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Reference Manual for the NETGEAR RangeMax™ Wireless Access Point WPN802
B-2
Wireless Networking Basics
202-10101-01, May 2005
Ad Hoc Mode (Peer-to-Peer Workgroup)
In an ad hoc network, computers are brought together as needed; thus, there is no structure or fixed
points to the network - each node can generally communicate with any other node. There is no
Access Point involved in this configuration. This mode enables you to quickly set up a small
wireless workgroup and allows workgroup members to exchange data or share printers as
supported by Microsoft networking in the various Windows operating systems. Some vendors also
refer to ad hoc networking as peer-to-peer group networking.
In this configuration, network packets are directly sent and received by the intended transmitting
and receiving stations. As long as the stations are within range of one another, this is the easiest
and least expensive way to set up a wireless network.
Network Name: Extended Service Set Identification (ESSID)
The Extended Service Set Identification (ESSID) is one of two types of Service Set Identification
(SSID). In an ad hoc wireless network with no access points, the Basic Service Set Identification
(BSSID) is used. In an infrastructure wireless network that includes an access point, the ESSID is
used, but may still be referred to as SSID.
An SSID is a thirty-two character (maximum) alphanumeric key identifying the name of the
wireless local area network. Some vendors refer to the SSID as network name. For the wireless
devices in a network to communicate with each other, all devices must be configured with the
same SSID.
The ESSID is usually broadcast in the air from an access point. The wireless station sometimes can
be configured with the ESSID
ANY.
This means the wireless station will try to associate with
whichever access point has the stronger radio frequency (RF) signal, providing that both the access
point and wireless station use Open System authentication.
Authentication and WEP Data Encryption
The absence of a physical connection between nodes makes the wireless links vulnerable to
eavesdropping and information theft. To provide a certain level of security, the IEEE 802.11
standard has defined these two types of authentication methods:
•
Open System
. With Open System authentication, a wireless computer can join any network
and receive any messages that are not encrypted.
Page 57 / 88
Reference Manual for the NETGEAR RangeMax™ Wireless Access Point WPN802
Wireless Networking Basics
B-3
202-10101-01, May 2005
•
Shared Key
. With Shared Key authentication, only those PCs that possess the correct
authentication key can join the network. By default, IEEE 802.11 wireless devices operate in
an Open System network.
Wired Equivalent Privacy (WEP) data encryption is used when the wireless devices are configured
to operate in Shared Key authentication mode.
802.11 Authentication
The 802.11 standard defines several services that govern how two 802.11 devices communicate.
The following events must occur before an 802.11 Station can communicate with an Ethernet
network through an access point, such as the one built in to the WPN802:
1.
Turn on the wireless station.
2.
The station listens for messages from any access points that are in range.
3.
The station finds a message from an access point that has a matching SSID.
4.
The station sends an authentication request to the access point.
5.
The access point authenticates the station.
6.
The station sends an association request to the access point.
7.
The access point associates with the station.
8.
The station can now communicate with the Ethernet network through the access point.
An access point must authenticate a station before the station can associate with the access point or
communicate with the network. The IEEE 802.11 standard defines two types of authentication:
Open System and Shared Key.
•
Open System Authentication
allows any device to join the network, assuming that the device
SSID matches the access point SSID. Alternatively, the device can use the “ANY” SSID
option to associate with any available Access Point within range, regardless of its SSID.
•
Shared Key Authentication
requires that the station and the access point have the same WEP
Key to authenticate. These two authentication procedures are described below.
Open System Authentication
The following steps occur when two devices use Open System Authentication:
1.
The station sends an authentication request to the access point.
Page 58 / 88
Reference Manual for the NETGEAR RangeMax™ Wireless Access Point WPN802
B-4
Wireless Networking Basics
202-10101-01, May 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 B-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 59 / 88
Reference Manual for the NETGEAR RangeMax™ Wireless Access Point WPN802
Wireless Networking Basics
B-5
202-10101-01, May 2005
This process is illustrated below.
Figure B-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
Page 60 / 88
Reference Manual for the NETGEAR RangeMax™ Wireless Access Point WPN802
B-6
Wireless Networking Basics
202-10101-01, May 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 B-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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