1
Randall Hall Hall
Michael A. Bond
CS 365 Networks / Data Communication
March 3, 2004
A Detailed Look at Wireless Computing
Imagine being an insurance claims adjustor who could take
pictures, file a report and submit a claim all at the scene of a
clients traffic accident. Imagine being a doctor or nurse with
the ability to view a patients chart, order medications, view
lab results, and submit a discharge request right at the
patients bedside. What if you were a sports fanatic stuck on a
long subway commute during your favorite teams championship
playoff game and could see real-time scores, statistics, playby-play coverage and even live video footage during the long
ride home. Does it all sound like something from a Sci-fi movie?
Well, believe it or not, this is not the future; its right now,
and right here. Wireless computing is a reality.
Unless you have been living under a rock for the last
several years youve heard of wireless computing, and most
likely used it whether you realize it or not. Wireless
technology has been around for years in taxi cab systems,
delivery and service trucks, and even in several electronic
components right in your very own home. But that type of
wireless technology is little more than inventory tracking,
vehicle location, and opening garage doors and changing TV
Hall 2
channels. It is not nearly as exciting as the earlier mentioned
useful and entertaining capabilities of wireless technology, is
it? The main differences between the wireless technology of
yesterday and the cutting-edge technology of today are speed,
range, bandwidth, and availability. Wireless technology today is
more than just a wireless connection; its high-speed, highbandwidth wireless computing. Entire networks and new devices
have been put in place to more fully take advantage of the
incredible technology that is wireless computing.
In order to gain a better understanding of what wireless
computing really is you need to familiarize yourself with
existing infrastructure, devices, capabilities and limitations.
Wireless networks are the backbone of wireless computing.
Wireless devices connect to these networks using recentlydeveloped and enhanced wireless protocols. Wireless security
features help safeguard information as it travels through the
air between client devices and network hardware. Wireless
devices, security components and the network infrastructure
itself together make up todays wireless computing.
Wireless networks are very similar to traditional wired
networks; in fact wired networks play a big part in wireless
computing. They form a major piece of what are called wireless
Local Area Networks, or wLANs. A wLAN is a type of local-area
network that uses high-frequency radio waves rather than wires
to communicate between nodes. (Webopedia. Online word
definition: wLAN) wLANs transmit and receive information through
the air using radio frequency (RF). The existing wired network
Hall 3
is used up to the point at which data transmission is required
to take place in the air. This point is referred to as the
access point, or AP. The AP is a physical piece of hardware
which handles the transmission and reception of wireless data.
Signals are sent from a networks access point to network
interface cards (NIC) on users devices. Both the access point
and the network interface cards act as receivers and
transmitters. Typically the AP and the NIC are attached to or
are embedded with some type of antenna to increase signal range.
The KnowledgeShare section of Vicomsoft.coms wireless
networking information website explains more about wireless
network access points and their range:
Typical indoor ranges are 150-300 feet, but can be
shorter if the building construction interferes with
radio transmissions. Longer ranges are possible, but
performance will degrade with distance. Outdoor ranges
are quoted up to 1000 feet, but again this depends
upon the environment. There are ways to extend the
basic operating range of Wireless communications, by
using more than a single access point or using a
wireless relay /extension point. (Vicomsoft. Online
Article)
Long range wireless access points and signal boosters are
becoming more readily available to the general public to enhance
the reach of a wireless network. The most common solution to
making the wLAN connection more widely available across the
distance of a site is installing multiple access points. The
Hall 4
reach of one access points signal can overlap a neighboring
access points signal without fear of loss of connection,
interference or collision. Device hardware such as NICs are such
that they will automatically switch from access point to access
point as needed, always seeking the strongest signal.
The AP translates wired network traffic into RF signals
typically by way of one of three RF data transmission standards
defined by the Institute of Electrical and Electronic Engineers
(IEEE) referred to as 802.11b, 802.11a and 802.11g. Each of
these three standards operates at a different frequencies and
offer different speeds and range. A white paper produced by
Citrix Systems, Inc. explains the primary differences between
the three IEEE standards:
802.11b is the currently most widely used standard for
wLAN. It has a maximum throughput of 11Mbps but actual
throughput depends on the signal strength and quality,
so often users only see 1 or 2Mbps.
