REDUNDANT ETHERNET COMMUNICATION
Redundancy is required where a single point of failure cannot be tolerated. It is required in critical applications
such as substation automation. Redundancy acts as an insurance policy, providing an alternative route if one
Ethernet communication redundancy is available for most General Electric products, using a Redundant Ethernet
Board (REB). The REB is a Network Interface Card (NIC), which incorporates an integrated Ethernet switch. The
board provides two Ethernet transmitter/receiver pairs.
By ordering option, a number of different protocols are available to provide the redundancy according to particular
In addition to the two Ethernet transmitter/receiver pairs, the REB provides link activity indication in the form of
LEDs, link fail indication in the form of watchdog contacts, and a dedicated time synchronisation input.
The dedicated time synchronisation input is designed to connect to an IRIG-B signal. Both modulated and un-
modulated IRIG-B formats are supported according to the selected option. Simple Network Time Protocol (SNTP) is
supported over the Ethernet communications.
A range of Redundant Ethernet Boards are available to support different protocols for different requirements. One
of the key requirements of substation redundant communications is "bumpless" redundancy. This means the
ability to transfer from one communication path to another without noticeable consequences. Standard protocols
of the time could not meet the demanding requirements of network availability for substation automation
solutions. Switch-over times were unacceptably long. For this reason, companies developed proprietary protocols.
More recently, however, standard protocols, which support bumpless redundancy (namely PRP and HSR) have
been developed and ratified.
As well as supporting standard non-bumpless protocols such as RSTP, the REB was originally designed to support
bumpless redundancy, using proprietary protocols (SHP, DHP) before the standard protocols became available.
Since then, variants have been produced for the newer standard protocols.
REB variants for each of the following protocols are available:
PRP (Parallel Redundancy Protocol)
HSR (High-availability Seamless Redundancy)
RSTP (Rapid Spanning Tree Protocol)
SHP (Self-Healing Protocol)
DHP (Dual Homing Protocol)
PRP and HSR are open standards, so their implementation is compatible with any standard PRP or HSR device
respectively. PRP provides "bumpless" redundancy. RSTP is also an open standard, so its implementation is
compatible with any standard RSTP devices. RSTP provides redundancy, however, it is not "bumpless".
SHP and DHP are proprietary protocols intended for use with specific General Electric products:
SHP is compatible with the C264-SWR212 as well as H35x multimode switches.
DHP is compatible with the C264-SWD212 as well as H36x multimode switches.
Both SHP and DHP provide "bumpless" redundancy.
The protocol you require must be selected at the time of ordering.
Chapter 18 - Communications