What is the best statement regarding the purpose of using the OSI model?

History

The development of the OSI model started in the late 1970s to support the emergence of the diverse computer networking methods that were competing for application in the large national networking efforts in the world (see Protocol Wars). In the 1980s, the model became a working product of the Open Systems Interconnection group at the International Organization for Standardization (ISO). While attempting to provide a comprehensive description of networking, the model failed to garner reliance during the design of the Internet, which is reflected in the less prescriptive Internet Protocol Suite, principally sponsored under the auspices of the Internet Engineering Task Force (IETF).

In the early- and mid-1970s, networking was largely either government-sponsored (NPL network in the UK, ARPANET in the US, CYCLADES in France) or vendor-developed with proprietary standards, such as IBM's Systems Network Architecture and Digital Equipment Corporation's DECnet. Public data networks were only just beginning to emerge, and these began to use the X.25 standard in the late 1970s.[5][6]

The Experimental Packet Switched System in the UK circa 1973–1975 identified the need for defining higher level protocols.[5] The UK National Computing Centre publication 'Why Distributed Computing' which came from considerable research into future configurations for computer systems,[7] resulted in the UK presenting the case for an international standards committee to cover this area at the ISO meeting in Sydney in March 1977.[8][9]

Beginning in 1977, the ISO initiated a program to develop general standards and methods of networking. A similar process evolved at the International Telegraph and Telephone Consultative Committee (CCITT, from French: Comité Consultatif International Téléphonique et Télégraphique). Both bodies developed documents that defined similar networking models. The OSI model was first defined in raw form in Washington, DC, in February 1978 by Hubert Zimmermann of France and the refined but still draft standard was published by the ISO in 1980.[10]

The drafters of the reference model had to contend with many competing priorities and interests. The rate of technological change made it necessary to define standards that new systems could converge to rather than standardizing procedures after the fact; the reverse of the traditional approach to developing standards.[11] Although not a standard itself, it was a framework in which future standards could be defined.[12]

In 1983, the CCITT and ISO documents were merged to form The Basic Reference Model for Open Systems Interconnection, usually referred to as the Open Systems Interconnection Reference Model, OSI Reference Model, or simply OSI model. It was published in 1984 by both the ISO, as standard ISO 7498, and the renamed CCITT (now called the Telecommunications Standardization Sector of the International Telecommunication Union or ITU-T) as standard X.200.

OSI had two major components, an abstract model of networking, called the Basic Reference Model or seven-layer model, and a set of specific protocols. The OSI reference model was a major advance in the standardisation of network concepts. It promoted the idea of a consistent model of protocol layers, defining interoperability between network devices and software.

The concept of a seven-layer model was provided by the work of Charles Bachman at Honeywell Information Systems.[13] Various aspects of OSI design evolved from experiences with the NPL network, ARPANET, CYCLADES, EIN, and the International Networking Working Group (IFIP WG6.1). In this model, a networking system was divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacted directly only with the layer immediately beneath it and provided facilities for use by the layer above it.

The OSI standards documents are available from the ITU-T as the X.200-series of recommendations.[14] Some of the protocol specifications were also available as part of the ITU-T X series. The equivalent ISO/IEC standards for the OSI model were available from ISO. Not all are free of charge.[15]

OSI was an industry effort, attempting to get industry participants to agree on common network standards to provide multi-vendor interoperability.[16] It was common for large networks to support multiple network protocol suites, with many devices unable to interoperate with other devices because of a lack of common protocols. For a period in the late 1980s and early 1990s, engineers, organizations and nations became polarized over the issue of which standard, the OSI model or the Internet protocol suite, would result in the best and most robust computer networks.[9][17][18] However, while OSI developed its networking standards in the late 1980s,[19][20] TCP/IP came into widespread use on multi-vendor networks for internetworking.

The OSI model is still used as a reference for teaching and documentation;[21] however, the OSI protocols originally conceived for the model did not gain popularity. Some engineers argue the OSI reference model is still relevant to cloud computing.[22] Others say the original OSI model doesn't fit today's networking protocols and have suggested instead a simplified approach.[23][24]

Definitions

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Communication protocols enable an entity in one host to interact with a corresponding entity at the same layer in another host. Service definitions, like the OSI Model, abstractly describe the functionality provided to an (N)-layer by an (N-1) layer, where N is one of the seven layers of protocols operating in the local host.

At each level N, two entities at the communicating devices (layer N peers) exchange protocol data units (PDUs) by means of a layer N protocol. Each PDU contains a payload, called the service data unit (SDU), along with protocol-related headers or footers.

Data processing by two communicating OSI-compatible devices proceeds as follows:

1. The data to be transmitted is composed at the topmost layer of the transmitting device (layer N) into a protocol data unit (PDU).
2. The PDU is passed to layer N-1, where it is known as the service data unit (SDU).
3. At layer N-1 the SDU is concatenated with a header, a footer, or both, producing a layer N-1 PDU. It is then passed to layer N-2.
4. The process continues until reaching the lowermost level, from which the data is transmitted to the receiving device.
5. At the receiving device the data is passed from the lowest to the highest layer as a series of SDUs while being successively stripped from each layer's header or footer until reaching the topmost layer, where the last of the data is consumed.

Standards documents

The OSI model was defined in ISO/IEC 7498 which consists of the following parts:

• ISO/IEC 7498-1 The Basic Model
• ISO/IEC 7498-2 Security Architecture
• ISO/IEC 7498-3 Naming and addressing
• ISO/IEC 7498-4 Management framework

ISO/IEC 7498-1 is also published as ITU-T Recommendation X.200.

Layer architecture

The recommendation X.200 describes seven layers, labelled 1 to 7. Layer 1 is the lowest layer in this model.

Layer 1: Physical layer

The Physical Layer is responsible for the transmission and reception of unstructured raw data between a device, such as a network interface controller, Ethernet hub, or network switch, and a physical transmission medium. It converts the digital bits into electrical, radio, or optical signals. Layer specifications define characteristics such as voltage levels, the timing of voltage changes, physical data rates, maximum transmission distances, modulation scheme, channel access method and physical connectors. This includes the layout of pins, voltages, line impedance, cable specifications, signal timing and frequency for wireless devices. Bit rate control is done at the physical layer and may define transmission mode as simplex, half duplex, and full duplex. The components of a physical layer can be described in terms of a network topology. Physical layer specifications are included in the specifications for the ubiquitous Bluetooth, Ethernet, and USB standards. An example of a less well-known physical layer specification would be for the CAN standard.

The Physical Layer also specifies how encoding occurs over a physical signal, such as electrical voltage or a light pulse. For example, a 1 bit might be represented on a copper wire by the transition from a 0-volt to a 5-volt signal, whereas a 0 bit might be represented by the transition from a 5-volt signal to 0-volt signal. As a result, common problems occurring at the Physical Layer are often related to the incorrect media termination, EMI or noise scrambling, and NICs and hubs that are misconfigured or do not work correctly.

Layer 2: Data link layer

The data link layer provides node-to-node data transfer—a link between two directly connected nodes. It detects and possibly corrects errors that may occur in the physical layer. It defines the protocol to establish and terminate a connection between two physically connected devices. It also defines the protocol for flow control between them.

IEEE 802 divides the data link layer into two sublayers:[26]

• Medium access control (MAC) layer – responsible for controlling how devices in a network gain access to a medium and permission to transmit data.
• Logical link control (LLC) layer – responsible for identifying and encapsulating network layer protocols, and controls error checking and frame synchronization.

