Cellular Network Infrastructure

This is a spin-off from the discussion in #4619 (where the MSC-pooling tests leave osmo-bsc in a state of assuming presence of MSCs that have disconnected)
and also related to #2623 (which is actually more about sending RESET upon re-connect)

The aim is to be able to immediately notify of disconnected peers across the STP (e.g. BSC <-> MSC).

laforge wrote:

On Fri, Aug 07, 2020 at 01:44:00PM +0000, neels [REDMINE] wrote:

Now I need to pinpoint what exactly the right mechanism would be for osmo-bsc to realize that an MSC is no longer connected.

Without any active calls (SCCP connections) you don't really know.

The only situations are:

• SCCP connection timers timing out (if there are any active SCCP connections)
• SCCP network informing the user about unavailability of a given point code
  • we don't imlpement this in Osmocom so far, but there are messages like
    M3UA DUNA/DAVA that can be used by an STP to notify M3UA ASPs like the BSC about
    availability/unavailability of a given point code.
  • libosmo-sigtan would have to parse such messages and send N-NOTICE.indication
    from the SCCP provider to the SCCP user (local SCCP user like MSC, BSC, ...),
    as well as N-INFO.indication for active SCCP connections