[OpenSIPS-Devel] Question on dispatcher routing.

Liviu Chircu liviu at opensips.org
Mon Oct 17 10:44:51 CEST 2016

Hi surya,

> 1. How dispatcher manages to send 200 OK for the NOTIFY to correct server.
> 2. Where does dispatcher maintain the entries to match REPLY to correct
> server?
Short answer: it doesn't! Dispatcher is completely agnostic to any reply 
matching logic, as that is solved inside the SIP stack. This is possible 
with the lovely Via headers, which guide the routing of a reply back to 
the UAC.

However, you do need to double-check you are using a correct dispatching 
algorithm, that ensures all PUB/SUB requests of a user always end up on 
the same presence server. Dispatching by hashing the From URI would be a 
good place to start.
> 3. Can reply pass thru ds_select_dst()?
By default, no. This is because they are transparently routed back by 
the SIP stack. If you want to work on your replies, you need to write 
some script code in the "onreply_route" [1] as well.

[1]: http://www.opensips.org/Documentation/Script-Routes-2-3#toc4

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