This is a list of places to troubleshoot by doing traceroutes and pings from around the world. You can use these providers to figure out if there are any issues connecting to your site.
Major internet bandwidth providers:
PCCW – http://lookingglass.pccwglobal.com/
Telia – http://looking-glass.telia.net/
Hurricane Electric – https://lg.he.net/
NTT – https://www.us.ntt.net/support/looking-glass/
Cogent – http://www.cogentco.com/en/network/looking-glass
Level 3 – http://lookingglass.level3.net/
GTT – http://www.as3257.net/lg/
Pacnet – http://ops.pacific.net.sg/tools/
China Telecom – http://ipms.chinatelecomglobal.com/public/lookglass/lookglassDisclaimer.html
China Unicom – http://lg.hkunicom.com/lg
Zayo – http://lg.zayo.com/lg.cgi
Sprint – https://www.sprint.net/lg/
XO Communications – http://xostats.xo.com/cgi-bin/xostats/diagtool-pub
Tata Communications – http://lg.teleglobe.net/bin/lg.cgi
Other looking glasses:
SoftLayer – http://lg.softlayer.com/
Eastlink – http://lg.eastlink.ca/