| 摘要 |
The invention is directed to a technique for recalculating a bit interleave parity (BIP) byte for byte interleaved SONET/SDH frames. An interleaved SONET/SDH frame consists of a plurality (N) of base STS-1 frames that are byte interleave multiplexed. Each STS-1 frame contains transport overhead bytes, including a BIP byte (B2) and a remote error indication byte (M1). The M1 byte is associated with error over an entire interleaved STS-N frame and not a particular individual STS-1 frame. Each B2 byte is associated with a particular STS-1 frame and is calculated over selected overhead bytes, including the M1 byte, and all of the payload bytes of the previous STS-1 frame. When SONET frames are multiplexed, the M1 byte values are changed and the B2 parity calculations for each STS-1 frame must be updated. Existing systems generally update the affected B2 bytes by performing the B2 parity calculation over all of the respective overhead bytes and payload bytes for each frame. The techniques of the invention calculates the updated B2 byte using the original and modified M1 and B2 bytes of each affected STS-1 frame. The original B2 byte of the previous frame is EXORed with the affected B2 byte and the result is EXORed with the new B2 byte. The original and modified M1 bytes are likewise EXORed to update the affected B2 byte of the next frame. As a result, the number of EXOR calculations is greatly reduced.
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