The MAC and LLC layers of IEEE 802 networks such as 802.3 Ethernet, 802.11 Wi-Fi, and 802.15.4 ZigBee operate at the data link layer.

The Point-to-Point Protocol (PPP) is a data link layer protocol that can operate over several different physical layers, such as synchronous and asynchronous serial lines.

The ITU-T G.hn standard, which provides high-speed local area networking over existing wires (power lines, phone lines and coaxial cables), includes a complete data link layer that provides both error correction and flow control by means of a selective-repeat sliding-window protocol.

Security, specifically (authenticated) encryption, at this layer can be applied with MACSec.

Layer 3: Network layer

The network layer provides the functional and procedural means of transferring packets from one node to another connected in "different networks". A network is a medium to which many nodes can be connected, on which every node has an address and which permits nodes connected to it to transfer messages to other nodes connected to it by merely providing the content of a message and the address of the destination node and letting the network find the way to deliver the message to the destination node, possibly routing it through intermediate nodes. If the message is too large to be transmitted from one node to another on the data link layer between those nodes, the network may implement message delivery by splitting the message into several fragments at one node, sending the fragments independently, and reassembling the fragments at another node. It may, but does not need to, report delivery errors.

Message delivery at the network layer is not necessarily guaranteed to be reliable; a network layer protocol may provide reliable message delivery, but it need not do so.

A number of layer-management protocols, a function defined in the management annex, ISO 7498/4, belong to the network layer. These include routing protocols, multicast group management, network-layer information and error, and network-layer address assignment. It is the function of the payload that makes these belong to the network layer, not the protocol that carries them.[27]

Layer 4: Transport layer

Main article: Transport layer

The transport layer provides the functional and procedural means of transferring variable-length data sequences from a source host to a destination host from one application to another across a network, while maintaining the quality-of-service functions. Transport protocols may be connection-oriented or connectionless.

This may require breaking large protocol data units or long data streams into smaller chunks called "segments", since the network layer imposes a maximum packet size called the maximum transmission unit (MTU), which depends on the maximum packet size imposed by all data link layers on the network path between the two hosts. The amount of data in a data segment must be small enough to allow for a network-layer header and a transport-layer header. For example, for data being transferred across Ethernet, the MTU is 1500 bytes, the minimum size of a TCP header is 20 bytes, and the minimum size of an IPv4 header is 20 bytes, so the maximum segment size is 1500-(20+20) bytes, or 1460 bytes. The process of dividing data into segments is called segmentation; it is an optional function of the transport layer. Some connection-oriented transport protocols, such as TCP and the OSI connection-oriented transport protocol (COTP), perform segmentation and reassembly of segments on the receiving side; connectionless transport protocols, such as UDP and the OSI connectionless transport protocol (CLTP), usually do not.

The transport layer also controls the reliability of a given link between a source and destination host through flow control, error control, and acknowledgments of sequence and existence. Some protocols are state- and connection-oriented. This means that the transport layer can keep track of the segments and retransmit those that fail delivery through the acknowledgment hand-shake system. The transport layer will also provide the acknowledgement of the successful data transmission and sends the next data if no errors occurred.

Reliability, however, is not a strict requirement within the transport layer. Protocols like UDP, for example, are used in applications that are willing to accept some packet loss, reordering, errors or duplication. Streaming media, real-time multiplayer games and voice over IP (VoIP) are examples of applications in which loss of packets is not usually a fatal problem.

The OSI connection-oriented transport protocol defines five classes of connection-mode transport protocols ranging from class 0 (which is also known as TP0 and provides the fewest features) to class 4 (TP4, designed for less reliable networks, similar to the Internet). Class 0 contains no error recovery and was designed for use on network layers that provide error-free connections. Class 4 is closest to TCP, although TCP contains functions, such as the graceful close, which OSI assigns to the session layer. Also, all OSI TP connection-mode protocol classes provide expedited data and preservation of record boundaries. Detailed characteristics of TP0-4 classes are shown in the following table:[28]

An easy way to visualize the transport layer is to compare it with a post office, which deals with the dispatch and classification of mail and parcels sent. A post office inspects only the outer envelope of mail to determine its delivery. Higher layers may have the equivalent of double envelopes, such as cryptographic presentation services that can be read by the addressee only. Roughly speaking, tunnelling protocols operate at the transport layer, such as carrying non-IP protocols such as IBM's SNA or Novell's IPX over an IP network, or end-to-end encryption with IPsec. While Generic Routing Encapsulation (GRE) might seem to be a network-layer protocol, if the encapsulation of the payload takes place only at the endpoint, GRE becomes closer to a transport protocol that uses IP headers but contains complete Layer 2 frames or Layer 3 packets to deliver to the endpoint. L2TP carries PPP frames inside transport segments.

Although not developed under the OSI Reference Model and not strictly conforming to the OSI definition of the transport layer, the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite are commonly categorized as layer-4 protocols within OSI.

Transport Layer Security (TLS) does not strictly fit inside the model either. It contains characteristics of the transport and presentation layers.[29][30]

Layer 5: Session layer

The Session Layer creates the setup, controls the connections, and ends the teardown, between two or more computers, which is called a "session". Since DNS and other Name Resolution Protocols operate in this part of the layer, common functions of the Session Layer include user logon (establishment), name lookup (management), and user logoff (termination) functions. Including this matter, authentication protocols are also built into most client software, such as FTP Client and NFS Client for Microsoft Networks. Therefore, the Session layer establishes, manages and terminates the connections between the local and remote application. The Session Layer also provides for full-duplex, half-duplex, or simplex operation, and establishes procedures for checkpointing, suspending, restarting, and terminating a session between two related streams of data, such as an audio and a video stream in a web-conferencing application. Therefore, the session layer is commonly implemented explicitly in application environments that use remote procedure calls.

Layer 6: Presentation layer

The Presentation Layer establishes data formatting and data translation into a format specified by the application layer during the encapsulation of outgoing messages while being passed down the protocol stack, and possibly reversed during the deencapsulation of incoming messages when being passed up the protocol stack. For this very reason, outgoing messages during encapsulation are converted into a format specified by the application layer, while the conversation for incoming messages during deencapsulation are reversed.

The Presentation Layer handles protocol conversion, data encryption, data decryption, data compression, data decompression, incompatibility of data representation between OSs, and graphic commands. The presentation layer transforms data into the form that the application layer accepts, to be sent across a network. Since the presentation layer converts data and graphics into a display format for the Application Layer, the Presentation Layer is sometimes called the syntax layer.[31] For this reason, the Presentation Layer negotiates the transfer of syntax structure through the Basic Encoding Rules of Abstract Syntax Notation One (ASN.1), with capabilities such as converting an EBCDIC-coded text file to an ASCII-coded file, or serialization of objects and other data structures from and to XML.[4]

Layer 7: Application layer

The application layer is the layer of the OSI model that is closest to the end user, which means both the OSI Application Layer and the user interact directly with software application that implements a component of communication between the client and server, such as File Explorer and Microsoft Word. Such application programs fall outside the scope of the OSI model unless they are directly integrated into the Application layer through the functions of communication, as is the case with applications such as Web Browsers and Email Programs. Other examples of software are Microsoft Network Software for File and Printer Sharing and Unix/Linux Network File System Client for access to shared file resources.

