Presented by
SUMIT KUMAR BEHERA

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What is WLAN ?
 WLAN is a wireless local area network which is the linking of two or more computers or devices without using wires.
 uses radio waves for communication between devices in a limited area.
 WLAN is based on the IEEE 802.11 standard.
Why WLAN ?
• WLAN are implemented as an extension to wired LANs and provide connectivity between a wired network and the mobile user.
• It’s mainly used in college campuses, office buildings, and many public areas .
• Its benefits are:
Architecture
 Basic service set (BSS) : It is a set of all stations that can communicate with each other.
 There are two types of BSS: Independent BSS and infrastructure BSS.
a) Independent BSS (IBSS) is an ad-hoc network that contains no access points. So, it can not connect to any other basic service set
b) Infrastructure BSS has an access point. So, it can communicate with other BSSs through access points.
 Extended Service Set (ESS): it is a set of connected BSSs .
 Each ESS has an 32-byte ID called the SSID (service set identifier).
 Access points in an ESS are connected by a distribution system.
WLAN technology
• There are three unlicensed bands: 900 MHz, 2.4 Ghz combinedly called “ISM”(Industry Scientific And Medical )and 5.7 GHz called “UNII”(Unlicensed National Information Infrastructure) which implement WLAN.
• Frequencies for these bands are as follows:
900-MHz band: 902 MHz to 928 MHz.
2.4-GHz band: 2.4GHz to 2.4835 GHz. (In Japan, it extends to 2.495 GHz.)
5.7-GHz band: 5.725 GHz to 5.825 GHz.
Wireless standards
 There are several different wireless standards in the market today
Wi-Fi certification
802.11b standard
802.11a standard
802.11g standard
 Wi-Fi Certification :This certification assures the consumer that the wireless LAN device will work with other Wi-Fi devices.
Wireless standards
WLAN Devices
 Wireless access point: handles the ingoing and outgoing traffic from and to wireless LAN users.
 acts as the gateway for wireless users to access a wired LAN
 It contains following security features :
 Built-in firewall
 Network Address Translation (NAT)
 Wired Equivalent Protection (WEP)
 Wireless Ethernet pc card : It is a slim Ethernet card that connects a notebook computer to a wireless network.
 Wireless PCI Adapter : It connects desktops to wireless network.
 Wireless USB adapter : provide high-speed wireless networking for USB-enabled desktops or notebooks
 Wireless range extenders : It is an indoor omni-directional antenna that can be attached to several of the WL products to increase signal strength.
WLAN Security
• To secure a WLAN, these steps are required:
Control and Integrity
Authentication
Privacy and Confidentiality
Intrusion Detection System (IDS)
Protection and Availability
In 802.11 networks, clients can authenticate with an AP using one of the following methods:
open authentication - No authentication method is used. Any client is offered open access to the AP.
pre-shared key (PSK) authentication - It uses a long Wireless Equivalence Protocol (WEP) key that is stored on the client and the AP. If the keys match, the client is permitted to have access.
Disadvantages
 WLAN may not be desirable due to some following limitations:
 Security - Wardrivers can easily crack into wireless network as there is no physical protection for data packets
 encryption technologies like WPA (Wi-Fi protected Access) must be used.
 Range - The typical range of a common 802.11g network with standard equipment is of the order of tens of meters.
 For extra range, additional APs required which costs high.
 Speed – the speed on most wireless network (1-54 Mbps) is reasonably slow compared to the wired networks (10Mbps- 10Gbps).