Bundles (such as IMA and MLPPP) can be protected with APS through the use of Bundle Protection Groups (BPGRP). For APS-protected bundles, all members of a working bundle must reside on the working port of an APS group. Similarly all members of a protecting bundle must reside on the protecting circuit of that APS group. Bundles are not supported on TDM satellite.
IMA APS protection is supported only when the router is connected to another piece of equipment (possibly through an ADM) running a single IMA instance at the far end. By design, the IMA APS implementation is expected to keep the IMA protocol up as long as the far end device can tolerate some frame loss. Similarly, the PPP protocol state machine for PPP channels and MLPPP bundles remains UP when a switchover occurs between the working and protect circuits.
When APS protects IMA groups, IMA control cells, but not user traffic, are sent on the inactive circuit (as well as the active) to keep the IMA protocol up during an APS switch.
For details on MLFR/FRF.12 support with APS see MLFR/FRF.12 support of APS, BFD, and mirroring features.