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APPENDIX 4: EAPS & RSTP - "RING PROTECTION"
Ethernet wiring schemes are based on a 'star'-wiring topology. Ring (or loop) data wiring – where the last device in a chain is
wired back to the first device without RSTP or EAPS setup will quickly 'break' your network. Only one data path between
any two devices is allowed.
Pure star-wiring layouts leave your network prone to a single point of failure. Unlike DMX512 networks, passive data "thru"
connections are not possible with Ethernet. A severed cable or power loss to a switch can mean the loss of some or even all
show control.
Ring Protection allows the deliberate – and designed – use of a ring wiring system for Ethernet communications. With EAPS
or RSTP enabled, PWVIA switches ignore data traffic on one segment of the ring, while monitoring the integrity of the remaining
connections. If an interruption is detected, the unused ring segment is activated and full communication is restored.
Ethernet Automatic Protection Switching (EAPS) uses dedicated tagged ports whereas Rapid Spanning Tree Protocol
(RSTP) can use any two ports on a switch. Fail-over time when using EAPS on dedicated ports is between 50 and 75
milliseconds, or two to four DMX packets.
Using RSTP, the healing process can take a second or two. Unlike EAPS, RSTP only requires you to turn on the feature on all
the switches in the network. No further dedicated port configuration or special wiring considerations need to be adhered to.
PWVIA will block data flow on redundant links and report "Blocked by RSTP" in the link status. The algorithm that decides
which ports to block is based on a stringent set of rules that ensure the fastest network possible.
REQUIREMENTS AND LIMITATIONS
VLANs must be enabled to use Ring Protection. EAPS uses a dedicated VLAN to monitor the integrity of the ring. By default,
VLAN 4094 is used. The Ring Protection VLAN must be outside of the established VLAN range.
Only ports 11 through 14 support this feature.
EAPS works with VIA switches only. Switches from other manufacturers can co-exist on the network, but should not be
placed in-line with the ring.
DEFINITIONS FOR EAPS
Master switch monitors the integrity of communications. Only one switch on the network may be configured as the
master.
Transit switches receive and forward the ring monitoring packets. All switches other than the Master must be set as
transit switches.
Primary port is the main (active) UPLINK connection link on the Master switch, joining to the rest of the network. All transit
switches must also have one port configured as the primary. Only ports 11 through 14 are available to be used as the primary
port.
Secondary port is an UPLINK port "ignored" (logically blocked) by the Master switch to break the ring topology. All transit
switches also must have one port configured as the secondary port. The secondary port is actively used on transit switches.
Only ports 11 through 14 are available to be used as the secondary port.
Control VLAN is a unique VLAN ID dedicated to monitoring the health of the network. All switches must use the same control
VLAN. The default is VLAN ID 4094.
NOTE: Ring Protection wiring topology is not structured. Primary ports can be connected to either the Primary or Secondary
port on the next VIA.
July 2021
PWVIA RM P12 Ethernet Switches - Manual
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