I am unable to download all android packages when i start sdk manager.exe it is displaying error message as "Failed to fetch URL http://"

I am trying to install in my ofce but network people also not able to resolve the problem,

when i install the SDK Manager.exe it is displaying only installed packages and displaying error message Failed to fetch URL http://ift.tt/1m5Yc5M, reason: IO Unknown Host dl-ssl.google.com

please provide me solutions to overcome this one...

please help me in this one