Connection-oriented protocol
A communication link or connection (English connection or call) is a communication path ( connection), which is due to a choice of information (call) that identifies a target, between terminals connected in any communications network to exchange messages. In this case, the physical path sections use different transmission methods:
If a communication link between the transmitter and receiver must be established and maintained for the transmission of user data, called connection-oriented communication type. This can be done through the mediation of a line or by building a logical channel. A communication link has three phases:
Two terminals connected, this is called a point-to -point connection (unicast ), there are more than two, as a multi- point connection. Special forms of multicast may include broadcast services such as (broadcast) or group ( multicast).
In contrast, connectionless transmissions, for example, radio (broadcast) or message distribution (multicast).
Placement types
A communication link may be connected by either fixed or circuit switching ( circuit switching ) or in packet switching ( switching of packetized messages) are established and maintained.
A leased line is a permanent communication link, which is not going through the switching devices in the switching centers.
A semi-permanent connection (SPV ) is performed via permanently switched communications paths in central offices and can not be degraded by the end user. Another name for the SPV is Pre-ordered Dauerwählverbindung.
In the general case communication links of switches are switched. The totality of terminals, communication paths and switching centers, which serve together for the establishment of communication links to the message exchange, is referred to as a news network or simply network ( communication network).
With circuit switching is provided with a fixed bandwidth for the connection, a switched (physical ) channel. The store and forward is a logical, so provided by addressing predefined channel; physically transfer the individual sections but are used in the multiplexing of multiple logical connections. Therefore, a memory -switched connection is also referred to as a virtual connection (virtual call).
A packet switching leads connecting physically on changing non-permanent paths. It is ensured by a control logic in the terminals and the switching node, the connection property.
Selection and signaling procedures with which connections are established and terminated, there are very many. In circuit switching for voice communication include pulse dialing, tone dialing and Digital Subscriber System No.. 1 to the packet switching in the Internet protocol stack TCP / IP.