[Freeswitch-users] DNS SRV != ENUM

Lee JJ jengjr at gmail.com
Thu Aug 21 10:30:23 PDT 2008


Hello Brian :

>From the message
http://lists.freeswitch.org/pipermail/freeswitch-users/2008-August/005544.html
>*
*>>* 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  *
*<--- this is ENUM way , if I want to call an old fashion "Telephone No"
you can see the domain always go to "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.

http://www.voip-info.org/wiki-DNS+SRV
A Domain Name Server (DNS) SRV record helps connecting to a SIP user in a
similar way that an MX record helps email delivery.

http://mit.edu/sip/sip.edu/dns.shtml

For example
sip:billing at voip.apnic.net <sip%3Abilling at voip.apnic.net>
sip:0702058888 at sip.ttn.net <sip%3A0702058888 at sip.ttn.net>

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 !
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