1. A method of reliably receiving, at a device having a recipient identifier, multicast packets and unicast packets in a network, comprising upon receiving a first packet having a sequence number from a source, transmitting an acknowledgment to said source, said acknowledgment indicating said recipient identifier; upon receiving a second packet having an indicator representative of a set of destinations for which an acknowledgment was not received, entering a conditional-receive mode if said indicator is not representative of said recipient identifier; and upon receiving a third packet having an indicator representative of conditional receipt, receiving said third packet only when in said conditional-receive mode.