service
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... transport protocols for SIP services at domain B, and the relative
preferences of those transport protocols ...
...
Since SIP is used for the establishment of interactive communications
services, the time it takes to complete a transaction between a
caller ...
... Scalability and high availability are important in SIP. SIP services
scale up through clustering techniques. Typically, in a realistic
version ...
... query for the domain in the URI. The services relevant for the task
of transport protocol selection are those with NAPTR ...
... of transport protocol selection are those with NAPTR service fields
with values "SIP+D2X" and "SIPS+D2X", where X is a letter that
...
... transport protocol in the
NAPTR services field. The resource record will contain an empty
regular expression ...
... transport protocols, there will be multiple NAPTR records,
each with a different service value. As per RFC 2915(-> 3404prop | 3403prop | 3402prop | 3401) [3], the client ...
... 3], the client
discards any records whose services fields are not applicable. For
the purposes of this specification, several rules are defined.
...
... First, a client resolving a SIPS URI MUST discard any services that
do not contain "SIPS" as the protocol in the service field. The
...
... SIPS URI MUST discard any services that
do not contain "SIPS" as the protocol in the service field. The
converse is not true, however. A client resolving a SIP URI ...
... TLS. Second, a client MUST discard any service fields that identify
a resolution service whose value is not "D2X", for values of X that
...
... client MUST discard any service fields that identify
a resolution service whose value is not "D2X", for values of X that
indicate transport protocols supported by the client ...
... NAPTR records, there MUST be at least three
records - one with a "SIP+D2T" service field, one with a "SIP+D2U"
service field ...
... service field, one with a "SIP+D2U"
service field, and one with a "SIPS+D2T" service field. The records
with SIPS as the protocol in the service field ...
... SIP+D2U"
service field, and one with a "SIPS+D2T" service field. The records
with SIPS as the protocol in the service field SHOULD be preferred
...
... service field, and one with a "SIPS+D2T" service field. The records
with SIPS as the protocol in the service field SHOULD be preferred
(i.e., have a lower value of the order field) above records with SIP
...
... (i.e., have a lower value of the order field) above records with SIP
as the protocol in the service field. A record with a "SIPS+D2U"
service field ...
... service field. A record with a "SIPS+D2U"
service field SHOULD NOT be placed into the DNS, since it is not
possible to use TLS ...
... query for that specific
transport, using the service identifier "_sips" for SIPS URIs. For a
...
... SIP URI, if the client wishes to use TLS, it also uses the service
identifier "_sips" for that specific transport ...
... client
should "try to connect to the (protocol, address, service)" without
giving any details on what happens in the event of failure. Those
details are described here for SIP ...
... SRV records at that domain name using the
service identifier "_sips" if the Via transport is "TLS ...
... cache whether or not
its NAPTR records contain SIPS in the services field. If such
records were present, but in later queries cease to appear, it is a
...
... DDDS defines applications, which can make use of
the NAPTR record for specific resolution services. This application
is called the Transport Determination Application, and its goal is to
...
...
Application Unique String: The Application Unique String (AUS) is
the input to the resolution service. For this application, it
is the URI to resolve.
...
... The usage of NAPTR records described here requires well known values
for the service fields for each transport supported by SIP. The
...
... transport supported by SIP. The
table of mappings from service field values to transport protocols is
to be maintained by IANA ...
... registration in the RFC MUST include the following information:
Service Field: The service field being registered. An example for
a new fictitious transport protocol ...
...
Service Field: The service field being registered. An example for
a new fictitious transport protocol called NCTP might be
...
... Protocol: The specific transport protocol associated with that
service field. This MUST include the name and acronym for the
protocol, along with reference to a document that describes the
...
... Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for Specifying the Location of Services (DNS SRV)", RFC 2782prop, February 2000. ...