Apparatus, computer program products and methods allow inclusion and segmentation of multiple SDUs within a PDU, and generate information (such as header information) necessary to identify, e.g., the position of the segmented SDUs within the PDU. Prior knowledge of the typically used (i.e., predetermined) SDU size is used to perform segmentation operations, hi one exemplary variant, apparatus, methods and computer program products determine if a particular one of a set of input data units (SDUs) is to be segmented in order to fit a portion of the set, including a segment of the particular input data unit, into an output data unit (PDU); segment the input data unit in response to determining the particular input data unit is to be segmented; add the portion of the set to a data portion of the output data unit, and add into the output data unit an indication of a position of the segment in the data portion. In another variant, apparatus, computer program products and methods receive first data units, each of the first data units including a plurality of data portions having a plurality of second data units, each of at least two of the first data units including an indication of a position of a segment of a second data unit in associated ones of the data portions; combine using at least the indications the segments to create a complete second data unit; and output the complete second data unit.