802.11a is a newer standard that is gaining popularity
due to its increased maximum throughput of 54Mbps, but
high cost and reduced range are currently limiting
this technologys appeal. It also suffers reduced
throughput as the signal strength and quality reduces.
802.11g is an imminent standard extending the
capabilities currently offered by 802.11b while
remaining backward-compatible in respects such as
frequency usage and maximum coverage distance from the
AP.(Citrix 2)
Hall 5
The following comparison chart also helps illustrate the
pros and cons of each of the three standards:
(Linksys. Online Image)
The decision of which standard to implement tends to be a
compromise between speed, compatibility, and cost.
With the increased public availability and popularity of
wireless computing security has become an issue. Considering the
Hall 6
fact that high security entities such as the US Government, the
US Military, and law enforcement agencies clearly benefit from
wireless computing technologies and have employed its use for
years, a high encryption security standard had to be developed.
Lower-level security needed for schools, hospitals and
businesses has also become apparent. One of the security
solutions that were first put in place was Wired Equivalent
Privacy (WEP).
WEP - A security protocol for wireless local area
networks (WLANs) defined in the 802.11b standard. WEP
is designed to provide the same level of security as
that of a wired LAN. LANs are inherently more secure
than WLANs because LANs are somewhat protected by the
physicalities of their structure, having some or all
part of the network inside a building that can be
protected from unauthorized access. WLANs, which are
over radio waves, do not have the same physical
structure and therefore are more vulnerable to
tampering. WEP aims to provide security by encrypting
data over radio waves so that it is protected as it is
transmitted from one end point to another. However, it
has been found that WEP is not as secure as once
believed. WEP is used at the two lowest layers of the
OSI model - the data and link physical layers; it
therefore does not offer end-to-end security.
(Webopedia. Online word definition: WEP)
Hall 7
Although WEP provides a good level of security it still has
its flaws. Researchers at UC Berkley have shown that WEP has
several weaknesses. Thus, a replacement has been developed named
Wi-Fi Protected Access (WPA) (Comer 619) WPA, it seems, is also
exploitable, yet less so than WEP. Some industry experts believe
wLANs will never be as secure as wired LANs and therefore should
not be implemented in any environment where data security is
critical. Such is the opinion of Lisa Phifer, author of
Wireless Privacy: An Oxymoron? an article on Wi-FiPlanet.com:
802.11b wireless LANs can be easier to deploy and less
expensive than traditional wired networks, but they
are also inherently less secure. Service providers
considering 802.11b for public access broadband or
fixed wireless Internet access should appreciate the
risks associated with this emerging technology.
Ethernet NICs broadcast packets over a physical medium
coaxial cable, unshielded twisted pair, fiber.
Wireless NICs broadcast spread-spectrum radio signals
over the air. Both are vulnerable to unauthorized use
and eavesdropping, but there's an important
difference. Wireless LANs can be tapped passively,
without physical access or sophisticated equipment.
All an attacker needs is an inexpensive wireless NIC
and a tiny bit of know-how.
[] The default method, Open System Authentication,
actually provides no authentication at all. In Open
Hall 8
System Authentication, any station is permitted to
join [the wLAN].
If the station proposes Shared Key Authentication, the
AP generates a random 128-bit challenge. The station
returns the challenge, encrypted with a shared keya
"secret" configured into both the station and AP. The
AP decrypts the challenge, using a CRC to verify its
integrity. If the decrypted frame matches the original
challenge, the station is considered authentic. The
challenge/response handshake is repeated in the
opposite direction for mutual authentication.
Unfortunately, an attacker who captures these frames
possesses the plaintext, ciphertext, and the
initialization vector (IV) used to turn the plaintext
into ciphertext. Because WEP uses RC4 encryption, this
is enough information to derive the RC4 keystreamthe
stream of bits XORed with plaintext to generate
ciphertext. Knowing a legitimate IV and keystream lets
the attacker successfully respond to any future
challenge, without knowing the actual shared key. The
attacker has a free pass to join the wireless LAN.
[] Authentication must be combined with access
control measures that permit or deny traffic from a
particular station. To be effective, access control
must be based on a value that is not easily spoofed.
