Latency is a time interval between a cause and response that it invokes in a system being observed. Network latency in a packet-switched network is a one-way (or round-trip delay time) for a signal to travel from the source to the destination. Latency includes the time necessary for intermediary network devices to receive, process and send data on its way. In the given scenario, if you want to find the source of the latency, you will need to use traceroute. Ping can only help in confirming latency but not really identify the source.