TABLE OF CONTENTS At the level above Frames, data are grouped into two higher-level constructs, termed Sequences and Exchanges. A Sequence is a set of one or more related Frames transmitted unidirectionally from one N_Port to another N_Port with corresponding Link Control Frames (ACKs, BSY, or RJT Frames) transmitted in response. An Exchange is a set of one or more related Sequences that may flow in the same or in opposite directions (but not simultaneously) between a pair of N_Ports.
This chapter describes in detail the rules for initiating, managing, and terminating Sequences and Exchanges. It also describes the format and handling of the Sequence Status Block and Exchange Status Block constructs, which are used to track the status of open and active Sequences and Exchanges at each N_Port of an Exchange.
An N_Port which transmits a Sequence is termed the Sequence Initiator and the N_Port which receives the Sequence is termed the Sequence Recipient. Error recovery is performed on Sequence boundaries, if required. If a Frame does not arrive intact, and the Exchange Error Policy requires error recovery, the entire Sequence will be retransmitted. Each Sequence is identified by an identifier value in every Frame, the SEQ_ID. The length of each Sequence is unbounded, since a Sequence can consist of an arbitrary number of Frames.
All Frames have SOF and EOF Ordered Sets as delimiters. A Sequence is initiated by a Frame with a SOFi1, SOFi2, SOFi3, or SOFc1 delimiter. All intermediate Frames...
