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. LAN CONFIGURATIONS (TOPOLOGIES) The physical arrangement of a LAN’s components is called its configuration or topology. The three major types  of  LAN  configurations,  or  topologies,  are  the star, the bus, and the ring. You can also create hybrid topologies   by   combining   features   of   these configurations. For example, several bus networks can be joined together to form a ring of buses. Each  topology  requires  LAN  components  to  be connected   in   a   different   arrangement.   These components are also referred to as nodes. Remember, a node is any point on a network where data can be sent (transmitted)  or  received—a  workstation,  server,  and  so on. The Star Network In a star network, each component is connected directly to the central computer or network server, as 1-9