By Markus Kriechhammer Wireless LAN By Markus Kriechhammer

Wireless LAN - Overview What is a wireless LAN (WLAN) Devices The most important standards Security issues Advantages / Disadvantages

What ist WLAN Wireless local area network Ethernet-Frame are transmitted via „air“ Network-protocols can be TCP/IP, IPX/SPX and Apple Talk

Devices

The most important Standards IEEE 802.11b up to 11 Mbps, 2,4 GHz unlicensed, frequency shared IEEE 802.11a up to 54 Mbps, 5 GHz unlicensed, only in US IEEE 802.11g up to 54 Mbps, 2,4 GHz unlicensed, fs, compatible with 802.11b IEEE 802.11i extending wireless security features

Basic technology concepts Frequency band 2.4GHz 5GHz Max data rate 11Mbps 54Mbps availability Worldwide US Interference sources Cordless phone Microwave oven Bluetooth Hiperlan devices

Basic technology concepts @100Mw 802.11a @40Mw 802.11g 50 ft 11Mbps 54Mbps 100 ft 36Mbps 125 ft 12Mbps 150 ft 5.5Mbps 6Mbps 250 ft 2Mbps ? 350 ft 1Mbps

WLAN Modes (802.11b) Ad Hoc is the term used to explain when a user is connecting to another 802.11b device directly without an access point. The user must decide what IP address and subnet to communicate. Infrastructure is the term used to explain when a user is connecting to the wireless LAN using an Access Point. The Access Point or another network device can provide services like DHCP and NAT

Security issues All the normal Internet issues and more Open WLANs are everywhere Vendor defaults are usually open Many types of attacks Attackers can be miles away

Common WLAN Security Needs Private – Homes Information Security Companies Access Monitoring Accounting Firewall

Solving the security problems Solve the problem at the application layer with encryption (e.g. ssh, ssl) and/or better authentication/authorization (e.g. Kerberos, secur-id) Solve the problem at the network level through link encryption (WEP, EAP) or VPN (IPSEC)

Example VPN Configuration

Advantages Disadvantages Mobility Cost advantages Easy to install Easy to integrate into existing networks Weak native encryption Default settings of manufacturers Easy to „hack“ Configuration (vendor – depending)

References www.howstuffworks.com www.cisco.com www.wireless-lans.de

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