Issues when updating from Fedora 21 Alpha

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I have installed Fedora 21 workstation Alpha just after it's release and used to update it regularly. Then I did n't perform update for last one month. Yesterday, I tried to perform update operations using yum. But it shows me error message as follows.

    Loaded plugins: fastestmirror, langpacks
Could not get metalink https://mirrors.fedoraproject.org/metalink?repo=fedora-21&arch=x86_64 error was
14: curl#7 - "Failed to connect to mirrors.fedoraproject.org port 443: Network is unreachable"
fedora                                                      | 3.8 kB  00:00     
http://mirrors.yun-idc.com/fedora/development/21/x86_64/os/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for fedora
Trying other mirror.
fedora                                                      | 3.8 kB  00:00     
http://mirrors.hustunique.com/fedora/development/21/x86_64/os/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for fedora
Trying other mirror.
fedora                                                      | 3.8 kB  00:00     
http://mirror.dhakacom.com/fedora/linux/development/21/x86_64/os/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for fedora
Trying other mirror.
fedora                                                      | 3.8 kB  00:00     
http://ftp.kaist.ac.kr/fedora/development/21/x86_64/os/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for fedora
Trying other mirror.
fedora                                                      | 3.8 kB  00:00     
http://mirrors.ispros.com.bd/fedora/development/21/x86_64/os/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for fedora
Trying other mirror.
fedora                                                      | 3.8 kB  00:00     
http://ftp.yzu.edu.tw/Linux/Fedora/linux/development/21/x86_64/os/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for fedora
Trying other mirror.
http://ftp.jaist.ac.jp/pub/Linux/Fedora/development/21/x86_64/os/repodata/repomd.xml: [Errno 14] curl#7 - "Failed to connect to ftp.jaist.ac.jp port 80: Network is unreachable"
Trying other mirror.
Could not get metalink https://mirrors.fedoraproject.org/metalink?repo=updates-testing-f21&arch=x86_64 error was
14: curl#7 - "Failed to connect to mirrors.fedoraproject.org port 443: Network is unreachable"
updates-testing                                             | 4.9 kB  00:00     
http://mirrors.hustunique.com/fedora/updates/testing/21/x86_64/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for updates-testing
Trying other mirror.
http://mirror.dhakacom.com/fedora/linux/updates/testing/21/x86_64/repodata/repomd.xml: [Errno 14] curl#7 - "Failed to connect to mirror.dhakacom.com port 80: Network is unreachable"
Trying other mirror.
updates-testing                                             | 4.9 kB  00:00     
http://ftp.kaist.ac.kr/fedora/updates/testing/21/x86_64/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for updates-testing
Trying other mirror.
updates-testing                                             | 4.9 kB  00:00     
http://ftp.riken.jp/Linux/fedora/updates/testing/21/x86_64/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for updates-testing
Trying other mirror.
updates-testing                                             | 4.9 kB  00:01     
http://mirrors.ispros.com.bd/fedora/updates/testing/21/x86_64/repodata/repomd.xml: [Errno -1] repomd.xml does not match metalink for updates-testing
Trying other mirror.
updates-testing                                             | 4.9 kB ...