pdu in the trblk is a fragment of an sdu or not this process can be described in a generalized form along the lines of fig1 sdus or fragments of sdus are taken from a buffer and it is then determined whether the sdu or fragment of an sdu fits in the remaining size of the transport block which might be the whole of the transport block or only a part thereof if the full sdu or fragment of the sdu fits in the remaining size of the transport block a pdu is created from this sdu this pdu is then inserted in the transport block the transport block is checked whether there is any size remaining if there is the process starts over again if there is not the indicators are added and the transport block is transmitted with the indicators if however the sdu or fragment of the sdu does not fit in the remaining size of the transport block the sdu is fragmented and a pdu is created from a fragment of the sdu to fit into the remaining size of the transport block the second fragment of the sdu is put in the buffer and the pdu is then inserted into the transport block and the indicators added the first fragmentation flag fff indicates whether the first pdu in the transport block is a fragment of sdu or not and the second fragmentation flag sff indicates whether the.