FCP Notes

raymanan

1. IPI: Intelligent Peripheral Interface

2. F_CTRL
Exchange Context
An Exchange shall be started by the Originator LCF within an Nx_Port. The other Nx_Port of the Exchange shall be known as the Responder. If the Exchange Context bit (bit 23) is set to zero, the S_ID is associated with the Exchange Originator. If the bit is set to one, the S_ID is associated with the Exchange Responder.

Sequence Context
A Sequence shall be started by a Sequence Initiator facility within an Nx_Port. The destination FC_Port of the Sequence shall be known as the Sequence Recipient. If the Sequence Context (bit 22) bit is set to zero, it indicates that the S_ID is associated with the Sequence Initiator. If the bit is set to one, it indicates that the S_ID is associated with the Sequence Responder. This indicates the Sequence Context.

Knowledge of Sequence context is required for proper handling of Link_Control frames received in response to Data frame transmission in Class 2. When a Busy frame is received, it may be in response to a Data frame (Sequence Initiator) or to an ACK frame (Sequence Recipient). This bit simplifies the necessary constructs to distinguish between the two cases.

First_Sequence
The First_Sequence bit (bit 21) shall be set to one on all frames in the First Sequence of an Exchange. It shall be set to zero for all other Sequences within an Exchange.

Last_Sequence
The Last_Sequence bit (bit 20) shall be set to one on the last Data frame in the Last Sequence of an Exchange. However, it may be set to one on a Data frame prior to the last frame. Once it is set to one, it shall be set to one on all subsequent Data frames in the last Sequence of an Exchange. It shall be set to zero for all other Sequences within an Exchange. This bit shall be set to the same value in the Link_Control frame as the Data frame to which it corresponds.

End_Sequence
The End_Sequence bit (bit 19) shall be set to one on the last Data frame of a Sequence. In Class 1 or Class 6, if this bit is set to one in the ACK corresponding to the last Data frame, it confirms that the Sequence Recipient recognized it as the last Data frame of the Sequence. In Class 2, the final ACK with this bit set to one confirms the end of the Sequence, however, the SEQ_CNT shall match the last Data frame delivered that may not be the last Data frame transmitted. This indication is used for Sequence termination by the two Nx_Ports involved in addition to EOFt or EOFdt . This bit shall be set to zero for all other frames within a Sequence.


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