Cell Relay Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] [Q]: Division of work between CS and SAR sublayers in AAL?
Hi, ploughing through different books about ATM, I found the division of work between the convergence sublayer (CS) and the segmentation and reassembly (SAR) sublayer quite confusing. In several places it is mentioned that one of the task SAR has to perform, is segementing longer messages into cells of the appropriate size (44 to 48 octets). This seems kind of natural considering the name ``SAR''. On the other hand it is stated explicitely several times and explained in detail (sometimes in the same books) that the convergence sublayer breaks the incoming bitstream or messages coming from the higher layers into cells and that it is those cells that are handed over from the CS down to the SAR, and that the SAR sublayer only adds SAR-PDU headers/trailers to the cells. This leaves then the question why the SAR layer is called ``segmentation and reassembly'' if this task is already performed by the CS. Does anybody know what is the right point of view there? Thanks Martin |
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