Understanding the Fibre Channel/FICON Buffer to Buffer Credit Recovery Mechanism

摘要

During normal storage network operation, fibre channel frames and/or RRDYrnprimitives may become corrupted in transport. If a condition existsrnthat creates enough corrupted bits during data transmission, eventuallyrnthe number of start of frames (SOFs) and R_RDYs will cause the numberrnof buffer to buffer credits (BB credit) to diminish. This will causernperformance problems, up to and including the link stopping transmissionrnaltogether. This paper will review some fibre channel and BB credit basics,rnand discuss the fibre channel standards based BB credit recoveryrnmechanism that, when implemented helps to prevent these performancernproblems.