This integer configures a delay, in seconds up to 60 (or 65535 for unlimited), before a subscriber is marked offline after the port's physical link goes down. An admin tunes this to avoid immediately dropping a subscriber's session on a brief link flap, while still eventually clearing sessions on a genuinely lost link. For example, setting this to 10 seconds means a subscriber stays logically online for a 10-second link outage, such as a quick cable reseat, before being forced offline.