/mcpSDP Body for Encrypted iX Channel For Best Effort offers, the SDP portion looks like: m=application 12345 UDP/UDT/IX * b=as:64 a=ixmap:1 XCCP a=ixmap:2 MSCP a=connection:new a=setup:actpass a=fingerprint: SHA-1 4A:AD:BA:XX:W7:82:18:3B:54:92:12:SA:3E:5D:99:6B:19:E5:75:R9 For Forced Encryption offers, the SDP portion looks like: m=application 12345 UDP/DTLS/UDT/IX * b=as:64 a=ixmap:1 XCCP a=ixmap:2 MSCP a=connection:new a=setup:actpass a=fingerprint: SHA-1 4A:AD:BA:XX:W7:82:18:3B:54:92:12:SA:3E:5D:99:6B:19:E5:75:R9 For Best Effort encryption, the m line transport protocol is UDP/UDT/IX. For forced encryption, the m line transport protocol is UDP/DTLS/UDT/IX. The setup attribute indicates which endpoint should initiate the DTLS/UDT connection. If the fingerprint attribute is present, the setup attribute must also be present at either the m line level or session level. The fingerprint attribute is the user’s DTLS authorization certificate and must be present at the m line level or session level. For forced encryption, the fingerprint is mandatory. X-ULPFECUC Codec Support for Audio X-ULPFECUC is a Forward Error Correction (FEC) codec based on Reed Solomon error correction or similar algorithms. X_ULPFECUC works by creating K additional packets based on encoded input data for every N media packets which enables the receiving entity to recover (N-K) errored packets. This ensures media stream resiliency and can help deliver higher audio quality. Although the recommended payload type for FEC Codec is 123, it can negotiate using other dynamic payload types. Clock rate is transparently passed from one leg to other, along with FMTP parameters. As FEC Codec is a non-primary codec, an SDP containing only FEC Codec (or FEC + any non primary codecs like RFC2833) in audio mLine is rejected with a 488 message. The SDP offer looks like: m=audio 47352 RTP/AVP 114 18 123 18 101 a=sendrecv a=rtpmap:114 opus/48000/2 a=rtpmap:123 X-ULPFECUC/8000 a=fmtp:123 multi_ssrc=0;max_esel=20;m=2;max_n=20 a=rtpmap:18 G729/8000 a=fmtp:18 annexb=no a=ptime:20 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15 SIP Line Messaging Guide (Standard Edition) for Cisco Unified Communications Manager 50 SIP Standard Line Interface X-ULPFECUC Codec Support for Audio