The present invention relates to a data storage unit for a communication system node, a method for data storage and a communication system node. More particularly it relates to storing buffering data and control data in a unit located outside of a Communication Controller on system or host-controller level, wherein a time-triggered protocol runs on the node. By locating control and buffering related data, including format and behavior, outside the Communication Controller it becomes far more flexible, extendable, and re-configurable as data buffering related restrictions, e.g. buffer sizes and number of buffers, are moved from Communication Controller level to system level.