Application-layer functions typically include file sharing, message handling, and database access, through the most common protocols at the application layer, known as HTTP, FTP, SMB/CIFS, TFTP, and SMTP. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. The most important distinction in the application layer is the distinction between the application-entity and the application. For example, a reservation website might have two application-entities: one using HTTP to communicate with its users, and one for a remote database protocol to record reservations. Neither of these protocols have anything to do with reservations. That logic is in the application itself. The application layer has no means to determine the availability of resources in the network.[4]

Cross-layer functions

Further information: Cross-layer optimization

Cross-layer functions are services that are not tied to a given layer, but may affect more than one layer.[32] Some orthogonal aspects, such as management and security, involve all of the layers (See ITU-T X.800 Recommendation[33]). These services are aimed at improving the CIA triad—confidentiality, integrity, and availability—of the transmitted data. Cross-layer functions are the norm, in practice, because the availability of a communication service is determined by the interaction between network design and network management protocols.

Specific examples of cross-layer functions include the following:

• Security service (telecommunication)[33] as defined by ITU-T X.800 recommendation.
• Management functions, i.e. functions that permit to configure, instantiate, monitor, terminate the communications of two or more entities: there is a specific application-layer protocol, common management information protocol (CMIP) and its corresponding service, common management information service (CMIS), they need to interact with every layer in order to deal with their instances.
• Multiprotocol Label Switching (MPLS), ATM, and X.25 are 3a protocols. OSI subdivides the Network Layer into three sublayers: 3a) Subnetwork Access, 3b) Subnetwork Dependent Convergence and 3c) Subnetwork Independent Convergence.[34] It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram-based service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames. Sometimes one sees reference to a Layer 2.5.
• Cross MAC and PHY Scheduling is essential in wireless networks because of the time-varying nature of wireless channels. By scheduling packet transmission only in favourable channel conditions, which requires the MAC layer to obtain channel state information from the PHY layer, network throughput can be significantly improved and energy waste can be avoided.[35]

Programming interfaces

Neither the OSI Reference Model, nor any OSI protocol specifications, outline any programming interfaces, other than deliberately abstract service descriptions. Protocol specifications define a methodology for communication between peers, but the software interfaces are implementation-specific.

For example, the Network Driver Interface Specification (NDIS) and Open Data-Link Interface (ODI) are interfaces between the media (layer 2) and the network protocol (layer 3).

Comparison to other networking suites

The table below presents a list of OSI layers, the original OSI protocols, and some approximate modern matches. It is very important to note that this correspondence is rough: the OSI model contains idiosyncrasies not found in later systems such as the IP stack in modern Internet.[24]

Comparison with TCP/IP model

See also: Internet protocol suite § Comparison of TCP/IP and OSI layering

The design of protocols in the TCP/IP model of the Internet does not concern itself with strict hierarchical encapsulation and layering. RFC 3439 contains a section entitled "Layering considered harmful".[41] TCP/IP does recognize four broad layers of functionality which are derived from the operating scope of their contained protocols: the scope of the software application; the host-to-host transport path; the internetworking range; and the scope of the direct links to other nodes on the local network.[42]

Despite using a different concept for layering than the OSI model, these layers are often compared with the OSI layering scheme in the following manner:

• The Internet application layer maps to the OSI application layer, presentation layer, and most of the session layer.
• The TCP/IP transport layer maps to the graceful close function of the OSI session layer as well as the OSI transport layer.
• The internet layer performs functions as those in a subset of the OSI network layer.
• The link layer corresponds to the OSI data link layer and may include similar functions as the physical layer, as well as some protocols of the OSI's network layer.

These comparisons are based on the original seven-layer protocol model as defined in ISO 7498, rather than refinements in the internal organization of the network layer.

The OSI protocol suite that was specified as part of the OSI project was considered by many as too complicated and inefficient, and to a large extent unimplementable.[43] Taking the "forklift upgrade" approach to networking, it specified eliminating all existing networking protocols and replacing them at all layers of the stack. This made implementation difficult and was resisted by many vendors and users with significant investments in other network technologies. In addition, the protocols included so many optional features that many vendors' implementations were not interoperable.[43]

Although the OSI model is often still referenced, the Internet protocol suite has become the standard for networking. TCP/IP's pragmatic approach to computer networking and to independent implementations of simplified protocols made it a practical methodology.[43] Some protocols and specifications in the OSI stack remain in use, one example being IS-IS, which was specified for OSI as ISO/IEC 10589:2002 and adapted for Internet use with TCP/IP as RFC 1142.

See also

• Common Management Information Service (CMIS)
• GOSIP, the (U.S.) Government Open Systems Interconnection Profile
• Hierarchical internetworking model
• Layer 8
• List of information technology initialisms
• Management plane
• Recursive Internetwork Architecture
• Service layer
• Session multiplexing

Further reading

• John Day, "Patterns in Network Architecture: A Return to Fundamentals" (Prentice Hall 2007, ISBN 978-0-13-225242-3)
• Marshall Rose, "The Open Book" (Prentice-Hall, Englewood Cliffs, 1990)
• David M. Piscitello, A. Lyman Chapin, Open Systems Networking (Addison-Wesley, Reading, 1993)
• Andrew S. Tanenbaum, Computer Networks, 4th Edition, (Prentice-Hall, 2002) ISBN 0-13-066102-3
• Gary Dickson; Alan Lloyd (July 1992). Open Systems Interconnection/Computer Communications Standards and Gossip Explained. Prentice-Hall. ISBN 978-0136401117.
• Russell, Andrew L. (2014). Open Standards and the Digital Age: History, Ideology, and Networks. Cambridge University Press. ISBN 978-1-139-91661-5.

