The essential criteria for a data communications network are performance, security, and reliability. Performance is concerned with how data is transmitted without error. It is determined by the response time, which is the time taken between the end of placing a request and the beginning of a reply. Performance is always affected by the number of users, transmission speed, media type, hardware type, and software application.
Security is an important aspect that aims at protecting data from illegal operations such as hacking, changing data format, viruses, and incomplete transmissions. Securing a network require password protection, limiting a user’s ability to access unauthorized data, using firewalls, protecting data through encryption, and using anti-virus programs to detect and remove viruses.
Reliability aims at determining the usability of a network. A network should be able to withstand failures for users to continue using it. This can be realized by installing several network devices that can help each other in case of failure. Reliability is determined by the rate of failure, the duration a network takes to recover from the error, and the ability to withstand failures. In most cases, determining reliability is very complex due to the changing data rate supplied in the network and the usage of the network during busy times.