A communication system or communication network, and especially with regard to telecommunication, a telecommunication system or telecommunication network is a term in communication technology for the combined features of the message traffic in a communication network . In the narrower sense, a communication system is a device or an infrastructure for the transmission of information. Communications systems provide to communication links between multiple terminals ago. Open communication systems allow free communication between all connected terminals. An important prerequisite for open communication systems is the standardization of the interfaces and the logical functions . In data networks ( data networks ), this is achieved by orienting towards hierarchically structured architecture models with several standardized protocol levels. The generally accepted architecture model is the OSI model .
The term communication systems is used in particular to describe the properties and the classification of various technical communication networks. Properties of communication relationships in networks are listed below.
It is estimated that the global technical capacity to receive information over (analog and digital) networks has grown from 433 (optimally compressed) exabytes in 1986 to 2,000 (optimally compressed) exabytes (or 2 zettabytes) in 2007. This is the informational equivalent of a little over 55 daily newspapers per person per day in 1986 and 181 daily newspapers per person per day in 2007. The vast majority of the information received worldwide is still via (unidirectional) broadcast and radio networks. Only 3.5% of the information (in bytes) is transmitted via (bidirectional) telecommunications networks (the vast majority of it via landline internet access , around 96% of it).
Circuit switched / packet switched / message switched
There are three basic forms of switching technology :
- Message brokerage - the message is completely delivered to the recipient via an intermediary ( e.g. messenger / letter )
- Line switching - exclusive line switching between the communication partners ( e.g. telephone network )
- Packet switching - message is broken down into packets and transmitted to the recipient (e.g. Internet )
In message-switched communication, the message is brought in one piece from the sender to the recipient. When a message extends over time, it is usually transmitted gradually. In the case of line switching, a communication connection is established between the terminals in which all parts take the same route. In packet switching , each part (packet) is processed individually as a piece and can thus take different routes, for example depending on the router that is currently selecting the fastest route.
Connection-oriented - connectionless
Identifies the property of whether a message connection must be established before the message can be transmitted . In connection-oriented communication systems, communication is divided into the three phases of connection establishment, message transmission and connection disconnection. In the case of connectionless services, the connection is not established and cleared; in the case of multipoint connections , the actual message is placed in an envelope on which the destination of the message is recorded. Permanent line switching can remain connectionless.
Confirmed - unconfirmed
Describes the property of whether the sender can know that the message has arrived correctly at the recipient (for example within a period of time). In the case of letter post, this is the acknowledgment of receipt, in connectionless networks usually an acknowledgment message is sent back for confirmation, and in connection-oriented systems a line check can be carried out at regular intervals, if the correctness of this, an error-free transmission of the data that is transmitted in the meantime is assumed.
Synchronous - asynchronous
Describes the properties of the time consumption of message transmission, especially in the case of periodic message connections. With synchronous communication connections, the terminals run in the same cycle, the information always arrives at the right time via the transmission path. In asynchronous communication systems, parts of the message can travel for different lengths of time and, on different routes, also arrive interchanged.
Temporary - static - permanent
In the case of a temporary dial-up connection , a message connection is only established when required and is cleared down again after the data transfer has been completed. No guarantee can be given that sufficient resources will be available for a connection. With static leased lines, a connection between selected endpoints is maintained over a longer period of time, even if it is not used. In the case of permanent connections, the end points cannot be changed, and there is no need to establish or disconnect connections.
Simplex / duplex - half duplex / full duplex
With simplex only one participant can send ( implicit unconfirmed connection). With duplex , both participants can send and receive. In full duplex the participants can send and receive simultaneously, in half-duplex is alternately transmitted or received.
Stationary - quasi-stationary - mobile
The local reference is fixed for stationary terminals. In the case of quasi-stationary connections, the terminal is mobile, but remains in the same place during the message transmission. With mobile connections, the message transmission remains independent of the change of location.
Network structure, topology
Describes the possible paths that messages can take in the communication network. The arrangement and properties of the paths are called topology , particularly in relation to the structure of a computer network .
User-related / device-related
Describes the type of addressing of an end point of the message transmission. If it is terminal-related, the message is brought to the location of the device and must be recorded there by the user. In the case of a personalized communication system, the person is designated regardless of the connection to the communication system.
When using, in particular, the exclusive reserved use for one connection stands compared to a shared connection for several users. The message transmission can be designed as a broadcast to many unknown recipients, or it can enable interactive switching with a return channel.
The tariffing of services can take place according to parameters of the connection or the message. For example, according to duration, time of day and distance of the connection, or according to volume, weight, type of message form. The tariff can also include the option of having the sender, the recipient or both of them pay pro rata for each message, or they can be settled using a flat rate ( flat rate ).
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