OSI protocols

Information exchange standards

OSI model
by layer

7. Application layer

* NNTP
* SIP
* SSI
* DNS
* FTP
* Gopher
* HTTP (HTTP/3)
* NFS
* NTP
* SMPP
* SSH
* SMTP
* SNMP
* Telnet
* DHCP
* NETCONF
* more....

6. Presentation layer

* MIME
* XDR
* ASN.1
* ASCII
* TLS
* PGP

5. Session layer

* Named pipe
* NetBIOS
* SAP
* PPTP
* RTP
* SOCKS
* X.225[1]

4. Transport layer

* TCP
* UDP
* SCTP
* DCCP
* QUIC
* SPX

3. Network layer

* IP
* IPv4
* IPv6
* ICMP (ICMPv6)
* IPsec
* IGMP
* IPX
* IS-IS
* AppleTalk
* X.25
* PLP

2. Data link layer

* ATM
* ARP
* SDLC
* HDLC
* CSLIP
* SLIP
* GFP
* PLIP
* IEEE 802
* LLC
* MAC
* L2TP
* Frame Relay
* ITU-T G.hn DLL
* PPP
* X.25 LAPB
* Q.922 LAPF

1. Physical layer

* RS-232
* RS-449
* ITU-T V-Series
* I.430
* I.431
* PDH
* SONET/SDH
* PON
* OTN
* DSL
* IEEE 802
* IEEE 1394
* ITU-T G.hn PHY
* USB
* Bluetooth
* X.21

* v
* t
* e

Internet history timeline

Early research and development:

* 1960–1962: J. C. R. Licklider networking ideas
* 1960–1964: RAND networking concepts developed
* 1962–1964: ARPA networking ideas
* 1965 (1965): NPL network concepts conceived
* 1966 (1966): Merit Network founded
* 1967 (1967): ARPANET planning begins
* 1967 (1967): Symposium on Operating Systems Principles
* 1969 (1969): NPL followed by the ARPANET carry their first packets
* 1970 (1970): Network Information Center (NIC)
* 1971 (1971): Tymnet switched-circuit network
* 1972 (1972): Merit Network's packet-switched network operational
* 1972 (1972): Internet Assigned Numbers Authority (IANA) established
* 1973 (1973): CYCLADES network demonstrated
* 1973 (1973): PARC Universal Packet development begins
* 1974 (1974): Transmission Control Program specification published
* 1975 (1975): Telenet commercial packet-switched network
* 1976 (1976): X.25 protocol approved and deployed on public data networks
* 1978 (1978): Minitel introduced
* 1979 (1979): Internet Activities Board (IAB)
* 1980 (1980): USENET news using UUCP
* 1980 (1980): Ethernet standard introduced
* 1981 (1981): BITNET established

Merging the networks and creating the Internet:

* 1981 (1981): Computer Science Network (CSNET)
* 1982 (1982): TCP/IP protocol suite formalized
* 1982 (1982): Simple Mail Transfer Protocol (SMTP)
* 1983 (1983): Domain Name System (DNS)
* 1983 (1983): MILNET split off from ARPANET
* 1984 (1984): OSI Reference Model released
* 1985 (1985): First .COM domain name registered
* 1986 (1986): NSFNET with 56 kbit/s links
* 1986 (1986): Internet Engineering Task Force (IETF)
* 1987 (1987): UUNET founded
* 1988 (1988): NSFNET upgraded to 1.5 Mbit/s (T1)
* 1988 (1988): Morris worm
* 1988 (1988): Complete Internet protocol suite
* 1989 (1989): Border Gateway Protocol (BGP)
* 1989 (1989): PSINet founded, allows commercial traffic
* 1989 (1989): Federal Internet Exchanges (FIX East|FIXes)
* 1990 (1990): GOSIP (without TCP/IP)
* 1990 (1990): ARPANET decommissioned
* 1990 (1990): Advanced Network and Services (ANS)
* 1990 (1990): UUNET/Alternet allows commercial traffic
* 1990 (1990): Archie search engine
* 1991 (1991): Wide area information server (WAIS)
* 1991 (1991): Gopher
* 1991 (1991): Commercial Internet eXchange (CIX)
* 1991 (1991): ANS CO+RE allows commercial traffic
* 1991 (1991): World Wide Web (WWW)
* 1992 (1992): NSFNET upgraded to 45 Mbit/s (T3)
* 1992 (1992): Internet Society (ISOC) established
* 1993 (1993): Classless Inter-Domain Routing (CIDR)
* 1993 (1993): InterNIC established
* 1993 (1993): AOL added USENET access
* 1993 (1993): Mosaic web browser released
* 1994 (1994): Full text web search engines
* 1994 (1994): North American Network Operators' Group (NANOG) established

