default korean mirror has been dead for one month

This is true. KAIST server has been daed for over a month. http://kr.archive.ubuntu.com/ should be reassigned ASAP.

I'm assigning this to the mirror admis, but I think it is a good idea if you send an email about it to <email address hidden> too.

I sent an email to <email address hidden>. Thank you for helping.

I have emailed the mirror admin asking about the down time.

Recently, KAIST(ftp.kaist.ac.kr) mirror SO unstable. I agree changing default mirror to daum(ftp.daum.net).
Daum is a portal site like Yahoo!. At least in korea Daum is more famous than Yahoo! or Google. Maybe I think they have quite solid network infrastructure.

We are experiencing connection problem to KAIST mirror again since yesterday.

In addition, because of the down, update-manager doesn't work when upgrading from Feisty to Gutsy. See http://www.youtube.com/watch?v=0tUjw5Z7yNE for detail.

One of the KAIST students said, "we are remodeling the building, so connection to the KAIST mirror could be unstable for now."

We are experiencing connection problem again.

I have contacted the kr.archive.ubuntu.com admin about this issue and await their response and explanation on the down time.

The current mirror admin of kr.archive.ubuntu.com reports that they did have some down time but now expect the mirror to no longer suffer from any problems. Closing bug.

Kaist mirror server doesn't work again.
However it's not a special situation. Because Kaist server is down sometimes. As Barosl said, two-three times in a month for last 3 years. But ftp.daum.net is not. It's very stable.

Actually for last few years it wasn't matter. But nowadays really many new users rush to ubuntu. and they ask us "why can't I update?" Please reassign kr.archive.ubuntu.com to ftp.daum.net

And check this report https://bugs.launchpad.net/ubuntu/+bug/331222