HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

Advanced Features 389
ENUM Resolution Support
RvSipRegClientSetTranscTimers()
Sets the timers in a reg-client object. Setting timers in a reg-client effects all the
transactions that this object handles.
Note For all objects, you can also reset the timer back to the configuration values
with the same API function, by supplying NULL to the set function instead of the
RvSipTimers pointer.
ENUM
RESOLUTION
S
UPPORT
According to RFC 3824, ENUM (E.164 Number Mapping) is a system that uses
DNS (Domain Name Service) to translate certain telephone numbers, such as
[phone], into URIs (Uniform Resource Identifiers). The SIP protocol
handles telephone numbers that cannot be routed in the SIP context by using
ENUM.
URIs, which include PSTN phone numbers in E.164 format, must include the
“tel:” schema. This way, the SIP Stack will refer to them as TEL URIs. Once the
SIP Stack encounters a TEL URI, it will try to resolve it to a SIP URI using an
ENUM NAPTR query. The result of the NAPTR query is a regular expression,
and applying this regular expression on the original TEL URI phrase may result
in a SIP URI. The SIP Stack, however, does not evaluate regular expressions
and asks the application to resolve the regular expression using a callback. If the
resolution of a TEL URI fails at any stage, the SIP Stack will try to resolve it as
a regular Other URI. For more information, see the Other URI Extension
Support chapter.
INITIATING AN ENUM
Q
UERY
The two basic ways of initiating an ENUM NAPTR query are as follows:
 Using the RvSipResolverResolve() function with the
RVSIP_RESOLVER_MODE_FIND_URI_BY_NAPTR.
resolution mode. For more information, see the Working with
Resolvers chapter.
 Sending a message to a TEL URI destination over one of the
SIP Stack objects (such as call-leg, transmitter and so on). The
SIP Stack supplies a new API function in the Message layer for
creating TEL URIs. For more information, see the SIP Stack
Message Layer Reference Guide.
RETRIEVING AN ENUM
R
ESULT
According to RFC 3764, generally there is no need to have more than one
ENUM NAPTR record under a single telephone number (section 4). Thus, the
SIP Stack keeps only a single entry of an ENUM query result element within a