A read-only value giving the Permanent Interface Identifier, or PII, of the DSL port associated with a given loop test, serving as the index into this test table. This lets an admin identify exactly which physical DSL port a particular loop-test entry refers to when multiple tests might be tracked across different ports. When several SDSL ports are being tested during a truck-roll, the admin uses cmSDSLTestIndex to make sure they're reading results for the correct port's PII.