Session layer

Session
In the seven-layer OSI model of computer networking, the session layer is layer 5.wikipedia
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Session (computer science)

sessionsessionssession management
The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue.
Communication Transport may be implemented as part of protocols and services at the application layer, at the session layer or at the transport layer in the OSI model.

OSI model

OSIOSI Reference Modellayer 2
In the seven-layer OSI model of computer networking, the session layer is layer 5.
The session layer controls the dialogues (connections) between computers.

Presentation layer

Presentationdata presentationfront end
Within the service layering semantics of the OSI network architecture, the session layer responds to service requests from the presentation layer and issues service requests to the transport layer.
Encryption is typically done at this level too, although it can be done on the application, session, transport, or network layers, each having its own advantages and disadvantages.

Transport layer

transporttransport protocollayer 4
Within the service layering semantics of the OSI network architecture, the session layer responds to service requests from the presentation layer and issues service requests to the transport layer. OSI's session management in connection with the typical transport protocols (TCP, SCTP), is contained in the transport-layer protocols, or otherwise considered the realm of the application layer protocols.
Multiplexing: Ports can provide multiple endpoints on a single node. For example, the name on a postal address is a kind of multiplexing, and distinguishes between different recipients of the same location. Computer applications will each listen for information on their own ports, which enables the use of more than one network service at the same time. It is part of the transport layer in the TCP/IP model, but of the session layer in the OSI model.

NetBIOS

NetBIOS session serviceNetBIOS/NetBEUIIBM NetBIOS Extended User Interface (NetBEUI) v 3.0
NetBIOS, Network Basic Input Output System
NetBIOS is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network.

AppleTalk

NBPZIPAARP
Other examples of session layer implementations include Zone Information Protocol (ZIP) – the AppleTalk protocol that coordinates the name binding process, and Session Control Protocol (SCP) – the DECnet Phase IV session-layer protocol.

SOCKS

SOCKS5Socket SecureSOCKS 4 and SOCKS 5 protocols
SOCKS, the SOCKS internet protocol, see Internet socket
SOCKS performs at Layer 5 of the OSI model (the session layer, an intermediate layer between the presentation layer and the transport layer).

Application layer

Applicationapplication protocolapplication-layer
OSI's session management in connection with the typical transport protocols (TCP, SCTP), is contained in the transport-layer protocols, or otherwise considered the realm of the application layer protocols.
OSI also explicitly distinguishes additional functionality below the application layer, but above the transport layer at two additional levels: the session layer, and the presentation layer.

Computer network

networknetworkingcomputer networking
In the seven-layer OSI model of computer networking, the session layer is layer 5.

Remote procedure call

RPCremote procedure callsremoting
Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs).

Open Systems Interconnection

OSIopen systemOpen System Interconnection
An example of a session-layer protocol is the OSI protocol suite session-layer protocol, also known as X.225 or ISO 8327.

Duplex (telecommunications)

half-duplexfull-duplexduplex
If a connection is not used for a long period, the session-layer protocol may close it and re-open it. It provides for either full duplex or half-duplex operation and provides synchronization points in the stream of exchanged messages.

Synchronization (computer science)

synchronizationsynchronoussynchronization primitive
If a connection is not used for a long period, the session-layer protocol may close it and re-open it. It provides for either full duplex or half-duplex operation and provides synchronization points in the stream of exchanged messages.

DECnet

CCNET
Other examples of session layer implementations include Zone Information Protocol (ZIP) – the AppleTalk protocol that coordinates the name binding process, and Session Control Protocol (SCP) – the DECnet Phase IV session-layer protocol.

Application checkpointing

checkpointingcheckpointJob checkpointing
Session restoration (checkpointing and recovery)

Enterprise JavaBeans

EJBCMPEnterprise Java Beans
An example usage of the session layer is session beans, which are only active as long as the session is active, and are deleted when the session is disconnected.

Web conferencing

webinarwebinarsonline conferencing
An example application is web conferencing, in which the streams of audio and video must be synchronous to avoid so-called lip sync problems.

Lip sync

lip-synchinglip-synclip-synch
An example application is web conferencing, in which the streams of audio and video must be synchronous to avoid so-called lip sync problems.

Flow control (data)

flow controlhardware flow controlCTS
Flow control ensures that the person displayed on screen is the current speaker.

Live television

livelive broadcastbroadcast live
Another application is in live TV programs, where streams of audio and video need to be seamlessly merged and transitioned from one to the other to avoid silent airtime or excessive overlap.

H.245

Call Control Protocol for Multimedia CommunicationSonata, H.245
H.245, Call Control Protocol for Multimedia Communication