Abstract-To properly operate closed industrial control networks, it is required that communication with nearly constant delay bounds be supported. In [24] the authors introduced FlexTDMA in order to provide this support, and with minimal delay-jitter in an asynchronous network, under unicast communication. In this paper we consider providing this support for simultaneous multicasting, and introduce the FlexTDMA++ protocol. Under this protocol, and with periodic on-off traffic that is directed to multiple receivers, frame losses and switch failures are managed in the presence of component clock drifts and bandwidth loads.