Computer Network Technology Corporation

Bret Ketchum

William C Collette

Steve Flattum

Mark J Vogel

Mark J Moran

Robert Engebretson

Mike Morandi

Richard Kelley

A method and apparatus is presented for performing a sequence-level CRC calculation on fiber channel communications within a switching platform domain. A CRC generator searches the data communication for frames that contain the type of data for which a sequence-level CRC is desired, such as for a sequence containing SCSI data. If found, and the type of data allows multiple frames per sequence, the present invention creates a CRC value for the sequence. An intermediate CRC value is stored in a queue to allow the simultaneous calculation of sequence level CRC values for multiple frames. With inbound data, the sequence-level CRC is appended to the end of the sequence data. With outbound data, the calculated value is compared with the appended, expected value, With single-frame fiber channel protocols, the frame-level CRC value is obtained directly from the frames entering the switching platform domain. This value is placed in a local queue, from which it is appended to the data payload by a processor for transmission within the switching platform. When the single frame is leaving the switching platform domain, the flow of data leaving the switching platform domain is monitored and the frame-level CRC value calculated by the fiber channel controller is replaced with the original frame-level CRC value.

Frame-level fibre channel CRC on switching platform

A storage router and related method are presented for combining multiple Fibre Channel frames together into a single IP datagram for tunneling transmission over an Internet protocol network. The storage router operates by storing incoming Fibre Channel frames in a Fibre Channel frame buffer. When there is sufficient data in the buffer, multiple Fibre Channel frames are taken from the buffer and combined into a single IP datagram. The number of Fibre Channel frames to be combined can be established through a variety of tests, including total bytes of data, number of frames, or through a time-out mechanism. The network layer then fragments the datagram into data link level frames, such as 1500 byte Ethernet frames. When the IP datagram arrives at the final destination, the segmented IP datagram is reconstructed, and the multiple Fibre Channel frames are extracted from the IP datagram and passed on to the recipient Fibre Channel network.

Fibre channel frame batching for IP transmission

A method and apparatus is presented for performing a sequence-level CRC calculation on fiber channel communications within a switching platform domain. Specifically, the disclosed invention utilizes a CRC generator to monitor data communication between an external interface and a fiber channel controller. The CRC generator searches the data communication for frames that contain the type of data for which a sequence-level CRC is desired, such as for a sequence containing SCSI data. When found, the CRC generator performs an 8B/10B decode, strips off any fill bytes, and performs a CRC calculation on the data payload. If the found frame is the first frame in the sequence, the CRC is done starting with a reset value. If the frame is not the first, an intermediate value containing the previous CRC calculation results for this sequence is retrieved and used to perform the CRC calculations. Upon completion of the calculation for the frame, a determination is made whether the sequence is complete. If so, the calculated value is the sequence-level CRC. If not, the calculated value is stored in memory for use with the next frame in that sequence. With inbound data, the calculated sequence-level CRC is appended to the end of the data comprising that sequence. With outbound data, the calculated value is compared with the appended, expected value, and a CRC error is generated if the values do not match. The sequence-level CRC value appended to the sequence data is typically removed before the data exits the switching platform domain.

Fiber channel CRC for internal error checking on a switching platform

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Anoka, MN, United States of America

Bret Ketchum