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Selecting Necessary WLAN Services

Now that you have considered the preceding questions and determined the technology you want to use (or at least have a good idea), you need to determine what other functions are important to your installation. Previous chapters have discussed VLANs, QoS, roaming, security, load balancing, and interoperability, and it is important that you understand the issues that some of these services and their support (or, in some cases, lack of support) will cause. This will also be an important part of choosing the proper WLAN products.

VLANs

VLANs are a relatively new feature in many of the WLAN products on the market. A VLAN enables you to separate traffic into separate virtual LANs over the RF. In the past, this had to be done at the switch, and for every VLAN, you needed a separate WLAN system (separate APs).

Why would you want VLANs over the wireless? One reason is for guest traffic in an enterprise system. Typically, a security system is set up on the WLAN for the "normal" users. When guests arrive, giving them access to the network is not necessarily easy (or even desired), because passwords and accounts need to be set up, and these visitors may change on a day-to-day basis. By using VLANs, you can provide one internal-user VLAN that incorporates certain security modes (PEAP, LEAP, EAP-TLS, WPA, and so forth) and permits access to the corporate network, and you can provide a separate VLAN for guest users with static wired equivalent privacy (WEP), or perhaps no WEP at all. The latter VLAN would funnel the guest user only to certain network areas or perhaps even just the "dirtynet" for Internet access only. With the use of VLANs, both types of users can share the same AP.

If you plan to carry voice traffic over your WLAN equipment, you probably also want to configure your WLAN equipment such that all the voice traffic is carried over dedicated VLANs to ensure that the low-latency traffic (voice in this case) is not competing with data that has lower latency after it hits the wireless network.

See Chapter 10, "Using Site Surveying Tools," for more on VLANs.

Quality of Service

QoS is necessary if you intend to support VoIP, and if you want to differentiate traffic by port, application, or user. Various QoS schemes are on the market today, with most being proprietary. Most vendors comply with the IEEE 802.11e standard for QoS. Chapter 10 provides more detail on QoS as well.

IP Subnet Roaming

Chapter 10.)

Security

Security is a major concern. This book does not go into detail on security because there are numerous books dedicated to that topic. Aside from brief introductory comments, security is not possible to cover in detail here. You need to verify that the security solution you select and the products you select are compatible, keeping in mind again that you will have no higher level of security than the least-sophisticated device on your network. An example is a health-care facility in which the patient-records application runs on standard laptop computers that support many different versions of security (PEAP, LEAP, EAP-TLS, WPA, and so forth), but the pharmaceutical application requires bar coding, and the bar code scanners may or may not support the same security solution.

To resolve this issue, you can use VLANs to separate the devices (and their security types). Devices with lower-level security may have a VLAN that accesses only network systems with minimally sensitive data. At the same time, network systems that have highly sensitive data may be on a separate VLAN and accessed only by devices that can use higher levels of security. So take care to select products that support the security method that you have chosen.

Load Balancing

Load balancing and hot standby in APs are also things to consider. Most of the higher-end enterprise-type APs support these functions, but in some cases may require your attention to how they are configured. However, many of the lower-end products (products targeted for the SOHO markets) that IT professionals may be inclined to evaluate (based on pressure from upper-level management to lower costs) do not support most of these advanced types of WLAN services.

Interoperability

Interoperability is also a concern when you are selecting products. Make sure that any product you select is Wi-Fi certified (and not just that they use the term Wi-Fi in their literature). Go to the Wi-Fi Alliance website (www.wi-fi.com) and view the list of certified devices. This at least provides some basic level of interoperability testing and certification. Also be aware that there are several different Wi-Fi certifications, such as 802.11a, 802.11b, 802.11g, security, quality of service, and so on. The packages of newer Wi-Fi certified products include a certification compliance label that lists the features supported by the product (802.11a, 802.1b, WPA, QoS, and so forth).