-32 2 A METHOD AND APPARATUS FOR A TWO-STEP CALCULATION OF CRC-32

摘要

The present invention is directed to a method and apparatus for computing a CRC-32 code that is cyclic redundancy checking of a bit stream while improving processing time and facilitating implementation. Frame Check Sequence (FCS) of bit stream messages transmitted over a fixed size packet network when it is required to reduce the processing time at the network access node for high speed operation. CRC-32 calculation is used for the error checking code. This CRC-32 calculation is also used for FCS checking even within the network equipment that receives the packetized bit stream message. The present invention is particularly applicable to messages carried over AAL5 type cells in an Async. Transfer Mode (ATM) network.;The principle of the present invention consists in replacing the prior art byte-by-byte CRC-32 calculation with a simple byte-by-byte CRC-R calculation followed by one pass CRC-32 calculation of the R bit stream. CRC-R codes are generator polynomials of degree 32;G (X) = X ³² + X ²⁶ + X ²³ + X ²² + X ¹⁶ + X ¹² + X ¹¹ + X ¹⁰ + X ⁸ + X ⁷ + X ⁵ + X ⁴ + X ² + X + 1;Generated by a polynomial M (X) of multiplier of and of order R, where the Galois Field generator constitutes a CRC-32 code.