This preserves the value of sysUpTime, in hundredths of a second, at which a now-expired control tunnel was started, per its description. It anchors the tunnel's history entry to a specific point in the device's uptime, letting an admin correlate that tunnel's start with other uptime-based events like a reload, an interface flap, or another tunnel's simultaneous establishment. Comparing this against a known event's own uptime timestamp lets an admin confirm whether a given tunnel came up right after, say, a WAN interface recovering from an outage.