最顶层的服务器列表：http://www.eecis.udel.edu/~mills/ntp/clock1a.html
次级的服务器列表：
http://www.eecis.udel.edu/~mills/ntp/clock2a.html
ping了几个地址，选择的基准服务器为：
server 164.67.62.194 prefer
server 128.175.60.175
server 66.92.68.246
亚洲地区的ntp服务器
Bangladesh — bd.pool.ntp.org (0)
China — cn.pool.ntp.org (3)
Hong Kong — hk.pool.ntp.org (1)
India — in.pool.ntp.org (2)
Indonesia — id.pool.ntp.org (2)
Iran — ir.pool.ntp.org (0)
Israel — il.pool.ntp.org (3)
Japan — jp.pool.ntp.org (5)
Korea — kr.pool.ntp.org (4)
Malaysia — my.pool.ntp.org (3)
Philippines — ph.pool.ntp.org (0)
Singapore — sg.pool.ntp.org (3)
Taiwan — tw.pool.ntp.org (7)
Thailand — th.pool.ntp.org (1)
Turkey — tr.pool.ntp.org (1)
United Arab Emirates — ae.pool.ntp.org (0)
210.72.145.44 陕西国家授时中心
见 http://www.pool.ntp.org/zone/asia