The first number in fetch-quota-params specifies how often, in number of queries to the server, to recalculate its fetch quota. The fetch-quota-params option specifies four parameters that control how the per-server fetch limit is calculated.įor example: fetches-per-server 200 fail When fetches-per-server is enabled, the default behaviour when rate-limiting is active is to SERVFAIL queries that exceed the limit. The default value for fetches-per-server is 0, which disables this feature. The adjustments up and down are not linear instead they follow a curve that is initially aggressive but which has a long tail. It also allows you to select what to do with the queries that are being limited - either drop them, or send back a SERVFAIL response.īased on a moving average of the timeout ratio for each server, the server's individual quota will be periodically adjusted up or down.
The lower limit is 2% of fetches-per-server, but never below 1. The fetches-per-server option sets a hard upper limit to the number of outstanding fetches allowed for a single server. queries which cannot be resolved, or which take too long to resolve) on local recursive server resource use. This feature is intended to optimize recursive server behavior in favor of good client queries, whilst at the same time limiting the impact of bad client queries (e.g.
The Recursive Client Rate Limiting feature was introduced in BIND 9.11 (and was also made available as a build-time option in BIND 9.9.8 and 9.10.3)
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