References

1. ^ "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 24 November 2021.
2. ^ ISO/IEC 7498-1:1994 Information technology — Open Systems Interconnection — Basic Reference Model: The Basic Model. June 1999. Introduction. Retrieved 26 August 2022.
3. ^ "What is the OSI Model?". Forcepoint. 10 August 2018. Retrieved 20 May 2022.
4. ^ a b c Tomsho, Greg (2016). Guide to Networking Essentials (7th ed.). Cengage. Retrieved 3 April 2022.
5. ^ a b Davies, Howard; Bressan, Beatrice (26 April 2010). A History of International Research Networking: The People who Made it Happen. John Wiley & Sons. pp. 2–3. ISBN 978-3-527-32710-2.
6. ^ Roberts, Dr. Lawrence G. (November 1978). "The Evolution of Packet Switching" (PDF). IEEE Invited Paper. Retrieved 26 February 2022.
7. ^ Down, Peter John; Taylor, Frank Edward (1976). Why distributed computing?: An NCC review of potential and experience in the UK. NCC Publications. ISBN 9780850121704.
8. ^ Radu, Roxana (2019). "Revisiting the Origins: The Internet and its Early Governance". Negotiating Internet Governance. Oxford University Press. doi:10.1093/oso/9780198833079.003.0003. ISBN 9780191871405.
9. ^ a b Andrew L. Russell (30 July 2013). "OSI: The Internet That Wasn't". IEEE Spectrum. Vol. 50, no. 8.
10. ^ "OSI The Internet That Wasn't". IEEE Spectrum. March 2017.
11. ^ Sunshine, Carl A. (1989). Computer Network Architectures and Protocols. Springer Science & Business Media. p. 35. ISBN 978-1-4613-0809-6.
12. ^ Hasman, A. (1995). Education and Training in Health Informatics in Europe: State of the Art, Guidelines, Applications. IOS Press. p. 251. ISBN 978-90-5199-234-2.
13. ^ J. A. N. Lee. "Computer Pioneers by J. A. N. Lee". IEEE Computer Society.
14. ^ "ITU-T X-Series Recommendations".
15. ^ "Publicly Available Standards". Standards.iso.org. 30 July 2010. Retrieved 11 September 2010.
16. ^ Russell, Andrew L. (28 April 2014). Open Standards and the Digital Age: History, Ideology, and Networks. Cambridge University Press. ISBN 978-1-139-91661-5.
17. ^ Russell, Andrew L. "Rough Consensus and Running Code' and the Internet-OSI Standards War" (PDF). IEEE Annals of the History of Computing.
18. ^ "Standards Wars" (PDF). 2006.
19. ^ Network World. IDG Network World Inc. 15 February 1988.
20. ^ Network World. IDG Network World Inc. 10 October 1988.
21. ^ Shaw, Keith (22 October 2018). "The OSI model explained: How to understand (and remember) the 7 layer network model". Network World. Retrieved 16 May 2020.
22. ^ "An OSI Model for Cloud". Cisco Blogs. 24 February 2017. Retrieved 16 May 2020.
23. ^ Taylor, Steve; Metzler, Jim (23 September 2008). "Why it's time to let the OSI model die". Network World. Retrieved 16 May 2020.
24. ^ a b Crawford, JB (27 March 2021). "The actual OSI model".
25. ^ "Windows Network Architecture and the OSI Model". Microsoft Documentation. Retrieved 24 June 2020.
26. ^ "5.2 RM description for end stations". IEEE Std 802-2014, IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture. ieee. doi:10.1109/IEEESTD.2014.6847097. ISBN 978-0-7381-9219-2.
27. ^ International Organization for Standardization (15 November 1989). "ISO/IEC 7498-4:1989 -- Information technology -- Open Systems Interconnection -- Basic Reference Model: Naming and addressing". ISO Standards Maintenance Portal. ISO Central Secretariat. Retrieved 17 August 2015.
28. ^ "ITU-T Recommendation X.224 (11/1995) ISO/IEC 8073, Open Systems Interconnection - Protocol for providing the connection-mode transport service". ITU.
29. ^ Hooper, Howard (2012). CCNP Security VPN 642-648 Official Cert Guide (2 ed.). Cisco Press. p. 22. ISBN 9780132966382.
30. ^ Spott, Andrew; Leek, Tom; et al. "What layer is TLS?". Information Security Stack Exchange.
31. ^ Grigonis, Richard (2000). Computer telephony- encyclopaedia. CMP. p. 331. ISBN 9781578200450.
32. ^ Mao, Stephen (13 November 2009). "Chapter 8: Fundamentals of communication networks". In Wyglinski, Alexander; Nekovee, Maziar; Hou, Thomas (eds.). Cognitive Radio Communications and Networks: Principles and Practice. Elsevier. p. 201. ISBN 978-0-08-087932-1.
33. ^ a b "ITU-T Recommendation X.800 (03/91), Security architecture for Open Systems Interconnection for CCITT applications". ITU. Retrieved 14 August 2015.
34. ^ Hegering, Heinz-Gerd (24 August 1999). Integrated management of networked systems : concepts, architectures, and their operational application. Morgan Kaufmann. p. 54. ISBN 978-1558605718.
35. ^ Miao, Guowang; Song, Guocong (2014). Energy and spectrum efficient wireless network design. Cambridge University Press. ISBN 978-1107039889.
36. ^ "ITU-T Recommendation Q.1400 (03/1993)], Architecture framework for the development of signaling and OA&M protocols using OSI concepts". ITU. pp. 4, 7.
37. ^ ITU Rec. X.227 (ISO 8650), X.217 (ISO 8649).
38. ^ X.700 series of recommendations from the ITU-T (in particular X.711) and ISO 9596.
39. ^ a b "Internetworking Technology Handbook - Internetworking Basics [Internetworking]". Cisco. 15 January 2014. Retrieved 14 August 2015.
40. ^ "3GPP specification: 36.300". 3gpp.org. Retrieved 14 August 2015.
41. ^ "Layering Considered Harmful". Some Internet Architectural Guidelines and Philosophy. December 2002. sec. 3. doi:10.17487/RFC3439. RFC 3439. Retrieved 25 April 2022.
42. ^ Walter Goralski (2009). The Illustrated Network: How TCP/IP Works in a Modern Network (PDF). Morgan Kaufmann. p. 26. ISBN 978-0123745415.
43. ^ a b c Andrew S. Tanenbaum, Computer Networks, § 1.4.4.

External links

Wikimedia Commons has media related to OSI model.

• Microsoft Knowledge Base: The OSI Model's Seven Layers Defined and Functions Explained
• ISO/IEC standard 7498-1:1994 (PDF document inside ZIP archive) (requires HTTP cookies in order to accept licence agreement)
• ITU-T X.200 (the same contents as from ISO)
• "INFormation CHanGe Architectures and Flow Charts powered by Google App Engine". infchg.appspot.com. The ISO OSI Reference Model, Beluga graph of data units and groups of layers. Archived from the original on 26 May 2012.{{cite web}}: CS1 maint: others (link)
• Zimmermann, Hubert (April 1980). "OSI Reference Model — The ISO Model of Architecture for Open Systems Interconnection". IEEE Transactions on Communications. 28 (4): 425–432. CiteSeerX 10.1.1.136.9497. doi:10.1109/TCOM.1980.1094702. S2CID 16013989.
• Cisco Systems Internetworking Technology Handbook
• What is the OSI Model – 7 Layers of OSI Model Explained
• Guide to Networking Essentials, 7th Edition - Cengage

Retrieved from "https://en.wikipedia.org/w/index.php?title=OSI_model&oldid=1125771892"

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Electrical connector commonly used in telephone and computer networks

A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets.

Modular connectors were originally developed for use on specific Bell System telephone sets in the 1960s, and similar types found use for simple interconnection of customer-provided telephone subscriber premises equipment to the telephone network. The Federal Communications Commission (FCC) mandated in 1976 an interface registration system, in which they became known as registered jacks. The convenience of prior existence for designers and ease of use led to a proliferation of modular connectors for many other applications. Many applications that originally used bulkier, more expensive connectors have converted to modular connectors. Probably the best-known applications of modular connectors are for telephone and Ethernet.

Accordingly, various electronic interface specifications exist for applications using modular connectors, which prescribe physical characteristics and assign electrical signals to their contacts.

Nomenclature

Modular connectors are often referred to as modular phone jack and plug, RJ connector, and Western jack and plug. The term modular connector arose from its original use in modular wiring components of telephone equipment by the Western Electric Company in the 1960s.[1] This includes the 6P2C used for telephone line connections and 4P4C used for handset connectors.

