40:
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This may also be used by the application to do checkpointing. Synchronization points can be used to indicate that a checkpoint has been committed by the application, and after an application crash or a power failure, a resynchronization can be used to indicate that the application has recovered from
871:
This may also be used to interrupt / resume a dialogue at any time, not due to an application failure, but as planned by the application. The application may interrupt a dialogue, start another dialogue in the same session, and resume the previous dialogue in the same session or in another session.
863:
This may be used in real-time audio/video transmission. Synchronization points can be used to insert timestamps to the data flow, and a resynchronization may be used to reset the transmission to start from a new timestamp. For example, if the video stream lags behind the audio stream too much, the
825:
After a session connection is released, the underlying transport connection may be reused for another session connection. Also, a session connection may make use of multiple consecutive transport connections. For example, if, during a session, the underlying transport connection has a failure, the
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The session layer may provide three different dialogue types - two way simultaneous (full-duplex), two way alternate (half-duplex), and one way (simplex). It also provides the mechanisms to negotiate the type of the dialogue, and controls which side has the "turn" or "token" to send data or to
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In the OSI model, the transport layer is not responsible for an orderly release of a connection. Instead, the session layer is responsible for that. However, in modern TCP/IP networks, TCP already provides orderly closing of connections at the transport layer.
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session-layer protocol, also known as X.225 or ISO 8327. In case of a connection loss this protocol may try to recover the connection. 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
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does not concern itself with the OSI model's details of application or transport protocol semantics and therefore does not consider a session layer. OSI's session management in connection with the typical transport protocols (TCP, SCTP), is contained in the
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between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of
843:
for full-duplex operation, but many servers/proxies couldn't handle it correctly, and there was no dialogue negotiation mechanism to check whether full-duplex is usable or not, so its support was eventually dropped by most browsers.
838:
Dialogue control is not implemented in TCP/IP, and is left to the application layer to handle, if necessary. In the widely-used HTTP/1.1 protocol, the client and the server typically work in a half-duplex way. HTTP/1.1 also supports
879:. Activities can be interrupted and resumed explicitly. Compared to implicitly interrupting and resuming dialogues by resynchronization, activity support gives the application simpler control of these dialogues.
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At the minimum, the session layer allows the two sides to establish and use a connection, called a session, and allows orderly release of the connection.
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The session layer may also provide explicit support for managing multiple interruptible dialogues over one or more sessions. These dialogues are called
860:, which aborts the current transmission, sets the synchronization point to a certain value, and restarts transmission from that point.
1046:"X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification"
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Within the service layering semantics of the OSI network architecture, the session layer responds to service requests from the
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receiving side may issue a resynchronization request on the video stream, restarting its transmission from a later timestamp.
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protocol that coordinates the name binding process, and
Session Control Protocol (SCP) – the
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of operating scopes (application, host-to-host, network, link) and not detailed
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The session layer provides the mechanism for opening, closing and managing a
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1072:"What Is Remote Procedure Call (RPC)? Definition from SearchAppArchitecture"
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The session layer may also allow the two sides to insert
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Other examples of session layer implementations include
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protocols, or otherwise considered the realm of the
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ISO-SP, OSI session-layer protocol (X.225, ISO 8327)
64:. Unsourced material may be challenged and removed.
903:Call Control Protocol for Multimedia Communication
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762:An example of a session-layer protocol is the
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18:Layer in standard computer networking model
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124:Learn how and when to remove this message
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1052:from the original on February 1, 2021
779:in the stream of exchanged messages.
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814:Connection establishment and release
62:adding citations to reliable sources
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801:and issues service requests to the
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985:Sockets Direct Protocol
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854:synchronization points
777:synchronization points
757:remote procedure calls
1076:SearchAppArchitecture
58:improve this article
1115:Apple.developer.com
737:computer networking
731:In the seven-layer
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47:This article
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16:
1136:. Retrieved
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786:(ZIP) – the
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114:October 2009
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56:Please help
51:verification
48:
20:
15:
970:SOCKS, the
773:half-duplex
769:full duplex
671:IEEE 802.16
666:IEEE 802.15
661:IEEE 802.11
585:IEEE 802.11
556:Frame Relay
1133:www.w3.org
1033:References
877:activities
656:IEEE 802.3
580:Q.922 LAPF
551:IEEE 802.3
531:IEEE 802.2
318:Named pipe
84:newspapers
1159:OSI model
1138:August 4,
1081:August 4,
1056:March 10,
928:NetBIOS,
883:Protocols
788:AppleTalk
733:OSI model
691:Bluetooth
676:IEEE 1394
636:SONET/SDH
597:1.
482:2.
460:AppleTalk
404:3.
358:4.
309:5.
263:6.
155:7.
140:OSI model
25:OSI model
1153:Category
1050:Archived
1021:See also
809:Services
759:(RPCs).
250:more....
901:H.245,
752:session
745:layer 5
323:NetBIOS
244:NETCONF
98:scholar
29:Layer 8
958:SMPP,
952:RTCP,
940:PPTP,
922:L2TP,
910:iSNS,
889:ADSP,
792:DECnet
739:, the
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606:RS-232
573:
434:ICMPv6
234:Telnet
198:HTTP/3
189:Gopher
100:
93:
86:
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27:, see
1111:(PDF)
1108:"ZIP"
983:SDP,
977:ZIP,
972:SOCKS
964:SCP,
946:RPC,
934:PAP,
916:L2F,
895:ASP,
626:I.431
621:I.430
511:CSLIP
455:IS-IS
440:IPsec
347:X.225
343:SOCKS
287:ASCII
282:ASN.1
146:layer
105:JSTOR
91:books
1140:2022
1083:2022
1058:2023
996:The
575:LAPB
571:X.25
546:L2TP
526:PLIP
516:SLIP
506:HDLC
501:SDLC
465:X.25
445:IGMP
430:ICMP
423:IPv6
418:IPv4
387:QUIC
382:DCCP
377:SCTP
333:PPTP
272:MIME
239:DHCP
229:SNMP
224:SMTP
214:SMPP
194:HTTP
164:NNTP
77:news
771:or
743:is
735:of
686:USB
651:DSL
646:OTN
641:PON
631:PDH
566:PPP
541:MAC
536:LLC
521:GFP
496:ARP
491:ATM
470:PLP
450:IPX
392:SPX
372:UDP
367:TCP
338:RTP
328:SAP
297:PGP
292:TLS
277:XDR
219:SSH
209:NTP
204:NFS
184:FTP
179:DNS
174:SSI
169:SIP
144:by
60:by
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413:IP
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