The simplest wireless network consists of two or more PCs communicating
directly with each other sans cabling or any other intermediary hardware.
More complicated wireless networks use a WAP to centralize wireless
communication and bridge wireless network segments to wired network
segments. These two different methods are called ad-hoc mode and infrastructure
wireless NIC wireless access point
Ad-Hoc mode is sometimes called peer to peer mode, which each wireless
node in direct contact with
each other node in a decentralized free for all. This is suited for
wireless networks use in small groups
Ad Hoc Mode
Wireless networks running in infrastructure mode use one or more WAPs
to connect the wireless network nodes to a wired network segment,
as shown above. A single WAP servicing a given area is called a Basic
Service Set (BSS). This service area can be extended by adding more
WAPs. This is called, appropriately, an Extended basic Service Set
Wireless networks running in infrastructure mode require more planning
and are more complicated to configure than ad-hoc mode networks, but
they also give you finer control over how the networks operates. Infrastructure
mode is better suited to business networks or networks that need to
share dedicated resources like Internet connections and centralized
databases. If you plan setting up a wireless network for a large number
of PCs, or need to have centralized control over the wireless network,
then infrastructure mode is what you need.
One of the major complaints against wireless networking is that it
offers weak security. In many cases, the only thing you need to do
to access a wireless network is walk into a WAP’s coverage area
and turn on your wireless device! Further, data packets are floating
through the air instead of safely wrapped up inside network cabling.
What’s to stop an unscrupulous PC tech with the right equipment
from grabbing those packets out of the air and reading that data himself?
Wireless networks use three methods to secure access to the network
itself and secure the data that’s’ being transferred.
The SSID (network name) parameter ensures that only wireless network
devices configured with the same SSID are permitted access to the
network. You can tighten security even further by employing MAC filtering,
a way of creating a list of machines that are permitted to access
the network. Enabling wireless encryption through either Wireless
Equivalency Privacy (WEP) or Wi-Fi Protected Access (WPA) ensures
that the data packets themselves are secure while in transit
Wireless Networking Security (War Chalking, War Driving and Hot Spots)
Wireless Antennas (Omni Directional vs. Yagi Directional Antennas)
Wireless Channels (mostly use 1, 6 and 11) Beacon advertise wireless presence
The service set identification (SSID), sometimes called a network
name, is a 32bit identification string that's inserted into the header
of each data packet processed by a wireless access point. This provides
the basic unit of wireless security.
MAC filtering, a method that enables you to limit access
to your wireless network based on the physical, hard wired addresses
of the wireless network adapters you support
Wireless Equivalency Privacy (WEP) uses a 64bit-128bit encryption
algorithm to scramble data packets as sent in a wireless transmission
WPA addresses the weaknesses of WEP, and acts as a sort of security
protocol upgrade to WEP-enabled devices. WPA offers security enhancement
such as an encryption key integrity-checking feature and user authentication
through the industry-standard Extensible Authentication Protocol (EAP).
The use of EAP is a huge security improvement over WEP’s MAC
address authentication scheme. After all, MAC addresses are fairly
easy to “sniff” out, since they’re transmitted in
unencrypted, clear-text format. User names and passwords are encrypted,
and therefore much more secure.
Even with these enhancements, WPA is only intended as an interim security
solution until the IEEE 802.11i security standard is finalized and
To gain better understanding of wireless network technology, let’s
take a brief look at the standards they use.
802.11-Based Wireless Networking
The IEEE 802.11 wireless Ethernet standard defines methods by which
devices may communicate using spread-spectrum radio waves. Spread-spectrum
broadcast data in small, discrete chunks over different frequencies
available within a certain frequency range. All of the 802.11-based
wireless technologies broadcast and receive at 2.4 GHz (with the exception
of 802.11a, which uses 5 GHz). The original 802.11 standard has been
extended to 802.11a, 802.11b, and 802.11g variations used in Wi-Fi
wireless networks, and also hybridized (combined with another wireless
communication technology) to form the Shared Wireless Access Protocol
(SWAP) used in Home RF networks.
The 802.11 standard defines two different spread-spectrum broadcasting
methods, direct-sequence spread-spectrum (DSSS) and frequency-hopping
spread-spectrum (FHSS). DSSS sends data out on different
frequencies at the same time, while FHSS sends data on one frequency
at a time, constantly shifting (or hopping) frequencies. DSSS uses
considerably more bandwidth than FHSS, around 22 MHz as opposed to
1 MHz. DSSS is capable of greater data throughput, but DSSS is also
more prone to interference than FHSS. Home RF wireless networks are
the only type that uses FHSS; all of the other 802.11-based wireless
networking standards use DSSS The newest spread spectrum broadcast today is OFDM Orthogonal Frequency Division Multiplexing.
Devices that use the original 802.11 (with no letter) standard are
a rarity these days. You’re most likely to find them in service
on some brave early adopter’s network.
