This week, we look at the hurdles to enterprise WLANs. Yesterday we covered Quality of Service. Today, we look at management.
Managing a few APs in conference rooms is not hard, but as enterprises start to deploy dozens, updating them with authentication keys, firmware upgrades, and policies might become a difficult IT challenge.
Enterprise-class APs permit remote updating via software tools, accessing the APs' settings, typically through MIBs (management information bases). These are capability specifications called through SNMP, and widely used for wired routers, gateways, and switches. Wireless devices, however, have additional configurations related to managing the radio strength: for these,there are no standard MIBs.
"The original philosophy (for 802.11) was to put the power in the end nodes, like Ethernet, but this has put an additional burden on the task of doing handoff because more control is needed by the intermediate devices that don't have that control," HP's Congdon says.
To deal with this issue, today's enterprises must standardise their wireless APs, gateways, switches, and routers from one vendor and rely on that vendor's proprietary management tools or use a solution from a third-party tool provider - such as Airespace, AirMagnet, AirWave, Aruba, Cognio, Legra, Roving Planet, Trapeze or Wavelink - that manages multiple vendors' hardware. Congdon says that the use of switches for AP coordination can also help make WLAN management less of a burden until appropriate standards are developed.
Can CAPWAP give us control?
The IETF is developing the CAPWAP (Control and Provisioning of Wireless Access Points) taxonomy to describe the interfaces and protocols used by various WLAN management devices and to delineate their advantages and disadvantages. The goal is to create a common understanding of these mechanisms so that vendors and IT managers can deploy the appropriate ones. The IETF is also coordinating this taxonomy with the IEEE 802 network interconnections standards, including 802.11.
Although wireless management devices use SNMP MIBs to manage hardware, standards for wireless-specific MIBs would be useful for measuring utilisation, managing RF output power, and switching channels, BelAir's Belanger says.
"Standards are needed for the generation of the information," adds Jack Winters, chief scientist at antenna maker Motia. "How you use it is up to you." There's also a need to get settings, policies, and parameters from the client, which now "doesn't contribute any information to the access point to help manage the RF signals," says Martin Brewer, senior product manager at wireless management tools provider Wavelink.
Debate exists as to how far standards should extend. "The switch vendors are reluctant to make it easy to provide the same capabilities to other vendors," Roving Planet's Simpson says. Summit Strategies' Wilson agrees that as long as the wireless hardware is SNMP-aware, third-party LAN management software vendors' offerings will be capable of handling hardware feature differences. As switches gain wider use, enterprises may start using lightweight APs, which are managed in groups by controllers in a hierarchy of nodes and branches.
This situation reduces the complexity and cost of APs but can lead to reduced interoperability among vendors' hardware, Airespace's O'Hara notes. "That is ripe for standardisation," he says, noting that the IETF has developed a draft for such a standard, which would discourage the use of proprietary, single-vendor lightweight hardware.
How would wireless back-haul connections be managed? Today, wireless APs are linked to one another and to switches and routers through the wired LAN, so management-related back-haul data is carried through the higher-capacity, more-secure LAN. (User traffic is also routed to the back-haul wired LAN at these connections.) In many environments, however, connecting APs via wires is difficult or expensive. To address that problem, the IEEE is developing 802.11s, which would manage wireless back-haul connections and create what are called mesh networks so that not every AP would need a direct connection to the wired LAN. The trick, says Motia's Winters, "is to figure out how not to interfere with the clients' traffic."
On Friday: Towards roaming between networks.
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