Networking Media
Media installation

It is important to calculate all costs involved when designing networks. The impact of building design and construction must be considered when installing LAN media. Some important factors to consider include existing heating, ventilation, and air conditioning (HVAC), water, drain, lighting, and electrical systems. The structural materials such as drywall, concrete, wood, and steel, as well as fire codes, must also be considered. Many walls have a structural and a fire containment role, and cannot be punctured without taking special steps to restore their integrity.

LANs will quickly become a mixture of wired and wireless systems, depending on the network needs and design constraints. In larger enterprise networks, the core and distribution layers will continue to be wired backbone systems, typically connected by fiber optics and UTP cables. The layer closest to the end user, the access layer, will be the one most affected by wireless deployment.

Building-to-building Wireless Links
Building-to-building connections are typically made using fiber optics, because of the high available speeds and the avoidance of the ground protection measures required with copper media. Installing fiber-optic cable between buildings is very expensive and time consuming. Even short distances are difficult to cover due to existing underground utilities, concrete, and other structural obstacles. Lashed aerial installation is an alternative installation choice. WLANs have currently become a popular choice since installation is limited to building mounted antennas. What about building-to-building connections where distances exceed property bounds or cabling limitations? Most businesses utilize WAN connectivity between distant metropolitan sites. Some businesses use microwave between distant sites. With wireless LAN bridges, buildings up to 32 km (20 miles) away can be connected at speeds up to 11 Mbps.

Typically, the greater the distance between buildings the higher the cost of wireless LAN installation. The standard, rubber duck antennas will not be adequate. Towers and special high-gain antennas are required. Tower installations can be expensive, depending on the height and construction requirements. The initial cost may be recovered within the first year. Savings are generated from increased productivity using greater bandwidth and discontinued monthly leased-line fees.

Cisco wireless bridges offer many advantages over more costly alternative connections. For example, a T-I line typically costs approximately 400 to 1000 U.S. dollars per month. For a site with four buildings, that could cost anywhere from 15,000 to 36,000 U.S. dollars per year. With a wireless system, payback for the hardware costs could actually occur in less than a year.

If a T-I line is not available or the buildings are located on the same property, an underground cable could be put in place. However, trenching can cost over 100 U.S. dollars for every 0.3 m (1 ft), depending upon the task. To connect three buildings located 305 m (1000 ft) apart from each other, the cost could exceed 200,000 U.S. dollars.

Microwave is a possible solution. With microwave a government license is usually required. In the United States, this is obtained from the Federal Communications Commission (FCC). This license serves as a registration process that allows the license holder to take legal action against those who interfere. The cost of the equipment is typically over 10,000 U.S. dollars per site, which does not include the cost of installation items. Performance may be severely degraded in the event of heavy fog, rain, or snow. Microwave also tends to be point-to-point. Multipoint connections are usually not possible.

Regardless of whether they are wired or wireless, modern networks must be able to handle higher bandwidth, more users, more applications, and more mobility. Mixtures of both wired and wireless technologies are required to provide the solutions. The network designer is responsible for providing the most cost-effective design and solution that meets or exceeds the organizational needs.

A site survey must be completed before deployment decisions are made. For instance, initial plans may include a wireless solution, but the site survey could indicate that wireless will be ineffective. Conversely, a wired solution may be initially planned and the final survey may prove wireless to be a better choice. Site design, preparation, and survey will be covered in detail later in the course.


Lab Activity

Lab Exercise: Wireless Component and Media Identification

The student will identify the basic media characteristics of WLANs and the components of a WLAN. Students will also describe the functions of these wireless components.