Registered jack designations describe the signals and wiring used for voice and data communication at customer-facing interfaces of the public switched telephone network. It is common to use a registered jack number to refer to the physical connector itself; for instance, the 8P8C modular connector type is often labeled RJ45 because the registered jack standard of that name specified 8P8C modular connectors. Similarly, various six-position modular connectors may be called RJ11. Likewise, the 4P4C connector is sometimes called RJ9 or RJ22 though no such official designations exist.[citation needed]

History

The first types of small modular telephone connectors were created by AT&T in the mid-1960s for the plug-in handset and line cords of the Trimline telephone.[1] Driven by demand for multiple sets in residences with various lengths of cords, the Bell System introduced customer-connectable part kits and telephones, sold through PhoneCenter stores in the early 1970s.[2] For this purpose, Illinois Bell started installing modular telephone sets on a limited scale in June 1972. The patents by Edwin C. Hardesty and coworkers, US 3699498  (1972) and US 3860316  (1975), followed by other improvements, were the basis for the modular molded-plastic connectors that became commonplace for telephone cords by the 1980s. In 1976, these connectors were standardized nationally in the United States by the Registration Interface program of the Federal Communications Commission (FCC), which designated a series of Registered Jack (RJ) specifications for interconnection of customer-premises equipment to the public switched telephone network (PSTN).[3][4]

Gender

Modular connectors have gender: plugs are considered to be male, while jacks or sockets are considered to be female. Plugs are used to terminate cables and cords, while jacks are used for fixed locations on surfaces of walls, panels, and equipment. Other than telephone extension cables, cables with a modular plug on one end and a jack on the other are rare. Instead, cables are usually connected using a female-to-female coupler, having two jacks wired back-to-back.

Latching tab and orientation

Most modular connectors are designed with a latching mechanism that secures the physical connection. As a plug is inserted into a jack, a plastic tab on the plug locks against a ridge in the socket so that the plug cannot be removed without disengaging the tab by pressing it against the plug body. The standard orientation for installing a jack in a vertical surface is with the tab down.

The modular plug is often installed with a boot, a plastic covering over the tab and body, to prevent the latching tab to hook into other cords or edges, which may cause excessive bending or breaking of the tab. Such snagless cords, are usually constructed by installing the protective boot before the modular plug is crimped.

Size and contacts

Modular connectors are designated using two numbers that represent the maximum number of contact positions and the number of installed contacts, with each number followed by P and C, respectively. For example, 6P2C is a connector having six positions and two installed contacts. Alternate designations omit the letters while separating the position and contact quantities with either an x (6x2) or a slash (6/2).

When not installed, contacts are usually omitted from the outer positions inward, such that the number of contacts is almost always even. The connector body positions with omitted or unconnected contacts are unused for the electrical connection but ensure that the plug fits correctly. For instance, RJ11 cables often have connectors with six positions and four contacts, to which are attached just two wires.

The contact positions are numbered sequentially starting from 1. When viewed head-on with the retention mechanism on the bottom, jacks will have contact position number 1 on the left and plugs will have it on the right. Contacts are numbered by the contact position. For example, on a six-position, two-contact plug, where the outermost four positions do not have contacts, the innermost two contacts are numbered 3 and 4.

Modular connectors are manufactured in four sizes, with 4-, 6-, 8-, and 10-positions. The insulating plastic bodies of 4P and 6P connectors have different widths, whereas 8P or 10P connectors share an even larger body width.

Insulation displacement contact types

• 

  8P8C plug with contacts for solid wire (left) and stranded wire (right)

• 

  Contacts for solid wire (top left) and stranded wire (bottom right)

Internally, the contacts on the plugs have sharp prongs that, when crimped, pierce the wire insulation and connect with the conductor, a mechanism known as insulation displacement. Ethernet cables, in particular, may have solid or stranded (tinsel wire) conductors and the sharp prongs are different in the 8P8C connectors made for each type of wire. A modular plug for solid (single-strand) wire often has three slightly splayed prongs on each contact to securely surround and grip the conductor. Modular plugs for stranded have prongs that are designed to connect to multiple wire strands. Connector plugs are designed for either solid or stranded wire and a mismatch between plug and wire type may result in an unreliable connection.

Interchangeability

Some modular connectors are indexed, meaning their dimensions are intentionally non-standard, preventing connections with connectors of standard dimensions. The means of indexing may be non-standard cross-sectional dimensions or shapes, retention mechanism dimensions or configuration. For example, a Modified Modular Jack using an offset latching tab was developed by Digital Equipment Corporation to prevent accidental interchange of data and telephone cables.

The dimensions of modular connectors are such that a narrower plug can be inserted into a wider jack that has more positions than the plug, leaving the jack's outermost contacts unconnected. The height of the plug's insertion area is 0.260 inches (6.60 mm) and the contacts are 0.040 inches (1.02 mm) apart (contact pitch), so the width is dependent on the number of pin positions.[7][8] However, not all plugs from all manufacturers have this capability, and some jack manufacturers warn that their jacks are not designed to accept smaller plugs without damage. If an inserted plug lacks slots to accommodate the jack's contacts at the outermost extremes, it may permanently deform those outermost contacts of an incompatible jack. Excessive resistance may be encountered when inserting an incompatible plug, as the outermost contacts in the jack are forcibly deformed.

Special modular plugs have been manufactured (for example, the Siemon UP-2468[9]) which have extra slots beyond their standard contacts, to accommodate the wider jack's outermost contacts without damage. These special plug connectors can be visually identified by carefully looking for the extra slots molded into the plug. The molded plastic bodies of the special plugs may also be colored with a light blueish tinge, to aid in quick recognition. The special plugs are preferred for test equipment and adapters, which may be rapidly connected to a large number of corresponding connectors in quick succession for testing purposes. The use of the special plugs avoids inadvertent damage to the equipment under test, even when a narrower plug is inserted into a nominally incompatible wider jack.

Termination

Termination of cables with modular connectors is similar across the various number of positions and contacts in the plug. The crimping tool contains a die which is often exchangeable and is closely matched to the shape and pin count of the modular plug.

A crimping die-set looks similar to an 8P8C jack, except for the eight teeth lining the top portion of the die. When the tool is operated, the die compresses around the 8P8C plug. As the die compresses, these teeth force the plug contacts into the conductors of the cable being terminated. The crimper may also permanently deform part of the plastic plug body in such a way that it grips the outer sheath of the cable for secure fastening and strain relief. These actions permanently attach the plug to the cable.

Pinout

The contact assignments (pinout) of modular connectors vary by application. Telephone network connections are standardized by registered jack designations, and Ethernet over twisted pair is specified by the ANSI/TIA-568 standard. For other applications, standardization may be lacking; for example, multiple conventions exist for the use of 8P8C connectors in RS-232 applications. For this reason, D-sub-to-modular adapters are typically shipped with the D-sub contacts (pins or sockets) terminated but not inserted into the connector body, so that the D-sub-to-modular contact pairing can be assigned as needed.

4P4C

The four-position four-conductor (4P4C) connector is the standard modular connector used on both ends of telephone handset cords, and is therefore often called a handset connector.[10]

This handset connector is not a registered jack, because it was not intended to connect directly to telephone lines. However it is often referred to as RJ9, RJ10, or RJ22.

Handset wiring

Handsets and often headsets for use with telephones commonly use a 4P4C connector. The two center pins are commonly used for the receiver, and the outer pins connect the transmitter so that a reversal of conductors between the ends of a cord does not affect the signal routing. This may differ for other equipment, including hands-free headsets.

