An access point (AP) provides the connection between one or more wireless client devices and a wired local area network (LAN). The AP is usually connected to the LAN via a Category-5 cable connection to a hub or switch. Client devices communicate with the AP over the wireless link, giving them access to all other devices through the hub or switch, including a router on the other side of the hub, which provides Internet access.
An AP that adheres to the IEEE 802.11b Standard for operation over the unlicensed 2.4-GHz band supports a wireless link with a data transfer speed of up to 11 Mbps, while an AP that adheres to the IEEE 802.11a Standard for operation over the unlicensed 5-GHz band supports a wireless link with a data transfer speed of up to 54 Mbps. Access points include a number of the following functions and features:
- Radio power control for flexibility and ease of networking setup.
- Dynamic rate scaling, mobile Internet Protocol (IP) functionality, and advanced transmit/receive technology to enable multiple access points to serve users on the move.
- Built-in bridging and repeating features to connect buildings miles apart (The use of specialty antennas increases range. The AP can support simultaneous bridging and client connections.)
- Wired Equivalent Privacy (WEP), which helps protect data in transit over the wireless link between the client device and the AP, via 64-, 128-, or 256-bit encryption.
- Access control list (ACL) and virtual private network (VPN) compatibility to help guard the network from intruders.
- Statistics on the quality of the wireless link.
- Configurability using the embedded Web browser
Consumer-level APs stress ease of setup and use. Many products are configured with default settings that allow the user to plug in the device and use the wireless connection immediately. Later, the user can play with the configuration settings to improve performance and set up security.
Although APs adhere to the IEEE 802.11 Standards, manufacturers can include some proprietary features that improve the data transfer speed of the wireless link. For example, one vendor advertises a “turbo mode” that optionally increases the maximum speed of IEEE 802.11b wireless links from 11 to 22 Mbps. When this turbo feature is applied to IEEE 802.11a wireless links, the maximum speed is increased from 54 to 72 Mbps.
Enterprise-level APs provide more management features, allowing LAN administrators to remotely set up and configure multiple APs and clients from a central location. For monitoring and managing an entire wireless LAN infrastructure consisting of hundreds or even thousands of access points, however, a dedicated management system is usually required.
Such systems automatically discover every AP on the network and provide real-time monitoring of an entire wireless network spread out over multiple facilities and subnets. These management systems support the Simple Network Management Protocol (SNMP) and can be tied into higher-level management platforms such as Hewlett-Packard’s OpenView.
Among the capabilities of these wireless managers is support of remote reboot, group configuration, or group software uploads for all the wireless infrastructure devices on the network. In addition, the LAN administrator can see how many client devices are connected to each access point, monitor those connections to measure link quality, and monitor all the access points for performance.
Some enterprise APs provide dual-band wireless connections to support both IEEE 802.11a and 802.11b client users at the same time. This is accomplished by equipping the AP with two plug-in radio cards—one that supports the 2.4-GHz frequency specified by the IEEE 802.11b Standard and one that supports the 5-GHz frequency specified by the IEEE 802.11a Standard.
The choice of a dual-band AP provides organizations with a migration path to the higher data transfer speeds available with IEEE 802.11a while continuing to support their existing investment in IEEE 802.11b infrastructure. Depending on manufacturer, these dual-band APs are modular so that they can be upgraded to support future IEEE 802.11 technologies as they become available, which further protects an organization’s investment in wireless infrastructure.
Access points are the devices that connect wireless client devices to the wired network. They are available in consumer and commercial versions, with the latter generally costing more because of more extensive management capabilities and troubleshooting features. They may have more security features as well and support both the 2.4- and 5- GHz frequency bands with separate radio modules that plug into the same unit.
