Jiri,

Thanks for the pointer!  I think I'll have to give this a look.
We are having specific problems with the DNS resolver on failover (when one DNS resolver is not reachable, the next is queried, and openser is not acting
predictably when this happens).  It is as if the tm module is not
properly threaded.  Like when one thread gets stuck waiting for
a response from DNS resolver, another thread picks up a retry
SIP message and doesn't know about the retry in process!

We see the bad resolver behavior when 2 resolvers are listed in /etc/ resolv.conf, and
we turn off the first one.

The DNS failover is also interesting. I think failover applies to A records
and SRV records (not NAPTR records).

-g

On Jan 16, 2007, at 7:12 AM, Jiri Kuthan wrote:

indeed, the stuff is not well linked, we are working on it. Here you go. http://cvs.berlios.de/cgi-bin/viewcvs.cgi/ser/sip_router/doc/ dns.txt?rev=HEAD&content-type=text/vnd.viewcvs-markup

-jiri

At 02:46 16/01/2007, T.R.  Missner wrote:
Greg,

This is a ref to SER. Apparently this functionality has been added to the new pre-release version. I did find some talk about it in the release notes. I couldn’t find any specific documentation. Admittedly I don’t understand the layout of SER’s site very well as I haven’t spent much time there.

-- TR


On 1/15/07 8:33 PM, "Greg Fausak" <[EMAIL PROTECTED]> wrote:

In the text below I quote Kerker 'SER does support DNS failover.'.
Is this ser or openser?  Where can I read more about this?

-g

On Jan 15, 2007, at 10:40 AM, Klaus Darilion wrote:


Staffan,





Kerker Staffan wrote:


...




Now, if I disable one of the Gateways, I hang every second call. OpenSER does


not


try the second A record address if the first doesn't answer. How can I solve


this? Shouldn't OpenSER fail over to the second A record listed in the NAPTR


=> SRV


resolving? Or will OpenSER continue to resend all SIP INVITES until timers


fire? Would


it help if the proxy recieved an ICMP port/destination unreachable from the


network? Is


there anyway to get around this? In the other direction, from POTS to sip,


the PGW2200


nicely switches over to the second of my two OpenSER servers if I shut one of


them down. These servers have the same DNS entries (but for another SIP domain, NAPTR =>


SRV => 2x A record).




Yes, OpenSER or for that matter every transaction stateful proxy should


do RFC 3263 based fail-over. But as you can imagine this is pretty


complex to implement and that's why openser does not support it yet, it


is listed on the development roadmap. The newest release of SER does


support DNS failover.








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Jiri Kuthan            http://iptel.org/~jiri/



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