It seems the agent in Korea for IE7 is not stable, so the test results can’t be credible. For more details, please see the following test results:
ID PLT
111223_FS_2M9BX 6947
111223_F7_2M9W8 10220
111226_SJ_2MZHN 18798
111226_93_2N04V 27252
I don’t see anything from those test results that indicate it being a problem with the test agent. The 4 tests have different sets of issues.
The first two tests have very different first byte times but the rest of the components all look to perform consistently so I’d be inclined to think that the difference is because of a back-end performance issue (though DNS performance is bad for both):
http://www.webpagetest.org/result/111223_FS_2M9BX/ - 5.1s TTFB
http://www.webpagetest.org/result/111223_F7_2M9W8/ - 3.8s TTFB
The second two have all sorts of problems resolving different domains. 12007 is “ERROR_INTERNET_NAME_NOT_RESOLVED”. Can you reproduce the issue with other sites as well (like www.google.com)? That will help identify if it is an issue with the ISP’s DNS or somewhere further down the chain.
Thanks,
-Pat
Thanks a lot for your reply, I’m a newbie in web page performance area, hope will get faimilar with it soon. 
For the page (Microsoft 365 설명서 | Microsoft Docs) that I posted above, test results on other agents are almostly ok (maybe there was one failure out of five times of run), only results of Korea so not stable that I have to pick one out of dozens of times of run. Per your suggestion, I tested http://www.google.com/ on Seoul, South Korea IE7, the results were not good, the following results show details, for the first run, DNS look up took more than 1 second, for the other two, test completed but no results after the page said “Test started about 5 minutes ago…”
http://www.webpagetest.org/result/120104_T6_2QV1T/
http://www.webpagetest.org/result/120104_RW_2QVE4/
http://www.webpagetest.org/result/120104_Z7_2QVEV/
However, when testing http://www.google.com/ on other agent like Sydney, AU - IE7, the results were stably:
http://www.webpagetest.org/result/120104_CE_2QVG1/
http://www.webpagetest.org/result/120104_FS_2QVKW/
http://www.webpagetest.org/result/120104_1K_2QVMA/
On Geneva, Switzerland - IE8, also good:
http://www.webpagetest.org/result/120104_6E_2QVKP/
http://www.webpagetest.org/result/120104_PB_2QVMF/
On Taipei, Taiwan - IE9, also good:
http://www.webpagetest.org/result/120104_CF_2QVMX/
http://www.webpagetest.org/result/120104_ZT_2QVN7/
Thanks (and sorry about that). Reaching out to Daum to have them look into the DNS issues on the test machine.
Daum found and fixed the DNS issues: http://www.webpagetest.org/result/120105_F1_a2896afda9ae7653d75d190c48d35c01/
I tried re-running your specific test though and it was erroring out so there may be something else going on that I need to take a look at.
Ok! Appreciate your quick response!