Comtech EF Data VMS v3.12.x Vipersat - Manual (Page 443)

Appendix C - Redundancy C-33
MN/22156, rev 12 N:M Hub Modem Redundancy
How N:M Redundancy Works
In the event of failure of any active device, a unit from the spare device pool is
configured with the configuration of the failed device, including its IP address,
and re-initialized without a hard reset. VMS switches off power to the failed
device immediately after detecting failure to ensure the failed device will not
conflict with its replacement device when the replacement device is booted into
service.
Note: Once a failed device has been detected, the total elapsed time to remove
power, configure a device from the spare pool with the failed device’s
configuration, and place that device into service in the satellite network is
generally less than 5 seconds.
Device Failure Detection
Each device protected by N:M redundancy in a satellite network transmits a
packet, called a heartbeat, at timed intervals whenever N:M redundancy is
enabled on the device. During registration, VMS establishes the heartbeat inter-
val for each protected device. The heartbeat packet contains the following infor-
mation:
• The unit’s IP address
• The unit’s health/fault status
• The unit’s receive and transmit health or fault status
The VMS monitors and analyzes each received heartbeat packet for information
for a switch trigger such as:
• No heartbeat is detected within the Timeout parameter setting in Vipersat
Manager (default is 10.25 seconds).
• The unit transmits a fault status indicating the unit’s health, or loss of
transmit or receive capability for a period of 25 seconds (default).
The Switch-Over Process
The switch-over process involves both the Vipersat Manager and the Redun-
dancy Manager.
Vipersat Manager
Activity in the Vipersat Manager starts when the VMS N:M redundancy capa-
bility is enabled, then proceeds as follows:
1. VMS monitors error messages and heartbeat packets from protected units for
an event indicating that a redundancy switch is required.
NOTE