Comparing the Different Options

 < Day Day Up > 



The typical smart AP found in most corporate WLANs acts as a gatekeeper and a switch-both snatching and spewing forth packets in and out of the air, checking for authorization, applying various services to them, forwarding them to the wired network and, then, of course, relaying packets back in the other direction. In functionality these devices perform much in the same way as network switches on the edge of a wired network. Examples of this type of AP model include Cisco's Aironet, Proxim's Orinoco, and Symbol's Spectrum24.

In many instances, however, it is better to let an access point do what it does best-radio frequency control. That's why some enterprise-class access point vendors are backing away from the smart AP model. These innovative vendors, while taking different approaches, are building simple or fit APs and pairing them with some type of intelligent box. The box provides all or most of the "smarts" needed for deploying and managing large-scale enterprise wireless networks. With this model, to access any necessary additional information, features, or functions, the simple APs tap into the intelligent box, which is sitting somewhere inside the wired LAN (e.g. a wiring closet).

There are advantages to using stripped down APs, and pairing them with a centralized intelligent box that can handle the majority of the WLAN's system functions (with the help of the wired network's switches). One such benefit of using this model in a corporate WLAN is that by centralizing the configuration and management of the APs, the management of those APs is greatly simplified.

As the 802.11 series of standards matures, network managers will need to upgrade or even replace access points to keep pace with the evolving standards (which, in all likelihood will affect such things as performance and security). A wireless LAN architecture that is designed around the simple AP and intelligent box model, whether the vendor dubs its "box" an access controller (Proxim, etc.), a switch (Symbol, etc.), a router (Chantry Networks) or a gateway (Bluesocket), just may be the wave of the future. Such an architecture can always reduce management costs and complexity, and many times can even lower deployment costs (depending on the size of the WLAN). These intelligent devices typically use a virtual LAN architecture and policy-based networking to deliver bandwidth, security, and networking services by device, by user, by application, and by location, all from a single access port.

start sidebar
PORTAL

To integrate the IEEE 802.11 architecture with a traditional wired LAN, the IEEE introduced a final logical architectural component. This component, which the IEEE calls a "portal," functions as a "translation-bridge" between the WLAN and an existing wired LAN. In other words, a portal can provide logical integration between existing 802-type wired LANs (e.g. Ethernet and Token Ring) and 802.11 LANs.

The 802.11 series of standards does not constrain the composition of the network's distribution system; therefore, it may be 802 compliant or non-standard. If data frames need transmission to and from a non-IEEE 802.11 LAN, then those frames, as defined by the 802.11 standard, enter and exit through a logical point, the portal. Where the "intelligent box" concept falls under the IEEE's definition of a portal is up for debate, especially since the portal and access point can be on a single physical entity or provided by separate devices.

end sidebar

When considering whether to go with a network design that utilizes APs paired with an intelligent box, versus using smart APs alone, keep the following in mind:

  • Smart APs cost more per unit, but since they are connected directly to the wired network, no additional hardware is needed (except for the NIC).

  • Simple APs are inexpensive, but must be paired with some type of intelligent device, e.g. an access controller or a switch. But if the WLAN requires a lot of APs, costing for this method is less, even when you factor in the expense of the extra box to manage them.

  • APs can be "smart" and still be centrally managed—centralized management is a must for large WLANs, regardless of whether the APs are simple, smart, or fit. Thus, the issue may be only whether the "smart" AP's per-unit cost is low enough to make it cost-efficient to buy them plus a centralized management system. For example, Cisco's IOS (a router operating system) is run in Cisco's smart APs, like the Aironet 1000 series, to distribute network services out as far as possible to the network edge. But the Cisco Wireless LAN Solutions Engine (a special management appliance that resides in a data center, plugged into a backbone switch) still can be used to manage the smart APs.

  • In terms of cost alone, it is the size of the network that may determine whether to look to a smart or simple WLAN infrastructure. For a small network, investing in simple APs and an intelligent box may be too costly, but for a large network, such a solution may actually be very cost-effective.

  • If the decision is to go with smart APs, ask the vendor what technical benefit there is to applying network services in the AP, rather than in a LAN switch, be it wired or wireless. Those benefits are not yet entirely clear.

While the smart AP will continue to thrive in some WLAN environments, the simple AP paired with an intelligent box will scale better in others. Before making your final decision, have potential vendors put in writing exactly what they and their product(s) can and will deliver. Have them delineate what their solution offers that you can't get elsewhere, e.g. technical advantages (e.g. Quality of Service, heightened security, performance) and business benefits (e.g. scalability, lower cost of management). Finally, ask them to prove how they can deliver all they promise.



 < Day Day Up > 



Going Wi-Fi. A Practical Guide to Planning and Building an 802.11 Network
Going Wi-Fi: A Practical Guide to Planning and Building an 802.11 Network
ISBN: 1578203015
EAN: 2147483647
Year: 2003
Pages: 273

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net