BIND and UDP tuning

Blake Hudson blake at
Fri Sep 28 15:30:47 UTC 2018

Alex wrote on 9/26/2018 11:52 AM:
>   This is all now running on a 165/35 cable system.

> Early in this thread or another, I provided a packet trace that showed
> what appears to me to never have received the replies - it just times
> out.

> It looks like there are periods of as many as 500 queries per second,
> although the usual amount is closer to 200 per second.

DOCSIS cable systems use an upstream request/grant system to avoid 
collisions (they act as a hub where only one cable modem in the node can 
transmit at the same time). This leads to low pps rates compared with 
ethernet. Even a 10M ethernet connection (1k-10k pps) will outperform a 
1gig cable connection (a few hundred pps).

Based on the info you've provided, I suspect that you may be running 
into this limit. As another poster suggested, you might consider moving 
your DNS server to a VPS hosted on an ethernet connection at a location 
more suited for DNS server operation or otherwise try to leverage your 
upstream provider's DNS or an outside DNS server.


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