Preparation

These concepts are important because when you deploy a WLAN, you are adding devices into your access layer and connecting them directly to your workgroup switches. Therefore, you must ensure that your workgroup switches have sufficient capacity for these access points. Typically they require a network port, power, and console access.

Connectivity

Because each access point requires an Ethernet port for connectivity, you must ensure that your network switches have sufficient port capacity to attach the AP to the rest of the network. Typically, this does not pose a problem in greenfield deployments. Deploying your WLAN in an established or mature networking environment, this becomes a significant consideration to address. Otherwise, you would have to budget accordingly for additional equipment. In addition, you should ensure that your Ethernet switches support at least 100BASE-T, as all the current WLAN standards (802.11a, 802.11b, and 802.11g) provide an aggregate nominal throughput of between 11 Mbps and 54 Mbps. Finally, you will have to ensure that the access point locations are within the cabling distance limit for the employed LAN technology. For example, the maximum transmission distance for 100BASE-T is 100 meters .

In summary, to ensure that your access points can establish connectivity, answer the following questions:

• Do you have sufficient Ethernet ports, or do you require additional switches?

• Do your switches provide 100BASE-T or higher?

• Is the cabling distance within defined limits?

Power

Electronic equipment requires electrical power. Generally speaking, you can power access points in two ways:

• Directly from AC mains power where the access points are located

• By providing power over the Ethernet cable

Powering the access points via AC is straightforward but requires that you provide AC outlets in the vicinity of the access point. This is often an expensive exercise that requires the use of certified electrical engineers , which can add significant cost and delays to your projects.

Powering the access points via the Ethernet cables is achieved via Power over Ethernet (PoE). This technology has been standardized as IEEE 802.1af and employs a previously unused pair of wires in category 5 (or better) cables to provide power to a device. PoE is popular because it avoids the need to install expensive additional power cables at each location and helps reduce costs.

When determining your power requirements, answer the following questions:

• Do you wish to use PoE?

• Do your existing Ethernet switches support PoE?

• If your existing Ethernet switches do not support PoE, do you want to upgrade your switches or use alternative power injectors instead?

Console Access

Many enterprises provide console access, also known as out of band management , to their network equipment for support and management purposes. You should account for providing console-port access if required or desired. Note that not all access points support console access. If this is a requirement or standard for your organization, you should ensure that the access point make and model under consideration supports console access, and that your wired infrastructure has sufficient capacity to provide it.

When planning your WLAN, answer the following questions:

• Do you wish to provide console access?

• Do you have sufficient console server ports?

• Are your console servers within cabling limits?

Environmental Considerations

Many enterprises decide to physically locate the access points in the interstitial space between the ceiling tiles and roof. This plenum area has strict fire regulations associated with it in most countries . In the United States, for example, all equipment and cabling installed in the plenum space must be " plenum-rated ," a term denoting that it is fire-resistant.

Certain environments have stringent controls on what electrical equipment can be deployed in other areas. Examples include government or military installations, hazardous environments (mining, petroleum, gas, mineral exploitation, and so on), certain manufacturing locations (munitions, "clean-room" environments, and so on), and many healthcare- related buildings or campuses. In these circumstances, the electrical equipment must be deemed "intrinsically safe," a term denoting that the equipment does not create electrical interference or even very small electromagnetic discharges. Most electrical equipment, including access points, is not "intrinsically safe" and can therefore create very small electromagnetic discharges or interference. To address these stringent environmental controls, access points can be installed in special shielding containers. In the United States, these are called National Electrical Manufacturers Association (NEMA) enclosures. (Further information on NEMA and NEMA enclosures can be found at http://www.nema.org/prod/be/enclosures/.)

In the United States, there are also national health and safety regulations to be considered, and local and national building standards. It is important for you to follow due diligence on potential environment or safety standard issues that are specific to your organization's context. Be sure to investigate and understand your obligations and ensure that your equipment complies with all relevant standards. The use of an experienced or professional deployment team will help in this area. Enterprises that work in such environments or that have equipment sensitive to environmental factors often have a safety or standards officer who can approve any wireless LAN installations or at least provide guidance. Ensure that they are represented in the project.

