Wireless FAQ
General FAQ
Advanced FAQ
Security FAQ
Basic FAQ
1.
What is a Wireless LAN ?
Wireless LANs provide all the
functionality of wired LANs, without the need for physical connections (wires).
Data is modulated onto a radio frequency carrier and transmitted through the
ether. Typical bit-rates are 11Mbps and 54Mbps, although in practice data
throughput is half of this. Wireless LANs can be formed simply by
equipping PC's with wireless NICs. If connectivity to a wired LAN is
required an Access Point (AP) is used as a bridging device. AP's are typically
located close to the centre of the wireless client population.
b. Installation Speed and
Simplicity:
Installing a wireless LAN
system can be fast and easy and can eliminate the need to pull cable through
walls and ceilings.
c. Installation
Flexibility:
Wireless technology allows
the network to go where wire cannot go.
d. Reduced
Cost-of-Ownership:
While the initial investment
required for wireless LAN hardware can be higher than the cost of wired LAN
hardware, overall installation expenses and life-cycle costs can be
significantly lower. Long-term cost benefits are greatest in dynamic
environments requiring frequent moves and changes.
3.
What
are the disadvantages of Wireless LANs ?
The speed of
Wireless LAN is still relative slower than wired LAN. The most popular wired LAN
is operated in 100Mbps, which is almost 10 times of that of Wireless LAN
(10Mbps). A faster wired LAN standard (1000Mbps), which is 100 times faster,
becomes popular as well. The setup cost of Wireless LAN is relative high because
the equipment cost including access point and PCMCIA Wireless LAN card is higher
than hubs and CAT 5 cables.
4.
Where
can you find wireless 802.11 networks ?
Airports,
hotels, and even coffee shops like Starbucks are deploying 802.11 networks so
people can wirelessly browse the Internet with their laptops. As these types of
networks increase, this will create additional security risk for the remote user
if not properly protected.
5.
What
is an Access Point ?
The
AP (access point also known as a base station) is the wireless server that with
an antenna and a wired Ethernet connection that broadcasts information using
radio signals. AP typically act as
a bridge for the clients. It can pass information to wireless LAN cards that
have been installed in computers or laptops allowing those computers to connect
to the campus network and the Internet without wires.
6.
What is IEEE 802.11 ?
The
IEEE 802.11 is a wireless LAN industry standard, and the objective of IEEE
802.11 is to make sure that different manufactures' wireless LAN devices can
communicate to each other.802.11
provides 1 or 2 Mbps transmission in the 2.4 GHz ISM band using either FHSS or
DSSS.
7.
What is 802.11b ?
802.11b
is the first revision of 802.11 standard allowing data rates up to 11Mbps
in the 2.4GHz ISM band. Also known as 802.11 High-Rate and Wi-Fi. 802.11b only
uses DSSS, the maximum speed of 11Mbps has fallbacks to 5.5, 2 and
1Mbps.
8.
How
fast is 802.11b ?
The
IEEE 802.11b standard has a nominal speed of 11 megabits per second (Mbps).
However, depending on signal quality and how many other people are using the
wireless ethernet through a particular Access Point, usable speed will be much
less (on the order of 4 or 5 Mbps, which is still substantially faster than most
dialup, cable and DSL modems).
10.
What is 802.11g ?
802.11g
is an extension to 802.11b. 802.11g increases 802.11b's data rates to 54 Mbps
and still utilize the the 2.4 GHz ISM. Modulation is based upon OFDM
(orthogonal frequency division multiplexing) technology. An 802.11b radio card
will interface directly with an 802.11g access point (and vice versa) at 11 Mbps
or lower depending on range. The range at 54 Mbps is less than for 802.11b
operating at 11 Mbps.
11.
Is
it possible to use products from a variety of vendors
?
Yes.
As long as the products comply to the same IEEE 802.11 standard. The Wi-Fi logo
is used to define 802.11b compatible products. Wi-Fi5 is a compatibility
standard for 802.11a products running in the 5GHz band.
12.
What
is Wi-Fi ?
The
Wi-Fi logo signifies that a product is interoperable with wireless networking
equipment from other vendors. A Wi-Fi logo product has been tested and certified
by the Wireless Ethernet Compatibility Alliance (WECA). The Socket Wireless LAN
Card is Wi-Fi certified, and that means that it will work (interoperate) with
any brand of Access Point that is also Wi-Fi certified.
14. Does the 802.11 interfere with Bluetooth devices
?
Any time devices are operated in the same frequency band, there is the potential for interference.
