| 摘要 |
<p>A method and an apparatus for generation and checking of a check field to be appended to unnumbered cells or fixed-size packets in a data communications network where they are manipulated by cell-device equipment for the purpose of verifying that all of the following statements hold: the contents of the cells was not altered, the cell delivery order was preserved, all cells were received, no replicated or misinserted cell was found. This, on a per virtual connection basis while cells are routed towards their final destination. The solution consists in adding (modulo 2) to the check field, first computed as a standard CRC, the value of a connection cell counter, running modulo a value compatible with the degree of the polynomial used to compute CRC, so that reception device, observing succesive results of the cell checkings, is able to detect not only cell content alterations but all sorts of sequence impairments too. <IMAGE></p> |
