Session LayerProtocols in theSessio

Session Layer
Protocols in theSession layercoordinate and maintain communications between two nodes
on the network. The termsessionrefers to a connection for ongoing data exchange between
two parties. Historically, it was used in the context of terminal and mainframe communications, in which theterminalis a device with little (if any) of its own processing or disk capacity that depends on a host to supply it with software and processing services. Today, the term
session is often used in the context of a connection between a remote client and an access
server or between a Web browser client and a Web server. When thinking in terms of the
OSI model, however, this is misleading. Modern networks don’t make use of Session layer
protocols for routine data exchange, such as Web page retrieval or file sharing. Yet applications that require precisely coordinated data exchanges, such as videoconferencing or voice
(telephone) communication, still use Session layer protocols.
Among the Session layer’s functions are establishing and keeping alive the communications
link for the duration of the session, keeping the communication secure, synchronizing the dialogue between the two nodes, determining whether communications have been cut off, and, if
so, figuring out where to restart transmission, and terminating communications. Session layer
services also set the terms of communication by deciding which node communicates first and
how long a node can communicate. If a connection is lost, the Session layer protocols will
detect that and initiate attempts to reconnect. If they cannot reconnect after a certain period
of time, they will close the session and inform your client software that communication has
ended. Finally, the Session layer monitors the identification of session participants, ensuring
that only the authorized nodes can access the session