Question


The bandwidth limit for the virtual server is only 3Mbps. However, we noticed spikes in the network interface usage which are above the limit set. What causes this and how can I resolve it?


Environment


Any OnApp version


Answer


In some cases, the incorrect network usage graph may be caused by the incorrect statistical data collection. It is recommended to contact OnApp Support to investigate the reasons. However, there are cases where the over-limit usage spikes may appear in clouds with the correctly working stats collector.


Cause


Network usage data for a certain virtual server is collected by reading TX and RX counters on the VS's NIC. Bandwidth shaping is performed by the kernel on the compute resource host. That is why the outgoing packets are passed through and counted on VS's NIC even if they are dropped by the compute resource host later.

For example, there is some software on the VS, which produces a lot of UDP traffic. It can flood network uplink without the need to control whether the data reached the destination (typical malware behavior). Network usage will appear much above the limit, but in fact, all the limit excess will never be passed to the compute resource host uplink.