This counter tracks packets dropped because the IP header's TTL (time to live) field reached zero before the router could forward them. A TTL-expired drop means the packet had already traversed too many hops before reaching this router, so a rising count here -- especially paired with the no-route counter -- often signals a routing loop somewhere upstream of the satellite link rather than a problem local to this device. Seeing this counter increase by exactly the packets that a traceroute shows bouncing between two routers in a misconfigured static-route setup would confirm the loop is the cause rather than legitimately long paths.