Safety and standards compliance are not the only environmental topics that can impact your planning phase. Simple issues such as ruggedness or waterproofing might also need to be considered. This is especially the case when you might be deploying wireless access points outdoors (in a university campus, for example).

Regulatory Restrictions or Requirements

As mentioned in Chapter 1, the regulations that apply to the use of 2.4-GHz and 5-GHz frequency ranges are not the same all over the world. At this stage, it is sufficient to note that you must take local and national regulations into account and plan accordingly. This is especially important if you are considering a large, transnational or global deployment because you might need to purchase different models for different countries.

Deployment Funding Strategies

There are many funding strategies for deploying wireless in an organization, including the following:

• Centrally funded

• Group funded

• Client funded

• Subscription funded

This section describes these common strategies along with their advantages and disadvantages. You learn more about funding strategies in Chapter 6, "Wireless LAN Deployment Considerations."

Centrally Funded Deployment

Centrally funded is perhaps the most common funding strategy. The entire cost is absorbed by a single entity; this can be the IT department, Finance, or the group responsible for business operations. In most small to medium deployments, this is the only model used.

Advantages of centrally funded deployment include

• Full visibility of program cost

• Ease of management

• Simplified cost and budgetary control

Disadvantages of centrally funded deployment include

• Requires entire project to be funded up front

• Requires careful monitoring and sometimes dedicated finance staff

Group-Funded Deployment

Group-funded deployment strategies are those where a division, department, or sometimes regional section of an enterprise funds the deployment from its own budget. It either engages external professional consultants to design and deploy the solution or uses the organization's existing IT department in a "professional services" model.

Advantages of group-funded deployment include the following:

• Ensures that each group/division funds its own deployment

• Tends to encourage financial prudence on the part of groups requesting WLAN services

• Avoids "rogue deployments" where groups self-fund and manage their own solution

Disadvantages of group-funded deployment include the following:

• Is more complex than centrally funded model

• Requires each group/division to control its own budget

• Requires each group/division to manage its own program cost

• Can sometimes result in different groups funding competing solutions

• Does not necessarily require each group/division to follow corporate or organizational standards

Client-Funded Deployment

A client-funded strategy is simply one whereby the IT department of the enterprise is responsible for installing and managing the deployment but utilizes a charge-back mechanism to the clients (usually other departments or divisions) to fund the installation. This strategy is usually adopted with a clear policy direction that ensures your IT department is the only group approved for deploying wireless networks. This ensures that you maintain a consistent architecture, a standard design and scope of work (equipment, manufacturer and model), wireless security standards, and a common support plan. Furthermore, it prevents several different departments from proceeding with their own installations that might not be compliant with your internal security and procurement policies.

Client-funded deployments are usually based upon an installation charge per AP or user , followed by an ongoing support cost.

Advantages of client-funded deployment include

• Ensures common architecture, standards, policies, and IT security strategy

• Avoids "rogue deployments" where groups self-fund and manage their own solution

• Helps control cost

• Encourages financial prudence, because each group must fund deployment from its own budget

Disadvantages of client-funded deployment include

• Is more complex to manage than centrally funded model

• Requires each group/division to control its own budget

• Requires each group/division to manage its own program cost

• Tends to result in staggered deployments, or "patchy" WLAN coverage

• Can cause user dissatisfaction when one group or area has WLAN coverage but others do not

Subscription-Funded Deployment

The subscription-based deployment strategy is also known as "pay as you go." In this model, the users or user groups pay a service fee for wireless network access. The subscription model ensures that you not only recover the costs associated with the service deployment but also recuperate ongoing support and maintenance costs.

This model is less common in most standard enterprise deployments but popular in environments where you have many different user types. Universities are a good example. The provision of wireless network access can be considered an added value service that the student body pays for on a per-user or per-class basis.

Advantages of subscription-funded deployment include the following:

• Ensures that ongoing support costs are recovered from end users/groups

• Reduces unnecessary or under-utilized deployments

Disadvantages of subscription-funded deployment include the following:

• Requires complex financial models and charge-back mechanisms

• Tends to limit breadth of deployment to those who can spare budget