As briefly mentioned earlier in this unit, a network needs to meet certain requirements, or criteria, to serve a particular situation. There are many different dimensions for such requirements.
Performance is the most important criterion as it affects users constantly. There are many parameters related to performance. From a single end user's perspective, transit time and response time are key performance parameters.
transit time
The transit time is the time a message needs to travel from the originating end of the network to the intended destination in the network.
response time
The response time of a network is the time between a user making a request for a network service and the network responding to this request.
For massive data transfers between network links, bandwidth and delay are key performance parameters.
bandwidth
The bandwidth limits the maximum data rate at which a user can send data across a network.
delay
The delay is the time measured from the time when the data first enter the network to the time the data finally exit the network to reach the intended destination.
The technology used in the computer network also affects the set of parameters. Performance depends on various factors; e.g. the number of simultaneous users, the number of connected computers — and their traffic profiles. Given these factors, we can design a network to meet the performance criteria. If network traffic increases beyond the designed capacity, performance will deteriorate.
Reliability is another key criterion of a network. Since computers and computer networks support our daily life, network reliability is an important criterion to ensure normalcy.
Computer networks are widespread and the Internet has made them conveniently accessible. Company data including customer profiles and financial information are extremely valuable to a company. Personal data are sensitive, and various governments including the Hong Kong SAR Government have data protection regulations. Inside a company, network security has become important to ensure proper access. With the advent of the Internet in the last decade, there has been a lot of concern and discussion about information security. Hence, a computer network needs to meet certain security criteria as well. You will learn more about network security in Unit 9.
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