SRV レコード
Service-location record — specifies host AND port for a named service.
SRV レコードとは?
SRV (RFC 2782) lets clients discover where a named service lives without hard-coding a hostname or port. It encodes priority, weight, port, and target host. Used heavily by XMPP, Microsoft Active Directory, SIP, Matrix, Minecraft and many VoIP / federated services.
ゾーンファイルの例
_xmpp-client._tcp.example.com. 300 IN SRV 10 60 5222 xmpp1.example.com.
代表的な用途
- ▸XMPP / Jabber federation — _xmpp-client._tcp.
- ▸Active Directory service location — _ldap._tcp, _kerberos._tcp.
- ▸SIP / Matrix federation — _sip._tls, _matrix._tcp.
- ▸Minecraft non-standard server port — _minecraft._tcp.
よくある落とし穴
Many client libraries only honour SRV for specific protocols; HTTP/HTTPS infamously do NOT use SRV (despite RFC drafts). For HTTP, use CNAME / A.