing any data for it
The client radio will wake up periodically in time to receive regular beacon signals from the access point.
The beacon includes information regarding which stations have traffic waiting for them
The client awake on beacon notification and receive its data
13 802.11 Media Access Control(cont.)
Each pkt has a CRC checksum calculated and attached to ensure that the data was not corrupted in transit
14 Elements of a WI-FI Network
Access Point (AP) - The AP is a wireless LAN transceiver or base station that can connect one or many wireless devices simultaneously to the Internet.
Wi-Fi cards - They accept the wireless signal and relay information.They can be internal and external.(e.g PCMCIA Card for Laptop and PCI Card for Desktop PC)
Safeguards - Firewalls and anti-virus software protect networks from uninvited users and keep information secure.
15 How a Wi-Fi Network Works
Basic concept is same as Walkie talkies.
A Wi-Fi hotspot is created by installing an access point to an internet connection.
An access point acts as a base station.
When Wi-Fi enabled device encounters a hotspot the device can then connect to that network wirelessly.
A single access point can support up to 30 users and can function within a range of 100 150 feet indoors and up to 300 feet outdoors.
Many access points can be connected to each other via Ethernet cables to create a single large network.
16 Wi-Fi Network Topologies
AP-based topology (Infrastructure Mode)
Peer-to-peer topology (Ad-hoc Mode)
Point-to-multipoint bridge topology
17 AP-based topology
The client communicate through Access Point.
BSA-RF coverage provided by an AP.
ESA-It consists of 2 or more BSA.
ESA cell includes 10-15 overlap to allow roaming.
18 Peer-to-peer topology
AP is not required.
Client devices within a cell can communicate directly with each other.
It is useful for setting up of a wireless network quickly and easily.
19 Point-to-multipoint bridge topology
This is used to connect a LAN in one building to a LANs in other buildings even if the buildings are miles apart.These conditions receive a clear line of sight between buildings. The line-of-sight range varies based on the type of wireless bridge and antenna used as well as the environmental conditions.
Attacks on higher layer protocol (TCP/IP protocol)
28 Wi-Fi Security
The requirements for Wi-Fi network security can be broken down into two primary components
Keeping unauthorized users off the network
Authentication Server is used
Username and password
Data (username password) send before secure channel established
Prone to passive eavesdropping by attacker
Establishing a encrypted channel before sending username and password
30 Authentication (cont..)
Digital Certificate is used
Validation of digital certificate occurs automatically within client software
31 Wi-Fi Security Techniques
Service Set Identifier (SSID)
Wired Equivalent Privacy (WEP)
802.1X Access Control
Wireless Protected Access (WPA)
32 Service Set Identifier (SSID)
SSID is used to identify an 802.11 network
It can be pre-configured or advertised in beacon broadcast
It is transmitted in clear text
Provide very little security
33 Wired Equivalent Privacy (WEP)
Provide same level of security as by wired network
Original security solution offered by the IEEE 802.11 standard
Uses RC4 encryption with pre-shared keys and 24 bit initialization vectors (IV)
key schedule is generated by concatenating the shared secret key with a random generated 24-bit IV
32 bit ICV (Integrity check value)
No. of bits in keyschedule is equal to sum of length of the plaintext and ICV
34 Wired Equivalent Privacy (WEP) (cont.)
64 bit preshared key-WEP
128 bit preshared key-WEP2
Encrypt data only between 802.11 stations.once it enters the wired side of the network (between access point) WEP is no longer valid
Security Issue with WEP
Offers very little security at all
35 802.1x Access Control
Designed as a general purpose network access control mechanism
Not Wi-Fi specific
Authenticate each client connected to AP (for WLAN) or switch port (for Ethernet)
Authentication is done with the RADIUS server which tells the access point whether access to controlled ports should be allowed or not
AP forces the user into an unauthorized state
user send an EAP start message
AP return an EAP message requesting the users identity
Identity send by user is then forwared to the authentication server by AP
Authentication server authenticate user and return an accept or reject message back to the AP
If accept message is return the AP changes the clients state to authorized and normal traffic flows
36 802.1x Access Control 37 Wireless Protected Access (WPA)
WPA is a specification of standard based interoperable security enhancements that strongly increase the level of data protection and access control for existing and future wireless LAN system.
TKIP (Temporal Key Integrity Protocol) encryption
RC4 dynamic encryption keys (session based)
48 bit IV
per packet key mixing function
Fixes all issues found from WEP
Uses Message Integrity Code (MIC) Michael
Ensures data integrity
Old hardware should be upgradeable to WPA
38 Wireless Protected Access (WPA)(cont.)
WPA comes in two flavors
use pre-shared key
For SOHO environments
Single master key used for all users
For large organisation
Most secure method
Unique keys for each user
Separate username password for each user
39 WPA and Security Threats
Data is encrypted
Protection against eavesdropping and man-in-the-middle attacks
Denial of Service
Attack based on fake massages can not be used.
As a security precaution if WPA equipment sees two packets with invalid MICs within a second it disassociates all its clients and stops all activity for a minute
Only two packets a minute enough to completely stop a wireless network
Provides standard for WLAN security
AES protocol is used
Secure fast handoff-This allow roaming between APs without requiring client to fully reauthenticate to every AP.
Will require new hardware
Ease of Installation
Use unlicensed part of the radio spectrum
Degradation in performance
High power consumption
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