Super fast dns resolution times

[Jesse Gersenson]

The site in this report seems to have blisteringly fast dns resolution times. How do they do it?

http://www.webpagetest.org/result/131207...1/details/

[iSpeedLink.com]

Their DNS Lookup Time is 30-109 milliseconds as reported by PHP's curl in my Test Routines.

THE PHP CODE:

PHP Code:

$dnsTime = curl_getinfo($ch, CURLINFO_NAMELOOKUP_TIME); 


This number reported by my testing routines are fairly consistent.

These number are for the just the index page no other page elements.

Routine #1,
THESE ARE THE RESULTS FROM THE FIRST TEST RUN IN A SERIES OF TESTS.
Base Page Size: 15,848 Bytes
Transmission Speed: 367,550 Bytes/Sec.
Compression: Your Web server is NOT Compressing HTML
HTML Whitespace: 1.0%
Bytes Transmitted: 15,848 Bytes
HTML Transfer Rate: 367,550 Bytes/Sec.

Resolve Domain Name: 0.109 Sec.
Connect Time: 0.152
Transfer Time: 0.043 Sec.
Generate HTML: 0.044 Sec.
Total Time: 0.239 Sec.

Server Transfer Rate: 373,363 Bytes/Sec.
Data Transfer Rate: 373,363 Bytes/Sec. (No gzip compression)
Packet Transfer Rate: 83,426 Bytes/Sec. (includes overhead of pre-first byte time)

Resolve Domain Name: 60.180 mS.
Connect Time: 42.943 mS.
Wait on Server: 43.839 mS.
Pretranfer time: 103.123 mS.
Time To First Byte Time: 146.962 mS.
Transfer Time: 43.001 mS.
Total Time: 190.069 mS.
total_time: 189.963 mS.
Get Packet Time: 202.727  15,848 Bytes

Get Packet Time is a simplified method:

PHP Code:

$getTime=microtime(true);
$data = file_get_contents($url);
$getTime= microtime(true) - $getTime; 


Then 10 back to back iterations I get a DNS Resoulution range from 28.644 mS. to 30.602 mS.

I consider a DNS Resolution time of less than 0.040 to be "good".

Back to back testing of DNS with only 200 mS between tests is a best case response time.
Some of the test data variables are probably still in the Name Server's microprocessor's L2 cache, and I ran these test around 4:00am Sunday morning.

The DNS must have been cached for the results you linked to.

Looking at the header it's really not an impressive page.
HTTP/1.1 200 OK
Date: Sun, 08 Dec 2013 11:06:49 GMT
Server: Apache
Last-Modified: Sun, 08 Dec 2013 08:02:08 GMT
Accept-Ranges: bytes
Content-Length: 15848
Connection: close
Content-Type: text/html

No cache
No gzip
No expiration date
No Keep Alive

This is so bad that ETag would be an improvement whereas ETag is usually in my minus column.

A 30 mS DNS resolution is Good, but nothing to write home to mother about.

[robzilla]

I'm guessing the browser has it in its cache, hence the non-existent ("-") lookup times. Same test machine, different browser:
http://www.webpagetest.org/result/131208_VR_G3C/

DNS Lookup: 155 ms

[Jesse Gersenson]

The question stands, how did this site achieve a dns look-up time of 0ms?

[robzilla]

Seems to be limited to IE9 on the LA test machine. Probably a bug?

[pmeenan]

yeah, has to be an issue with the LA agent - I'll look into it. WPT clears the OS DNS cache (and kills the browser between runs) so the DNS lookups should always be at least the configured RTT.