| Disadvantage Of Wireless Lan |
Wireless LAN technology, while replete with the conveniences and advantages
described above, has its share of downfalls. For a given networking situation,
wireless LANs may not be desirable for a number of reasons. Most of these have
to do with the inherent limitations of the technology.
- Security: Wireless LAN transceivers are designed to serve
computers throughout a structure with uninterrupted service using radio
frequencies. Because of space and cost, the antennas typically present on
wireless networking cards in the end computers are generally relatively
poor. In order to properly receive signals using such limited antennas
throughout even a modest area, the wireless LAN transceiver utilizes a
fairly considerable amount of power. What this means is that not only can
the wireless packets be intercepted by a nearby adversary's poorly-equipped
computer, but more importantly, a user willing to spend a small amount of
money on a good quality antenna can pick up packets at a remarkable
distance; perhaps hundreds of times the radius as the typical user. In fact,
there are even computer users dedicated to locating and sometimes even
cracking into wireless networks, known as wardrivers. On a wired network,
any adversary would first have to overcome the physical limitation of
tapping into the actual wires, but this is not an issue with wireless
packets. To combat this consideration, wireless networks users usually
choose to utilize various encryption technologies available such as Wi-Fi
Protected Access (WPA). Some of the older encryption methods, such as WEP
are known to have weaknesses that a dedicated adversary can compromise.
(See main article: Wireless security.)
- Range: The typical range of a common 802.11g network with
standard equipment is on the order of tens of meters. While sufficient for a
typical home, it will be insufficient in a larger structure. To obtain
additional range, repeaters or additional access points will have to be
purchased. Costs for these items can add up quickly. Other technologies are
in the development phase, however, which feature increased range, hoping to
render this disadvantage irrelevant. (See WiMAX)
- Reliability: Like any radio frequency transmission, wireless
networking signals are subject to a wide variety of interference, as well as
complex propagation effects (such as multipath, or especially in this case
Rician fading) that are beyond the control of the network administrator. In
the case of typical networks, modulation is achieved by complicated forms of
phase-shift keying (PSK) or quadrature amplitude modulation (QAM), making
interference and propagation effects all the more disturbing. As a result,
important network resources such as servers are rarely connected wirelessly.
- Speed: The speed on most wireless networks (typically 1-108 Mbit/s)
is reasonably slow compared to the slowest common wired networks (100 Mbit/s
up to several Gbit/s). There are also performance issues caused by TCP and
its built-in congestion avoidance. For most users, however, this observation
is irrelevant since the speed bottleneck is not in the wireless routing but
rather in the outside network connectivity itself. For example, the maximum
ADSL throughput (usually 8 Mbit/s or less) offered by telecommunications
companies to general-purpose customers is already far slower than the
slowest wireless network to which it is typically connected. That is to say,
in most environments, a wireless network running at its slowest speed is
still faster than the internet connection serving it in the first place.
However, in specialized environments, the throughput of a wired network
might be necessary. Newer standards such as 802.11n are addressing this
limitation and will support peak throughputs in the range of 100-200 Mbit/s.
Wireless LANs present a host of issues for network managers. Unauthorized
access points, broadcasted SSIDs, unknown stations, and spoofed MAC addresses
are just a few of the problems addressed in WLAN troubleshooting. Most network
analysis vendors, such as Network Instruments, Network General, and Fluke, offer
WLAN troubleshooting tools or functionalities as part of their product line.
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