OSI protocols

The OSI model
7 Application layer
6 Presentation layer
5 Session layer
4 Transport layer
3 Network layer
2 Data link layer
LLC sublayer MAC sublayer
1 Physical layer

The Open Systems Interconnection (OSI) protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T starting in 1977.

While the seven-layer OSI model is still often referenced, of the protocols themselves only X.400, X.500, and IS-IS have had much lasting impact. The goal of a series of open, non-proprietary network protocols is now met by the competing TCP/IP stack.

1 Overview
2 Layer 1: physical layer
3 Layer 2: data link layer
4 Layer 3: network layer
5 Layer 4: transport layer
6 Layer 5: session layer
7 Layer 6: presentation layer
8 Layer 7: application layer
- 8.1 Common-Application Service Elements (CASEs)
- 8.2 Application processes
9 Routing protocols
10 See also
11 References

Overview

OSI protocols stacks are split into seven layers. The layers form a hierarchy of functionality starting with the physical hardware components to the user interfaces at the software application level. Each layer receives information from the layer above, processes it and passes it down to the next layer. Each layer adds its own encapsulation information (header) to the incoming information before it is passed to the lower layer. Headers generally include address of destination and source, check sums (for error control), type of protocol used in the current layer, and other options such as flow control options and sequence numbers (used to ensure data is sent in order).

The Manufacturing Automation Protocol (MAP) user group, focused on real-time control of manufacturing robots of various types, implements layer 1 (physical), a two-sublayer layer 2 (data link) with LLC Type 3 on top of the medium access layer, and then the layer 7 Manufacturing Message System on top. Layers 3 to 6 are not present. This stack is intended just for the robots themselves; the robot controller would load files with a full seven-layer stack with FTAM file transfer on top. Parts of the Signaling System 7 stack are OSI derivatives.

Layer 1: physical layer

This layer deals with the physical plugs and sockets and electrical specification of signals only.

This is the medium over which the digital signals are transmitted. It can be twisted pair, coaxial cable, optical fiber, wireless, or other transmission media.

Layer 2: data link layer

The data link layer packages raw bits from the physical layer into frames (logical, structured packets for data). It is specified in ITU-T Rec. X.212 [ISO/IEC 8886], ITU-T Rec. X.222 and others. This layer is responsible for transferring frames from one host to another. It might perform error checking.

Layer 3: network layer

Connectionless Network Service (CLNS) – ITU-T Rec. X.213 [ISO/IEC 8348]. SCCP is based on X.213.
Connectionless Network Protocol (CLNP) – ITU-T Rec. X.233 [ISO/IEC 8473-1].
Connection-Oriented Network Service (CONS) – ITU-T Rec. X.213 [ISO/IEC 8348].
Connection-Oriented Network Protocol (X.25) – ITU-T Rec. X.233 [ISO/IEC 8878]. This is the use of the X.25 protocol to provide the CONS.
Network Fast Byte Protocol – ISO/IEC 14700
End System to Intermediate System Routing Exchange Protocol (ES-IS) - ISO/IEC 9452 (reprinted in RFC 995).
Intermediate System to Intermediate System Intra-domain Routing Protocol (IS-IS) - ISO/IEC 10589 (reprinted in RFC 1142), later adapted for the TCP/IP model.
End System Routing Information Exchange Protocol for use with ISO/IEC 8878 (SNARE) – ITU-T Rec. X.116 [ISO/IEC 10030].

This level is in charge of transferring data between systems in a network, using network-layer addresses of machines to keep track of destinations and sources. This layer uses routers and switches to manage its traffic (control flow control, error check, routing etc.) So here it takes all routing decisions, it deals with end to end data transmission.

Layer 4: transport layer

The connection-mode and connectionless-mode transport services are specified by ITU-T Rec. X.214 [ISO/IEC 8072]; the protocol that provides the connection-mode service is specified by ITU-T Rec. X.224 [ISO/IEC 8073], and the protocol that provides the connectionless-mode service is specified by ITU-T Rec. X.234 [ISO/IEC 8602].

Transport Protocol Class 0 (TP0)
Transport Protocol Class 1 (TP1)
Transport Protocol Class 2 (TP2)
Transport Protocol Class 3 (TP3)
Transport Protocol Class 4 (TP4)
Transport Fast Byte Protocol – ISO 14699

The transport layer transfers data between source and destination processes. Generally, two connection modes are recognized, connection-oriented or connectionless. Connection-oriented service establishes a dedicated virtual circuit and offers various grades of guaranteed delivery, ensuring that data received is identical to data transmitted. Connectionless mode provides only best-effort service without the built-in ability to correct errors, which includes complete loss of data without notifying the data source of the failure. No logical connection, and no persistent state of the transaction exists between the endpoints, lending the connectionless mode low overhead and potentially better real-time performance for timing-critical applications such as voice and video transmissions.

Layer 5: session layer

Session service – ITU-T Rec. X.215 [ISO/IEC 8326]
Connection-oriented Session protocol – ITU-T Rec. X.225 [ISO/IEC 8327-1]
Connectionless Session protocol – ITU-T Rec. X.235 [ISO/IEC 9548-1]

The session layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. The OSI model made this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session checkpointing and recovery, which is not usually used in the Internet Protocol Suite. The session layer is commonly implemented explicitly in application environments that use remote procedure calls.

