Session Layer

The fifth layer of the seven OSI model in computer networking is known as the session layer. The session layer offers the apparatus for opening, closing and managing a session between end user application processes. In other words, this layer finds connections which are otherwise known as sessions. Many file downloads are requested by a specific FTP application which the session layer keeps record of, or multiple connections from a single terminal client or web page retrievals.

The examples of session

For instance, session layer protocol is the OSI protocol suite session layer protocol, otherwise known as X.225 or ISO 8327. If there is a connection loss this protocol may try to retrieve the connection and if connection is not use for long time, the session layer protocol may close it and re-open it. This offers for either full duplex or half-duplex operation and offers synchronization points in the stream of exchanged messages.

The other examples of session layer implementations are Zone Information Protocol and the Apple Talk protocol which coordinates the name binding process, and Session Control Protocol of the DECnet phase IV session layer protocol. Inside the service layering semantics of the OSI network build up, the session layer responds to service requests from the presentation layer and issues service requests to the transport layer.

The functions and benefits of the session layer

The transport layer is responsible for services such as Authentication, Permissions and Session restoration. The primary duty of this layer is session check-pointing and recovery. This permits information of different streams, may originate from various resources to be properly combined or synchronized. For an instance, web conferencing is an application in which the streams of audio and video must be synchronous to avoid so called lip synch problems. Floor control makes sure that the person displayed on screen is the current speaker. And live TV programs, where streams of audio and video require be seamlessly joining and transitioning to and fro to avoid silent airtime or excessive overlap.

To compare to the TCP/IP model which do not concern with the OSI model’s details of application or transport protocol semantics and therefore does not think about a session layer. OSI's session management in link with the classic transport protocols, is contained in the transport layer protocols, or otherwise believed the sphere of the application layer protocol. TCP/IP’s layers are narrations of operating scopes and not detailed instructions of operating procedures or data semantics.

Questions:

• What is session layer?
• State briefly the functions of session layer.