IANA-registered
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... independent of the protocol that may be used to offer it. Each
application service will be associated with an IANA-registered tag.
For example, retrieving mail is a type of application service that
...
... application protocol" is used to implement the application
service. These are also associated with IANA-registered tags. Using
the mail example above, "POP3" and "IMAP4 ...
... app-service = experimental-service / iana-registered-service
app-protocol = experimental-protocol ...
... app-protocol = experimental-protocol / iana-registered-protocol
experimental-service = "x-" 1*30ALPHANUMSYM
...
... experimental-protocol = "x-" 1*30ALPHANUMSYM
iana-registered-service = ALPHA *31ALPHANUMSYM
iana-registered-protocol ...
... iana-registered-service = ALPHA *31ALPHANUMSYM
iana-registered-protocol = ALPHA *31ALPHANUM
ALPHA ...
...
The "app-service" must be an IANA-registered service; see Section 7
for instructions on registering new application service tags ...