Layer 6: presentation layer

Presentation service – ITU-T Rec. X.216 [ISO/IEC 8822]
Connection-oriented Presentation protocol – ITU-T Rec. X.226 [ISO/IEC 8823-1]
Connectionless Presentation protocol – ITU-T Rec. X.236 [ISO/IEC 9576-1]

This layer defines and encrypts/decrypts data types from the application layer. Protocols such as MIDI, MPEG, and GIF are presentation layer formats shared by different applications.

Layer 7: application layer

Common-Application Service Elements (CASEs)

Association Control Service Element (ACSE) – ITU-T Rec. X.217 [ISO/IEC 8649], ITU-T Rec. X.227 [ISO/IEC 8650-1], ITU-T Rec. X.237 [ISO/IEC 10035-1].
Reliable Transfer Service Element (RTSE) – ITU-T Rec. X.218 [ISO/IEC 9066-1], ITU-T Rec. X.228 [ISO/IEC 9066-2].
Remote Operations Service Element (ROSE) – ITU-T Rec. X.219 [ISO/IEC 9072-1], ITU-T Rec. X.229 [ISO/IEC 9072-2]. TCAP is related to X.219.
Commitment, Concurrency, and Recovery service element (CCRSE)
Security Exchange Service Element (SESE)

This keeps track of how each application talks to another application. Destination and source addresses are linked to specific applications.

Application processes

Common management information protocol (CMIP) – ISO 9596 / X.700
Directory services (DS) – X.500, later modified for the TCP/IP stack as LDAP
File transfer, access, and management (FTAM)^[1]
Message handling system (MHS) – X.400
Virtual terminal protocol (VT) - ISO 9040/9041
Remote Database Access (RDA)
Distributed Transaction Processing (OSI TP)
Interlibrary Loan Application Protocol (ILAP)
Document Transfer And Manipulation (DTAM)
Document Printing Application (DPA)
Document Filing and Retrieval (DFR)

Routing protocols

Intermediate System to Intermediate System (IS-IS) – ISO 10589 (reprinted in RFC 1142)
End System to Intermediate System (ES-IS) – ISO 9542 (reprinted in RFC 995)
Interdomain Routing Protocol (IDRP) – ISO 10747

References

^ FTAM support claimed by IBM, Novell, Sun, Unisys etc, Joint Interoperability Test Command

ISO standards

Lists Daftar/Tabel -- ISO standards Daftar/Tabel -- ISO romanizations Daftar/Tabel -- IEC standards Categories Category:ISO standards Category:OSI protocols

1–9999	1 2 3 4 5 6 7 9 16 31 -0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 128 216 217 226 228 233 259 269 302 306 428 518 519 639 -1 -2 -3 -5 -6 646 690 732 764 843 898 1000 1004 1007 1073-1 1413 1538 1745 2014 2015 2022 2108 2145 2146 2240 2281 2709 2711 2788 2852 3029 3103 3166 -1 -2 -3 3297 3307 3602 3864 3901 3977 4031 4157 4217 5218 5775 5776 5800 5964 6166 6344 6346 6425 6429 6438 6523 6709 7001 7002 7098 7185 7200 7498 7736 7810 7811 7812 7813 7816 8000 8178 8217 8571 8583 8601 8632 8652 8691 8807 8820-5 8859 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 -14 -15 -16 8879 9000/9001 9075 9126 9293 9241 9362 9407 9506 9529 9564 9594 9660 9897 9945 9984 9985 9995

10000–19999	10006 10118-3 10160 10161 10165 10179 10206 10218 10303 -11 -21 -22 -28 -238 10383 10487 10585 10589 10646 10664 10746 10861 10957 10962 10967 11073 11170 11179 11404 11544 11783 11784 11785 11801 11898 11940 11941 11941 (TR) 11992 12006 12182 12207 12234-2 13211 -1 -2 13216 13250 13399 13406-2 13407 13450 13485 13490 13567 13568 13584 13616 14000 14031 14396 14443 14496 -2 -3 -6 -10 -11 -12 -14 -17 -20 14644 -1 -2 -3 -4 -5 -6 -7 -8 -9 14649 14651 14698 -2 14750 14882 14971 15022 15189 15288 15291 15292 15408 15444 15445 15438 15504 15511 15686 15693 15706 -2 15707 15897 15919 15924 15926 15926 WIP 15930 16023 16262 16750 17024 17025 17369 17799 18000 18004 18014 18245 18629 18916 19005 19011 19092 -1 -2 19114 19115 19125 19136 19439 19501:2005 19752 19757 19770 19775-1 19794-5

20000+	20000 20022 21000 21047 21827:2002 22000 23270 23271 23360 24613 24707 25178 25964-1 26000 26300 26324 27000 series 27000 27001 27002 27003 27004 27005 27006 27007 27729 27799 28000 29110 29199-2 29500 31000 32000 38500 42010 80000 (-2)

See also All articles with prefix "ISO"

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