Brocade Communications Systems IP250 user manual Frame types, Scsi RW

34 Frame Monitor

Frame types

The frame type can be a standard type (for example, a SCSI read command filter that counts the number of SCSI read commands that have been transmitted by the port) or a user-defined frame type customized for your particular use.

Pre-defined frame types

Pre-defined frame types include the following:

•ABTS (Abort Sequence Basic Link Service command)

•BA_ACC (Abort Accept)

•IP

•SCSI

•SCSI Read

•SCSI Write

•SCSI RW

•SCSI-2 Reserve

•SCSI-3 Reserve

Custom frame types

In addition to the standard frame types, you can create custom frame types to gather statistics that fit your needs. To define a custom frame type, you must specify a series of offsets, bitmasks, and values. For all transmitted frames, the switch performs these tasks:

•Locates the byte found in the frame at the specified offset.

•Applies the bitmask to the byte found in the frame.

•Compares the new value with the given value.

•Increments the filter counter if a match is found.

You can specify up to four values to compare against each offset. If more than one offset is required to properly define a filter, the bytes found at each offset must match one of the given values for the filter to increment its counter. If one or more of the given offsets does not match any of the given values, the counter does not increment. The value of the offset must be between 0 and 63, in decimal format. Byte 0 indicates the first byte of the Start of Frame (SOF), byte 4 is the first byte of the frame header, and byte 28 is the first byte of the payload. Thus only the SOF, frame header, and first 36 bytes of payload can be selected as part of a filter definition. Offset 0 is a special case, which can be used to monitor the first 4 bytes of the frame (SOF). When the offset is set to 0, the values 0–7 that are checked against that offset are predefined as shown in Table 91.

TABLE 91	Predefined values at offset 0
Value	SOF	Value	SOF
0	SOFf	4	SOFi2
1	SOFc1	5	SOFn2
2	SOFi1	6	SOFi3
3	SOFn1	7	SOFn3

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