[enum-wg] ENUM RFC insight

Rui Ribeiro wrote:
> Hi all,
> 
> We are having some dificulties with a manufacturer of equipment in order to
> put ENUM queries working.
> 
> The manufacturer says that the in order to comply with ENUM we must use
> NAPTR with "s". They have exemplified as:
> 
> $ORIGIN 1.1.1.1.1.5.3.e164.arpa.
> 1.1.7.3 IN  NAPTR 101 50 "u" "sip+E2U" "!^.*$!sip:3711 at foo.com!i"
> 4.1.7.3 IN  NAPTR 101 50 "s" "sip+D2U" "" _sip._udp.sip.server.foo.com.
>         IN  NAPTR 101 50 "s" "sip+D2T" "" _sip._tdp.sip.server.foo.com.

Hi Rui!

The above is wrong. The NAPTR records for SIP server location are 
independent from ENUM. ENUM records and SIP records are totally unrelated.

What you usually have is:

$ORIGIN 1.1.1.1.1.5.3.e164.arpa.
1.1.7.3 IN  NAPTR 101 50 "u" "sip+E2U" "!^.*$!sip:3711 at foo.com!i"

$ORIGIN foo.com
@ IN  NAPTR 50 50 "s" "SIP+D2U" "" _sip._udp.sip.server.foo.com.
@ IN  NAPTR 90 50 "s" "SIP+D2T" "" _sip._tdp.sip.server.foo.com.

             ^^^^^^                  ^^^^^^^^^^
             different               you still need _sip._udp.foo.com
             priority                as NAPTR lookups inf RFC 3263
                                     are optional

> Although I understand how this may work, in fact the 3711 extension will not
> work by it self since the system don't use the SRV RR for URI dialling (SRVs
> are in place). They have proposed the 3714 extension solution instead. This
> may work to some, but for sure, not to all destinations.
> 
> In RFC 3403 (Page 8) there is reference that suggests that one must add,
> next to the SRV records for a domain, the following.
> 
> $ORIGIN foo.com.
> 	  IN NAPTR 100  50  "s"    "sip+D2U"  ""   sip.server.foo.com.
> 	  IN NAPTR 100  50  "s"    "sip+D2T"  ""   sip.server.foo.com.
> 
> The "million dollar" questions.
> 
> 1. In order to comply with ENUM do you MUST have any NAPTR with an "s" flag
> somewhere on the resolution tree? 

No. ENUM itself does not care about the algorithm to find the server of 
the underlying service (e.g. in your case SIP, but there can be also 
entries for other service types like email, h323, ...).

> 2. It is a good pratice (or is it a MUST to) had the NAPTR "s" flag to the
> domain? [RFC3263]

It is not often used yet, as the NAPTR lookup in RFC3263 is optional. 
Nevertheless you have to add NAPTR records if you like to announce a 
preferred transport protocol.

> 3. What are the current (offical) way to describe services  "sip+D2U" or
> "D2U+sip"? [RFC3263 vs RFC4415/RFC3761]

It is SIP+D2U. ENUM (3761) is a DDDS application which has defined the 
syntax "E2U+......" as service type whereas RFC3263 describes another 
DDDS application which has defined "SIP+..." as syntax for the service type.

regards
klaus


> 
> Thanks for your help.
> 
> Rui Ribeiro
> racr at fccn.pt
>