Technology

The Parallel Redundancy Protocol (PRP) allows seamless communication in the face of a single network disruption (for instance cable, driver, switch or controller failure).

Critical nodes (DANs) have two network connections. To achieve high-availability configuration the first interface is connected to LAN_A and the second to LAN_B. The topologies of LAN_A and LAN_B are open and the networks could be utilizing other redundancy approaches.

A DAN transmits its packets on both interfaces and hence over both networks. In an error-free environment a second DAN receives the same packets on both interfaces, possibly with a time delay between them. The receiving DAN will use the first of these packets, ignoring the second. PRP needs no reconfiguration or path switching.

PRP can be implemented as a software sub-layer or as hardware solution (RedBox). Both solutions are entirely transparent to the application and to network communication.

PRP is defined in the standard IEC 62439. The goal of this international standard is provide a deterministic recovery time and a protocol-independent solution applicable to a reasonable set of real-time Ethernet as included in IEC 61784.