RR
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... Naming Authority Pointer (NAPTR) DNS Resource Record (RR)
specified here was originally produced by the URN Working Group ...
... Service Parameter combination.
When multiple RRs have the same "order" and all other criteria being
equal, the client should use the value of the preference field to
...
... Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782prop ...