Some access points can be programmed with a MAC
address Access Control List that permits a specific
Hall 9
group of stations and blocks unauthorized stations
from associating with the AP. Unfortunately, MAC
addresses are easy to sniff because they are
transmitted in plaintext. All an attacker needs to
masquerade, as a legitimate station is a wireless NIC
operating in promiscuous mode for capture, with a
configurable address to enable spoofing.
Some stations can be programmed with an SSID they must
present in order to associate with an access point.
Unfortunately, because SSID is broadcast in plaintext
in many 802.11b frames, it also easy to sniff and
spoof.
Another technique is to combine station-level
authentication with user-level authentication for
tighter access control. In this case, the station user
actually logs into the wireless network by supplying a
username/password that the AP can check against a
RADIUS serversimilar to traditional Internet access.
Effectiveness depends upon the authentication method
used and whether it requires confidentiality. (Phifer
Wireless Privacy: An Oxymoron?)
Security mechanisms will continue to improve. Speeds and
bandwidth will increase. More and more devices will be created
for the sole purpose of being implemented as a component of a
Hall 10
wireless network. Wireless computing will become more prevalent
and more proliferate as new technologies are developed.
What does the future hold for wireless computing? Are there
more than business uses of wireless network technologies? How
much can it change everyday life for you in your own home? Will
wireless networks overtake wired networks completely? Some of
these questions are hard to answer. Others might come to pass
sooner than you would expect. An article by Jonathan D. Salant
in the San Francisco Chronicle states that [FCC] Regulators
said Thursday they would help bring high-speed Internet
connections to rural areas by expanding the spectrum of
frequencies for wireless devices that do not require modems and
phone jacks. (March 4, 2004) It seems that some consumers are
skeptical. However, it may soon be that wireless internet
service providers (wISP) will offer wireless connections to
rural residential customers. There may be red tape to cut
through as the same article indicates but the potential for such
a service realistically exists:
[] The Federal Communications Commission said the
action would mean an 80 percent boost in the amount of
spectrum that these wireless networks could use to
connect computers and other electronic devices to the
Internet.
Hall 11
"Wireless broadband is increasingly a reality in the
marketplace," FCC Chairman Michael Powell said.
The Media Access Project said the new frequencies are
not powerful enough to handle long-range broadband
connections through lightly populated rural areas.
Harold Feld, associate director of the watchdog group,
said the frequencies instead will be used by "Wi-Fi"
providers, which allow users in a small area to access
the Internet with wireless connections.
"This works great for short-range, low-power Wi-Fi
connections that don't need to go through walls or
trees," said Feld, calling on the government instead
to open up lower frequency bands for wireless
providers. (San Francisco Chronicle March 4, 2004)
History dictates that the envelope will continually be
pushed. Limitations will be exceeded and overcome. Who knows
what the future will bring. Whatever it is, it appears that
wireless computing will play a major part in it.
Hall 12
Works Cited
Comer, Douglas E. Computer Networks and Internets with Internet
Applications. Upper Saddle River: Pearson Prentice Hall,
2004.
Linksys. "Wireless Technology Comparison Chart" No date. Online
image. Wireless Standards. 3 May 2003.
< http://www.linksys.com/edu/wirelessstandards.asp>
Phifer, Lisa. Wireless Privacy: An Oxymoron? Wi-Fi Planet
April 26, 2001
<http://www.wifiplanet.com/columns/article.php/1781_786641_1>
Salant, Jonathan D. FCC expands frequencies for wireless
Internet. San Francisco Chronicle March 4, 2004
"The CIOs Guide to Mobile Wireless Computing." Citrix Systems,
Inc. September 2002: 2.
Vicomsoft. Wireless Networking Q&A No Date. Online White
Paper. Vicomsoft. 3 May 2003.
Hall 13
<http://www.vicomsoft.com/knowledge/reference/wireless1.htm
l#3>
Webopedia. Online Word Definition: wLAN No Date. Online
Article. Webopedia. 3 May 2003.
<http://www.webopedia.com/TERM/W/WLAN.html>
Webopedia. Online Word Definition: WEP No Date. Online
Article. Webopedia. 3 May 2003.
< http://www.webopedia.com/TERM/W/WEP.html>