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Reference Manual for the 54 Mbps Wireless Router WGR614 v6
D-4
Wireless Networking Basics
202-10099-01, April 2005
2.
The access point authenticates the station.
3.
The station associates with the access point and joins the network.
This process is illustrated below.
Figure 7-1:
Open system authentication
Shared Key Authentication
The following steps occur when two devices use Shared Key Authentication:
1.
The station sends an authentication request to the access point.
2.
The access point sends challenge text to the station.
3.
The station uses its configured 64-bit or 128-bit default key to encrypt the challenge text, and
sends the encrypted text to the access point.
4.
The access point decrypts the encrypted text using its configured WEP Key that corresponds
to the station’s default key. The access point compares the decrypted text with the original
challenge text. If the decrypted text matches the original challenge text, then the access point
and the station share the same WEP Key and the access point authenticates the station.
5.
The station connects to the network.
If the decrypted text does not match the original challenge text (the access point and station do not
share the same WEP Key), then the access point will refuse to authenticate the station and the
station will be unable to communicate with either the 802.11 network or Ethernet network.
FVM318
Access Point
1) Authentication request sent to AP
2) AP authenticates
3) Client connects to network
802.11b Authentication
Open System Steps
Cable or
DLS modem
Client
attempting
to connect
Page 127 / 154
Reference Manual for the 54 Mbps Wireless Router WGR614 v6
Wireless Networking Basics
D-5
202-10099-01, April 2005
This process is illustrated below.
Figure 7-2:
Shared key authentication
Overview of WEP Parameters
Before enabling WEP on an 802.11 network, you must first consider what type of encryption you
require and the key size you want to use. Typically, there are three WEP Encryption options
available for 802.11 products:
1.
Do Not Use WEP:
The 802.11 network does not encrypt data. For authentication purposes, the
network uses Open System Authentication.
2.
Use WEP for Encryption:
A transmitting 802.11 device encrypts the data portion of every
packet it sends using a configured WEP Key. The receiving device decrypts the data using the
same WEP Key. For authentication purposes, the network uses Open System Authentication.
3.
Use WEP for Authentication and Encryption:
A transmitting 802.11 device encrypts the data
portion of every packet it sends using a configured WEP Key. The receiving device decrypts the
data using the same WEP Key. For authentication purposes, the wireless network uses Shared Key
Authentication.
Note:
Some 802.11 access points also support
Use WEP for Authentication Only
(Shared Key
Authentication without data encryption).
FVM318
Access Point
1) Authentication
request sent to AP
2) AP sends challenge text
3) Client encrypts
challenge text and
sends it back to AP
4) AP decrypts,and if correct,
authenticates client
5) Client connects to network
802.11b Authentication
Shared Key Steps
Cable or
DLS modem
Client
attempting
to connect
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Reference Manual for the 54 Mbps Wireless Router WGR614 v6
D-6
Wireless Networking Basics
202-10099-01, April 2005
Key Size
The IEEE 802.11 standard supports two types of WEP encryption: 40-bit and 128-bit.
The 64-bit WEP data encryption method allows for a five-character (40-bit) input. Additionally, 24
factory-set bits are added to the forty-bit input to generate a 64-bit encryption key. The 24
factory-set bits are not user-configurable). This encryption key will be used to encrypt/decrypt all
data transmitted via the wireless interface. Some vendors refer to the 64-bit WEP data encryption
as 40-bit WEP data encryption since the user-configurable portion of the encryption key is 40 bits
wide.
The 128-bit WEP data encryption method consists of 104 user-configurable bits. Similar to the
forty-bit WEP data encryption method, the remaining 24 bits are factory set and not user
configurable. Some vendors allow passphrases to be entered instead of the cryptic hexadecimal
characters to ease encryption key entry.
128-bit encryption is stronger than 40-bit encryption, but 128-bit encryption may not be available
outside of the United States due to U.S. export regulations.
When configured for 40-bit encryption, 802.11 products typically support up to four WEP Keys.
Each 40-bit WEP Key is expressed as 5 sets of two hexadecimal digits (0-9 and A-F). For
example, “12 34 56 78 90” is a 40-bit WEP Key.
When configured for 128-bit encryption, 802.11 products typically support four WEP Keys but
some manufacturers support only one 128-bit key. The 128-bit WEP Key is expressed as 13 sets of
two hexadecimal digits (0-9 and A-F). For example, “12 34 56 78 90 AB CD EF 12 34 56 78 90”
is a 128-bit WEP Key.
Table D-1:
Encryption Key Sizes
Note:
Typically, 802.11 access points can store up to four 128-bit WEP Keys but some 802.11
client adapters can only store one. Therefore, make sure that your 802.11 access and client
adapters’ configurations match.