Commercialization, privatization, broader access leads to the modern Internet:

* 1995 (1995): New Internet architecture with commercial ISPs connected at NAPs
* 1995 (1995): NSFNET decommissioned
* 1995 (1995): GOSIP updated to allow TCP/IP
* 1995 (1995): very high-speed Backbone Network Service (vBNS)
* 1995 (1995): IPv6 proposed
* 1996 (1996): AOL changes pricing model from hourly to monthly
* 1998 (1998): Internet Corporation for Assigned Names and Numbers (ICANN)
* 1999 (1999): IEEE 802.11b wireless networking
* 1999 (1999): Internet2/Abilene Network
* 1999 (1999): vBNS+ allows broader access
* 2000 (2000): Dot-com bubble bursts
* 2001 (2001): New top-level domain names activated
* 2001 (2001): Code Red I, Code Red II, and Nimda worms
* 2003 (2003): UN World Summit on the Information Society (WSIS) phase I

* 2003 (2003): National LambdaRail founded
* 2004 (2004): UN Working Group on Internet Governance (WGIG)
* 2005 (2005): UN WSIS phase II
* 2006 (2006): First meeting of the Internet Governance Forum
* 2010 (2010): First internationalized country code top-level domains registered
* 2012 (2012): ICANN begins accepting applications for new generic top-level domain names
* 2013 (2013): Montevideo Statement on the Future of Internet Cooperation
* 2014 (2014): NetMundial international Internet governance proposal
* 2016 (2016): ICANN contract with U.S. Dept. of Commerce ends, IANA oversight passes to the global Internet community on October 1st

Examples of Internet services:

* 1989 (1989): AOL dial-up service provider, email, instant messaging, and web browser
* 1990 (1990): IMDb Internet movie database
* 1994 (1994): Yahoo! web directory
* 1995 (1995): Amazon online retailer
* 1995 (1995): eBay online auction and shopping
* 1995 (1995): Craigslist classified advertisements
* 1995 (1995): AltaVista search engine
* 1996 (1996): Outlook (formerly Hotmail) free web-based e-mail
* 1996 (1996): RankDex search engine
* 1997 (1997): Google Search
* 1997 (1997): Babel Fish automatic translation
* 1998 (1998): Yahoo Groups (formerly Yahoo! Clubs)
* 1998 (1998): PayPal Internet payment system
* 1998 (1998): Rotten Tomatoes review aggregator
* 1999 (1999): 2ch Anonymous textboard
* 1999 (1999): i-mode mobile internet service
* 1999 (1999): Napster peer-to-peer file sharing
* 2000 (2000): Baidu search engine
* 2001 (2001): 2chan Anonymous imageboard
* 2001 (2001): BitTorrent peer-to-peer file sharing
* 2001 (2001): Wikipedia, the free encyclopedia
* 2003 (2003): LinkedIn business networking
* 2003 (2003): Myspace social networking site
* 2003 (2003): Skype Internet voice calls
* 2003 (2003): iTunes Store
* 2003 (2003): 4chan Anonymous imageboard
* 2003 (2003): The Pirate Bay, torrent file host
* 2004 (2004): Facebook social networking site
* 2004 (2004): Podcast media file series
* 2004 (2004): Flickr image hosting
* 2005 (2005): YouTube video sharing
* 2005 (2005): Reddit link voting
* 2005 (2005): Google Earth virtual globe
* 2006 (2006): Twitter microblogging
* 2007 (2007): WikiLeaks anonymous news and information leaks
* 2007 (2007): Google Street View
* 2007 (2007): Kindle, e-reader and virtual bookshop
* 2008 (2008): Amazon Elastic Compute Cloud (EC2)
* 2008 (2008): Dropbox cloud-based file hosting
* 2008 (2008): Encyclopedia of Life, a collaborative encyclopedia intended to document all living species
* 2008 (2008): Spotify, a DRM-based music streaming service
* 2009 (2009): Bing search engine
* 2009 (2009): Google Docs, Web-based word processor, spreadsheet, presentation, form, and data storage service
* 2009 (2009): Kickstarter, a threshold pledge system
* 2009 (2009): Bitcoin, a digital currency
* 2010 (2010): Instagram, photo sharing and social networking
* 2011 (2011): Google+, social networking
* 2011 (2011): Snapchat, photo sharing
* 2012 (2012): Coursera, massive open online courses
* 2016 (2016): TikTok, video sharing and social networking

The Open Systems Interconnection protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T. The standardization process began in 1977.

