Based on its name, range, and read-only access, this value reports the actual negotiated or measured operating speed, in bits per second, of the synchronous data circuit, as opposed to the configured nncExtSdcSpeed value. Admins compare it against nncExtSdcSpeed to confirm the circuit is actually running at its configured rate rather than a fallback or degraded speed. As an illustrative example, an actual speed of 0 while a nonzero speed is configured would indicate the circuit is not currently synchronized or active.