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1. Very brief history of telecom and datacom networks

    1.1 Telecommunication networks

Originally was the telecommunication network, mainly based on voice transfer. The main advantage of this network is its ability to convey information within a short known time. Its architecture is built so it can afford a suitable quality of service to any user. The main shortcoming is that prior to any communication, a path, or circuit, has to be established. Then the information always follows the same path during all the communication time. This means that even if data is transmitted, i.e. if one or both parties do not speak, the communication uses network resources (bandwidth).

    1.2 Data networks

Meanwhile, during the last thirty years, something called the Internet began to emerge. The idea was set up a system that could convey information from one point to another, using a path that could change during a communication in case a node break down, preventing this communication to be interrupted. Toa achieve this goal, a protocol has been developed, the now famous Internet Protocol. The idea is to cut the information to transmit into several small pieces that can find their way by themselves. At the beginning, only text information was transmitted, so there was no use to develop a real-time protocol. The way information is conveyed is known as best effort, meaning that the network resources will "do their best" to deliver the information, but they cannot ensure that it will be done in a short time, or even if it will simply be done. The good point is that if their no data to be transmitted, no hardware resource is reserved. These resources are used only if they need to be used.