The preferred way of checking for internet availability is a UDP based traceroute to the following IP addresses in a random manner:
* 22.214.171.124 * 126.96.36.199 * 188.8.131.52 * 184.108.40.206 * 220.127.116.11 * 18.104.22.168 * 22.214.171.124 * 126.96.36.199 * 188.8.131.52
If any of the IP addresses are reached, the check is successful. However, if none of these IPs can be reached via traceroute, the node will try an HTTP based "ping" to all of the following URLs:
* google.com * yahoo.com * alltheweb.com
If any of the URLs are reached, the check is successful. If that also fails, the node will try to download a page from checkin.cloudtrax.com as a last resort.