4
{ If both ends are G_Ports, they both work as E_Ports.
{ If the peer is an F_Port, the negotiation fails.
• NP_Port—Connects to an F_Port on another FC switch. For more information about NP_Port, see
"Configuring NPV."
E_
Ports connect FC switches to form a fabric, and F_Ports connect the nodes to FC switches in the fabric.
Communication flow
FC switches provide data transmission services. Through FC switches, a server sends instructions and
data to disk devices and reads data from disk devices.
Figure 4 FC SAN communication model
The following takes a server accessing a disk device as an example to see how data communication
occurs in an FC SAN.
1. The server and the disk device send fabric login (FLOGI) packets to register with the FC switches.
Then, the FC switches assign FC addresses to their directly-connected nodes.
A FLOGI packet contains information that includes the port WWN, node WWN, and the
expected FC address.
2. The registered server and disk device send name service registration requests to their respective
access FC switches to register name service information, including FC4 information. Finally, each
FC switch in the fabric stores the name service information for all nodes. For more information
about FC4 information, see "Configuring and obtaining FC4 information of nodes."
3. The s
erver sends a name service query request to its access FC switch to obtain the list of disk
devices in the fabric and their WWNs and FC addresses.
4. The server sends an FC frame destined to the FC address to its access FC switch.
5. The access FC switch queries its FIB table and forwards the FC frame to the next-hop FC switch.
6. The next-hop FC switch forwards the FC frame in the same way, until the FC switch at the last hop
forwards the FC frame to the destination disk device.
NOTE:
FIB table is generated by the FC switch through calculation based on the FC routing protocol or
configured static routes.
VSAN
In actual applications, the data is insecure if the data of all users is transmitted in the same FC SAN. You
can divide one physical FC SAN into multiple virtual storage area networks (VSANs). VSANs are
separated from one another and provide independent services. This enhances adaptability and security
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