[Users] SRV Lookups
klaus.mailinglists at pernau.at
Thu Nov 24 11:25:24 CET 2005
Douglas Garstang wrote:
> I'm trying to get SRV lookups to work with OpenSER 1.0.0. I've
> exhausted every avenue of documentation including newsgroups, various
> forums etc.
> Using t_relay, OpenSER seems to be performing the correct DNS SRV
> queries and obtaining a list of hosts to try. Below are the relevant
> sections of my DNS zone file. We're talking UDP, and based on the
> priority and weights below, OpenSER should be basically doing a
> round-robin approach, and it seems to be.
> The problem occurs when one of the hosts is not contactable. OpenSER
> simply stops and does not try the next host in it's list. I would
> have thought that for OpenSER to fully support SRV lookups, it should
> try each until it is successful. After all, that's a large part of
> the whole point of SRV records.
(open)ser does not support SRV failover. It just looks for
_sip._protocol and uses the first found record. No failover if there is
a problem with the destination.
> Does the t_relay() function have logic within itself to keep trying
> hosts until it gets a connection? What would be the definition a
> failure that would make it move onto the next host be anyway? Network
> failure certainly, but would a 'Not found' be considered a failure
> that would cause it to move on? Would anything other than an ACK be a
If you receive a SIP response, than there is no transport failure -> no
failover to other SRV hosts.
> Is there some variable I can set or some function I can call that
> causes t_relay() to retry all hosts in it's SRV list? Without this
> feature, OpenSER's usefulness is very limited.
> Help very much appreciated. Doug
> bil-pdev-3 IN A 192.168.10.4
> proxy1 IN CNAME bil-pdev-3
> proxy2 IN CNAME bil-pdev-3
> proxy.bil.voip.com. IN NAPTR 50 50 "s"
> "SIPS+D2T" "" _sips._tcp.proxy.bil.voip.com. proxy.bil.voip.com.
> IN NAPTR 60 60 "s" "SIP+D2U" "" _sip._udp.proxy.bil.voip.com.
> proxy.bil.voip.com. IN NAPTR 70 40 "s"
> "SIP+D2T" "" _sip._tcp.proxy.bil.voip.com.
> _sips._tcp.proxy.bil.voip.com. IN SRV 100 10 5061
> proxy1.proxy.bil.voip.com. _sips._tcp.proxy.bil.voip.com. IN
> SRV 100 10 5061 proxy2.proxy.bil.voip.com.
> _sip._udp.proxy.bil.voip.com. IN SRV 100 10 5060
> proxy1.proxy.bil.voip.com. ; This line and the next are SRV records
> being looked up _sip._udp.proxy.bil.voip.com. IN SRV
> 100 10 5060 proxy2.proxy.bil.voip.com. ;
> _sip._tcp.proxy.bil.voip.com. IN SRV 100 10 5060
> proxy1.proxy.bil.voip.com. _sip._tcp.proxy.bil.voip.com. IN
> SRV 100 10 5060 proxy2.proxy.bil.voip.com.
> *._tcp IN SRV 0 0 0
> . *._udp IN SRV 0 0
> 0 . ;
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