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List:       opensuse
Subject:    [opensuse] Re: When I have downloads running, DNS fails.
From:       Linda Walsh <suse () tlinx ! org>
Date:       2014-07-11 5:56:27
Message-ID: 53BF7C8B.7090804 () tlinx ! org
[Download RAW message or body]

Carlos E. R. wrote:
> On 2014-07-11 04:10, Linda Walsh wrote:
>   
>> Have you looked at the package
>> 'qos'-1.0.1 Rel 2.1.2 in opensuse 13.1?
>> (> rpm -qf /etc/rc.d/qos
>> qos-1.0.1-2.1.2.noarch)
>>
>>
>> It uses filters in both directions to help prioritize.
>>     
>
>
> In this particular case, that alone would not help.
>
> I was querying my router for DNS service, and it is this one which
> failed. The pipe to the router was not a problem.
>
> I just told my named/bind to query instead my ISP DNS servers, and it
> works - using the same pipe.
>   
----
Your router for DNS?   How odd.  I've never heard of having a linux box, 
then using
a small underpowered microprocessor to do DNS....

Um... why are you using a router?   My linux box does my routing and DNS 
(and a score or
two of other things).  I.e. your linux box has to do queries to resolve DNS.

If it does so from the root, then it has to send out ...  1 request to a 
root server to see
who owns the TLC, then to the TLC to see who owns the domain... then to 
the domain to see
what the ip of it's servers is...

That's about 3 requests minimum (assuming a cold cache)...

The thing is, a small solid-state router won't have alot of cache memory to
hold many entries.  You are talking to a server that likely only has to 
make 1 trip--
google I read?  They likely have the root and TLC's at least in their 
cache all the time,
as well as the website addrs of all the major sites.

I.e. likely to be at most 1 round trip from them -- but more likely, *0* 
roundtrips.

All that is needed is for them to satisfy your request from cache.

So color me unconvinced.. but having your lower powered router look up
a DNS addr, is alot more likely to run into traffic contention problems 
given the
round trips to all the authoritative servers for each level.  Google 
will just hand you
a cached value... and have paid for a ton of Band/wth -- unlike the traffic
between you and each DNS host.

Someone else pointed out that if udp is too slow, it would fall back to TCP.

But thing is -- when you point at google there's a reasonable chance it 
would
be TCP from the start, coming from your computer... but the tiny-router 
box --
it would more likely use UDP because of its lower overhead.

So you can't really compare the two and claim that lack of B/W, up or down,
(both need to be available) or "being busy" isn't the problem.


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