Response time check

None.

Availability.

All nameserver IP addresses.

Every 5 minutes.

Low.

None.

Purpose

The response time check measures the response time for each authoritative DNS server IP.

By using specially crafted DNS query packets for five consecutive queries the average response time is calculated. This will result in a reasonable correct response time measurement.

In addition to response times the check will also discover if packets are being dropped as we add a 2 second lifetime to every packet. Dropped packets, or time-outs, does not affect the response times but will have an effect on the Availability metric.

The query type used for these measurements is the SOA record since it is always present in every zone and is roughly of the same size. And since all name servers keep a copy of the zone in RAM the difference in response times for other records is negligible.

The response times will usually differ between measurements from the different locations due to different routing paths and normal Internet latency.

Event severities and messages

This check will not result in any severities. Response times are displayed in miliseconds.