In RTMFP I can define a TURN proxy, for cases where dirrect P2P link between peers is not available (e.g. symmetric nat). To do that I define a RTMFPTURNProxy value in file mms.cfg. The problem is - I can not find any implementation of TURN proxy on the internet that follows draft-ietf-behave-turn-08 (Which RTMFP requires and was a TURN version when FP10 was released). So the question is - Is there any TURN proxy that works with RTMFP?
Probably best to ask this one on the flashmedia mailing list where there are a few people who deal with these types of issues (similar questions have been asked in the past). Ultimately though you’re better having a fallback rtmp connection through a remote server rather than having a pure p2p solution for all users.