Mailinglist Archive: opensuse (1420 mails)

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Re: [opensuse] optimizing resolv.conf
On 2014-01-01 10:01 (GMT-0500) Anton Aylward composed:

Felix Miata composed:

My web browsers often seem to spend a lot of time reporting "looking up host
<blah>". I'd like to see less of that in 2014, and spend less time watching
nothing happen in the browser's viewport.

http://www.edwin.io/optimized-resolv-conf seems to make sense, but it
includes no discussion of a local nameserver, such as the one typically
enabled by default in an internet router, only using Google IPs. Anyone have
anything to add or dispute what it says?

Yes, lots!
Visit http://pgl.yoyo.org/adservers/ and read up on a few other items.

Some I knew about, some was new.

First, filtering out ads, either by this method or using an adblock
plugin for Firefox, means fewer looks & delays and less screen real
estate taken up by adverts. That also means faster rendering.

Second, by routing a whole pile of advert sites at the DNS level rather
than just within the adblock level you are blocking them for all
machines on your LAN and for all types of access. You may find this a
better 'parental control' but it also means a while pile of malicious
"Call home" services are blocked. And I don't mean just botnets. Read
the 'cyber-News" of the last few months.

89kb, 2526 lines, from there now appended to dnsmasq.conf.

Yes this too takes maintenance.

How often is your habit?

Are those using routers better off using the one it includes? Better off
avoiding?

No. In my config 8.8.8.8 is the LAST entry.
The first is for my local caching DNS server.

Read that again: *C*A*C*H*I*N*G*
That means it has instantaneous response from the cache rather than
looking up yet again at Google.

The benefit of google, presumably, is that they are running a ****-ing
huge caching server on a machine or cluster that is very fast and has a
very fat pipe. Which is why I list them at all.

But not first!

Many people consider it unsociable to block adverts since they are what,
ultimately, pays for the services. I've heard this same thing said
about TV adverts. You may consider it even more unsociable to block
google-analytics since that lookup takes time as well. That might
amount to the height of 'Net unsociability!

Is there any convenient way to evaluate average response times from various
servers?

Well you could start by pinging them.
How fast they will resolve as DNS servers depends on the load being
placed on them by other users. In general that's not something you have
control over. Since, however, my #1 DNS server is the server under my
desk that also handles email, I do know about its load. There's only me
using it.

Are there logical reasons for avoiding Google's or other high visibility
servers?

Are there reasons why the servers provided by the ISP subscribed to shouldn't
be preferred?

Quite the converse. Assuming you have a good ISP who knows that they
are doing, then their caching DNS server is just a scaled down version
of Google's. But the point is that its closer!

Ping it and look at at the response times. Ping your ISP then ping google.

Bad 404 behavior makes my ISP's lousy choice regardless of competence otherwise.

I get:

--- server ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3999ms
rtt min/avg/max/mdev = 0.236/0.261/0.294/0.030 ms

--- Router ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4006ms
rtt min/avg/max/mdev = 1.733/2.003/2.551/0.341 ms

--- 8.8.8.8 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4004ms
rtt min/avg/max/mdev = 33.696/34.659/35.935/0.794 ms

I think that makes a strong case for why *I* use a local DNS server.

Clearly.

--- 207.69.188.186 ping statistics --- # earthlink.net DNS1
9 packets transmitted, 0 received, 100% packet loss, time 7999ms

--- 8.8.8.8 ping statistics --- # google
5 packets transmitted, 5 received, 0% packet loss, time 4005ms
rtt min/avg/max/mdev = 67.896/68.765/70.057/0.895 ms

--- 199.166.31.3 ping statistics --- # OpenDNS
5 packets transmitted, 5 received, 0% packet loss, time 4004ms
rtt min/avg/max/mdev = 22.184/41.325/59.765/16.284 ms

--- 207.69.188.187 ping statistics --- # earthlink.net DNS2
3 packets transmitted, 0 received, 100% packet loss, time 1999ms

--- 192.168.1.1 ping statistics --- # router
4 packets transmitted, 4 received, 0% packet loss, time 2999ms
rtt min/avg/max/mdev = 0.282/0.302/0.320/0.014 ms

--- 127.0.0.1 ping statistics --- # localhost
4 packets transmitted, 4 received, 0% packet loss, time 2999ms
rtt min/avg/max/mdev = 0.026/0.030/0.036/0.007 ms

Can anyone explain why the default timeout is 5s and not more or less? Is it
a holdover from times past when the internet was less busy, and often less
speedy via dialup or ISDN instead of broadband?

It only makes sense, as fr as I can tell, if you are using round robin
and a few other details that arise out of performance testing of those
particular servers from that particular location. It would make no
sense for me.

If my local DNS server can't find the relevant record in its config or
cache the it will hit my ISP. That's the first timeout that matters.
My ISP has a big pipe and they probably end up checking with google
eventually, so there's little point in timing out with them and going to
google. My going to google would be really slow.

If I were to use the resolv.conf in the article then my system would
become very very slow and unresponsive.

I see. Thanks!

Any chance all this plays a part in IRC timeouts that can be tailored to reducing them?
--
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata *** http://fm.no-ip.com/
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