Thursday, December 4, 2008

Wireless Modes exposed

Each 802.11a/b/g device can operate in one of four possible modes:

1. Master mode (also called AP or infrastructure mode) is used to create a service that looks like a traditional access point. The wireless card creates a network with a specified name (called the SSID) and channel, and offers network services on it. While in master mode, wireless cards manage all communications related to the network (authenticating wireless clients, handling channel contention, repeating packets, etc.) Wireless cards in master mode can only communicate with cards that are associated with it in managed mode.
2. Managed mode is sometimes also referred to as client mode. Wireless cards in managed mode will join a network created by a master, and will automatically change their channel to match it. They then present any necessary credentials to the master, and if those credentials are accepted, they are said to be associated with the master. Managed mode cards do not communicate with each other directly, and will only communicate with an associated master.
3. Ad-hoc mode creates a multipoint-to-multipoint network where there is no single master node or AP. In ad-hoc mode, each wireless card communicates directly with its neighbors. Nodes must be in range of each other to communicate, and must agree on a network name and channel.
4. Monitor mode is used by some tools (such as Kismet, chapter six) to passively listen to all radio traffic on a given channel. When in monitor mode, wireless cards transmit no data. This is useful for analyzing problems on a wireless link or observing spectrum usage in the local area. Monitor mode is not used for normal communications.
5. B only mode
6. G only mode
7. B/G mode

Access Point Modes
The only configuration mode of an access point that is compliant with the 802.11 standard is known as root mode. The main purpose of an AP is to serve as a portal to a distribution system. The normal default setting of an access point is root mode, which allows the AP to transfer data back and forth between the DS and the 802.11 wireless medium. The default root configuration of an AP allows it to operate as part of a basic service set (BSS). There are, however, other nonstandard modes in which an AP may be configured.
1)Bridge mode The AP is converted into a wireless bridge.
2)Workgroup Bridge mode The AP is transformed into a workgroup bridge.
3)Repeater mode The AP performs as a repeater access point.
4)Scanner mode The access point radio is converted into a sensor radio allowing the access point to integrate into a wireless intrusion detection system (WIDS) architecture.
Client Modes
1) Infrastructure mode (which consists of BSS and ESS)
2) Ad-hoc mode

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