30-07-2013, 03:03 PM
WiFi Technology
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Introduction.
The Market for wireless communication has grown rapidly since the introduction of
802.11b wireless local area networking (WLAN) standards, which offer performance
more nearly comparable to that of Ethernet.
WLAN (or WiFi) was created specifically to operate as a wireless Ethernet. It is an
open-standard technology that enables wireless connectivity between equipments and
local area networks. Public access WLAN services are designed to deliver LAN
services over short distances, typically 50 to 150 meters. In these cases, WLANs are
connected to a local database, and give the end user access through a kiosk or portable
device.
Internet access through public WLANs is a new and very hot trend, providing many
benefits and conveniences over other types of mobile Internet access.
First, performance is 50 to 200 times faster than dial-up Internet connections or
cellular data access. Second, users do not have to worry about cords, wires or sharing
an access point, such as a phone jack.
Wi-Fi devices
The cost of Wi-Fi components is dropping rapidly. Wi-Fi radio chips which cost
around $100 in 2000 now cost only $15, and fierce competition amongst commodity
radio manufacturers promises to push this price even lower. A future with ubiquitous
Wi-Fi networks in homes, offices and in public spaces will be filled with all kinds of
Wi-Fi enabled devices:
WLAN Networks Implementation Considerations
When implementing a WLAN solution, customers are confronted with a number of
options and trade-offs that may make one system more suitable than the next. No one
WLAN solution at present can deliver all things to all customers, some, as we have
mentioned, deliver higher speeds, some have better range, etc. The following is a list
of considerations network managers must confront before implementing a wireless
LAN:
Interoperability and Compatibility—The first, and most important job of any
network manager, is to insure that any WLAN products conform to wired
infrastructure interconnection standards. Standards-based interoperability makes the
wireless portion completely transparent to the rest of the network, and is generally
based on Ethernet or Token Ring.
Also, older WLAN systems from different vendors may not always interoperate, even
if they are using the same technology (DSSS or FHSS) and the same frequency band.
A wireless NIC from one vendor may have difficulty connecting to an access point
from another vendor, because vendors may adjust their hardware or software to meet
their own customization requirements and quality standards.
However, the Wireless Ethernet Compatibility Alliance (WECA) now certifies
WLAN vendors whose products are interoperable. The WECA seal (Wi-Fi
Certification) guarantees that WLAN products from different vendors will work
together.
TCP/IP:
Each station on the network is assigned a unique IP address, which consists of 4
bytes. 3 bytes of them represents the IP address of the network, and 1 byte represents
the host IP (or the station IP).
The IP address is unique and fixed to each station, which prevents the mobility and
roaming between networks.
Mobile IP:
Mobile IP provides a mechanism within TCP/IP protocol to support mobility.
In mobile IP, computers are given a home address , which is a static address, on their
home network. The computer also has a home agent, which keeps track of where the
mobile computer is located.
When the mobile computer roams to another network (called a Foreign Network),a
foreign agent provides routing services to the mobile computer and it assigns him a
new, but temporary IP number. So when a data is sent to the mobile computer, to its
home address, the home agent forward it to the foreign agent.
To respond to the original sender, the mobile computer uses traditional IP routing
instead of tunneling back toward its home agent.
Wi-Fi Security
Special precautions must be taken to maintain security in wireless network. However,
no one approach works for all environments and situations. The optimal solution(s) in
a particular network depends on factors such as the level of security required, size of
the network, whether access is required for remote workers, and so forth.
Securing WLANs is provided through two process: Authentication and Encryption.
Authentication is the means by which one STA is verified to have authorization to
communicate with a second STA. In the infrastructure mode, authentication is
established between an AP and each STA. Authentication is a prerequisite for
association. Association is the establishment of communication services between the
STA and the AP, and mapping the STA to the AP to provide the mobile node with
access to the wired LAN.
Authentication can be either Open System or Shared Key. An Open System, any
requesting STA may be granted authentication. However, success is not guaranteed.
The STA receiving the request may still deny authentication. In Shared Key system,
only stations which possess a secret key can be authenticated. Obviously transmission
of the Shared Key could lead to its interception by unauthorized users. It is therefore
encrypted prior to encryption. Shared Key authentication is available to systems
having the optional encryption capability.
Wired Equivalent Privacy (WEP):
Wireless transmissions are easier to intercept than transmissions over wired networks.
The 802.11 standard currently specifies the WEP security protocol to provide
encrypted communication between the client and an AP. WEP employs the symmetric
key encryption algorithm, Ron’s Code 4 Pseudo Random Number Generator (RC4
PRNG).
Under WEP, all clients and APs on a wireless network typically use the same key to
encrypt and decrypt data. The key resides in the client computer and in each AP on
the network. The 802.11 standard does not specify a key-management protocol, so all
WEP keys on a network usually must be managed manually unless they are used in
conjunction with a separate key-management protocol. For example, 802.1X
provides WEP key management. Support for WEP is standard on most current 802.11
cards and APs. WEP specifies the use of a 40-bit encryption key and there are also
implementations of 104-bit keys. The encryption key is concatenated with a 24-bit
“initialization vector” (IV), resulting in a 64- or 128-bit key. This key is input into a
pseudorandom number generator. The resulting sequence is used to encrypt the data
to be transmitted. (WEP keys can be entered in alphanumeric text or hexadecimal
form).
