Is there any China OEM supplier who is still Building ToIP phone, based on PalmMicro chipset like PA1688,PA3288, or PA6488 , like Yuxin 201 based on PA1688?
I'm searching for a ToIP phone which is able like this last one, able to send its Ringing music through RTP stream to the caller (in extra Asterisk allows this stream to pass through it ! )
This has a big impact when a phone is behind a firewall. Because when a phone like this received a call behind its firewall
(it possible because the translation UDP NAT table is hold open for SIP PDU by regular REGISTER sip, send by the phone to its outside SIP proxy/registrar: so any INVITE sip can come from the outside: we have just to choose a REGISTER sip period less than the UDP NAT time out in the firwall system, generally 120s: the case in Linux kernel)
Then the outcoming RINGING tone, transported by RTP toward the outside IPBX, open a UDP NAT translation table in the firewall. So the following incoming RTP can also go through the firewall.
Finally the outgoing ringging tone of PA chip series is acting for RTP, as REGISTER act for SIP.
Both set in place UDP NAT tables translation. Doing so, no extra service as STUN server is required when a phone is behind a firewall, with dynamic public IP address.
This behavior is a very EXTRA +++++
Of course I understand that this is a clever choice of PalmMicro firmware implementation to offer this facility. and nowadays I desperately searching a current made ToIP phone having this valuable feature.