Mailinglist Archive: opensuse (1420 mails)

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Re: [opensuse] optimizing resolv.conf
  • From: Greg Freemyer <greg.freemyer@xxxxxxxxx>
  • Date: Fri, 3 Jan 2014 09:48:37 -0500
  • Message-id: <CAGpXXZK3jqfPZArBZ7sCvQKBnUvap_Yjb23sBbq=pFvx0HUOMw@mail.gmail.com>
On Thu, Jan 2, 2014 at 10:20 PM, James Knott <james.knott@xxxxxxxxxx> wrote:
James Knott wrote:
Isn't a DNS cache included in the browser or operating system already?

Check nscd. It's used in openSUSE for name server caching. man nscd
for details. Firefox also has a DNS cache. So, using a caching DNS
server won't provide much improvement for a single computer.

slightly OT:

I just used wireshark to watch chrome page refresh with Windows 7. I
happened to have susestudio open on a page with no advertising and few
graphics. the result was 4 outbound DNS queries for susestudio.com to
my DNS server in 3 seconds. So chrome v31 does not cache DNS even
during a single page refresh. And neither does Windows 7.

I repeated the test with firefox, and I got no DNS queries for
susestudio.com, so it does seem to cache internally.

Thus anyone with Windows 7 / Chrome as part of their local LAN should
realize they are pounding their DNS server heavily. If that DNS
server is 10 or 20 milliseconds away, a heavily graphic'ed webpage
could be slowed down a second or two just making the DNS queries. I'm
using my ISPs DNS server on that windows laptop and it is taking about
20 millisecs to respond to a DNS query.

Greg
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