The original 802.11 standard was hampered by both slow speeds (2 Mbps
maximum) and limited range (about 150 feet). However, 802.11 employed
some of the same features that are in use in the current wireless
standards. 802.11 uses the same 2.4 GHz broadcast range, and security
is provided by the use of industry-standard WEP and WAP encryption.
Despite the “a” designation for this extension to the
802.11 standard, 802.11a was actually developed after 802.11b. 802.11a
differs from the other 802.11-based standards in significant ways.
Foremost is that it operates in a different frequency range, 5 GHz.
This means that devices that use this standard are less prone to interference
from other devices that use the same frequency range. 802.11a also
offers considerably greater throughput than 802.11 and 802.11b at
speeds up to 54 Mbps, though its actual throughput is no more than
25 Mbps in normal traffic conditions. While it’s theoretical
range tops out at about 150 feet, in a typical office environment,
its maximum range will be slower. Despite the superior speed of 802.11a,
it it is not’t widely adopted in the PC world.
802.11b is practically ubiquitous in wireless networking. The 802.11b
standards supports data throughput up to 11 Mbps (with actual throughput
averaging 4 to 6 Mbps)-on par with older wired 10BaseT networks- and
a maximum range of 300 feet under ideal conditions. In a typical office
environment, its maximum range will be lower.
802.11b networks can be secured through the use of WEP and WPA encryption.
The main downsize to using 802.11b is, in fact, that it’s most
widely used standard. The 2.4 GHz frequency is already a crowded place,
so you’re likely to run into interference from other wireless
The latest-and-greatest version of 802.11g offers data transfer speeds
equivalent to 802.11a, up to 54 Mbps, with the wider 300-foot range
of 802.11b. More importantly, 802.11g is backwards-compatible with
802.11b, meaning that the same 802.11g WAP can service both 802.11b
and 802.11g wireless nodes.
||54 up to (108)Mbps
||100 up to (600)Mbps
filtering, WEP, WPA (TKIP) WPA2 (AES)
or Infrastructure Mode
(MIMO) Multiple Input/Multiple Output (Found on some wireless networks
Wireless networking using infrared technology is largely overlooked
these days, probably due to explosion of interest in the newer and
faster wireless standards. This is a shame, because infrared provides
an easy way to transfer data, often without the need to purchase or
install any additional hardware or software on your PCs.
Infrared Data Association Standard
Communication through infrared devices is enabled via the Infrared
Data Association (IrDA) protocol. The IrDA protocol stack is widely
supported industry standard, and has been included in all versions
of Windows since Windows 95.
range wise, infrared isn’t very impressive. Infrared devices
are capable of transferring data up to 4 Mbps. Not
too shabby, but hardly stellar. The maximum distance between
infrared devices is 1 meter.
Infrared links are direct line-of-sight, and are susceptible to interference.
Infrared devices operate at half-duplex, meaning that while one is
talking, the other is listening-they can’t talk and listen at
the same time. IrDA has a mode that emulates full-duplex communication,
but it’s really half-duplex.
Security-wise, the IrDA protocol offers exactly nothing in the way
of encryption or authentication. Infrared’s main security feature
is the fact that you have to be literally within arm’s reach
to establish a link.
Clearly, infrared is not the best solution for a dedicated network
connection, but for a quick file transfer or print job without getting
your hands dirty, it’ll do in a pinch.
is best suited for quick, small transfers, such as transferring
files from one PDA to another PDA and sending print jobs to
an Infrared capable printer
Bluetooth wireless technology (named for 9th century Danish king Harald
Bluetooth) is designed to create small wireless Personal Area Networks
(PANs) that link PCs to peripheral devices such as PDAs and printers,
scanners, web cams, input devices like keyboards, joystick and mice,
and even consumer electronics like cell phones, head sets, home stereos,
televisions, home security systems, and so on.
Bluetooth Operation Modes
Scheme in which one master device can control up to seven active slave
devices go to four stages to find each other and start talking.
Discovery Service – Broadcast it’s MAC
address as well as what type of device it is
Name Discovery – Device identifies itself by
a friendly name such as Motorola headsets
Association – Bonding, Pairing or Joining the
device officially joins your Bluetooth network
Service Discovery – Device tells what kind
of service or profile it provides
is not designed to be a full-function networking solution, nor is
it meant to compete with either Wi-Fi or HomeRF. If anything, Bluetooth
is poised to replace infrared as a means to connect PCs to peripherals.
The IEEE organization has made Bluetooth the basis for its forthcoming
802.15 standard for wireless PANs. Bluetooth uses the FHSS spread-spectrum
broadcasting method, switching between any of the 79 frequencies available
in the 2.45 GHz range. Bluetooth hops frequencies some 1,600 times
per second, making it highly resistant to interference. Some high-powered
Bluetooth devices have throughput speed of a whopping 2 Mbps and a
maximum range of up to 300 feet, but these are uncommon.
and Slave (up to 7 devices)
with peripheral devices
special thanks to linksys, belkin, dlink,
microsoft, jabra, motorola