The Retry Interval (RETRY) is a field found in the Start of Authority (SOA) record of a DNS (Domain Name System) zone. It specifies the amount of time (in seconds) that secondary DNS servers should wait before attempting to contact the primary DNS server again after a failed zone transfer or refresh attempt.

Here’s what the RETRY field in the SOA record signifies:

  1. Zone Refresh Attempt: Secondary DNS servers periodically contact the primary DNS server to refresh their copy of the zone data. The RETRY value comes into play if a previous attempt to refresh the zone data fails. For example, this might occur if the primary server is temporarily unreachable or if there are communication issues.
  2. Delay Before Retrying: After a failed attempt to refresh the zone data, the secondary server will wait for the duration specified in the RETRY field before making another attempt to contact the primary server. This delay is intended to prevent excessive network traffic caused by frequent and unsuccessful retry attempts.
  3. Maintaining Secondary Server Data: The RETRY value ensures that secondary servers are patient and don’t overwhelm the primary server with frequent retry requests. It helps maintain a healthy balance between keeping the secondary server’s data up-to-date and preventing excessive network traffic or load on the primary server.

In essence, the RETRY interval defines the time secondary DNS servers should wait before making a new attempt to refresh their zone data from the primary server after a failure. It is an important parameter for the proper functioning of DNS zone transfers and data synchronization in a distributed DNS infrastructure.