Re: [gentoo-user] Best caching dns server?

[Michael Mol]

On Sun, May 20, 2012 at 8:43 PM, Nilesh Govindrajan
<contact@××××××××.com> wrote:
> On Mon, May 21, 2012 at 1:17 AM, Alan McKinnon <alan.mckinnon@×××××.com> wrote:
>>> Slow connection. See my previous reply to the list. I'm using pdnsd,
>>> which can persist records and has every damn feature I wanted.
>>>
>>
>> Fair enough, but consider this:
>>
>> If your connection is slow, the only thing you speeded up is the DNS
>> lookups. Thereafter, everything else is still as slow as it ever was.
>> And if you feel the need to speed up DNS lookups then the odds are very
>> good that "everything else" is too slow i.e. not exactly usable.
>>
>> We get this a lot from our customers too, and the advise we give them
>> is to look closely at their traffic throttling. In almost every case
>> all UDP traffic has had the living crap throttled out of it somewhere
>> by folk that don't really think things through, severely affecting
>> dns and ntp as well as AV streaming.
>>
>> Throttled DNS rapidly gets out of hand, IIRC the last time we did some
>> measurements it only takes around 5% of dns lookups to go wonky for the
>> situation to rapidly spiral out of control - when dns fails the cache
>> will try a TCP lookup and that's like wading through molasses.
>>
>> Our advice to customers is to first unthrottle dns and ntp completely,
>> give it the highest possible priority (these are extremely light
>> protocols and seldom show up on the radar when you do this), and see
>> how that goes.
>>
>> It just seems to me that you *might* be trying a very unusual solution
>> for a problem that is better handled one layer lower down.
>>
>
> Strictly speaking, my connection isn't too slow. I have a transfer
> rate of 64 K/s (might sound ridiculous to you, but this costs 18$/mo
> here).
> OpenDNS lookups from my connection take something like 300 msec+ and
> Google DNS lookups around 50 msec.
>
> I can obviously use Google DNS, but as I said earlier, OpenDNS gives
> me phishing protection and other that sort of stuff.
>
> And hence I must use a local cache.

Side note: Honestly, you should be using a local cache, regardless.
It'll improve performance for you, *especially* when there's any risk
of packet drops between you and the your ISP's core equipment. When I
was on a 6Mb/s-down ADSL connection, the improvement I experienced
simply from running bind9 as a recursive resolver was *massive*. I
still do so, even though I'm now on a pretty reliable cable
connection.


-- 
:wq