Method and apparatus for a simple calculation of CRC-10

Claim 1

A method for generating a packet, the integrity of which may be checked upon receipt at a destination node to which the packet is sent through a packet network, said method comprising the steps of: calculating a FCS (Frame Check Sequence) value based on CRC (Cylical Redundancy Check) code generated by the polynomial generator of degree 10, G10(X)=X 10 +X 9 +X 5 +X 4 +X+1, of a packet payload by calculating (520) CRC code generated by the polynomial generator of degree 9, G9(d)=X 9 +X 4 +1, of the packet payload and storing the resulting 9-bit stream FCS in 9-bit storage means, calculating (510) the parity of said payload, setting (580) the most significant bit of a 10-bit storage to zero, if the payload parity is odd (590), adding (597) the 9-bit stream FCS to a bit stream representation of the generator polynomial of degree 9, G9(X)and storing the 10-bit stream resulting from the addition of the previous step in the 10-bit storage means, this stored 10-bit stream representing the payload FCS, if the payload parity is even, storing (595) the 9-bit stream FCS in the least significant bits of the 10-bit storage means, the 10-bit stream of the 10-bit storage means representing the payload FCS; retrieving the packet for which the foregoing calculations were performed and the 10-bit stream representing the payload FCS; and generating a packet suitable for transmission by adding the retrieved payload FCS to the payload of the retrieving packet.

Claim 2

A method for generating a packet, the integrity of which may be checked upon receipt at a destination node to which the packet is sent through a packet network, said method comprising the steps of: calculating a FCS (Frame Check Sequence) value based on CRC (Cylical Redundancy Check) code generated by the polynomial generator of degree 10, G10(X)=X 10 +X 9 +X 5 +X 4 +X+1, of a packet payload by calculating (520) CRC code generated by the polynomial generator of degree 9, G9(d)=X 9 +X 4 +1, of the packet payload and storing the resulting 9-bit stream FCS in 9-bit storage means, calculating (510) the parity of said payload, setting (580) the most significant bit of a 10-bit storage to zero, if the payload parity is odd (590), adding (597) the 9-bit stream FCS to a bit stream representation of the generator polynomial of degree 9, G9(X)and storing the 10-bit stream resulting from the addition of the previous step in the 10-bit storage means, this stored 10-bit stream representing the payload FCS, if the payload parity is even, storing (595) the 9-bit stream FCS in the least significant bits of the 10-bit storage means, the 10-bit stream of the 10-bit storage means representing the payload FCS; retrieving the packet for which the foregoing calculations were performed and the 10-bit stream representing the payload FCS; and generating a packet suitable for transmission by adding the retrieved payload FCS to the payload of the retrieving packet.

Claim 3

A method for checking the integrity of a packet in a packet network, having an extended payload field comprising an n-bits data bytes payload extended with a 10-bit stream FCS (Frame Check Sequence) calculated on the payload, said 10-bit FCS being based on CRC (Cyclic Redundancy Check) code generated by the polynomial generator of degree 10, G 10 (X)=X 10 +X 9 +X 5 +X 4 +X+1, said method comprising the steps of: calculating (520) the CRC code generated by the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1, of the extended payload and storing the resulting 9-bit stream FCS in 9-bit storage means by a) sequentially receiving a sequence of data bytes in the 9-bit storage means (220), b) pushing each byte of said data byte sequence into said 9-bit storage means until said 9-bit storage means is full, c) multiplying (210) the contents of said 9-bit storage means by the bit stream corresponding to α n , an element of Galois Field generated by the generator polynomial G9 (X), α being an irreducible polynomial, root of said Galois Field, d) updating the content of said 9-bit storage means by loading the result of said multiplying step into said 9-bit storage means, and e) repeating steps c, d, e until all data bytes have been pushed into said 9-bit storage means; testing (540) if all the bits of the resulting 9-bit stream are equal to zero, the result of packet integrity checking being negative (560) if all said bits are not equal to zero; if all the bits of the resulting 9-bit stream are equal to zero, testing the 1-bit parity of said extended payload, the result of packet integrity checking being negative (560) if said 1-bit parity is not equal to zero, the result of packet integrity checking being positive (570) if said 1-bit parity is equal to zero.

