[Freeswitch-users] FreeSWITCH and OpenSER

Mikael A. Bjerkeland mikael at bjerkeland.com
Wed Apr 16 01:27:56 PDT 2008


I am trying to look up information on the use of FreeSWITCH together
with OpenSER. I am doing a configuration on my own without much
experience on the configuration of OpenSER. In my setup OpensSER acts as
a registrar and proxy. I have multiple FreeSWITCH servers for media,
routing and PSTN termination, but I am not sure if my approach is the
"right way".
All SIP traffic goes to the OpenSER proxy which in turn routes the call
with the LCR module to a FreeSWITCH server. This has proven to work fine
in my limited testing environment. I am using ENUM on the FreeSWITCH
server to look up dialed numbers. If the dialed number was found in our
ENUM registry and belongs to the proxy, we call back to OpenSER:

SIP UA (subscriber 56195122) -> INVITE 25929511 -> FreeSWITCH -> ENUM
lookup -> Found -> Routed back to OpenSER -> SIP UA (subscriber

If the call is not found:
SIP UA (subscriber 56195122) -> INVITE 95018615 -> FreeSWITCH -> ENUM
lookup -> Not found -> Routed to PSTN gateway or SIP peer

I am not using aliases in OpenSER as it seems that ENUM provides the
same functionality, but please correct me if I'm wrong. I also made this
decision because it seems easier to implement features like call
forwarding (unconditional, busy, no answer and timed) in FreeSWITCH
rather than in OpenSER. This brings me back to my current issue: Call

Outbound and inbound calling with ENUM lookups in FreeSWITCH to my test
phones works fine. So does calls to the PSTN gateway. My problem has to
do with transfers. I can do a an attended transfer from my Polycom phone
when I'm in a call. The second call is set up and I can talk to the
person I want to transfer to. I hit the transfer button. Nothing
happens, and FS and OpenSER try to look up
number_to_transfer_to at openser-registrar. The call is routed to OpenSER
which complains that it cannot find the subscriber/alias, which makes
sense as there isn't configured an alias. But this also happens when I
transfer to a PSTN number. Do I need to take special actions on REFERs?
Are there any examples of a working OpenSER + FreeSWITCH setup out
there? I believe FreeSWITCH and OpenSER complement each other great but
I found the lack of information on the two applications used together a
Has anyone implemented phone service based on OpenSER and FreeSWITCH who
can explain their setup a bit?


More information about the FreeSWITCH-users mailing list