[Pool] DNS queries per second

Dave Hart davehart at gmail.com
Wed Mar 23 01:01:57 UTC 2011

On Wed, Mar 23, 2011 at 12:06 AM, Chuck Swiger wrote:
> A tenfold increase in query rate doesn't strike me as surprising.  Even a T1 or
> 1.5Mbs symmetric DSL/cable link should be able to handle 1000 NTP queries
> per second and still have most of its bandwidth left over.

When you start to run into issues with a high rate of queries, i
suspect bandwidth isn't the chokepoint, but packets/sec.  And it's
likely to be a problem with a router not an end host.

On DSL in particular, the encoding of IP packets into AAL 53-byte ATM
cells means small packets carry a disproportionate bandwidth impact,
as they're often just over the size that would fit in one ATM cell,
meaning they consume two cells, the 2nd mostly empty, and eat nearly
twice the bandwidth you'd predict.  For more on this "ATM tax" for
DSLs see:


And if you find that a good read, I encourage you to take a look at:


Dave Hart

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