I have a network run to a Gig-E switch in the office area. Performance is variable. I notice better performance when connected to the head-end switch that the Gig-E switch is connected to. This tells me that either the Gig-E switch has a problem, or the head-end port, or the cable in between.
How do I determine where the problem is? Repeated pings every second show no packet loss and 1ms latency. What other tests can I use?