SYSTEM RESTORATION

The network is the most error-prone of the system components. Usually, multiple vendors are involved, and too few qualified personnel are available to support all the implemented networks. Due to these inherent problems with the network, system degradation is a part of operation, and getting the system back into normal operation is of great importance.

Three primary methods are used to provide service restoration after system degradation. They are as follows: l Redundancy. Redundancy refers to duplicate

hardware and network facility segments that are available at all times. If the primary path fails, a secondary path can continue network operation. l Rerouting. Rerouting is the transmission of

information along alternative paths. The end-to-end transmission initially required is still obtained.

l Reconfiguration. Reconfiguration is the manual or automatic reconfiguration of equipment and/or lines to achieve the original end-to-end connections. Reconfiguration may be the most costly method in time because it requires knowledgeable personnel and the appropriate switching of equipment.

These three modes of operation are short-term solutions meant to keep information moving. A better solution is to correct the degraded or failed circuit and/or equipment so normal operation is restored.

NETWORK DESIGN

The first step in designing a network is to decide whether or not a network is needed. This decision is made easier by soliciting network requests from the command. Once the decision is made to design and install a network, you need to look at the capacity and reliability of the network and the design options.

Many design options are available for designing and building a LAN. Four interrelated factors

contribute to this great flexibility. They are physical layout (topology), access method (protocol), physical connection (cabling), and networking operating system (NOS). There is one additional factor to be considered when designing a network, the need for security. This need for security is met by the implementation of a firewall.

NETWORK REQUESTS

Before committing the money to install a network, you need to research the need for a network for the command. The best way to conduct this research is by using a network request. Always make sure you have all the available information to guide your planning. The following are some guidelines to use when beginning to plan for a network:

Calculate your needs as completely as possible. This will help you decide what components and services will need to be included in the network.

Determine what resources are available at your command for planning, implementing, and running a network.

Determine who needs access to the network and where these people are located. This information will help determine whether a network is a necessary or feasible solution for the command's needs. It will also provide information regarding cabling requirements.

Get to know the current usage and needs in detail. This information will also help decide whether a network is the best solution.

Get a detailed drawing of office locations, existing wiring, and possible server locations.

After gathering and evaluating the information, the decision can be made as to whether or not a network is the way to go. If it is decided to go with a network, it is time to determine what resources are available.

CALCULATING NETWORK CAPACITY

After you've determined the available resources, use only a portion of these for your working calculations. This downsizing will protect you against the losses of these resources.

The amount by which you should decrease your estimates depends on the possible costs if your network is a failure and on how stable the resources are. A general rule to follow is to assume that your available resources will be anywhere from 10 to 50 percent less than estimated. Let's say, that you have 25 PC workstations available to connect to the network. You should plan on connecting 22 (12% less than available), which would leave you with 3 spare workstations. Another example would be: if your NOS is capable of having 250 accounts, reducing this quanity by 10% (25) will help reduce the time that the users will be waiting for the network to respond to their request.

The opposite of this rule is applied when it comes to the cost calculations. When you decide how much time and money it is going to cost, it is a good idea to add an amount or a percentage to the calculations. Projects like networks never seem to be completed on time or at cost, due to unforeseen circumstances.