This trap serves two purposes, one for informing that the total number of rejected sessions in a minute has breached the high water mark (HMW) and for informing when the rejected sessions reduced below the low water mark (LWM). Possible reasons for the high number of rejected sessions are - APN Resolution fails, MCC-MNC not defined in the system, system memory full for the PDP Context. Other valid reasons are Blacklisted subscriber or IP. If there are lots of rejected sessions then action is to check the configuration.