Claim 4

A method for checking the integrity of a packet in a packet network, having an extended payload field comprising an n-bits data bytes payload extended with a 10-bit stream FCS (Frame Check Sequence) calculated on the payload, said 10-bit FCS being based on CRC (Cyclic Redundancy Check) code generated by the polynomial generator of degree 10, G 10 (X)=X 10 +X 9 +X 5 +X 4 +X+1, said method comprising the steps of: calculating (520) the CRC code generated by the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1, of the extended payload and storing the resulting 9-bit stream FCS in 9-bit storage means by a) sequentially receiving a sequence of data bytes in the 9-bit storage means (220), b) pushing each byte of said data byte sequence into said 9-bit storage means until said 9-bit storage means is full, c) multiplying (210) the contents of said 9-bit storage means by the bit stream corresponding to α n , an element of Galois Field generated by the generator polynomial G9 (X), α being an irreducible polynomial, root of said Galois Field, d) updating the content of said 9-bit storage means by loading the result of said multiplying step into said 9-bit storage means, and e) repeating steps c, d, e until all data bytes have been pushed into said 9-bit storage means; testing (540) if all the bits of the resulting 9-bit stream are equal to zero, the result of packet integrity checking being negative (560) if all said bits are not equal to zero; if all the bits of the resulting 9-bit stream are equal to zero, testing the 1-bit parity of said extended payload, the result of packet integrity checking being negative (560) if said 1-bit parity is not equal to zero, the result of packet integrity checking being positive (570) if said 1-bit parity is equal to zero.

Claim 6

An apparatus to calculate the FCS (Frame Check Sequence) based on CRC (Cyclic Redundancy Check) code generated by the polynomial generator of degree 10, G10(X)=X 10 +X 9 +X 5 +X 4 +X+1, of a packet payload in a packet network to be sent onto a network line, said apparatus comprising the following means: means (200, 210, 220) for calculating the CRC code generated by the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1, of the fixed length packet payload and storing the resulting 9 bit stream FCS in 9-bits storage means; means for calculating the parity of said payload and storing it in a 1-bit storage means (247); means for setting 10-bit storage means to zero; means (240) for adding to each of the 9-bit stream read from the 9-bit stream storage means the 1 bit storage means and to the resuting 9-bit stream, the 10-bit stream representing the to the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1; means (250) for storing the 10-bit stream resulting of the addition of the previous step in the 10-bit storage means, this stored 10-bit stream representing the payload FCS that was to be calculated.

Claim 7

An apparatus to calculate the FCS (Frame Check Sequence) based on CRC (Cyclic Redundancy Check) code generated by the polynomial generator of degree 10, G10(X)=X 10 +X 9 +X 5 +X 4 +X+1, of a packet payload in a packet network to be sent onto a network line, said apparatus comprising the following means: means (200, 210, 220) for calculating the CRC code generated by the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1, of the fixed length packet payload and storing the resulting 9 bit stream FCS in 9-bits storage means; means for calculating the parity of said payload and storing it in a 1-bit storage means (247); means for setting 10-bit storage means to zero; means (240) for adding to each of the 9-bit stream read from the 9-bit stream storage means the 1 bit storage means and to the resuting 9-bit stream, the 10-bit stream representing the to the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1; means (250) for storing the 10-bit stream resulting of the addition of the previous step in the 10-bit storage means, this stored 10-bit stream representing the payload FCS that was to be calculated.

Claim 8

An apparatus for checking in a network node, the integrity of a packet in a packet network, having a payload field comprising an extended field with the 10-bit stream FCS (Frame Check Sequence) calculated on the payload before extension, said 10-bits FCS being based on CRC (Cyclic Redundancy Check) code generated by the polynomial generator of degree 10, G10(X)=X 10 +X 9 +X 5 +X 4 +X+1, said appparatus comprising the following means: means (200, 210, 220) for calculating the CRC code generated by the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1, of the fixed length extended payload and means for storing the resulting 9-bit stream FCS in 9-bit storage means; means for testing the resulting 9-bit stream, if all the bits are not equal to zero, the result of packet integrity checking is negative; means for calculating, if all the bits of the resulting 9-bit stream are equal to zero, the 1-bit parity of said extended payload, the result of packet integrity checking being negative if the 1-bit parity is not zero and positive if the 1-bit parity is zero.

Claim 9

An apparatus for checking in a network node, the integrity of a packet in a packet network, having a payload field comprising an extended field with the 10-bit stream FCS (Frame Check Sequence) calculated on the payload before extension, said 10-bits FCS being based on CRC (Cyclic Redundancy Check) code generated by the polynomial generator of degree 10, G10(X)=X 10 +X 9 +X 5 +X 4 +X+1, said appparatus comprising the following means: means (200, 210, 220) for calculating the CRC code generated by the polynomial generator of degree 9, G9(X)=X 9 +X 4 +1, of the fixed length extended payload and means for storing the resulting 9-bit stream FCS in 9-bit storage means; means for testing the resulting 9-bit stream, if all the bits are not equal to zero, the result of packet integrity checking is negative; means for calculating, if all the bits of the resulting 9-bit stream are equal to zero, the 1-bit parity of said extended payload, the result of packet integrity checking being negative if the 1-bit parity is not zero and positive if the 1-bit parity is zero.