FC-2 Features
96122 • Revision: F Chapter 5 Fibre Channel Operations 63
Sequence Management
Sequence management deals with the actual order and transfer of frames across
Fibre Channel. The SEQ_ID and SEQ_CNT identify the order of frames for
reassembly at the responder.
Refer to the FC–PH documents for rules and guidelines pertaining to Class 2
operation.
Sequence Open
The library considers a sequence open from the time that the first frame of the
sequence (the frame with the SOFi3 delimiter) is sent until one of the following
occurs:
■ An end-of-frame (EOF) delimiter is sent with the last sequence bit set
■ A LOGO is sent to, or received from, the sequence responder
■ The sequence is aborted with ABTS
The library as a sequence responder considers a sequence open from the time that
the first frame of the Sequence (the frame with the SOFi3 delimiter) is received
until one of the following occurs:
■ An end-of-frame (EOF) delimiter is sent with the last sequence bit set
■ The Sequence is aborted using ABTS
■ A LOGO is sent to, or received from, the Sequence originator
Sequence Identifier Usage
The sequence identifier (SEQ_ID) is a field in the frame header that sets one frame
apart from another and indicates the order in which frames occur. The following
paragraphs summarize the rules governing the reuse of SEQ_IDs.
For sequences which transfer Sequence Initiative:
■ An NL_Port can reuse a SEQ_ID for the same Exchange following the
confirmation of sequence delivery.
■ An NL_Port can reuse the SEQ_ID with a different exchange (to the same, or a
different destination NL_Port) immediately following transmission of the last
frame of the sequence, without waiting for confirmation of Sequence delivery.
TABLE 5-15 Sequence Content Header
Word Byte 0 Byte 1 Byte 2 Byte 3
0 R_CTL Destination_ID
1CS_CTL Source_ID
2Type F_CTL
3 SEQ_ID DF_CTL SEQ_CNT
4OX_ID RX_ID
5 Parameter
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