Siemens RUGGEDCOM ROX II User Manual page 704

Chapter 14
Network Redundancy
Redundant Network Access (RNA) provides instead hitless network recovery by deploying the Parallel Redundany
Protocol (PRP).
CONTENTS
• Section 14.4.1.1, "Parallel Redundancy Protocol (PRP)"
• Section 14.4.1.2, "Supervision Frames"
• Section 14.4.1.3, "PRP Requirements"
Section 14.4.1.1
Parallel Redundancy Protocol (PRP)
Defined by the IEC 62439-3 standard, the Parallel Redundancy Protocol (PRP) replicates each data packet over
two physically independent Ethernet networks (LAN A and LAN B) to guarantee the delivery of at least one of the
packets should one network fail.
In a PRP redundant network, there are Double Attached Nodes (DANs), Singly Attached Nodes (SANs), Virtual
DANs (VDANs) and RedBox devices.
• DANs
Double Attached Nodes (DANs) are PRP-aware devices that have a network port connected to LAN A and
and a network port connected to LAN B. DANs duplicate each received data packet and assign them both
a Redundancy Check Trailer (RCT) before sending them simultaneously to their destination nodes. An RCT
contains a sequence number that helps the destination node identify which packets are duplicates. Destination
nodes remove the RCT from the first packet they receive and then consume them. If a second packet is received,
the destination node knows to discard it.
• SANs
Singly Attached Nodes (SANs) are PRP-unaware devices connected to either LAN A or LAN B.
• RedBox
RedBox devices, or PRP Redundancy Boxes, function similarly to DANs, except they also act as proxies on behalf
of other devices that are PRP-unaware and have only one network port.
• VDANs
A Virtual DAN (VDAN) is any device that sits behind a RedBox. While these devices are unable to connect directly
to the redundant network like other PRP-aware devices, they can function like a DAN through the RedBox.
In a PRP redundant network, RUGGEDCOM MX5000 and MX5000RE devices are configured as RedBox devices.
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RUGGEDCOM ROX II
CLI User Guide
Parallel Redundancy Protocol (PRP)