134 | Data Center Bridging (DCB)
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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 configura-
tion TLVs are enabled.
Default DCBX port role: Manual.
DCB Configuration Exchange
On an MXL Switch, the DCBX protocol supports the exchange and propagation of configuration
information for the following DCB features.
• Enhanced transmission selection (ETS)
• Priority-based flow control (PFC)
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 with the
requirement that each configured parameter value is the same for the configurations to be compatible.
For example, PFC uses an symmetric exchange of parameters between DCBX peers.
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.
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