Encryption Key Size
# of Hexadecimal Digits
Example of Hexadecimal Key Content
64-bit (24+40)
10
4C72F08AE1
128-bit (24+104)
26
4C72F08AE19D57A3FF6B260037
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Reference Manual for the 54 Mbps Wireless Router WGR614 v6
Wireless Networking Basics
D-7
202-10099-01, April 2005
WEP Configuration Options
The WEP settings must match on all 802.11 devices that are within the same wireless network as
identified by the SSID. In general, if your mobile clients will roam between access points, then all
of the 802.11 access points and all of the 802.11 client adapters on the network must have the same
WEP settings.
Note:
Whatever keys you enter for an AP, you must also enter the same keys for the client adapter
in the same order. In other words, WEP key 1 on the AP must match WEP key 1 on the client
adapter, WEP key 2 on the AP must match WEP key 2 on the client adapter, and so on.
Note:
The AP and the client adapters can have different default WEP Keys as long as the keys are
in the same order. In other words, the AP can use WEP key 2 as its default key to transmit while a
client adapter can use WEP key 3 as its default key to transmit. The two devices will communicate
as long as the AP’s WEP key 2 is the same as the client’s WEP key 2 and the AP’s WEP key 3 is
the same as the client’s WEP key 3.
Wireless Channels
The wireless frequencies used by 802.11b/g networks are discussed below.
IEEE 802.11b/g wireless nodes communicate with each other using radio frequency signals in the
ISM (Industrial, Scientific, and Medical) band between 2.4 GHz and 2.5 GHz. Neighboring
channels are 5 MHz apart. However, due to spread spectrum effect of the signals, a node sending
signals using a particular channel will utilize frequency spectrum 12.5 MHz above and below the
center channel frequency. As a result, two separate wireless networks using neighboring channels
(for example, channel 1 and channel 2) in the same general vicinity will interfere with each other.
Applying two channels that allow the maximum channel separation will decrease the amount of
channel cross-talk, and provide a noticeable performance increase over networks with minimal
channel separation.
The radio frequency channels used in 802.11b/g networks are listed in
Table D-2
:
Table D-2:
802.11b/g Radio Frequency Channels
Channel
Center Frequency
Frequency Spread
1
2412 MHz
2399.5 MHz - 2424.5 MHz
2
2417 MHz
2404.5 MHz - 2429.5 MHz
3
2422 MHz
2409.5 MHz - 2434.5 MHz
Page 130 / 154
Reference Manual for the 54 Mbps Wireless Router WGR614 v6
D-8
Wireless Networking Basics
202-10099-01, April 2005
Note:
The available channels supported by the wireless products in various countries are different.
For example, Channels 1 to 11 are supported in the U.S. and Canada, and Channels 1 to 13 are
supported in Europe and Australia.
The preferred channel separation between the channels in neighboring wireless networks is 25
MHz (5 channels). This means that you can apply up to three different channels within your
wireless network. There are only 11 usable wireless channels in the United States. It is
recommended that you start using channel 1 and grow to use channel 6, and 11 when necessary, as
these three channels do not overlap.
WPA and WPA2 Wireless Security
Wi-Fi Protected Access (WPA and WPA2) is a specification of standards-based, interoperable
security enhancements that increase the level of data protection and access control for existing and
future wireless LAN systems.
The IEEE introduced the WEP as an optional security measure to secure 802.11b (Wi-Fi) WLANs,
but inherent weaknesses in the standard soon became obvious. In response to this situation, the
Wi-Fi Alliance announced a new security architecture in October 2002 that remedies the
shortcomings of WEP. This standard, formerly known as Safe Secure Network (SSN), is designed
to work with existing 802.11 products and offers forward compatibility with 802.11i, the new
wireless security architecture that has been defined by the IEEE.
4
2427 MHz
2414.5 MHz - 2439.5 MHz
5
2432 MHz
2419.5 MHz - 2444.5 MHz
6
2437 MHz
2424.5 MHz - 2449.5 MHz
7
2442 MHz
2429.5 MHz - 2454.5 MHz
8
2447 MHz
2434.5 MHz - 2459.5 MHz
9
2452 MHz
2439.5 MHz - 2464.5 MHz
10
2457 MHz
2444.5 MHz - 2469.5 MHz
11
2462 MHz
2449.5 MHz - 2474.5 MHz
12
2467 MHz
2454.5 MHz - 2479.5 MHz
13
2472 MHz
2459.5 MHz - 2484.5 MHz
Table D-2:
802.11b/g Radio Frequency Channels
Channel
Center Frequency
Frequency Spread

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