9.374 Modem-Protection-Controller

The Modem-Proection-Controller logical device builds together with the Protection-Switch-N-To-M device a n:m redundancy solution for satellite modulators, which supports a pool of backup modems from which one modem is taken in case of failure of an operative modem. In case of a redundancy switch all modem parameters are mirrored to the spare modem, so all modems in the pool (active and spare ones) must be exactly of the same type.

For n:m redundancy, one Protection-Switch-N-To-M device and for each managed modulator a Modem-Protection-Controller device are configured in the M&C device setup. This distribution across two device types enables a very flexible configuration of the redundancy, so there is no explicit limit on the number of managed modulators.

The devices are based on the following device configuration:

• The user has a freely definable number of identical modulators, some of which act as spare devices, the rest are operational.
• The modulators receive their input signal via IP, so that when switching, the input signal is also switched by mirroring the modulator parameters.
• The outputs of all modulators are wired to the inputs of a crosspoint-based switching matrix.

In the event of a switchover, all crosspoints belonging to the first modulator are copied to the second one, and all crosspoints of the first modulator are deactivated.

The Modem-Protection-Controller device carries out the actual task of monitoring and redundancy switching. One Modem-Protection-Controller device is configured for each of the modulators involved. Whether the individual modulator is an operational or a spare device can be switched "on the fly" using a configuration parameter. In addition, a modem protection controller device can be configured to the INACTIVE state, which designates a device that is neither PRIMARY nor SPARE, e.g. as a placeholder for later extensions or if a modulator is temporarily unavailable.

Each Modem-Protection-Controller device monitors two configurable fault flags. The first faul is labeled "general fault" and should combine all fault which prevent a modem from being used. The second fault ("operational fault") should be active with fault conditions that shall trigger a redundancy switching but shall not prevent a spare modem from being used if this fault is active. A missing input signal is an example for this type of fault.

When performing a redundancy switch, the device first requests a free spare modulator from the Protection-Switch-N-to-M device. It mirrors the settings of the modulator to be replaced on this and then copies the associated matrix crosspoints in such a way that the output of the spare modulator is routed to the destinations that were previously served by the replaced modulator. The output of the replaced device is separated from all destinations in the matrix.

The redundancy switch can also be triggered manually by clicking REPLACE-BY-SPARE. In the same way, after the replaced device has been repaired/checked, it can be switched back to operational mode (SWITCH-BACK). The original matrix configuration of the device is restored, but no modulator parameters from the spare device are mirrored back to the primary one.

Modem controllers configured as SPARE may be bound to a certain primary modem. In this case the spare modem is no longer part of the spare modem pool, instead it acts as a 1:1 backup for the selected primary modem. Use the 'reserved for' parameter to configure this feature. Modem controllers which have the 'reserved for' parameter set to NONE are part of the spare modem pool.

By default modem parameters are mirrored after the primary modem has been set offline at the switch matrix and before the backup modem gets online. For 1:1 modem pairs a different approac may be configured. If the '121MirrorMode' config parameter is set to IMMEDIATE at the primary modem, mirroring is skipped during the switchover procedure, thus speeding this up significantly. Instead mirroring the modem parameter is triggered by the following events:

• A backup modem is configured as 'reserved for' for this primary modem
• The primary modem changes its 'tx.on' parameter to ON (this assumes, that configuring this device has been completed).
• The operator clicks the MIRROR NOW button.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- This page controls the operational parameters of the device.
• --- The faults page. * --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameter which must be set to interconnect the redundancy switch with the devices it shall monitor and control.

Variables defined by this device driver