  In multipoint-to-point connections, the traffic at the root (destination) is
the combination of all traffic originating at the leaves. A crucial concern in
the case of multiple senders is how to define fairness within a multicast group
and among groups and point-to-point connections. Fairness definition can be
complicated since the multipoint connection can have the same identifier
(VPI/VCI) on each link, and senders might not be distinguishable in this case.
Many rate allocation algorithms implicitly assume that there is only one sender
in each VC, which does not hold for multipoint-to-point cases. We give various
possibilities for defining fairness for multipoint connections, and show the
tradeoffs involved. In addition, we show that ATM bandwidth allocation
algorithms need to be adapted to give fair allocations for multipoint-to-point
connections.
