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
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
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.
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"  as well.
3. Can reply pass thru ds_select_dst()?
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