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.
2. What
are the advantages of Wireless LANs ?
a. Mobility:
Wireless LAN systems can provide LAN users with access
to real-time information anywhere in their organization. This mobility supports
productivity and service opportunities not possible with wired networks.
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 benef
e. Scalability:
Wireless LAN systems can be configured in a variety of topologies to meet the
needs of specific applications and installations. Configurations are easily
changed and range from peer-to-peer networks suitable for a small number of
users to full infrastructure networks of thousands of users that enable roaming
over a broad area.
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 acts 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 it is known as 802.11 High-Rate
and Wi-Fi. 802.11b only uses the 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 megab
9. What is 802.11a?
802.11a the second revision of 802.11 that operates in the unlicensed 5 GHz
band and allows transmission rates of up to 54Mbps. 802.11a uses OFDM
(orthogonal frequency division multiplexing) as opposed to FHSS or DSSS. Higher
data rates are possible by combining channels. Due to higher frequency, range
is less than lower frequency systems (i.e., 802.11b and 802.11g) and can
increase the cost of the overall solution because a greater number of access
points may be required. 802.11a is not directly compatible with 802.11b or
802.11g networks. In other words, a user equipped with an 802.11b or 802.11g
radio card will not be able to interface directly to an 802.11a access point.
Multi-mode NICs will solve this problem.
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 utilise
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.
13. What types of devices
use the 2.4GHz Band?
Various spread spectrum radio communication applications use the 2.4 GHz
band. This includes WLAN systems (not necessarily of the type IEEE 802.11b), cordless phones, wireless medical telemetry
equipment and Bluetooth™ short-range wireless applications, which include
connecting printers to computers and connecting modems or hands-free k
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
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 connect to the wired LAN backbone. Wireless
clients have their configurations set for "infrastructure mode" in
order to utilise 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
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
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.
Can 128-bit WEP communicate with 64-bit WEP?
No. 128-bit WEP can
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 (
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 transm
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.
WPA is
designed for use with an 802.1X authentication server, which distributes
different keys to each user. The Wi-Fi Alliance calls the pre-shared key
version WPA-Personal or WPA2-Personal and the 802.1X
authentication version WPA-Enterprise
or WPA2-Enterprise.
Data
is encrypted using the RC4 stream cipher, with a 128-bit key and a 48-bit
initialization vector (IV). WPA uses Temporal Key Integrity Protocol (TKIP),
which dynamically changes keys as the system is used. When combined with the
much larger IV to defeat the well-known key recovery attacks on WEP.
The cyclic
redundancy check (CRC) used in WEP is inherently insecure; it is possible to
alter the payload and update the message CRC without knowing the WEP key. A
more secure message authentication code (usually known as a MAC, but here
termed a MIC for "Message
Integrity Code") is used in WPA, an algorithm named "Michael".
The MIC used in WPA includes a frame counter, which prevents replay attacks
being executed; this was another weakness in WEP.
WPA
was formulated as an intermediate step towards improved 802.11 security for two
reasons: first, 802.11i's work lasted far longer than originally anticipated,
spanning four years, during a period of ever-increasing worries about wireless
security; second, it encompasses as a subset of 802.11i only elements that were
backwards compatible with WEP for even the earliest 802.11b adopters. WPA
firmware upgrades have been provided for the vast majority of wireless network
interface cards ever shipped; 802.11 access points sold before 2003 generally
needed to be replaced.
By
increasing the size of the keys and IVs, reducing the number of packets sent
with related keys, and adding a secure message verification system, WPA makes
breaking into a Wireless LAN far more difficult. The Michael algorithm was the
strongest that WPA designers could come up with that would still work with most
older network cards; however it is subject to a packet forgery attack. To limit
this risk, WPA networks shut down for 60 seconds whenever an attempted attack
is detected.
WPA2
is the certified form of IEEE 802.11i tested by the Wi-Fi Alliance. WPA2
implements the mandatory elements of 802.11i. In particular, the Michael
algorithm is replaced by a message authentication code, CCMP, that is
considered fully secure and RC4 is replaced by AES.
All contents copyright © 2006 ZyXEL Communications Corporation.