[Netalyzr] DNS latency threshold
nweaver at ICSI.Berkeley.EDU
Sat Jan 16 07:16:54 PST 2010
On Jan 15, 2010, at 10:16 PM, Zhen Cao wrote:
> Thanks for the reply.
> Another question followed: which DNS is under test?
> I am configuring my DNS at 22.214.171.124 (google public dns), but the
> analysis result indicates that "Your NAT has a built in DNS proxy. The
> DNS request was received from 126.96.36.199". So the DNS performance
> in done between my NAT box and the outside internet?
> And when i am accessing the web, i checked that the DNS response is
> actually received from the 188.8.131.52.
> Thanks for the help.
Actualyl, we test Multiple DNS 'things':
Most tests are through the recursive resolver you set (so in this case, google public DNS), however, the IP we report for it in the server identification test is not the IP you use, as many of these DNS setups are clusters, so your request goes to one IP, it gets bounced around internally, and comes out to our server using a different IP.
But we also do low level tests that check other things. EG, the applet sends a message to what it guesses is your NAT, to see if your NAT also acts as either a DNS server or forwarder (most do, and we'd like to know the percentage, because some of these are broken and causing havoc with various issues.).
And we also send a series of messages directly to our server to make sure that direct DNS access is blocked by the network.
> On Sat, Jan 16, 2010 at 1:59 PM, Nicholas Weaver
> <nweaver at icsi.berkeley.edu> wrote:
>> 750. And we set a threshold simply because we don't have gradiants: either it raises an alert or not, so we have to pick a number that is somewhat sensible.
>> On Jan 15, 2010, at 9:55 PM, Zhen Cao wrote:
>>> Hi Netalyzr Contributors and All,
>>> I'd like to know what's DNS latency threshold in Netalyzr. In one
>>> test, I got a DNS lookup latency of 770ms and it reported "Your ISP's
>>> DNS server is slow to lookup names". In another test, I got 740ms and
>>> did not see that warning. Did you set a threshold between 740ms and
>>> 770ms and why?
>>> Netalyzr mailing list
>>> Netalyzr at mailman.ICSI.Berkeley.EDU
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