SAN256N Director 2045-N16
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Troubleshooting link level errors
Link-level errors are caused by abnormal conditions that affect data sent or received
over a communications link. These errors can impact the capability of a channel, control
unit, or director, to correctly route the data. Therefore, a link subject to link errors cannot
be brought online. The integrity of the information sent over the link can be affected.
A link-level error can be associated with the following conditions:
• The link header or link trailer of a frame
• Validity or use of transmission characters
• The integrity of the link or the signal sent over the link
• The structure of the link
• The link address used
For a channel or control unit, errors are classified into two categories. These categories
depend on the Cyclical Redundancy Checking (CRC) checking process. A link error
detected before CRC checking has priority over one detected after the CRC checking
process, because the data contained in the frame cannot be read or interpreted by the
link-level facility.
Link-level errors reported on Enterprise Manager
The following link-level errors are displayed on the Enterprise Manager Director View:
• CRC errors
• Frames without End of Frame (EOF) delimiters
• Frames with disparity errors
• Loss of synchronization
• Loss of signal
• Address I/O errors
• Primitive sequence protocol errors
• Link reset in
• Link reset out
• OLS in
• OLS out
• Invalid Tx words
• Link failures
Link level errors before CRC checking
Link-level errors before CRC checking are mainly related to the quality of the signal that
the receiver gets over the link. They also deal with the ability of the receiver to decode
existing characters and interpreting the frame delimiters Start of Frame (SOF) and End
of Frame (EOF). The link-level errors consist of the following:
• Connection errors:
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