What does Windows error code 9912 (DNS_ERROR_RRL_INVALID_WINDOW_SIZE) mean?

 
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DNS_ERROR_RRL_NOT_ENABLED DNS_ERROR_RRL_INVALID_IPV4_PREFIX

DNS_ERROR_RRL_INVALID_WINDOW_SIZE

What the window controls

DNS_ERROR_RRL_INVALID_WINDOW_SIZE is returned while Windows DNS Server validates an RRL configuration. The affected setting is exposed by PowerShell as WindowInSec and defines the period over which RRL measures and averages a pattern of queries from the same subnet that produce the same response. The protocol specification identifies the underlying field as dwWindowSize and requires Windows to reject an invalid value; the Win32 status text specifically requires a value of at least one second.

The window is not a DNS TTL and does not change zone data or caching. It defines how long the server retains the rate-limiting context for a response pattern. A short window can react to a sharp burst but may be less representative of sustained traffic. A longer window keeps the pattern relevant for longer and can make a broad source-prefix choice more consequential.

How to diagnose the failure

  • Read the current setting with Get-DnsServerResponseRateLimiting and check the value passed to Set-DnsServerResponseRateLimiting -WindowInSec.
  • Verify that automation sends a positive integer, not an empty variable, a duration string, or a value in milliseconds. The Windows field is measured in seconds.
  • Change the window together with the source prefix and response-rate settings only when the expected traffic population is understood. These fields form one policy, not independent tuning knobs.
  • Use LogOnly to observe the prospective policy before enabling preventive actions on a busy DNS server.

Relationship to other implementations

RRL is an implementation feature rather than a DNS wire-protocol field. BIND documents a rolling window and a token-bucket style account for each response/client grouping. That is useful background for why the parameter exists, but BIND's accepted range and defaults are not a substitute for Windows validation rules.

References

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