While the seven-layer OSI model is often used as a reference for teaching and documentation,[2] the protocols originally conceived for the model did not gain popularity, and only X.400, X.500, and IS-IS have achieved lasting impact. The goal of an open-standard protocol suite instead has been met by the Internet protocol suite, maintained by the Internet Engineering Task Force (IETF).

## Overview

[edit]

The OSI protocol stack is structured into seven conceptual 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 encapsulation information (header) to the incoming information before it is passed to the lower layer. Headers generally include address of source and destination, error control information, protocol identification and protocol parameters such as flow control options and sequence numbers.

OSI model  Layer  | Protocol data unit (PDU)  | Function[3]

|
|

Host
layers  | 7  | Application | Data | High-level protocols such as for resource sharing or remote file access, e.g. HTTP.
6  | Presentation | Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
5  | Session | Managing communication sessions, i.e., continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes
4  | Transport | Segment | Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing
Media
layers  | 3  | Network | Packet, Datagram[4] | Structuring and managing a multi-node network, including addressing, routing and traffic control
2  | Data link | Frame | Transmission of data frames between two nodes connected by a physical layer
1  | Physical | Bit, Symbol | Transmission and reception of raw bit streams over a physical medium

## Layer 1: physical layer

[edit]

This layer deals with the physical plugs, sockets, electrical/optical specifications and the required line codes.

The physical layer includes 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

[edit]

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. This layer further consists of two sublayers: MAC and LLC.

## Layer 3: network layer

[edit]

* 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

[edit]

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

[edit]

* 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, and 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

[edit]

* 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

[edit]

### Common-Application Service Elements (CASEs)

[edit]

* 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

[edit]

* 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)[5]
* 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

[edit]

* 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

## See also

[edit]

* Protocol stack
* Protocol Wars
* WAP protocol suite

## References

[edit]

1. ^ "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 10 March 2023.
2. ^ Shaw, Keith (2018-10-22). "The OSI model explained: How to understand (and remember) the 7 layer network model". Network World. Archived from the original on 2020-06-15. Retrieved 2020-05-16.
3. ^ "Windows Network Architecture and the OSI Model". Microsoft Documentation. Retrieved 24 June 2020.
4. ^ "What is a packet? | Network packet definition". Cloudflare.
5. ^ FTAM support claimed by IBM, Novell, Sun, Unisys etc Archived 2013-03-02 at the Wayback Machine, Joint Interoperability Test Command

