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Date: Wed, 11 Jan 2023 15:53:57 +0000
From: "Laurent Bercot" <>
Cc: liudongxu <>, "Yulu(Brooklyn,RTOS)" <>,
 Nixiaoming <>, Wangxu <>, qiuguorui
 <>, "wangyunhe (A)" <>
Subject: Re: MAXNS should be increased

>It is not advisable to use localhost as a DNS server in embedded devices. It requires a resident process, which consumes many memory and bandwidth.
>We only provide devices, not servers. Servers are provided by carriers. We cannot write a build-in special servers on resolv.conf.

  That is, unfortunately, a common misconception - but a misconception
nonetheless, and if your aim is to provide quality devices that will
adequately serve your users, it would probably be a good idea to
understand the protocols you're implementing, to understand simple
orders of magnitude wrt resources used by software, and to follow
correct practices that won't give incoherent results.

  A caching resolver (which you're calling "server", but DNS servers are
an entirely different thing) can be very small, if chosen appropriately.
The one I use on all my devices consumes 324 kB plus 2 MB that I choose
to allocate as a cache (in order to save bandwidth). As another poster
said, it could go as low as 160 kB.
  Resident processes are not an issue with good system engineering
practices: they can be made reliable, and with proper choice of 
they can use a pretty tiny amount of resources.

  If you wish, you can even configure your caching resolver to forward
queries to the carrier's resolvers in all cases, ensuring your devices
don't even have to perform the burden of DNS resolution themselves.

  I realize these basics of systems engineering may not be common
knowledge to a company that is only [checks notes] the second largest
telecommunication equipment manufacturer in the world. Since this is
my area of expertise, I would be happy to help you on that subject.
Please contact me privately on the listed e-mail address for business


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