Cisco UCME users report that calls lose audio after being forwarded to certain users. Point-to-point calling appears to work normally, but, depending on the phone type, some forwarded calls lose audio. The trace header shows the following Allow methods: `INVITE,BYE,CANCEL,ACK,INFO,PRACK,COMET,OPTIONS,SUBSCRIBE,NOTIFY,REFER,REGISTER` Which method is missing and explains why the SRTP stream stops working?