* v
* t
* e

International Organization for Standardization (ISO) standards

List of ISO standards – ISO romanizations – IEC standards

1–9999|

* 1
* 2
* 3
* 4
* 6
* 7
* 9
* 16
* 17
* 31
* -0
* -1
* -3
* -4
* -5
* -6
* -7
* -8
* -9
* -10
* -11
* -12
* -13
* 68-1
* 128
* 216
* 217
* 226
* 228
* 233
* 259
* 261
* 262
* 302
* 306
* 361
* 500
* 518
* 519
* 639
* -1
* -2
* -3
* -5
* -6
* 646
* 657
* 668
* 690
* 704
* 732
* 764
* 838
* 843
* 860
* 898
* 965
* 999
* 1000
* 1004
* 1007
* 1073-1
* 1073-2
* 1155
* 1413
* 1538
* 1629
* 1745
* 1989
* 2014
* 2015
* 2022
* 2033
* 2047
* 2108
* 2145
* 2146
* 2240
* 2281
* 2533
* 2709
* 2711
* 2720
* 2788
* 2848
* 2852
* 2921
* 3029
* 3103
* 3166
* -1
* -2
* -3
* 3297
* 3307
* 3601
* 3602
* 3864
* 3901
* 3950
* 3977
* 4031
* 4157
* 4165
* 4217
* 4909
* 5218
* 5426
* 5427
* 5428
* 5725
* 5775
* 5776
* 5800
* 5807
* 5964
* 6166
* 6344
* 6346
* 6373
* 6385
* 6425
* 6429
* 6438
* 6523
* 6709
* 6943
* 7001
* 7002
* 7010
* 7027
* 7064
* 7098
* 7185
* 7200
* 7498
* -1
* 7637
* 7736
* 7810
* 7811
* 7812
* 7813
* 7816
* 7942
* 8000
* 8093
* 8178
* 8217
* 8373
* 8501-1
* 8571
* 8583
* 8601
* 8613
* 8632
* 8651
* 8652
* 8691
* 8805/8806
* 8807
* 8820-5
* 8859
* -1
* -2
* -3
* -4
* -5
* -6
* -7
* -8
* -8-I
* -9
* -10
* -11
* -12
* -13
* -14
* -15
* -16
* 8879
* 9000/9001
* 9036
* 9075
* 9126
* 9141
* 9227
* 9241
* 9293
* 9314
* 9362
* 9407
* 9496
* 9506
* 9529
* 9564
* 9592/9593
* 9594
* 9660
* 9797-1
* 9897
* 9899
* 9945
* 9984
* 9985
* 9995

10000–19999|

* 10006
* 10007
* 10116
* 10118-3
* 10160
* 10161
* 10165
* 10179
* 10206
* 10218
* 10279
* 10303
* -11
* -21
* -22
* -28
* -238
* 10383
* 10585
* 10589
* 10628
* 10646
* 10664
* 10746
* 10861
* 10957
* 10962
* 10967
* 11073
* 11170
* 11172
* 11179
* 11404
* 11544
* 11783
* 11784
* 11785
* 11801
* 11889
* 11898
* 11940 (-2)
* 11941
* 11941 (TR)
* 11992
* 12006
* 12052
* 12182
* 12207
* 12234-2
* 12620
* 13211
* -1
* -2
* 13216
* 13250
* 13399
* 13406-2
* 13450
* 13485
* 13490
* 13567
* 13568
* 13584
* 13616
* 13816
* 13818
* 14000
* 14031
* 14224
* 14289
* 14396
* 14443
* 14496
* -2
* -3
* -6
* -10
* -11
* -12
* -14
* -17
* -20
* 14617
* 14644
* 14649
* 14651
* 14698
* 14764
* 14882
* 14971
* 15022
* 15189
* 15288
* 15291
* 15398
* 15408
* 15444
* -3
* -9
* 15445
* 15438
* 15504
* 15511
* 15686
* 15693
* 15706
* -2
* 15707
* 15897
* 15919
* 15924
* 15926
* 15926 WIP
* 15930
* 15938
* 16023
* 16262
* 16355-1
* 16485
* 16612-2
* 16750
* 16949 (TS)
* 17024
* 17025
* 17100
* 17203
* 17369
* 17442
* 17506
* 17799
* 18004
* 18014
* 18181
* 18245
* 18629
* 18760
* 18916
* 19005
* 19011
* 19092
* -1
* -2
* 19114
* 19115
* 19125
* 19136
* 19407
* 19439
* 19500
* 19501
* 19502
* 19503
* 19505
* 19506
* 19507
* 19508
* 19509
* 19510
* 19600
* 19752
* 19757
* 19770
* 19775-1
* 19794-5
* 19831

20000–29999|

* 20000
* 20022
* 20121
* 20400
* 20802
* 20830
* 21000
* 21001
* 21047
* 21122
* 21500
* 21778
* 21827
* 22000
* 22275
* 22300
* 22301
* 22395
* 22537
* 23000
* 23003
* 23008
* 23009
* 23090-3
* 23092
* 23094-1
* 23094-2
* 23270
* 23271
* 23360
* 23941
* 24517
* 24613
* 24617
* 24707
* 24728
* 25178
* 25964
* 26000
* 26262
* 26300
* 26324
* 27000 series
* 27000
* 27001
* 27002
* 27005
* 27006
* 27729
* 28000
* 29110
* 29148
* 29199-2
* 29500

30000+|

* 30170
* 31000
* 32000
* 37001
* 38500
* 39075
* 40314
* 40500
* 42010
* 45001
* 50001
* 55000
* 56000
* 80000

* Category

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template