Specifications

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an Access Point to bridge the wireless network to the LAN. Depending on the type of building a single site
may need more then one Access Point.
HomeRF is an Intel led initiative to standardize on a low cost RF solution for home use. Data rate is
1.6mbps. The initial target is a wireless phone with data capability.
BlueTooth is addressing short-range (<10meters) personal area network (PAN) market. The goal is to link
multiple personal portable devices together. A higher power version extends the range to 100meters.
BlueTooth operates at a raw data rate of 1Mbp/s. Typical BlueTooth usage allows a PC, cell phone, and,
Palm Pilot to exchange data. BlueTooth devices form a piconet to communicate amount a small group of
devices. Piconets in turn can form scatternets to cover a longer distance. Deployment of BlueTooth has
been delayed due to technical issues. The first devices are just now reaching the market.
7.2.2.1 Wireless Security
Radio based communication is relatively easy to eavesdrop. This threat was recognized so wirelesses LANs
provide encryption to maintain privacy. This is especially important in a LAN because an attacker is able to
not only eavesdrop but may be able to modify and corrupt computer files. Security researchers have
discovered significant shortcomings to Wireless Equivalent Protocols (WEP) used in 802.11 and similar to
that used in BlueTooth. This weakness makes it relatively easy to break wireless encryption if significant
traffic exists. The IEEE recently created a revised version of WEP that improves security.
7.3 TCP/IP
The LAN uses the Internet Protocol (IP) to connect local devices. Using the same communication protocol
for both LAN and Internet simplifies configuration and management. IP is the mechanism used to deliver a
packet of data from one computer to another.
TCP stands for Transmission Control Protocol. IP is an unreliable delivery mechanism it launches packets
to the Internet; they may arrive out of order and not at all. TCP orders the incoming packets and requests
retransmission of any that are missing. When an application creates a TCP/IP connection the receiver sees
the same data stream that was transmitted.
A simpler mechanism, UDP/IP User Datagram Protocol, is used when end-to-end synchronization is not
required. UDP is a connectionless protocol. The transmitting station simply casts the packets out to the
Internet. Each packet is dealt with individually. UDP is often used with multimedia. If a packet is lost it
cannot be retransmitted in time so the receiver has to fake the missing information.
ICMP Internet Control Message Control Protocol handles control function such as PING. PING verifies a
remote host is reachable and how long it takes.
7.4 IP Address
Each IP device (host) must have an address. Addresses can be assigned, statically, automatically by DHCP
(Dynamic Host Control Protocol) or automatically by the client itself, AutoIP. Traditionally the system
administrator manually configured each device with a static address. This was labor intensive and error
prone. DHCP simplified the task by centralizing address assignment. The down side is a DHCP server is
required to allocate addresses. Recently the DHCP protocol has been extended to allow automatic
configuration if the host cannot find a DHCP server. In that case the device assigns itself an address after
failing to find a DHCP server and automatically determining the address is not in use. AutoIP is convenient
for small LANs that use IP and do not have access to a DHCP server. This occurs most commonly when
two PC’s are directly connected. Most Internet sharing packages and hardware access devices implement a
DHCP server.