This read-only value reports the negotiation level for a Network Services feature (such as data compression) on the associated port/station: disable(1) means the feature is not requested, negotiate(2) requests it but allows the circuit to come up without it, required(3) requires both ends to support it before the connection comes up, and forceOn(4) requires the feature for the circuit to come up at all. Admins use it to see how strictly a given port enforces the feature during call setup. For example, a level of required(3) means a virtual circuit on that port/station will only be established if both endpoints support the negotiated feature.