Perimeter security
Perimeter security is the protection of a site's outer boundary, its fence line, gates and the open ground inside them, so that an intrusion is detected at the edge rather than after someone is inside. On cameras it is done with line rules along the fence, zones over the ground and a scheduled round that checks the gates.
The perimeter is usually the longest and least watched part of a site. A guard sees a stretch of fence for a moment each hour; a camera sees its stretch continuously, and a detection turns that into an event when a person or vehicle crosses in.
Good perimeter rules are drawn to the boundary itself, so the road outside is outside the rule, and are directional where the crossing matters one way. A round adds the checks a detection cannot make: is the gate closed, is the fence intact, is the compound clear.
On Camzify perimeter security combines line intrusion along the fence, zones over the ground, camera tampering detection on the cameras themselves, and a patrol round with the gates on the checklist.