it’s used to monitor LapD availability and LapD congestion. It’s mostly useful to :
1. link a high call drop rate with a problem of LapD availability
2. link a high tch congestion rate or poor PDCH allocation (poor GPRS throughput) with a congestion in the LapD.
If the Abis is congested, the GPRS will be impacted : it is not possible to allocate the necessary Abis nibbles in order to reach max throughput.