Both the 802.11b and
Bluetooth devices occupy the same2.4-to-2.483-GHz unlicensed frequency range-the
same band. But a Bluetooth device would not interfere with other 802.11 devices
much more than another 802.11 device would interefere. While more collisions are
possible with the introduction of a Bluetooth device, they are also possible
with the introduction of another 802.11 device, or a new 2.4 GHz cordless phone
for that matter. But, BlueTooth devices are usually low-power, so the effects
that a Bluetooth device may have on an 802.11 network, if any, aren't
far-reaching.
15.
Can radio signals pass through walls ?
Transmitting
through a wall is possible depending upon the material used in its construction.
In general, metals and substances with a high water content do not allow radio
waves to pass through. Metals reflect radio waves and concrete attenuates radio
waves. The amount of attenuation suffered in passing through concrete will be a
function of its thickness and amount of metal re-enforcement used.
16.
What
are potential factors that may causes interference among WLAN products ?
Factors
of interference:
1. Obstacles: walls, ceilings, furniture… etc.
2.
Building Materials: metal door, aluminum studs.
3. Electrical devices:
microwaves, monitors, electric motors.
Solution :
1.Minimizing the
number of walls and ceilings
2.Antenna is positioned for best
reception
3.Keep WLAN products away from electrical devices, eg: microwaves,
monitors, electric motors,…, etc.
4. Add additional APs if necessary.
17.
What's
the difference between a WLAN and a WWAN ?
WLANs
are generally privately owned, wireless systems that are deployed in a
corporation, warehouse, hospital, or educational campus setting. Data rates are
high and there are no per-packet charges for data transmission.
WWANs are
generally publicly shared data networks designed to provide coverage in
metropolitan areas and along traffic corridors. WWANs are owned by a service
provider or carrier. Data rates are low and charges are based on usage.
Specialized applications are characteristically designed around short, burst
messaging.
Advanced FAQ
1. What is Ad Hoc mode ?
A wireless network consists of a number of stations without access points. Without using an access point or any connection to a wired network.
2.
What is Infrastructure mode
?
Infrastructure mode implies connectivity to a wired communications infrastructure. If such connectivity is required the Access Points must be used to connected to the wired LAN backbone. Wireless clients have their configurations set for "infrastructure mode" in order to
utilize access points relaying.
3.
How many Access Points are required in a given area ?
This depends on the surrounding terrain, the diameter of the client population, and the number of clients. If an area is large with dispersed pockets of populations then extension points can be used for extend
coverage.
4. What is Direct-Sequence Spread Spectrum Technology – (DSSS) ?
DSSS spreads its signal continuously over a wide frequency band. DSSS maps the information bearing bit-pattern at the sending station into a higher data rate bit sequence using a "chipping" code. The chipping code (also known as processing gain) introduces redundancy which allows data recovery if certain bit errors occur during transmission. The FCC rules the minimum processing gain should be 10, typical systems use processing gains of 20. IEEE 802.11b specifies the use of
DSSS.
5.
What is Frequency-hopping Spread Spectrum Technology – (FHSS) ?
FHSS uses a narrowband carrier which hops through a predefined sequence of several frequencies at a specific rate. This avoids problems with fixed channel narrowband noise and simple jamming. Both transmitter and receiver must have their hopping sequences synchronized to create the effect of a single "logical channel". To an unsynchronised receivers an FHSS transmission appears to be short-duration impulse noise. 802.11 may use FHSS or
DSSS.
6. Do I need the same kind of antenna on both sides of a link ?
No. Provided the antenna is optimally designed for 2.4GHz or 5GHz operation. WLAN NICs often include an internal antenna which may provide sufficient reception.
7. Why the 2.4 Ghz Frequency range ?
This frequency range has been set aside by the FCC, and is generally labeled the ISM band. A few years ago Apple and several other large corporations requested that the FCC allow the development of wireless networks within this frequency range. What we have today is a protocol and system that allows for unlicensed use of radios within a prescribed power level. The ISM band is populated by Industrial, Scientific and Medical devices that are all low power devices, but can interfere with each
other.
8. What is Server Set ID (SSID) ?
SSID is a configurable identification that allows clients to communicate to the appropriate base station. With proper configuration, only clients that are configured with the same SSID can communicate with base stations having the same SSID. SSID from a security point of view acts as a simple single shared password between base stations and clients.
9. What is an ESSID ?
ESSID stands for Extended Service Set Identifier and identifies the wireless LAN. The ESSID of the mobile device must match the ESSID of the AP to communicate with the AP. The ESSID is a 32-character maximum string and is case-sensitive.
Security FAQ
1.
How do I secure the data across an Access Point's radio link ?
Enable Wired Equivalency Protocol (WEP) to encrypt the payload of packets sent across a radio link.
