Re: [Linphone-users] Getting Linphone to lookup SRV records in a DNS zone as well as a NAPTR record

[Swinney C.]

Hey all,

I have been trying to read around this and I must say I'm a little confused as 
to what exactly the SIP client/server should do when attempting to dial a SIP 
URI, and exactly what records need to be added to the relevant DNS zones.

>From what I understand, should a SIP client make a VoIP call to a telephone 
>like number (as +44 181 300 4321, then this would resolve to an domain 
>something like 1.2.3.4.0.0.3.1.8.1..4.4.e164.arpa, and the lookup will be for 
>a NAPTR record in the ARPA zone. The client could then could receive some 
>information which transforms the original lookup into as a SIP URN, such as 
>sip:address@hidden 

A second NAPTR record is then looked up, but at this time it will be in the 
domain.com zone. This rule must also apply if the initial call from the SIP 
client was made directly to the same SIP URI - correct?

So, if the NAPTR record doesn't exist under the domain.com zone (which do not 
appear to be utilised that often), Linphone then resorts to using the zone A 
record. Correct?

However, the zone may still have an SRV record which indicates the relevant SIP 
service the calling SIP client can use. So why can't Linphone simply try to 
lookup the SRV record before falling back to the A record?

So the question still is, is there a way to get Linphone to lookup the zone SRV 
record? 

After speaking with our DNS guru, they seem to think the NAPTR records are not 
in widespread outside of the ARPA zone, and as such will not add these records 
to our own managed DNS zone.


Regards,


Chris
 
-------------------------------------------------------------------------------------------------------------
From: Swinney C. 
Sent: 27 April 2012 00:39
To: 'address@hidden'
Subject: Getting Linphone to lookup SRV records in a DNS zone as well as a 
NAPTR record

Hi All, 

We have been trialling several SIP client and whilst LinPhone looks quite good, 
there seems to be a drawback in its implementation when trying to resolve SIP 
URI domain names to get the registered SIP service for that domain name. 

We have only added SRV records to the DNS zone in order to point SIP URI 
lookups to our SIP service. We have register both UDP and TCP on 5060 to point 
to the public interface for our SIP entrance gatekeeper.

However, when you make a SIP call in LinPhone using a URI (e.g. 
address@hidden), LinPhone first gets the local DNS servers then tries to look 
up a NAPTR record. When this fails, LinPhone simply appends 5060 to the domain 
name lookup which resolve to  the standard A host record. Of course, the IP 
address resolved is actually pointing to the wrong server - in fact the web 
server. 

Other SIP clients do not seem to have this issue and resolve the correct IP 
address from the SRV record as expected.

Example debug output from LinPhone:
---------------------------------------------------------------------
message: eXosip_dnsutils_naptr: DNS server (0): localdnssrv.com
message: eXosip_dnsutils_naptr_lookup: About to ask for domain.com NAPTR'
message: DNS resolution with domain.com:5060
message: getaddrinfo returned the following addresses:
message: x.x.x.x port 5060 --------------------------- (Resolved IP address of 
web server on A record)
message: Message sent: (to dest=x.x.x.x:5060)
-------------------------------------------------------------------------------

Is there any way to force LinPhone to lookup the SRV record instead of the 
NAPTR record, or should we have NAPTR records in our DNS zone as well? We also 
utilise H.323 and IAX.

Cheers,

Chris