Maintenance Loops (Q112)

The information in this article applies to:

We have never heard of an endpoint that actually uses the Maintenace Loop procedures. Someone probably thought that it was a good idea at the time (H.245v1), but vendors apparently believe that the effort to implement it outweighs whatever benefit it would provide. Therefore, our recommendations are

1. to not implement the outgoing MLSE (or just never initiate the procedure); and
2. for the incoming MLSE, in response to MaintenanceLoopRequest just return MaintenanceLoopReject (with the corresponding type CHOICE, e.g., mediaLoop).

If you implement these procedures, note that while H.324 supports the mediaLoop and logicalChannelLoop CHOICEs (systemLoop is for further study as of H.324v2), H.323 only supports the mediaLoop CHOICE. Also, we believe that the bi-directional constraint mentioned in Annex C.11.1/H.245v7 is a mistake and should thererfore be ignored.