What is a sequence’ in a Fibre Channel (FC) data structure?

A.
Group of exchanges that are sent to another port to perform certain operations

B.
Contiguous set of information units that map to a frame header

C.
Upper layer protocol-specific information in a FC frame

D.
Contiguous set of frames that correspond to an information unit

Explanation:
Structure and Organization of FC Data

In an FC network, data transport is analogous to a conversation between two people, whereby a
frame represents a word, a sequence represents a sentence, and an exchange represents a
conversation.
Exchange: An exchange operation enables two node ports to identify and manage a set of
information units. Each upper layer protocol has its protocol-specific information that must be sent
to another port to perform certain operations. This protocol-specific information is called an
information unit. The structure of these information units is defined in the FC-4 layer. This unit
maps to a sequence. An exchange is composed of one or more sequences.
Sequence: A sequence refers to a contiguous set of frames that are sent from one port to another.
A sequence corresponds to an information unit, as defined by the ULP.
Frame: A frame is the fundamental unit of data transfer at Layer 2. An FC frame consists of five
parts: start of frame (SOF), frame header, data field, cyclic redundancy check (CRC), and end of
frame (EOF). The SOF and EOF act as delimiters. The frame header is 24 bytes long and
contains addressing information for the frame. The data field in an FC frame contains the data
payload, up to 2,112 bytes of actual data—in most cases, the SCSI data. The CRC checksum
facilitates error detection for the content of the frame. This checksum verifies data integrity by
checking whether the content of the frames was received correctly. The CRC checksum is
calculated by the sender before encoding at the FC-1 layer. Similarly, it is calculated by the
receiver after decoding at the FC-1 layer.
EMC E10-001 Student Resource Guide. Module 5: Fibre Channel Storage Area Network (FC
SAN)