Wireless? A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier. The last link with the users is wireless, to give a network connection to all users in a building or campus. The backbone network usually uses cables

Wireless Network Components Access Points NICs – Network Interface Cards PCMCIA USB PCI CompactFlash Other Wireless Devices Bridges and Routers Print Servers PCs, Laptops, PDAs

Connecting To a Legacy Network Access Points connect the wireless network to the legacy network.

Common Topologies Complete Wireless Networks The physical size of the network is determined by the maximum reliable propagation range of the radio signals. Referred to as ad hoc networks Are self-organizing networks without any centralized control Suited for temporary situations such as meetings and conferences.

Access Point Placement and Power Typically – mounted at ceiling height. Between 15 and 25 feet (4.5m to 8m) The greater the height, the greater the difficulty to get power to the unit. Solution: consider devices that can be powered using CAT5 Ethernet cable (CISCO Aironet 1200 Series). Access points have internal or external antennas

Connecting to the Wired LAN Consider user mobility If users move between subnets, there are challenges to consider. OSes like Windows XP and 2000, Linux support DHCP to obtain the new IP address for the subnet. Certain applications such as VPN will fail. Solution: access points in a roaming area are on the same segment.

Standards IEEE b –2.4GHz – 11Mbps IEEE a – 5GHz – 54 Mbps IEEE g – 2.4Ghz – Hybrid 11/54Mbps g is in the final stages of development. The current draft (V5.0) is open for comments until January 8, 2003.

Performance a offers speeds with a theoretically maximum rate of 54Mbps in the 5 GHz band b offers speeds with a theoretically maximum rate of 11Mbps at in the 2.4 GHz spectrum band g is a new standard for data rates of up to a theoretical maximum of 54 Mbps at 2.4 GHz.

What is ? A family of wireless LAN (WLAN) specifications developed by a working group at the Institute of Electrical and Electronic Engineers (IEEE) Defines standard for WLANs using the following four technologies Frequency Hopping Spread Spectrum (FHSS) Direct Sequence Spread Spectrum (DSSS) Infrared (IR) Orthogonal Frequency Division Multiplexing (OFDM) Versions: a, b, g, e, f, i

Transmission Most wireless LAN products operate in unlicensed radio bands 2.4 GHz is most popular Available in most parts of the world No need for user licensing Most wireless LANs use spread-spectrum radio Resistant to interference, secure Two popular methods Frequency Hopping (FH) Direct Sequence (DS)

802.11g Advantages Provides higher speeds and higher capacity requirements for applications Wireless Public Access Compatible with existing b standard Leverages Worldwide spectrum availability in 2.4 GHz Likely to be less costly than 5 GHz alternatives Provides easy migration for current users of b WLANs Delivers backward support for existing b products Provides path to even higher speeds in the future

Security (Encryption, Content Filtering, Privacy, etc.) Encryption Encryption on the pubic network can be used but would create administrative overhead. Encryption keys would have to be changed regularly and anyone using their own laptop would have to be given the key. Encryption works best in a network that does not allow people to use their own laptops. Encryption increases privacy, but can be thwarted, either by software, or by gaining access to a PC configured with wireless and writing down the key.

Security (Encryption, Content Filtering, Privacy, etc.) Viruses and Hacker Wireless does not add any additional threat in the way of viruses. Anyone, anywhere can attack a network that is connected to the Internet. Wireless does not increase that chance. Security measures such as firewalls, can reduce the risk.