Real-time communication

Last updated

Real-time communication(RTC) is a category of software protocols and communication hardware media that gives real-time guarantees, which is necessary to support real-time guarantees of real-time computing. [1] Real-time communication protocols are dependent not only on the validity and integrity of data transferred but also the timeliness of the transfer. Real-time communication systems are generally understood as one of two types: Hard Real-Time (HRT) and Soft Real-Time (SRT). [2] The difference between a hard and soft real-time communication system is the consequences of incorrect operation. Safety-critical systems capable of causing catastrophic consequences upon a fault, such as aircraft fly-by-wire systems, are designated as hard real-time, whereas non-critical but ideally real-time systems, such as hotel reservation systems, are designated as soft real-time. [3] The designation of a real-time communication system as hard or soft has significant influence on its design.

Contents

Hard real-time systems

Hard real-time communication systems are frequently electromechanically linked to a physical mechanism, often one that interfaces directly with people or property, which often contributes to or defines the potential danger of a fault. Due to their safety-critical nature, the communication protocols defined in a hard real-time system generally must be deterministic. [4] Hard real-time communication systems are particularly common in the transportation, industrial, and medical sectors. Common applications include control systems, automotive controllers, medical devices, and critical safety systems such as airbag firing computers.

Examples

Soft real-time systems

Unlike hard real-time communication systems, soft real-time communication systems generally do not have the capacity to cause catastrophic harm upon a fault, which allows for non-deterministic, less rigorous network infrastructure. [6] This allows soft real-time communication systems to operate over consumer networks such as residential internet connections and cellular networks. A large amount of soft real-time systems are telecommunications products such as VoIP systems and certain video calling platforms such as Discord [7] and Google Meet. [8] Data transmitted over a soft real-time communication system is not stored in a centralized server, and peers are connected directly to one another rather than through a server, although intermediary connecting nodes between peers are allowed when a direct link cannot be established. [9]

Examples

Related Research Articles

<span class="mw-page-title-main">Programmable logic controller</span> Programmable digital computer used to control machinery

A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.

<span class="mw-page-title-main">Token bus network</span> Implementation of Token Ring using a virtual ring on a coaxial cable

Token bus is a network implementing a Token Ring protocol over a virtual ring on a coaxial cable. A token is passed around the network nodes and only the node possessing the token may transmit. If a node doesn't have anything to send, the token is passed on to the next node on the virtual ring. Each node must know the address of its neighbour in the ring, so a special protocol is needed to notify the other nodes of connections to, and disconnections from, the ring.

A fieldbus is a member of a family of industrial digital communication networks used for real-time distributed control. Fieldbus profiles are standardized by the International Electrotechnical Commission (IEC) as IEC 61784/61158.

The Time-Triggered Protocol (TTP) is an open computer network protocol for control systems. It was designed as a time-triggered fieldbus for vehicles and industrial applications. and standardized in 2011 as SAE AS6003. TTP controllers have accumulated over 500 million flight hours in commercial DAL A aviation application, in power generation, environmental and flight controls. TTP is used in FADEC and modular aerospace controls, and flight computers. In addition, TTP devices have accumulated over 1 billion operational hours in SIL4 railway signalling applications.

<span class="mw-page-title-main">Industrial Ethernet</span> Use of Ethernet in an industrial environment

Industrial Ethernet (IE) is the use of Ethernet in an industrial environment with protocols that provide determinism and real-time control. Protocols for industrial Ethernet include EtherCAT, EtherNet/IP, PROFINET, POWERLINK, SERCOS III, CC-Link IE, and Modbus TCP. Many industrial Ethernet protocols use a modified media access control (MAC) layer to provide low latency and determinism. Some microprocessors provide industrial Ethernet support.

In computer networking, a reliable protocol is a communication protocol that notifies the sender whether or not the delivery of data to intended recipients was successful. Reliability is a synonym for assurance, which is the term used by the ITU and ATM Forum.

<span class="mw-page-title-main">Profinet</span> Computer network protocol

Profinet is an industry technical standard for data communication over Industrial Ethernet, designed for collecting data from, and controlling equipment in industrial systems, with a particular strength in delivering data under tight time constraints. The standard is maintained and supported by Profibus and Profinet International, an umbrella organization headquartered in Karlsruhe, Germany.

Avionics Full-Duplex Switched Ethernet (AFDX), also ARINC 664, is a data network, patented by international aircraft manufacturer Airbus, for safety-critical applications that utilizes dedicated bandwidth while providing deterministic quality of service (QoS). AFDX is a worldwide registered trademark by Airbus. The AFDX data network is based on Ethernet technology using commercial off-the-shelf (COTS) components. The AFDX data network is a specific implementation of ARINC Specification 664 Part 7, a profiled version of an IEEE 802.3 network per parts 1 & 2, which defines how commercial off-the-shelf networking components will be used for future generation Aircraft Data Networks (ADN). The six primary aspects of an AFDX data network include full duplex, redundancy, determinism, high speed performance, switched and profiled network.

