A communication connection or connection ( English connection or call ) is a communication path ( connection ) which is switched between terminals in any communication network on the basis of selection information ( call ), which designates a destination , in order to exchange messages. The physical path can use different transmission methods in sections:
If a communication link between sender and receiver has to be established and maintained in both directions for the transmission of user data, the type of communication is called connection-oriented . This can be done by switching a line or by establishing a logical channel. A regular communication link has three phases:
- Connection establishment
- Exchange of messages
Connectionless transmissions without transmission in the opposite direction are different .
If two terminals are connected, this is referred to as a point-to-point connection (unicast), if there are more than two, this is referred to as a multipoint connection. These include not the connectionless general radio ( broadcast ), but the various forms of news distribution ( multicast ) with feedback. Special forms of the multipoint connection to services like broadcast ( broadcast ) or multicast ( multicast ) included.
A semi-permanent connection (SPV) is routed to exchanges via fixed message paths and cannot be terminated by the terminals. Another name for an SPV is a pre-ordered permanent dial-up connection .
In the general case, communication connections are switched by exchanges . The totality of terminals, message paths and switching centers that are used together to set up message connections for message exchange is referred to as a message network or simply a network .
In the case of line switching, a switched (physical) channel with a fixed bandwidth is provided for the connection . In the case of storage switching , a logical channel, that is to say that is defined by addressing, is provided; physically, however, the individual transmission sections are used in multiplex operation by several logical connections. This is why a storage-switched connection is also known as a virtual connection ( virtual call ).
A packet switch physically leads the connection via changing, non-permanent paths. The connection properties are ensured by a control logic in the terminals and the switching nodes.
There are many dialing and signaling methods with which connections are set up and cleared down. In line switching for voice communication, pulse dialing , multi-frequency dialing and Digital Subscriber System No. 1 , the protocol stack TCP / IP in packet switching in the Internet .
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