application client
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... service exists. If bunyip.example
has no "WP:Whois++" NAPTR record, the application client MUST
backtrack and try the next available "WP:Whois++" option from
example.com. As there is none, the whole resolution fails.
...
... example.com. As there is none, the whole resolution fails.
An application client first queries for the NAPTR RRs ...
...
In the case of an application client that supports more than one
protocol for a given application service, it MUST pursue S-NAPTR ...