International Business Machines Corporation

Eric Saint-Georges

Claude R Galand

Jean L Calvignac

Victor Spagnol

Gerald Lebizay

Rene Gallezot

Jean-Marie L Munier

Claude Pin

Andre Pauporte

Bernard J Naudin

Daniel Mauduit

Jacques Feraud

Jean-Claude Bigey

Jean-Christophe Debos

Jean-Marie Munier

Daniel G Mauduit

A method and an apparatus to calculate in an intermediate node of a communication network, the new Frame Check Sequence (FCS) appended to a data bits message which has been modified in said intermediate network node. The invention is useful for high speed networks where the transit delay needs to be optimized in the network along with the computing resources in the intermediate network nodes in terms of computer cycles and memory size. The invention consists in calculating the difference between the FCS using the difference between the modified fields in the message and the distance in bits between the end of the modified field and the end of the message; the calculation consists in differentiating `short messages` in the data flow and to provide an optimized processing for the short messages, the processing for larger messages being based on this first optimized processing. The calculation of the modified FCS comprises operations on polynomials whose coefficients belong to the Galois's Field and whose degree is limited to the one of the polynomial generator of the corresponding CRC code. The calculations include also look up operations in tables limited in size. The choice between the possible implementations (full software, full hardware and mixed hardware and software with the usage of a Remult operator for the last two) will depend on the kind of the network (Frame Relay or other network) and the capacity of the intermediate network node.

Method and an apparatus to modify CRC in intermediate high speed network

A high performance data packet buffering method and a programmable data communication adapter for high speed packet transmission networks are disclosed. The line adapter includes programmable processing means, for receiving and transmitting data packets of fixed or variable length. This system is characterized in that it comprises

Programmable high performance data communication adapter for high speed

In a communication node (10) which comprises switching device (24) operating under control of a clock signal of period T for exchanging information slots carried in external frames of period T' comprising n slots, with each slot comprising a x-bit data byte, between external Time Division Multiplex TDM links (12,14) attached to the communication node, a synchronization device prevents the slippage phenomena due to the asynchronies between T and T' from causing a loss of data slots by generating at the input of the switching means internal frames from the received external frames. These internal frames are synchronous with the clock signal of period T and have a format which allows the slippage to be compensated.

Synchronization device for performing synchronous circuit switching

The bit streams, transporting the frames, received from lines (6) are placed in register 12 in such a way that n bits are processed in parallel during a time interval T. Parallel processor 10 counts the consecutive logical '1' bits beginning at the low order (left most) bit of the n bits received in interval T and from the bits received in the previous interval T-1, to determine when this number is found equal to 5 which bits have to be deleted, and when this number is found equal to 6 whether a flag is received. As a result, it reassembles N-bit characters, with N&lt;n, in register (16). The frame characters to be sent on lines (6) are stored into register (28), and processed in parallel in a time interval T by processor 10 which inserts 0 after five consecutive logical '1's' as a function of the value of the N bit and as a function of the bits of the previous character, to store into register (32), the bits which are sent on lines (6).

Parallel processing method and device for receiving and transmitting

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La Gaude, France

Eric Saint-Georges