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<div>Referencing: <a href="http://www.zytrax.com/books/dns/ch7/hkpng.html#rate-limit" target="_blank">
http://www.zytrax.com/books/dns/ch7/hkpng.html#rate-limit</a> and</div>
<div><a href="https://ftp.isc.org/isc/bind9/9.10.8-P1/doc/arm/Bv9ARM.pdf" target="_blank">https://ftp.isc.org/isc/bind9/9.10.8-P1/doc/arm/Bv9ARM.pdf</a> Page 119</div>
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<div>Definition:</div>
<div>Range allowed is 1 to very big number (actually 32 bit unsigned value, which is still a very big number). Default is not to apply qps-scaling. The rate limiting function calculates the approximate query per second load on the DNS from all sources (including
TCP queries). The <b>qps-scale</b>, if defined, is then applied which may result in a reduction of the user supplied limits, such as
<b>responses-per-second</b> during high-load situations. Thus, assume the user defined
<b>responses-per-second 10;</b> and a <b>qps-scale 200;</b> then if the DNS server is receiving queries (from all sources, including TCP) at a rate of 500 per second the following algorithm is applied (qps-scale/DNS query arrival rate) * responses-per-second
= effective rate-limit, substituting actual values gives (200/500) * 10 = 4, meaning that in the defined load conditions the 5th and subsequent identical response in any 1 second to any specific client will be dropped (or trigger any defined
<a href="http://www.zytrax.com/books/dns/ch7/hkpng.html#slip" class="t-db">slip</a> parameter action). The
<b>qps-scale</b> value, if used, should thus be set to the maximum desired DNS transaction (query response) rate for the server.</div>
<div><a href="http://www.zytrax.com/books/dns/ch7/hkpng.html#rate-limit" target="_blank">http://www.zytrax.com/books/dns/ch7/hkpng.html#rate-limit</a></div>
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<div>My questions:</div>
<div>With my understanding reading the definition above, the "DNS query arrival rate" is the current number of queries per second being sent to the DNS server which changes dynamically
<b>NOT</b> the capacity of queries per second the DNS server is able to handle.</div>
<div>Is my understanding true?</div>
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<div>How is the "DNS query arrival rate" calculated by the DNS server?</div>
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<div>If the qps-scale is defined, not 0, will the qps-scale formula <b>always </b>
be used?</div>
<div>For example: qps-scale 500; responses-per-second 50; "DNS query arrival rate" 200</div>
<div>(500 / 200) * 50 = 125 effective responses-per-second</div>
<div>or</div>
<div>is the qps-scale formula only used when the "DNS query arrival rate" is approximate or exceeds the qps-scale value?</div>
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<div>Thanks</div>
<div>Brent D<br>
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