This read-write value sets how many seconds elapse between keep-alive packets sent on trunk links specifically, not user PVC ports, with a valid range of 0 to 15 seconds and 0 meaning the keep-alive protocol is disabled entirely; the default is 1 second. An admin might raise this slightly on very stable trunks to reduce keep-alive chatter, but rarely disables it outright since keep-alives are what let the switch detect a dead trunk quickly. For example, leaving lportTrkKeepAliveTimer at its default of 1 means the trunk sends a keep-alive every second, so combined with lportTrkKeepAliveErrorThreshold's default of 5 missed packets, a dead trunk gets detected within about 5 seconds.