On Jan 16, 2007, at 8:17 AM, Jiri Kuthan wrote:
At 14:59 16/01/2007, Greg Fausak wrote:
Jiri,
Thanks for the pointer! I think I'll have to give this a look.
Hi Greg,
with pleasure. Just keep in mind that having robustness in there takes couple of other steps. Particularly IP blacklisting to avoid attempts to send to the DNS-conveyed destinations, which are unavailable and ...
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!
... building the ser script in a way that retransmissions are absorbed (kind of having "shock absorber" in place)
Retransmissions are good (most of the time). Somehow the ser script would need to know that there is another thread tending to a DNS lookup. How does my script know if a message is original, or a retransmission anyway?
It seems to me that the tm module should be reaping the retransmits.
-g
-jiri
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" lgfausak@gmail.com 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/
-- Jiri Kuthan http://iptel.org/~jiri/