[Freeswitch-users] gateways testing DNS SRV records

[William King]

At least some DNS servers will provide some of the additional record
info in the additional section of the dns response. I have seen dns
servers that send additional records, but not the top priority ones,
which does mean that the client would need to do additional lookups.

For instance in the sample case following, the 3 last SRV records
include the A record lookups, but my sip clients do requests for the
first ones:

quentusrex at quentusrex-thinkpad:~$ dig _sip._udp.callcentric.com SRV

; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> _sip._udp.callcentric.com SRV
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28623
;; flags: qr rd ra; QUERY: 1, ANSWER: 8, AUTHORITY: 3, ADDITIONAL: 3

;; QUESTION SECTION:
;_sip._udp.callcentric.com.	IN	SRV

;; ANSWER SECTION:
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha15.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha16.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha17.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha18.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha19.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha11.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha12.callcentric.com.
_sip._udp.callcentric.com. 600	IN	SRV	20 0 5080 alpha13.callcentric.com.

;; AUTHORITY SECTION:
callcentric.com.	1200	IN	NS	ns1.telengy.net.
callcentric.com.	1200	IN	NS	ns3.telengy.net.
callcentric.com.	1200	IN	NS	ns4.telengy.net.

;; ADDITIONAL SECTION:
alpha11.callcentric.com. 1200	IN	A	204.11.192.159
alpha12.callcentric.com. 1200	IN	A	204.11.192.160
alpha13.callcentric.com. 1200	IN	A	204.11.192.161

;; Query time: 277 msec
;; SERVER: 192.168.100.4#53(192.168.100.4)
;; WHEN: Tue Oct 29 12:45:07 2013
;; MSG SIZE  rcvd: 500


William King
Senior Engineer
Quentus Technologies, INC
1037 NE 65th St Suite 273
Seattle, WA 98115
Main:   (877) 211-9337
Office: (206) 388-4772
Cell:   (253) 686-5518
william.king at quentustech.com

On 10/24/2013 12:46 PM, Karl Schmidt wrote:
> On 10/24/2013 01:49 PM, Raymond Chandler wrote:
>> Yes, FreeSWITCH supports SRV records, and handles them correctly.  When
>> I use sofia_dig, I see the IP and the port that are returned from DNS
>> lookups via dig.  If you're not, then you or your provider must have
>> something misconfigured.
> 
> This is correct - I was able to see the details by setting sofia loglevel all 9
> 
> ( I must say that the SRV record syntax is poorly designed - and shouldn't have required multiple 
> lookups - needlessly complex. )
> 
> 
>>
>> On 10/24/2013 01:13 PM, Karl Schmidt wrote:
>>> I'm trying to figure out a way to see if a freeswitch gateway respects SRV records.
>>>
>>> I've been trying different sofia commands without finding the IP that it is using.
>>>
>>>
>>> sofia_dig returns just the A records.
>>>
>>>
>>> To be clear - let's say you are using example.com as your DID and have a gateway set up.
>>>
>>> The provider should have SRV records so that there can be graceful failures.
>>>
>>> To see the IPs to use - do
>>>
>>> dig SRV _sip._upd.example.com
>>>
>>>
>>> So my precise question is how to see the IP freeswitch is using for a gateway.  (I'm assuming that
>>> freeswitch knows how to use SRV records?)
>>>
> 
> 
> --------------------------------------------------------------------------------
> Karl Schmidt                                  EMail Karl at xtronics.com
> Transtronics, Inc.                              WEB http://secure.transtronics.com
> 3209 West 9th Street                             Ph (785) 841-3089
> Lawrence, KS 66049                              FAX (785) 841-0434
> 
> Taking subsidy money from the government is immoral.
> Realize that you are taking the money of people
> that work at McDonald’s by threat of force.
> kps
> 
> --------------------------------------------------------------------------------
> 
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