The use of computer networks has grown a lot in recent years, and organizations and institutions have started to establish networks. Each computer network must be designed and implemented according to the conditions and policies of each organization. In fact, computer networks provide the necessary infrastructure to share resources in the organization. If these infrastructures are not designed correctly, different problems will occur when using the network and a lot of money must be spent to maintain the network and adapt it to the desired needs. In general, before the physical design of a computer network, the needs must be identified and analyzed first, for example, why do we intend to create a network in a library and what services should this network provide. What actions should be taken to provide the services and services desired by the majority of users. Issues such as the desired protocol to use the network, network speed, and most importantly network security issues, each of these should be carefully examined. It has been tried, after presenting the basic definitions, to provide material about its practical applications, to help in better decision making.