NTP Pool is a project to off load some of the hits to the large public NTP servers which have been closing its access due to abuse to usage policy. So a volunteer pool of NTP servers was implemented by a group led by Adrian von Bidder and David Mills (the author of NTP) started this project to stave the tide and give an option that if people just need to sync their clocks, 200 ms (yes that is milli-seconds) one way or another is not a huge deal. So this group of about 200 servers world wide, has volunteered resources/bandwidth to to cause. Please whenever possible use one server to update others, if you are at a company sync with one server and then have all your clients update to YOUR server. This goes for any time server, please don’t be lazy. If you have NTP service already or better yet a stratum-0 clock then consider joining the cause. This is being a good net-citizen.