Since many embedded devices lack a hardware "real time clock", Ionic uses NTP to keep it's clock synchronized. Rather than relying on a single NTP server, Ionic is working with http://pool.ntp.org to ensure that multiple options are always available and that they are geographically "nearby". The following four NTP servers are used Ionic by default:
0.ionic.pool.ntp.org 1.ionic.pool.ntp.org 2.ionic.pool.ntp.org 3.ionic.pool.ntp.org
We are of course not just using pool.ntp.org as a free service. We are contributing 4 IPv4 servers and 4 IPv6 servers to the public pool of NTP servers.