[AVT] RTP topologies and terms

Dear RTP Experts,

Could anyone help to clarify the following: what is the RTP topology,
and what is the right term for end-point B?

The topology is as follows:

      +----+           +---+             +---+
       | A  |=====>| B | ----------->| C |
      +----+           +---+             +---+

- A sends a scalable bitstream of multiple layers using multiple RTP
sessions (layered multicast).
- B aggregates the input RTP streams from the multiple RTP sessions to
one RTP stream and sends to C. 

I failed to map the topology to any of those (or their combinations)
mentioned in draft-ietf-avt-topologies-06.txt , where all seem talking
about end points within one RTP session. Also I am wondering whether B
can be called a translator, mixer or (RTCP terminating) MCU? There are
multiple RTP sessions between A and B, and there seems to be only one
RTP sessions between B and C, therefore B terminates RTP sessions. If
this is true, then B can neither be called translator nor mixer,
according to the comment made by Colin earlier (on August 18 2007 in the
AVT reflector that "Neither an RTP translator or a RTP mixer terminate
the RTP session."). Or is it so that the one RTP stream from B to C are
still of multiple sessions (hence B does not terminate RTP sessions)?

BR, YK

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