Error Detection and Management
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T10000: Interface Reference Manual • January 2011
• E20425-01
Sequence Errors
Sequence errors are managed as defined in FC–Tape with the following
additions:
1. If a frame with an SOFi3 delimiter is received and the SEQ_CNT is not
equal to zero or +1 from the SEQ_CNT of the last frame of the previous
Sequence of that Exchange.
2. If the SEQ_CNT of a received frame with an SOFn3 delimiter is not +1
greater than the previous frame received for that Sequence (such as a
frame was lost).
This also detects the case where a frame with an SOFn3 delimiter is
received for a SEQ_ID that is not currently open since the SEQ_CNT of
the previous frame for that Sequence is undefined.
3. If a frame with an SOFi3 delimiter is received and the previous Sequence
of that Exchange is still open.
4. If the relative offset in the parameter field of a received frame with an
SOFn3 delimiter is not equal to the (relative the payload size) of
the previous frame received for that Sequence.
5. If the next frame of a Sequence is not received within E_D_TOV.
6. If, during the same Sequence Initiative, a Sequence is received which has
the same SEQ_ID as the previous Sequence of that Exchange.
When a Sequence error is detected by the tape drive, it discards that
Sequence, and all remaining Sequences for the Exchange containing the
Sequence in error. The tape drive attempts to take the appropriate action as
defined in FCP–2.
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Error Detection and Management
Error detection falls under two categories: Frame errors and link-level errors.
•
Frame errors result in missing or corrupted frames which may ultimately
involve Upper Level Protocols to resolve.
•
Link-level errors include errors such as loss of signal, loss of
synchronization, and timeouts.
Upper Level Protocols (ULP) provide for error detection and management by
using timeouts which is an inefficient mechanism to detect and recover from
frame transmission errors.
FC-2 layer protocols attempt to recover from errors through transmitting
frames, Extended Link Services commands, and Primitive Sequence
protocols (as defined in FCP-2)
A problem with Class 3 operation is that there is no confirmation of frame
delivery. Although, the originator can deduce some delivery of frames from:
Summary of Contents for Storage Tek T10000
Page 14: ...Tables xiv T10000 Interface Reference Manual January 2011 E20425 01...
Page 18: ...What s New xx T10000 Interface Reference Manual January 2011 E20425 01...
Page 82: ...Private Loop SCSI Target Discovery 64 T10000 Interface Reference Manual January 2011 E20425 01...
Page 286: ...Glossary 268 T10000 Interface Reference Manual January 2011 E20425 01...
