The learning curve with opensips is really high. There are specially three modules that lack examples (altought the documentation is good).
There should be at least some example routing code for this:
.- drouting, it's easy to migrate from lcr so, but since it's not yet in osipsconsole, doesn't look as appealing as it should be.
.- dialog, dialog + mediaproxy brings many possibilities to control the remote connecion being closed.
.- nathelper, although nathelper is a quite old module, it's difficult to have it working properly together with mediaproxy/rtpproxy, this has been the most frustating part for the implementation of a real server.