Ethernet Powerlink is a real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet POWERLINK Standardization Group (EPSG). It was introduced by Austrian automation company B&R in 2001.

<span class="mw-page-title-main">Computer network</span> Network that allows computers to share resources and communicate with each other

A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.

EtherCAT is an Ethernet-based fieldbus system developed by Beckhoff Automation. The protocol is standardized in IEC 61158 and is suitable for both hard and soft real-time computing requirements in automation technology.

The Time-Triggered Ethernet standard defines a fault-tolerant synchronization strategy for building and maintaining synchronized time in Ethernet networks, and outlines mechanisms required for synchronous time-triggered packet switching for critical integrated applications and integrated modular avionics (IMA) architectures. SAE International released SAE AS6802 in November 2011.

Sercos III is the third generation of the Sercos interface, a standardized open digital interface for the communication between industrial controls, motion devices, input/output devices (I/O), and Ethernet nodes, such as PCs. Sercos III applies the hard real-time features of the Sercos interface to Ethernet. It is based upon and conforms to the Ethernet standard. Work began on Sercos III in 2003, with vendors releasing first products supporting it in 2005.

The CC-Link Open Automation Networks Family are a group of open industrial networks that enable devices from numerous manufacturers to communicate. They are used in a wide variety of industrial automation applications at the machine, cell and line levels.

A networked control system (NCS) is a control system wherein the control loops are closed through a communication network. The defining feature of an NCS is that control and feedback signals are exchanged among the system's components in the form of information packages through a network.

WebRTC is a free and open-source project providing web browsers and mobile applications with real-time communication (RTC) via application programming interfaces (APIs). It allows audio and video communication to work inside web pages by allowing direct peer-to-peer communication, eliminating the need to install plugins or download native apps.

SafetyNET p is a standard for Ethernet-based fieldbus communication in automation technology. SafetyNET p is suitable as a drive bus due to its real-time behaviour, with cycle times of up to 62.5 µs. In accordance with the standard requirements from EN 61508 and EN 61511, it can be used in safety circuits up to and including Category 3, SIL 3.

Time-Sensitive Networking (TSN) is a set of standards under development by the Time-Sensitive Networking task group of the IEEE 802.1 working group. The TSN task group was formed in November 2012 by renaming the existing Audio Video Bridging Task Group and continuing its work. The name changed as a result of the extension of the working area of the standardization group. The standards define mechanisms for the time-sensitive transmission of data over deterministic Ethernet networks.

<span class="mw-page-title-main">Cyphal</span>

Cyphal is a lightweight protocol designed for reliable intra-vehicle communications using various communications transports, originally destined for CAN bus, but targeting various network types in subsequent revisions. OpenCyphal is an open-source project that aims to provide MIT-licensed implementations of the Cyphal protocol. The project was known as UAVCAN prior to rebranding in March 2022.

References

  1. ↑ Sundaresan, Sharad; Bettati, Riccardo (11 July 1997). Distributed Connection Management for Real-Time Communication over Wormhole-Routed Networks. people.engr.tamu.edu (Technical report). Archived from the original on 17 December 2023. Retrieved 17 December 2023– via Texas A&M University.
  2. ↑ Doyle, Paula (May–June 2004). "Introduction to Real-Time Ethernet I" (PDF). The Extension: A Technical Supplement to Control Network. Contemporary Control Systems, Inc. 5: 1–4. Archived from the original (PDF) on 16 March 2023.
  3. ↑ "IE304: Real Time Ethernet, Part 1". www.industrialethernetu.com. Retrieved 2022-03-26.
  4. ↑ Livani, M.A (1998). "Scheduling Hard and Soft Real-Time Communication in the Controller Area Network". IFAC Proceedings Volumes. 31: 13. doi:10.1016/S1474-6670(17)44865-8.
  5. ↑ Dr Barry M Cook; Paul Walker. "Ethernet over SpaceWire - software issues". 2007.
  6. ↑ Saravanan, R.; Ramaraj, N. (2009-01-31). "Providing Reliability in Replicated Middleware Applications". Journal of Computer Science. 5 (1): 11–22. doi: 10.3844/jcssp.2009.11.22 . ISSN   1552-6607.
  7. ↑ "How Discord Handles Two and Half Million Concurrent Voice Users using WebRTC". discord.com. Retrieved 2022-03-26.
  8. ↑ "How does Hangouts use WebRTC? webrtc-internals analysis". webrtcHacks. 2014-07-29. Retrieved 2022-03-26.
  9. ↑ "What is Real-Time Communications (RTC)?". www.realtimecommunicationsworld.com. Retrieved 2022-03-26.
  10. ↑ Bubley, Dean (June 2018). "Emerging RTC use-cases" (PDF). Disruptive Analysis.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.