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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] New iFCP draftWith regards to the new iFCP draft 5.3 Trailing iFCP CRC This original Fibre Channel CRC shall not be encapsulated into the iFCP message. Rather, iFCP MAY use a 32-bit field containing a CRC calculated over the data contained in the frame from the iFCP AUGMENTED DATA to the iFCP Payload (inclusive). This includes the Fibre Channel header and payload. The iFCP CRC follows the iFCP payload, and the CRC algorithm is the same used for the Frame Check Sequence (FCS) of IEEE 802.3 Ethernet frames. A bit in the iFCP FLAGS field in the iFCP header indicates the presence or absence of this 32-bit trailing CRC. I would suggest "Rather, iFCP MUST use a 32-bit field containing a CRC ..." unless ethernet provides an equivalent CRC elsewhere. The reason is that I believe gigabit ethernet uses the same physical layer as fibre channel. This physical layer is specified for fibre channel to have a data bit loss rate of 1 in 10^12 or less, and is not "perfect". I think the CRC is designed to throw out these imperfect frames instead of resulting in data corruption. Without the CRC, physical layer imperfections within fibre-channel specificaiton may lead to data corruption. Also, I am not intending to show preference for iSCSI or iFCP with this email. I just was skimming over the standard and thought this feedback might be helpful. Stephen Elliott
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