This counter reports the total kilobytes transmitted on a specific network interface of a Xen domain since that domain was created. An admin monitors it to track outbound network traffic volume per guest VM, useful for capacity planning or spotting VMs generating unexpectedly heavy egress traffic. For example, a VM's xenNetworkOutKBytes climbing far faster than its peers could indicate it's running a bandwidth-heavy workload or possibly compromised and exfiltrating data.