Brocade Fabric OS Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 33)

credits, RA_TOV, and ED_TOV. This is not a negotiation. If one or the other port’s link parameters do
not match, a link does not occur. Once an SW_ACC frame is received from the neighboring switch, the
new switch sends an Exchange Switch Capabilities (ESC) frame. The two switches exchange routing
protocols and agree on a common routing protocol. An SW_ACC frame is received from the
neighboring switch and the new switch sends an Exchange Fabric Parameters (EFP) frame to the
neighboring switch, requesting principal switch priority and the domain ID list. Buffer-to-buffer credits for
the device and switch ports are exchanged in the SW_ACC command sent to the device in response to
the FLOGI.
Fabric login process
A device performs a fabric login (FLOGI) to determine if a fabric is present. If a fabric is detected then it
exchanges service parameters with the fabric controller. A successful FLOGI sends back the 24-bit
address for the device in the fabric. The device must issue and successfully complete a FLOGI
command before communicating with other devices in the fabric.
Because the device does not know its 24-bit address until after the FLOGI, the source ID (SID) in the
frame header of the FLOGI request are zeros (0x000000).
Port login process
The steps in the port initialization process occur as the result of a protocol that functions to discover the
type of device connected and establish the port type and negotiate port speed. See
Port Types on page
69 for a discussion of available port types.
The Fibre Channel protocol (FCP) auto discovery process enables private storage devices that accept
the process login (PRLI) to communicate in a fabric.
If device probing is enabled, the embedded port performs a PLOGI and attempts a PRLI into the device
to retrieve information to enter into the name server. This enables private devices that do not explicitly
register with the Name Server (NS) to be entered in the NS and receive full fabric access.
A fabric-capable device registers its information with the name server during a FLOGI. These devices
typically register information with the name server before querying for a device list. The embedded port
still performs a PLOGI and attempts a PRLI with these devices.
If a port decides to end the current session, it initiates a logout. A logout concludes the session and
terminates any work in progress associated with that session.
To display the contents of a switch’s name server, use the nsShow or nsAllShow command. For more
information about these commands, refer to the Fabric OS Command Reference.
RSCNs
A Registered State Change Notification (RSCN) is a notification frame that is sent to devices that are
zoned together and are registered to receive a State Change Notification (SCN). The RSCN is
responsible for notifying all devices of fabric changes. The following general list of actions can cause an
RSCN to be sent through your fabric:
• A new device has been added to the fabric.
• An existing device has been removed from the fabric.
• A zone has changed.
• A switch name has changed or an IP address has changed.
• Nodes leaving or joining the fabric, such as zoning, powering on or shutting down a device, or zoning
changes.
Fabric login process
Fabric OS Administrators Guide 33
53-1003130-01