Hello In some SIP invite messages I see the below codec negotiation string, I am wandering what the "101 telephone-event/8000" means.... Which codec is that? a=rtpmap:0 PCMU/8000/1 a=rtpmap:3 GSM/8000/1 a=rtpmap:8 PCMA/8000/1 a=rtpmap:101 telephone-event/8000