Data Centre Bridging Capability Exchange Configuration
Overview
The Data Center Bridging Capability Exchange (DCBx) protocol extends the Link Layer Discovery Protocol (LLDP). It facilitates the exchange of Data Center Bridging (DCB) configuration parameters between directly connected devices, such as switches and network interface cards (NICs). DCBx enables automatic negotiation and configuration of DCB features to ensure consistent quality of service (QoS) and traffic prioritization across a network.
If LLDP is disabled on an interface, DCBX cannot operate on that interface. Attempting to enable DCBX on an interface where LLDP is disabled will result in a configuration commit failure.
DCBx plays a crucial role in modern data centers by enabling seamless configuration and interoperability between DCB-capable devices, ensuring efficient network performance.
Benefits
• Discovers the DCB capabilities of neighboring devices.
• Detects incorrect configurations or mismatches in DCB settings between peers.
• Configures DCB parameters on connected devices for interoperability.
Configuration
Configuring PFC parameter exchange typically involves enabling PFC mode, LLDP, activating DCBX, turning on PFC, and allowing the negotiation of control for each traffic priority (priorities 0–7).
DCBx for PFC via LLDP
The following procedure configures PFC parameters and sent them in LLDP messages.
lldp run
lldp tlv-select basic-mgmt system-name
lldp tlv-select ieee-8021-org-specific data-center-bridging
set lldp timer msg-tx-interval 5
lldp notification-interval 5
Note: To minimize the impact of PFC (Priority Flow Control) updates when operating in Auto mode via DCBx, this custom implementation ensures that PFC priority configurations remain consistent even during peer node reboots or interface flaps.
The mechanism locally caches the received DCBx PFC parameters and prevents unnecessary hardware resets of these values in the following scenarios:
When the LLDP session is re-established after such events, the node compares the newly received PFC parameters with the locally cached values:
• Peer node reboot or power cycle.
• Peer node software upgrade or downgrade.
• Interface flap or fiber cut.
When the LLDP session is re-established after such events, the node compares the newly received PFC
parameters with the locally cached values:
• If no change is detected, the PFC configuration remains untouched, avoiding reapplication.
• If a difference is detected, the new parameters are applied to ensure proper PFC behavior.
This feature is enabled by default from release 6.6.1 and applies exclusively to nodes operating in PFC Auto mode, requiring no additional configuration.
Key Benefit:
• Minimized Traffic Disruption:
Maintains stable traffic flow with reduced packet loss and network instability during peer node restarts or interface disruptions.