4.1. Architecture of the UCON/SNMP
One of the most critical issues in using UCON for enforcing access into SNMP environment is to use the concept of a reference monitor. The reference monitor (RM), which has been extensively used by the access control community for years, was introduced and published by the ISO as a standard for access control framework [10], and has been considered as the core control mechanism for access and usage of digital information. In classical access control, subjects can access digital objects only through the reference monitor (RM), which is a process inside the trusted computer base (TCB) that is always running and is a tamper proof.