Hi!

While writing the RTP proxy, I've been playing with the ip.access RTP related code for quite a bit. This is as far as I have understood it so far:

Setting up a voice call (for one MS) * sending IPACCESS_BIND via RSL, specifying * the GSM channel number IE * the IP speech mode IE, indicating * 0x1- : uni-directional, rx-only * 0x-1 : EFR (0: FR, 2: AMR) * receiving IPACCESS_BIND_ACK via RSL, specifying * the GSM channel number IE * the ip.access connection identifier * the locally-bound UDP port for RTP * the locally-bound IP address for RTP * optionally: the RTP payload type * sending IPACCESS_CONNECT via RSL, specifying * the GSM channel number IE * the ip.access connection identifier (from BIND_ACK) * the remote UDP port number for RTP * the remote IP address for RTP * the IP speech mode IE, indicating * 0x0-: bi-directional * 0x-1: EFR (0: FR, 2: AMR) * optionally: the RTP payload type, if BIND_CAK specified it

Misc observations: * if BIND is called with IP speech mode IE 0x10 (uni-directional FR), then no RTP payload type is returned in BIND_ACK. Instead, the standard type for GSM 06.10 (0x03) is used in the packets. * I'm not sure which RTP payload type (and IP speech mode) is which, i.e. if the payload type of BIND/BIND_ACK specifies "expect this payload type for incoming packets" or "use this payload type for all RTP packets originated by this side"