A Fibre Channel loop is an interconnection topology
During communication between devices, Read Link Status (RLS) error counts
Error counts are calculated from a baseline, which describes the error count values for each type of device in the Fibre Channel loop. Calculation occurs from the time when the baseline was established to the time at which the error count information is requested.
The baseline is automatically set by the controller. However, a new baseline may be set manually through the Read Link Status Diagnostics dialog. For more information, see Running the Read Link Status Diagnostic.
Analysis of the RLS error count data is based on the principle that the device immediately "downstream" of the problematic component should see the largest number of Invalid Transmission Word (ITW)
Important: Because the current error counting standard is vague about when the ITW count is calculated, different vendors' devices calculate errors at different rates. Analysis of the data must take this into account.
The analysis process involves obtaining an ITW error count for every component and device on the loop, viewing the data in loop order, and then identifying any large jumps in the ITW error counts. The following shows the typical error count information displayed in the Read Link Status Diagnostics dialog:
In addition to the ITW count, the following error counts are displayed in the Read Link Status Diagnostics dialog:
Error Count Type |
Definition of Error |
Link Failure (LF) |
When detected, link failures indicate that there has been a failure within the media module laser operation. Link failures may also be caused by a link fault signal, a loss of signal or a loss of synchronization. |
Loss of Synchronization (LOS) |
Indicates that the receiver cannot acquire symbol lock with the incoming data stream, due to a degraded input signal. If this condition persists, the number of Loss of Signal errors increases. |
Loss of Signal (LOSG) |
Indicates a loss of signal from the transmitting node, or physical component within the Fibre Channel loop. Physical components where a loss of signal typically occurs include the gigabit interface connectors, and the Fibre Channel fibre optic cable. |
Primitive Sequence Protocol (PSP) |
Refers to the number of N_Port A Link Reset Response (LRR) is issued by another N_Port in response to a link reset. |
Invalid Cyclic Redundancy Check (ICRC) |
Indicates that a frame has been received with an invalid cyclic redundancy check value. A cyclic redundancy check is performed by reading the data, calculating the cyclic redundancy check character, and then comparing its value to the cyclic check character already present in the data. If they are equal, the new data is presumed to be the same as the old data. |
If you are unable to determine which component or device on your Fibre Channel loop is experiencing problems, save the RLS Diagnostics results and forward them to technical support for assistance.