While such calls the speech is delayed for 1-2 seconds or even there is silence in the SIP-phone. The chan_sip module sends warning:
Don’t know how to respond via ‘SIP/2.0/TCP’
Actually, in the sources of the chan_sip only the responding via UDP is supported.
Also the chan_h323 (OOH323) send this warning:
Don’t know how to deal with mode 0x40 (slin)
Asterisk 1.4.0, SIP-phone - PhonerLite.
What is the reason of this problem? What configurations should I change to make it work?