[enum-wg] ENUM RFC insight

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.

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? 
2. It is a good pratice (or is it a MUST to) had the NAPTR "s" flag to the
domain? [RFC3263]
3. What are the current (offical) way to describe services  "sip+D2U" or
"D2U+sip"? [RFC3263 vs RFC4415/RFC3761] 

Thanks for your help.

Rui Ribeiro
racr at fccn.pt