[OpenSIPS-Users] Asterisk Cluster Scenario

[Andrew Pogrebennyk]

On 25.09.2010 20:45, Stefano Sasso wrote:
> In the OpenSIPS features we read "load balancing with failover", but
> we could not find any useful and complete configuration example.
> Is OpenSIPS able to know if an asterisk server is UP or DOWN, or must
> we use a 3rd part tool, like mon?
> 
> Anyone has experience in use OpenSIPS as SIP load balancer (not to
> work as "real" SIP proxy)?
> 
> Any hint/advice for this part, or for the global setup?

Stefano,
I guess a lot of people here use OpenSIPS as a SIP load balancer. You 
may refer to the load balancer tutorial link suggested above. The 
load_balancer module is able to determine if an asterisk server is UP or 
DOWN by using gw probing (OPTIONS ping), as well as dispatcher module:
http://www.opensips.org/html/docs/modules/1.6.x/load_balancer.html
http://www.opensips.org/html/docs/modules/1.6.x/dispatcher.html

However, since you say the call-center works both inbound and outbound 
you probably need to do not only dispatching of inbound calls to 
asterisk but also dynamic routing of some kind. In this case I recommend 
that you check the powerful drouting module:
http://www.opensips.org/html/docs/modules/1.6.x/drouting.html

It is able to accommodate both inbound and outbound calls routing. I can 
comment on its gateway probing implementation, though it's consistent 
with load_balancer. OpenSIPS will send an OPTIONS ping to each gateway 
each N seconds. If the gw doesn't respond to ping - mark it disabled; if 
it responds to the next ping successfully automatic reenabling kicks in.

Also, if opensips fails to terminate the call through the gw - you can 
disable it from failure route. If the next ping succeeds the gw will be 
automatically re-enabled. I would only disable the gw from failure route 
on some response codes, that indicate a server error. 500 and 603 
probably are the good candidates (but check your applications). 
Otherwise there is a good chance of false positive, if the number was 
misdialed or something.

BTW You can still take the gateway out of service, which happens to 
respond to the OPTIONS ping, if you disable in manually via MI command 
(supported in all 3 modules). This will completely stop the probing 
hence automatic re-enabling will not occur.

BTW2 Do you mean your asterisk servers are running behind NAT? If so how 
are they reached from outside? How do you send the calls in and out of 
your network? You may contact me with off the list if you need any 
further help or clarification.

-- 
Sincerely,
Andrew Pogrebennyk