Administering and Optimizing a Wireless LAN in Software

Encoding Data Matrix ECC200 in Software Administering and Optimizing a Wireless LAN

Single MAC model benefits include:

Less wired network traffic is required to manage the wireless stations More features are included within the APs themselves

Centralized management tools can reduce or even eliminate the costs associated with the single MAC model These tools allow you to update firmware, change configurations, and even perform dynamic radio adjustments automatically from a central controller The central device is usually a software application that runs on a server

Split MAC Model (Centralized)

The split MAC model is called such because a portion of the MAC layer operation is offset to centralized controllers and another portion remains in the AP These types of APs are often called thin APs or access ports because they do not perform as many functions as the traditional APs (fat APs or thick APs) The split MAC model is very popular in large networks today and is becoming more popular in smaller networks as well, as newer devices support the split-MAC model while implementing fewer APs There are costs and benefits associated with the split MAC model too Split MAC model costs include:

A possible single point of failure arises at the WLAN controller Increased wired network traffic is required to manage the wireless stations There are fewer features within the APs themselves when using truly thin APs

Split MAC model benefits include:

Centralized administration may reduce ongoing support efforts APs may or may not be less expensive, because they can have less memory

have to handle management processing overhead You may have noticed that, in a large way, the benefits of the split-MAC model are the costs of the single-MAC model and the benefits of the single-MAC

model are the costs of the split-MAC model While there are certainly more details involved than this, it is important to understand that you will be giving up something regardless of the model you choose The key is to determine what is best suited to fill the organizational and technical needs of the organization in which you are implementing the WLAN

Another key decision you must make is that between enterprise-class and consumergrade hardware The differences between these two categories of hardware are important If you attempt to install consumer-grade APs in an environment requiring dozens of APs, you will quickly discover that the lack of centralized management causes tremendous inefficiencies in administration For example, to change one single setting, you will have to connect to every AP individually and configure that setting This method of management is time-consuming and frustrating Table 8-1 provides a comparison of enterprise-class and consumer-grade hardware

Regardless of the hardware chosen, the hardware must be installed and configured correctly WLAN switches, controllers, encryption gateways, and other such devices will be located in switch closets and network operation centers The APs will be distributed throughput the facility Part of WLAN optimization is determining the best placement of antennas for transmission and reception The initial placement will be determined in the site survey, but changes to the environment may demand changes in antenna placement or orientation An entirely new site survey is not required You can usually just perform coverage validation for those users accessing the AP for which the antenna has been repositioned

TABLE 8-1

Usually provides centralized configuration Includes more features Provides PoE power May have more powerful hardware Often provides detachable antennas May provide enhanced security features

Usually requires individual configuration Includes fewer features Does not provide PoE power May have less powerful hardware Often provides detachable antennas Usually provides basic security features

8:

You have installed a WLAN During the first few months, the users did not complain about the performance of the WLAN Last week, the office manager had several new metal filing cabinets installed Now the users are complaining about weakened signals Should you buy new APs or adjust the antenna locations If the WLAN was performing acceptably before, you should adjust the antenna locations first This action will most likely resolve the performance problem, as small changes can make a big difference in WLAN functionality

One of the solutions to WLAN performance problems is antenna diversity Antenna diversity is discussed in greater detail in a later section of this chapter titled Multipath and Performance ; however, it is sufficient for now to know that antenna diversity uses more than one antenna in order to improve reception or transmission Interestingly, the solution uses only one antenna for actual communications and the two antennas of choice are usually within 5 or 6 inches of each other The fact that the antennas can be so close to one another and still provide very different communication capabilities should serve as a reminder that slight location differences can greatly enhance or depreciate wireless communications