2. What is WEP ?
Wired Equivalent Privacy. WEP is a security mechanism defined within the 802.11 standard and designed to make the security of the wireless medium equal to that of a cable (wire). WEP data encryption was designed to prevent access to the network by "intruders" and to prevent the capture of wireless LAN traffic through eavesdropping. WEP allows the administrator to define a set of respective "Keys" for each wireless network user based on a "Key String" passed through the WEP encryption algorithm. Access is denied by anyone who does not have an assigned key. WEP comes in 40/64-bit and 128-bit encryption key lengths. Note, WEP has shown to have fundamental flaws in its key generation
processing.
3. What is the difference between 40-bit and 64-bit WEP
?
40 bit WEP & 64 bit WEP are the same encryption level and can interoperate. The lower level of WEP encryption uses a 40 bit (10 Hex character) as "secret key" (set by user), and a 24 bit " Initialization Vector " (not under user control) (40+24=64). Some vendors refer to this level of WEP as 40 bit, others as 64
bit.
4. What is a WEP key
?
A WEP key is a user defined string of characters used to encrypt and decrypt
data.
5. A WEP key is a user defined string of characters used to encrypt and decrypt data
?
No. 128-bit WEP will not communicate with 64-bit WEP. Although 128 bit WEP also uses a 24 bit Initialization Vector, but it uses a 104 bit as secret key. Users need to use the same encryption level in order to make a connection.
6. Can the SSID be encrypted ?
WEP, the encryption standard for 802.11, only encrypts the data packets not the 802.11 management packets and the SSID is in the beacon and probe management messages. The SSID is not encrypted if WEP is turned on. The SSID goes over the air in clear text. This makes obtaining the SSID easy by sniffing 802.11 wireless
traffic.
7. By turning off the broadcast of SSID, can someone still sniff the SSID
?
Many APs by default have broadcasting the SSID turned on. Sniffers typically will find the SSID in the broadcast beacon packets. Turning off the broadcast of SSID in the beacon message (a common practice) does not prevent getting the SSID; since the SSID is sent in the clear in the probe message when a client associates to an AP, a sniffer just has to wait for a valid user to associate to the network to see the SSID.
8. What are Insertion Attacks ?
The insertion attacks are based on placing unauthorized devices on the wireless network without going through a security process and
review.
9. What is Wireless Sniffer ?
An attacker can sniff and capture legitimate traffic. Many of the sniffer tools for Ethernet are based on capturing the first part of the connection session, where the data would typically include the username and password. An intruder can masquerade as that user by using this captured information. An intruder who monitors the wireless network can apply this same attack principle on the
wireless.
10. What is the difference between Open System and Shared Key of
Authentication Type ?
Open System:
The default authentication
service that simply announces the desire to associate with another station or
access point. A station can authenticate with any other station or access point
using open system authentication if the receiving station designates open system
authentication.
Share Key:
The optional authentication that
involves a more rigorous exchange of frames, ensuring that the requesting
station is authentic. For a station to use shared key authentication, it must
implement WEP.
11.
What is 802.1x ?
IEEE 802.1x Port-Based Network Access Control is an IEEE (Institute of Electrical and Electronics Engineers) standard, which specifies a standard mechanism for authenticating, at the link layer (Layer 2), users' access to IEEE 802 networks such as Ethernet (IEEE 802.3) and Wireless LAN (IEEE 802.11). For IEEE 802.11 WLAN, IEEE 802.1x authentication can be based on username/password or digital certificate.
12. What is the difference between force-authorized, force-unauthorized and auto
?
force-authorized—disables 802.1X and causes the port to
transition to the authorized state without any authentication exchange required.
The port transmits and receives normal traffic without 802.1X-based
authentication of the client.
force-unauthorized—causes the port
to remain in the unauthorized state, ignoring all attempts by the client to
authenticate. The switch cannot provide authentication services to the client
through the interface.
auto—enables 802.1X and causes the port to
begin in the unauthorized state, allowing only EAPOL frames to be sent and
received through the port. The authentication process begins when the link state
of the port transitions from down to up, or when an EAPOL-start frame is
received. The switch requests the identity of the client and begins relaying
authentication messages between the client and the authentication server. Each
client attempting to access the network is uniquely identified by the switch by
using the client's MAC address.
13. What
is AAA ?
AAA is the acronym for Authentication, Authorization, and
Accounting and refers to the idea of managing subscribers by controlling their
access to the network, verifying that they are who they say they are (via login
name and password or MAC address) and accounting for their network
usage.
14. What
is RADIUS ?
RADIUS stands for Remote Authentication Dial-In User
Service. RADIUS is a standard that has been implemented into several software
packages and networking devices. It allows user information to be sent to a
central database running on a RADIUS Server, where it is verified. RADIUS also
provides a mechanism for accounting.
All contents copyright © 2004 ZyXEL Communications Corporation.