[Serusers] Problem with SER + Micronet SP/5050s gateway

[Ladislav Ivančík]

Hello, 

I have Micronet SP/5050s as a gateways to PSTN (connection to PSTN via
PBX), SER as a proxy server and some voip phones. Next picture shows my
topology:

 _________     _______      _________      _____ 
|SIP Phone|___|  SER  |____|SP 5050/S|____|PBX1 |____ PSTN
|_________|   |_______| |  |____1____|    |_____|
                        |
                        |     . . . 
                        |   _________      _____ 
                        |__|SP 5050/S|____|PBXn |____ PSTN	
                           |____n____|    |_____|
					(in other location)


If voip user calls some number, his UA sends INVITE message (to SER)
with Request-uri=To-uri=number1 at domena.sk.

My SER overwrite Reguest-uri to number2 at ip_address_of_micronet an sends
this INVITE message to Micronet. INVITE includes Reguest-uri which is
different from To-uri. I need dial number2 in PBX. 

Note: Number1 may contain prefix - it tell which PBX use. SER must
prepare real PSTN number - number2 and send INVITE message to corect
gateway.

My problem is that micronet gateway dials numbers from To-uri field, not
from Request-uri field of INVITE message. So it dials number1. All
numbers managed by SER are not available. 

I can overwrite called number (number1 from To-uri) in micronet gateway
too - gateway uses prefixes, but only 10 - it is few for me. And I need
more micronet gateways with different prefixes (I have more PBX each in
other place) - micronet's prefixes decentralize number logic from one
SER to more gateways.

I was trying to overwrite To-uri field of phone's INVITE message in SER,
but if SER sends other message with overwrite To-uri (200 OK, ACK, reply
from micronet) to phone, phone rejects it - message has wrong To-uri
field.

When I has Cisco 2600 as a PSTN gateway - it dialed numbers from
Reguest-uri field, but Cisco is more expensive.

Do you know some solution for me or other gateway, which can I use -
gateway must dial numbers from Reguest-uri field and its price is circa
300$ (PSTN gateway with 6 FXO ports).

Thank you,

Regards,
Laco