Data port

The Macintosh 128K, Macintosh 512K and Macintosh Plus from Apple as well as the Amiga 1000 from Commodore used 4P4C connectors to connect the keyboard to the main computer housing. The connector provided power to the keyboard on the outer two contacts and received data signals on the inner pair. The cable between the computer and the keyboard was a coiled cord with an appearance very similar to a telephone handset cable.[11] The connector on the Amiga 1000 used crossover wiring, similar to a telephone handset. The connector wiring on the Apple computers, however, required a polarized straight through pinout. Using a telephone handset cable instead of the supplied cable could short out the +5 volt DC supply and damage the Apple computer or the keyboard.[12]

Modular connectors are often used for data links, such as serial line connections, because of their compact dimensions. For example, some DirecTV set top boxes include a 4P4C data port connector with an adapter cord to a computer serial port so that remote control is possible from the computer.[13]

6P6C

Modular plugs are described by the maximum number of physical contact positions and the actual number of contacts installed in these positions. The 6P2C, 6P4C, and 6P6C modular connectors are probably best known for their use as RJ11, RJ14, and RJ25 registered jacks, respectively. These interfaces use the same six-position modular connector body, but have different numbers of pins installed.

RJ11 is a physical interface often used for terminating single telephone lines. RJ14 is similar, but for two lines, and RJ25 is for three lines. RJ61 is a similar registered jack for four lines, but uses an 8P8C connector.

RJ11 wiring

Cables sold as RJ11 often actually use 6P4C connectors (six positions, four contacts) and RJ14 wiring – four wires running to a central junction box. Two of its six possible contact positions connect tip and ring, and the other two contact positions may be unused or provide low-voltage power for night-light or other features on the telephone set. In some installations an extra contact was also required for the ground connection for selective ringers.

Pinout

The pins of the 6P6C connector are numbered 1 to 6, counting left to right when holding the connector tab side down with the opening for the cable facing the viewer.

Position	Pair	T/R	±	RJ11	RJ14	RJ25	Twisted pair colors	25-pair colors	Old colors[A]	German colors[B]	Australian colors	Diagram
1	3	T	+			T3	white/green	white/green	white	pink	orange	6P6C connector showing the location of pin 1
2	2	T	+		T2	T2	white/orange	white/orange	black	green	red
3	1	R	−	R1	R1	R1	blue	blue/white	red	white	blue
4	1	T	+	T1	T1	T1	white/blue	white/blue	green	brown	white
5	2	R	−		R2	R2	orange	orange/white	yellow	yellow	black
6	3	R	−			R3	green	green/white	blue	gray	green

1. ^ While the old solid color code was well established for pair 1 and usually pair 2, there are several conflicting conventions for pair 3 (and sometimes even pair 2). The colors shown above were taken from a vendor of silver satin flat 8-conductor phone cable that claims to be standard. 6-pair solid (old) bellwire cables previously used by the Bell System use white for pair 3 tip but some vendors' cable may substitute orange for white. At least one other vendor of flat 8-conductor cable uses the sequence blue, orange, black, red, green, yellow, brown and white/slate.[citation needed]
2. ^ This color scheme originates in the (withdrawn) national standard DIN 47100. The scheme shown here is the correct color code for interfacing with the RJ connector standards.

However, with German domestic telephone equipment, and that in some neighboring countries, 6P4C plugs and sockets are typically only used to connect the telephone cord to the phone base unit, whereas the mechanically different TAE connector is used at the other end to connect to a service provider interface. Older base units may accommodate the additional connectors of TAE (E, W, a2, b2) and may feature non-RJ standard sockets that can be connected directly to TAE plugs. Further, flat DIN 47100 cables typically place the wires in ascending order. When used directly with 6P4C plugs, the color coding may be undetermined.

Powered version of RJ11

In the powered version of the RJ11 interface, pins 2 and 5 (black and yellow) may carry low voltage AC or DC power. While the telephone line on pins 3 and 4 (red and green) supplies enough power for most telephone terminals, old telephone terminals with incandescent lights, such as the Western Electric Princess and Trimline telephones, need more power than the phone line can supply. Typically, the power on pins 2 and 5 is supplied by an AC adapter plugged into a nearby power outlet which potentially even supplies power to all of the jacks in the house.

Compatibility with structured cabling

Structured cabling networks adhering to ANSI/TIA-568, ISO/IEC 11801 (or ISO/IEC 15018 for home networks) are widely used for both computer networking and analog telephony. These standards specify the T568A or T568B wiring arrangements compatible with Ethernet. The 8P8C jack used by structured cabling physically accepts the 6-position connector used by RJ11, RJ14 and RJ25. Only RJ11 and RJ14 have full electrical compatibility because Ethernet-compatible pin-outs split the third pair of RJ25 across two separate cable pairs, rendering that pair unusable by an analog phone. Both the third and fourth pairs of RJ61 are similarly split. The incompatible T568A and T568B layouts were necessary to preserve the electrical properties of the third and fourth pairs for Ethernet, which operates at much higher frequencies than analog telephony. Because of these incompatibilities, and because RJ25 and RJ61 were never very common, the T568A and T568B conventions have largely displaced RJ25 and RJ61 for telephones with more than two lines.

8P8C

The 8 position 8 contact (8P8C) connector is a modular connector commonly used to terminate twisted pair and multi-conductor flat cable. These connectors are commonly used for Ethernet over twisted pair, registered jacks and other telephone applications, RS-232 serial communication using the ANSI/TIA-568 (formerly TIA/EIA-568) and Yost standards, and other applications involving unshielded twisted pair, shielded twisted pair, and multi-conductor flat cable.

An 8P8C modular connection consists of a male plug and a female jack, each with eight equally spaced contacts. On the plug, the contacts are flat metal bars positioned parallel to the connector body. Inside the jack, the contacts are metal spring wires angled away from the insertion interface. When the plug is mated with the jack, the contacts meet and create an electrical connection. The spring tension of the jack contacts ensures a good interface.

Although commonly referred to as RJ45 in the context of Ethernet and category 5 cables, RJ45 originally referred to a specific wiring configuration of an 8P8C connector.[14][15][16] The original telephone-system-standard RJ45 plug has a key which excludes insertion in an un-keyed 8P8C socket.[17]

The original RJ45S[a] was intended for high-speed modems, and is obsolete. The RJ45S jack mates with a keyed 8P2C modular plug,[18][19] and has pins 4 and 5 (the middle positions) wired for the ring and tip conductors of a single telephone line and pins 7 and 8 shorting a programming resistor. This is a different mechanical interface and wiring scheme than ANSI/TIA-568 T568A and T568B schemes with the 8P8C connector in Ethernet and telephone applications. Generic 8P8C modular connectors are similar to those used for the RJ45S variant, although the RJ45S plug is keyed and not compatible with non-keyed 8P8C modular jacks.

Telephone installers who wired RJ45S modem jacks or RJ61X telephone jacks were familiar with the pin assignments of the standard. However, the standard un-keyed modular connectors became ubiquitous for computer networking and informally inherited the name RJ45.

Standardization

The shape and dimensions of an 8P8C modular connector are specified for US telephone applications by the Administrative Council for Terminal Attachment (ACTA) in national standard ANSI/TIA-1096-A and international standard ISO-8877. This standard does not use the short term 8P8C and covers more than just 8P8C modular connectors, but the 8P8C modular connector type is the eight position connector type described therein, with eight contacts installed.

For data communication applications (LAN, structured cabling), International Standard IEC 60603 specifies in parts 7-1, 7-2, 7-4, 7-5, and 7-7 not only the same physical dimensions but also high-frequency performance requirements for shielded and unshielded versions of this connector for carrying frequencies up to 100, 250 and 600 MHz.

