cannot update with yum

[yufan]

When i was tring to update a remote system by using yum,it returns an error 
message:
yum update
Setting up Update Process
Setting up Repos
ftp://ftp.oss.eznetsols.org/linux/fedora/3/i386/os/repodata/repomd.xml: 
[Errno 4] IOError: <urlopen error (-2, 'Name or service not known')>
Trying other mirror.
Cannot open/read repomd.xml file for repository: base
failure: repodata/repomd.xml from base: [Errno 256] No more mirrors to try.

what's wrong with that?
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