Switching and Routing
Network control software is needed to create, route and manage
end-to-end data flows over different transmission networks.
In addition of Data also Control Information (CI) send between
network nodes. The rules with which the control software send
and receive control data are called protocols.
The data flows can be established, switched or routed through
the networks, and then closed using the control messages defined
According to the Open Systems Interconnection (OSI)-reference
model protocols are specified in seven layers. The two lowest
layers are transmission oriented (bearer control). The third and
fourth layer handle addressing, routing and Quality of Service
(connection control). The upper layers handle synchronization,
presentation and service specific features (service control).
The most used protocol standard sets are TCP/IP, OSI and SS#7.