Pinout

8P8C connectors are frequently terminated using the T568A or T568B assignments that are defined in ANSI/TIA-568. The drawings to the right show that the copper connections and pairing are the same, the only difference is that the orange and green pairs (colors) are swapped. A cable wired as T568A at one end and wired as T568B at the other end (Tx and Rx pairs reversed) is an Ethernet crossover cable. Before the widespread acceptance of auto MDI-X capabilities, a crossover cable was needed to interconnect similar network equipment (such as Ethernet hubs to Ethernet hubs). Crossover cables are sometimes still used to connect two computers together without a switch or hub, however most network interface cards (NIC) in use today implement auto MDI-X to automatically configure themselves based on the type of cable plugged into them. A cable wired the same at both ends is called a patch or straight-through cable, because no pin/pair assignments are swapped. If a patch or straight cable is used to connect two computers with auto MDI-X capable NICs, one NIC will configure itself to swap the functions of its Tx and Rx wire pairs.

Pin	T568A pair	T568A color	T568B pair	T568B color	10BASE-T/100BASE-TX signal[20]	1000BASE-T/10GBASE-T signal	Wire	Diagram
1	3	white/green stripe	2	white/orange stripe	TD+	DA+	tip	Pin numbering on plug. Connected pins on plug and jack have the same number.
2	3	green solid	2	orange solid	TD−	DA−	ring
3	2	white/orange stripe	3	white/green stripe	RD+	DB+	tip
4	1	blue solid	1	blue solid	NC	DC+	ring
5	1	white/blue stripe	1	white/blue stripe	NC	DC−	tip
6	2	orange solid	3	green solid	RD−	DB−	ring
7	4	white/brown stripe	4	white/brown stripe	NC	DD+	tip
8	4	brown solid	4	brown solid	NC	DD−	ring

Types and compatibility

Two types of 8P8C plugs and crimping tools for installing the plug onto a cable are commonly available: Western Electric/Stewart Stamping (WE/SS) and Tyco/AMP. While the two types are similar, the tooling and plug types cannot be interchanged.[b] WE/SS compatible plugs are available from a large number of manufacturers, whereas Tyco/AMP plugs are produced exclusively by Tyco Electronics.[citation needed] Both types of modular plugs can be mated with a standard 8P8C modular jack.

Both types of 8P8C plugs are available in shielded and unshielded varieties for different attenuation tolerances as needed. Shielded plugs are more expensive and require shielded cable, but have a lower attenuation, and may reduce electromagnetic interference.

Although a narrower 4-pin and 6-pin plug fits into the wider 8-pin jack and makes a connection with the available contacts on the plug, because the body of the smaller connector may stress the remaining contacts,[c] the smaller connector can potentially damage the springs of the larger jack.

Applications

8P8C connectors are commonly used in computer networking applications, where interconnecting cables are terminated at each end with an 8P8C modular plug wired according to TIA/EIA standards. Most wired Ethernet communications are carried over Category 5e or Category 6 cable terminated with 8P8C modular plugs. The connector is also used in other telecommunications connections, including ISDN and T1.

Where building network and telephone wiring is pre-installed, the center (blue) pair is often used to carry telephony signals. While this allows an RJ11 plug to connect, it may damage the modular jack; an approved converter prevents damage. In landline telephony, an 8P8C jack is used at the point a line enters the building to allow the line to be broken to insert automatic dialing equipment, including intrusion alarm panels.

The EIA/TIA-561 standard describes the use of 8P8C connectors for RS-232 serial interfaces.[23] This application is common as a console interface for network equipment, such as switches, routers, and headless computers.

8P8C modular connectors are also commonly used as a microphone connector for PMR, LMR, and amateur radio transceivers. Frequently the pinout is different, usually mirrored (i.e. what would be pins 1 to 8 in the ANSI/TIA-568 standard might be pins 8 to 1 in the radio and its manual).

In analog mobile telephony, the 8P8C connector was used to connect an AMPS cellular handset to its (separate) base unit; this usage is now obsolete.

The physical connector is standardized as the IEC 60603-7 8P8C modular connector with different categories of performance. The physical dimensions of the male and female connectors are specified in ANSI/TIA-1096-A and ISO-8877 standards and normally wired to the T568A and T568B pinouts specified in the ANSI/TIA-568 standard to be compatible with both telephone and Ethernet.

A similar standard jack once used for modem and data connections, the RJ45S, used a keyed variety of the 8P8C body with an extra tab that prevents it mating with other connectors; the visual difference compared to the more common 8P8C is subtle, but it is a different connector. The original RJ45S[18][24] keyed 8P2C modular connector, obsolete today, had pins 5 and 4 wired for tip and ring of a single telephone line and pins 7 and 8 shorting a programming resistor.

Electronics catalogs commonly advertise 8P8C modular connectors as RJ45. An installer can wire the jack to any pin-out or use it as part of a generic structured cabling system such as ISO/IEC 15018 or ISO/IEC 11801 using 8P8C patch panels for both phone and data.

Crossover cables

A router to router crossover cable uses two 8-position connectors and a unshielded twisted pair (UTP) cable with differently wired connectors at each end.

10P10C

The 10P10C connector is commonly referred to as an RJ50 connector, although this was never a standard registered jack. The 10P10C has 10 contact positions and 10 contacts.

The most common uses of the 10P10C connector are in proprietary data transfer systems,[25] such as the Digiboard[26] and Equinox Super-Serial multi-port TIA-232 adapters.[26] 10P10C connectors are also used to implement RS-485 interfaces, and for data link connections in uninterruptible power supplies.

This connector is also used by some vendors, for example, Cyclades (later absorbed by Equinox) used pin 1 as an RI (ring indicator) signal, which is seldom used, allowing an 8P8C plug to be inserted to their 10P10C socket for most applications. The Cisco Systems STS-10X terminal server features this connector. FordNet, a five-pair communications networking medium, also used the 10P10C between terminals.

Motorola uses the 10-pin connector as a microphone connector in several of their mobile radio product lines.[citation needed]

Polycom utilizes this connector on their Conference Link bus to connect their HDX and Group Series codecs and microphones to their SoundStructure audio mixers, although pins 1 and 10 are not used.[citation needed]

The 10-pin connector is also used by Demag Cranes AG in some pendant connections. National Instruments is also using the 10p10c connector for their NI 9237.[27]

MTS Systems Corporation is using the 10p10c connector for their MTS FlexTest Controller Family.[citation needed]

Standards

• ANSI/TIA-968-A: Telephone terminal equipment: Technical requirements for connection of terminal equipment to the telephone network at the Wayback Machine (archived 2018-09-28)
• ANSI/TIA-1096-A: Telecommunications telephone terminal equipment connector requirements for connection of terminal equipment to the telephone network
• IEC 60603-7-1: Connectors for electronic equipment: Part 7-1: Detail specification for 8-way, shielded free and fixed connectors with common mating features, with assessed quality
• IEC 60603-7-2: Connectors for electronic equipment: Part 7-2: Detail specification for 8-way, unshielded, free and fixed connectors, for data transmissions with frequencies up to 100 MHz
• IEC 60603-7-4: Connectors for electronic equipment: Part 7-4: Detail specification for 8-way, unshielded, free and fixed connectors, for data transmissions with frequencies up to 250 MHz
• IEC 60603-7-5: Connectors for electronic equipment: Part 7-5: Detail specification for 8-way, shielded, free and fixed connectors, for data transmissions with frequencies up to 250 MHz
• IEC 60603-7-7: Connectors for electronic equipment: Part 7-7: Detail specification for 8-way, shielded, free and fixed connectors, for data transmissions with frequencies up to 600 MHz
• ISO/IEC 8877, EN 28877: Information Technology—Telecommunications and Information Exchange between Systems—Interface Connector and Contact Assignments for ISDN Basic Access Interface Located at Reference Points S and T
• US government documents define registered jack applications of modular connectors for telecommunications.[d] See Registered jack § History and authority

