[2] RFC 1386 - The US Domain, 2/1/2021, 1:57:29 AM, 3/13/2021, 9:59:49 AM https://tools.ietf.org/html/rfc1386
[1] RFC 1480 - The US Domain (5/3/2015, 7:36:03 AM 版) http://tools.ietf.org/html/rfc1480
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