Hello Brian :

 

From the message

>
>> It should not query ENUM first .
>> 21  11.653138 210.2x.x.x -> 202.y.y.y DNS Standard query NAPTR 
>> 2.9.9.9.e164.org 

>Again you told it to go to enum... isn't that exactly what it should 
>do.  Why would we do a srv before that unless I'm missing your point 
>here.

 

A Domain Name Server (DNS) SRV record helps connecting to a SIP user in a similar way that an MX record helps email delivery.

 

 

For example

 

The pure dns query will get either an "A" record

;; QUESTION SECTION:
;voip.apnic.net.                        IN      A
;; ANSWER SECTION:
voip.apnic.net.         3600    IN      A       203.119.0.97

or a "SRV" record

;; QUESTION SECTION:
;sip.ttn.net.                   IN      SRV

;; ANSWER SECTION:
sip.ttn.net.            3600    IN      CNAME   nusip1.gogotalk.net.tw.

 

for openser  example

forward(destination)

Forward the SIP request to the given destination in stateless mode. This has the format of [proto:]host[:port]. Host can be an IP or hostname; supported protocols are UDP, TCP and TLS. (For TLS, you need to compile the TLS support into core). If proto or port are not specified, NAPTR and SRV lookups will be used to determine them (if possible).

http://www.opensips.org/index.php?n=Resources.DocsCoreFcn#parameters

for Asterisk sip.conf example

srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
                                ; Note: Asterisk only uses the first host
                                ; in SRV records
                                ; Disabling DNS SRV lookups disables the
                                ; ability to place SIP calls based on domain
                                ; names to some other SIP users on the Internet

So they are totally different !