Multiplexing
There are several  ways of multiplexing
§ Session multiplexing, where repair streams and the source MIU
are in different session (different dest address/port).
§ PT multiplexing, where repair streams and the source MIU have
different PT in FEC payload header but are transmitted in the
same session.
§ SSRC multiplexing ,where repair streams and the source MIU
have different SSRC but are transmitted in the same RTP
session.