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 ofreal-time computing.[1] Real-time communicationprotocols are dependent not only on thevalidity 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) andsoft 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 asaircraft 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.
Hard real-time communication systems are frequentlyelectromechanically 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 bedeterministic.[4] Hard real-time communication systems are particularly common in thetransportation,industrial, andmedical sectors. Common applications includecontrol systems,automotive controllers,medical devices, and critical safety systems such asairbag firing computers.
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 rigorousnetwork infrastructure.[6] This allows soft real-time communication systems to operate over consumer networks such asresidential internet connections andcellular networks. A large amount of soft real-time systems aretelecommunications products such asVoIP systems and certainvideo calling platforms such asDiscord[7] andGoogle Meet.[8] Data transmitted over a soft real-time communication system is not stored in a centralized server, and peers areconnected 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]