5.28.3. Restrictions 
- Route Optimization only works when the end partners of the standard route are analog/digital stations, analog/digital CO trunk circuits or Native SIP trunks. Analog interface circuits, S0PP functional devices, special equipment (VMX, VMS, paging, etc.), special configuration (e.g. SSTN in AMO SCSU) and COs (as A or C stations in consultation) are not supported.
- Route Optimization is not executed for consultation calls (i.e. because another transfer is expected) or when the second subunit of the phone is busy (e.g. second call).
- Route Optimization cannot be initiated by a transit OpenScape 4000 node in the standard route (only end to end route optimization is possible).
- An option for to repeat Route Optimization feature requests from a timer not provided e.g. in case of insufficient resources, after a collision or when busy etc. Where route optimization is not performed due to this reason, the standard route is maintained.