[1] [CITE@en[draft-cai-ssdp-v1-03 - Simple Service Discovery Protocol/1.0]]
( ([TIME[2011-03-21 00:41:36 +09:00]] 版))
<http://tools.ietf.org/html/draft-cai-ssdp-v1-03#section-4.2.1.1>

[2] [CITE@en[RFC 7505 - A "Null MX" No Service Resource Record for Domains That Accept No Mail]]
([TIME[2015-07-01 10:19:40 +09:00]] 版)
<https://tools.ietf.org/html/rfc7505>