NAPTR
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... services relevant for the task
of transport protocol selection are those with NAPTR service fields
with values "SIP ...
... SCTP. We
also establish an IANA registry for NAPTR service name to transport
protocol mappings.
...
... transport
protocol mappings.
These NAPTR records provide a mapping from a domain to the SRV record
...
... for contacting a server with the specific transport protocol in the
NAPTR services field. The resource record will contain an empty
...
... transport protocol. If the server supports
multiple transport protocols, there will be multiple NAPTR records,
each with a different service value. As per RFC 2915(-> 3404prop | 3403prop | 3402prop | 3401) ...
... indicate transport protocols supported by the client. The NAPTR
processing as described in RFC 2915(-> 3404prop | 3403prop | 3402prop | 3401) will result in the discovery of
...
... client that wishes to resolve
sip:user@example.com. The client performs a NAPTR query for that
domain ...
... query for that
domain, and the following NAPTR records are returned:
; order pref flags service ...
... service regexp replacement
IN NAPTR 50 50 "s" "SIPS+D2T" "" _sips._tcp.example.com.
IN NAPTR ...
... NAPTR 50 50 "s" "SIPS+D2T" "" _sips._tcp.example.com.
IN NAPTR 90 50 "s" "SIP+D2T" "" _sip._tcp.example.com
IN ...
... redirect server, or registrar is to be contacted
through the lookup of NAPTR records, there MUST be at least three
records - one with a "SIP+D2T" service field ...
...
It is not necessary for the domain suffixes in the NAPTR replacement
field to match the domain of the original query ...
... domain of the original query, even
if the NAPTR record is in a different domain. As an example, even
though the SRV record ...
... SRV records for the domain directly. If
these do not exist because the NAPTR replacement points to a
different domain, the client ...
... client will fail.
For NAPTR records with SIPS protocol fields, (if the server is using
a site certificate ...
... SRV query on the record returned
from the NAPTR processing of Section 4.1, if such processing was
performed. If it was not, because a transport was specified
...
... identifier "_sips" for that specific transport, otherwise, it uses
"_sip". If the NAPTR processing was not done because no NAPTR
records were found, but an SRV query ...
... transport, otherwise, it uses
"_sip". If the NAPTR processing was not done because no NAPTR
records were found, but an SRV query for a supported transport
protocol ...
... priority different (for example, using weights of
1000 and 1001 if two servers are equivalent, rather than assigning
both a weight of 1000), and similarly for NAPTR records. If the
first server is contacted successfully, the proxy can remain
...
... domain SHOULD cache whether or not
its NAPTR records contain SIPS in the services field. If such
records were present, but in later queries ...
... between the users of the system, are frequently the clients that
perform the NAPTR queries. It is therefore possible for a proxy to
...
...
This section more formally defines the NAPTR usage of this
specification, using the Dynamic Delegation Discovery System (DDDS ...
... framework as a guide [7]. DDDS represents the evolution of the NAPTR
resource record. DDDS defines applications, which can make use of
the NAPTR record ...
... NAPTR
resource record. DDDS defines applications, which can make use of
the NAPTR record for specific resolution services. This application
is called the Transport ...
...
The usage of NAPTR records described here requires well known values
for the service fields for each transport ...
... Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS Resource Record", RFC 2915(-> 3404prop | 3403prop | 3402prop | 3401), September 2000. ...