[attachment=56828]
Introduction.
The Market for wireless communication has grown rapidly since the introduction of
802.11b wireless local area networking (WLAN) standards, which offer performance
more nearly comparable to that of Ethernet.
WLAN (or WiFi) was created specifically to operate as a wireless Ethernet. It is an
open-standard technology that enables wireless connectivity between equipments and
local area networks. Public access WLAN services are designed to deliver LAN
services over short distances, typically 50 to 150 meters. In these cases, WLANs are
connected to a local database, and give the end user access through a kiosk or portable
device.
Internet access through public WLANs is a new and very hot trend, providing many
benefits and conveniences over other types of mobile Internet access.
First, performance is 50 to 200 times faster than dial-up Internet connections or
cellular data access. Second, users do not have to worry about cords, wires or sharing
an access point, such as a phone jack.
Wi-Fi devices
The cost of Wi-Fi components is dropping rapidly. Wi-Fi radio chips which cost
around $100 in 2000 now cost only $15, and fierce competition amongst commodity
radio manufacturers promises to push this price even lower. A future with ubiquitous
Wi-Fi networks in homes, offices and in public spaces will be filled with all kinds of
Wi-Fi enabled devices:
WLAN Networks Implementation Considerations
When implementing a WLAN solution, customers are confronted with a number of
options and trade-offs that may make one system more suitable than the next. No one
WLAN solution at present can deliver all things to all customers, some, as we have
mentioned, deliver higher speeds, some have better range, etc. The following is a list
of considerations network managers must confront before implementing a wireless
LAN:
Interoperability and Compatibility—The first, and most important job of any
network manager, is to insure that any WLAN products conform to wired
infrastructure interconnection standards. Standards-based interoperability makes the
wireless portion completely transparent to the rest of the network, and is generally
based on Ethernet or Token Ring.
Also, older WLAN systems from different vendors may not always interoperate, even
if they are using the same technology (DSSS or FHSS) and the same frequency band.
A wireless NIC from one vendor may have difficulty connecting to an access point
from another vendor, because vendors may adjust their hardware or software to meet
their own customization requirements and quality standards.
However, the Wireless Ethernet Compatibility Alliance (WECA) now certifies
WLAN vendors whose products are interoperable. The WECA seal (Wi-Fi
Certification) guarantees that WLAN products from different vendors will work
together.
TCP/IP:
Each station on the network is assigned a unique IP address, which consists of 4
bytes. 3 bytes of them represents the IP address of the network, and 1 byte represents
the host IP (or the station IP).
The IP address is unique and fixed to each station, which prevents the mobility and
roaming between networks.
Mobile IP:
Mobile IP provides a mechanism within TCP/IP protocol to support mobility.
In mobile IP, computers are given a home address , which is a static address, on their
home network. The computer also has a home agent, which keeps track of where the
mobile computer is located.
When the mobile computer roams to another network (called a Foreign Network),a
foreign agent provides routing services to the mobile computer and it assigns him a
new, but temporary IP number. So when a data is sent to the mobile computer, to its
home address, the home agent forward it to the foreign agent.
To respond to the original sender, the mobile computer uses traditional IP routing
instead of tunneling back toward its home agent.
Wi-Fi Security
Special precautions must be taken to maintain security in wireless network. However,
no one approach works for all environments and situations. The optimal solution(s) in
a particular network depends on factors such as the level of security required, size of
the network, whether access is required for remote workers, and so forth.
Securing WLANs is provided through two process: Authentication and Encryption.
Authentication is the means by which one STA is verified to have authorization to
communicate with a second STA. In the infrastructure mode, authentication is
established between an AP and each STA. Authentication is a prerequisite for
association. Association is the establishment of communication services between the
STA and the AP, and mapping the STA to the AP to provide the mobile node with
access to the wired LAN.
Authentication can be either Open System or Shared Key. An Open System, any
requesting STA may be granted authentication. However, success is not guaranteed.
The STA receiving the request may still deny authentication. In Shared Key system,
only stations which possess a secret key can be authenticated. Obviously transmission
of the Shared Key could lead to its interception by unauthorized users. It is therefore
encrypted prior to encryption. Shared Key authentication is available to systems
having the optional encryption capability.
Wired Equivalent Privacy (WEP):
Wireless transmissions are easier to intercept than transmissions over wired networks.
The 802.11 standard currently specifies the WEP security protocol to provide
encrypted communication between the client and an AP. WEP employs the symmetric
key encryption algorithm, Ron’s Code 4 Pseudo Random Number Generator (RC4
PRNG).
Under WEP, all clients and APs on a wireless network typically use the same key to
encrypt and decrypt data. The key resides in the client computer and in each AP on
the network. The 802.11 standard does not specify a key-management protocol, so all
WEP keys on a network usually must be managed manually unless they are used in
conjunction with a separate key-management protocol. For example, 802.1X
provides WEP key management. Support for WEP is standard on most current 802.11
cards and APs. WEP specifies the use of a 40-bit encryption key and there are also
implementations of 104-bit keys. The encryption key is concatenated with a 24-bit
“initialization vector” (IV), resulting in a 64- or 128-bit key. This key is input into a
pseudorandom number generator. The resulting sequence is used to encrypt the data
to be transmitted. (WEP keys can be entered in alphanumeric text or hexadecimal
form).