See also

• BS 6312 – British equivalent to RJ25
• EtherCON – ruggedized 8P8C Ethernet connector
• GG45
• TERA

Notes

1. ^ The often omitted S suffix indicates this is a wiring configuration supporting a single telephone line.
2. ^ WE/SS and Tyco/AMP 8P8C plugs have different spacings for the cable strain relief.[21][22] Using a WE/SS 8P8C crimp die set on a Tyco/AMP 8P8C plug crushes the top of the connector and damages the crimp die set, and vice versa.
3. ^ The body of a 6P6C or 4P4C plug typically projects out by more than one millimeter further than the contacts and presses the outermost contacts of the larger connector further than if a full-size connector were inserted.
4. ^ 4P4C and 10P10C connectors are not defined in these standards.

References

1. ^ a b Krumreich C.L., Mosing L.W., The Evolution of a Telephone, Bell Laboratories Record 44(1) p.14 (January 1966)
2. ^ Walden S.W., Telephone Sets Go Mod (Modular, That Is), Bell Laboratories Record, Vol. 52(8) p. 238 (Sept. 1974)
3. ^ AT&T, Registration Interface—Selection and General Information, Bell System Practices, Section 463-400-100 Issue 1, May 1976
4. ^ FCC 47 CFR Part 68 Connection of Terminal Equipment to the Telephone Network, Section 68.502 superseded by T1.TR5-1999
5. ^ "Six Conductor/Six Position Line Cord Module" (PDF). Bel-Stewart Connector. Bel. Retrieved 3 August 2021.
6. ^ "RJ-45 Plug for Proposed CAT 6 Specifications" (PDF). Molex #449150001, Modular Plug, Category 6, Long Body, Unshielded, 8/8. Molex, LLC. Retrieved 3 August 2021.
7. ^ "Six Conductor/Six Position Line Cord Module" (PDF). Bel-Stewart Connector. Bel. Retrieved 3 August 2021.
8. ^ "RJ-45 Plug for Proposed CAT 6 Specifications" (PDF). Molex #449150001, Modular Plug, Category 6, Long Body, Unshielded, 8/8. Molex, LLC. Retrieved 3 August 2021.
9. ^ "Universal Modular Plug".
10. ^ BICSI (October 7, 2002). "Background Information". Telecommunications Cabling Installation (2nd ed.). McGraw-Hill Professional. p. 88. ISBN 0-07-140979-3. 4-position and 4-contact connectors are used primarily for telephone handset cords.
11. ^ "Apple Macintosh Plus", My Old Computers, archived from the original on 2009-02-27, retrieved 2010-10-16.
12. ^ "Mac Plus Keyboard Cable", Syrinx, UK: Megadon, ...the cable is the same as the telephone cable that connects handsets to the phone, unfortunately [...] this type of cable and pretty much any type of pre manufactured cable [...] is wired wrong for the Mac Plus. Under no circumstances should you use this cable as you will damage your keyboard and/or your Mac!
13. ^ "Direc TV Channel Control" (wiki). GB-PVR. Archived from the original on 2008-10-19. Each end of a handset cord is wired opposite the other...
14. ^ Trulove 2005, pp. 23, 132: ‘Designing LAN Wiring Systems: The 8-pin modular jack is sometimes referred to as an "RJ-45", because the connector/jack components are the same. However, RJ-45 actually applies to a special purpose jack configuration that is not used in LAN or standard telephone wiring. […] Work Area Outlets: Modular jacks are often referred to as "RJ-45" jacks. This is not really the correct moniker, although it is in very common use.’
15. ^ Oliviero, Andrew; Woodward, Bill (July 20, 2009). "Connectors". Cabling: The Complete Guide to Copper and Fiber-Optic Networking (4th ed.). Sybex. p. 294. ISBN 978-0-470-47707-6. The RJ (registered jack) prefix is one of the most widely (and incorrectly) used prefixes in the computer industry; nearly everyone, including people working for cabling companies, is guilty of referring to an eight-position modular jack (sometimes called an 8P8C) as an RJ-45.
16. ^ Semenov, Andrey B.; Strizhakov, Stanislav K.; Suncheley, Igor R. (October 3, 2002). "Electrical Cable Connectors". Structured cable systems. Springer. p. 129. ISBN 3-540-43000-8. The traditional 8-contact connector, which is called Western Plug, 8PMJ (8-position modular jack), 8P8C (8 position 8 conductor), or somewhat incorrectly RJ-45, is used widely in SCS practice.
17. ^ Trulove 2005, p. 219: ‘User Cords and Connectors: This 8-pin modular plug is probably the most subject to name abuse, because it resembles the specialized RJ-45 connector. However, the RJ-45 wiring pattern (which includes an interface programming resistor) is so radically different from that of T568A and B that it really should not be called by that name at all.’
18. ^ a b Modular jack wiring, Ontario, California: HVS, archived from the original on 2010-02-08
19. ^ Modular wiring reference, Siemon
20. ^ IEEE 802.3 14.5.1 MDI connectors
21. ^ "Stewart Connector 937-SP-3088 – Eight conductor/eight position line cord module" (PDF). Glen Rock, Pennsylvania: Bel Stewart Connector. 2006-02-01. Archived from the original (PDF) on 2018-04-18. Retrieved 2018-04-18.
22. ^ "Tyco/AMP 5-554739-2 – Modular plug assembly, 8 position, flat oval cable" (PDF). Harrisburg, Pennsylvania: Tyco Electronics. 2008-03-31. Archived from the original (PDF) on 2011-07-24. Retrieved 2009-09-10.
23. ^ "RJ45", Layer 1, Zytrax.
24. ^ "Modular Wiring Reference". Siemon. Retrieved 2010-10-14.
25. ^ 10 pin RJ50 (10P10C) male (connector diagram and applications), Pinouts guide, archived from the original on 2013-05-18, retrieved 2010-10-17
26. ^ a b Digi PortServer TS 10P10C (RJ50) Modular RS-232 pinout, Pinouts guide.
27. ^ NI 9237 4-Channel, ±25 mV/V, 24-Bit Simultaneous Bridge Module specifications.

Bibliography

• Trulove, James (December 19, 2005), LAN wiring (3rd ed.), McGraw-Hill Professional, ISBN 0-07-145975-8.

External links

Wikimedia Commons has media related to Modular connectors.

• How to Make a Network Cable, a how-to article from wikiHow
• John R. Carlsen: On wiring modular telephone connectors[permanent dead link]
• Modular wiring reference[permanent dead link] showing differences between 8P8C, true RJ45 8-position keyed connector, 6P6C, and 6-position modified offset tab
• Common outlet configurations[permanent dead link] graphical representation of twisted pair pinouts
• Premium Modular Plugs at the Wayback Machine (archived 2013-02-15) Catalog page showing the difference between solid and stranded contacts
• 8 pin RJ45 (8P8C) male connector diagram and applications pinouts at the Wayback Machine (archived 2013-06-01)

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