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is generated. The network administrator must then reconfigure the peer device so that it advertises a
compatible DCB configuration.
The internally propagated configuration is not stored in the switch’s running configuration. On a DCBX
port in an auto-downstream role, all PFC, application priority, ETS recommend, and ETS configuration
TLVs are enabled.
Configuration
source
The port is configured to serve as a source of configuration information on the switch. Peer DCB
configurations received on the port are propagated to other DCBx auto-configured ports. If the peer
configuration is compatible with a port configuration, DCBx is enabled on the port.
On a configuration-source port, the link with a DCBx peer is enabled when the port receives a DCB
configuration that can be internally propagated to other auto-configured ports.
The configuration received from a DCBX peer is not stored in the switch’s running configuration.
On a DCBX port that is the configuration source, all PFC and application priority TLVs are enabled. ETS
recommend TLVs are disabled and ETS configuration TLVs are enabled.
Manual The port is configured to operate only with administrator-configured settings and does not auto-configure
with DCB settings received from a DCBx peer or from an internally propagated configuration from the
configuration source. If you enable DCBx, ports in Manual mode advertise their configurations to peer
devices but do not accept or propagate internal or external configurations. Unlike other user-configured
ports, the configuration of DCBx ports in Manual mode is saved in the running configuration.
On a DCBx port in a manual role, all PFC, application priority, ETS recommend, and ETS configuration
TLVs are enabled.
The default for the DCBx port role is manual.
NOTE:
On a DCBx port, application priority TLV advertisements are handled as follows:
● The application priority TLV is transmitted only if the priorities in the advertisement match the configured PFC priorities
on the port.
● On auto-upstream and auto-downstream ports:
○ If a configuration source is elected, the ports send an application priority TLV based on the application priority TLV
received on the configuration-source port. When an application priority TLV is received on the configuration-source
port, the auto-upstream and auto-downstream ports use the internally propagated PFC priorities to match against
the received application priority. Otherwise, these ports use their locally configured PFC priorities in application
priority TLVs.
○ If no configuration source is configured, auto-upstream and auto-downstream ports check to see that the locally
configured PFC priorities match the priorities in a received application priority TLV.
● On manual ports, an application priority TLV is advertised only if the priorities in the TLV match the PFC priorities
configured on the port.
DCB Configuration Exchange
The DCBx protocol supports the exchange and propagation of configuration information for the enhanced transmission selection
(ETS) and priority-based flow control (PFC) DCB features.
DCBx uses the following methods to exchange DCB configuration parameters:
Asymmetric
DCB parameters are exchanged between a DCBx-enabled port and a peer port without requiring that a
peer port and the local port use the same configured values for the configurations to be compatible. For
example, ETS uses an asymmetric exchange of parameters between DCBx peers.
Symmetric DCB parameters are exchanged between a DCBx-enabled port and a peer port but requires that each
configured parameter value be the same for the configurations in order to be compatible. For example,
PFC uses an symmetric exchange of parameters between DCBx peers.
936 FC Flex IO Modules