Service Manual

from peer devices. By applying a DCB map with PFC enabled, you enable PFC operations on ingress port trac. To achieve
complete lossless handling of trac, congure PFC priorities on all DCB egress ports.
NOTE: DCB maps are supported only on physical Ethernet interfaces.
•
To remove a DCB map, including the PFC conguration it contains, use the no dcb map command in Interface conguration
mode.
• To disable PFC operation on an interface, use the no pfc mode on command in DCB-Map conguration mode.
• Trac may be interrupted when you recongure PFC no-drop priorities in a DCB map or re-apply the DCB map to an interface.
• For PFC to be applied, the congured priority trac must be supported by a PFC peer (as detected by DCBx).
• If you apply a DCB map with PFC disabled (pfc off), you can enable link-level ow control on the interface using the
flowcontrol rx on tx on command. To delete the DCB map, rst disable link-level ow control. PFC is then
automatically enabled on the interface because an interface is PFC-enabled by default.
• To ensure no-drop handling of lossless trac, PFC allows you to congure lossless queues on a port (see Conguring Lossless
Queues).
• When you congure a DCB map, an error message is displayed if the PFC dot1p priorities result in more than two lossless queues.
• When you apply a DCB map, an error message is displayed if link-level ow control is already enabled on an interface. You cannot
enable PFC and link-level ow control at the same time on an interface.
• In a switch stack, congure all stacked ports with the same PFC conguration.
• Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the change satises the following
requirements in DCB maps already applied to S6000 interfaces:
• All 802.1p priorities mapped to the same queue must be in the same priority group.
• A maximum of two PFC-enabled, lossless queues are supported on an interface.
Otherwise, the reconguration of a default dot1p-queue assignment is rejected.
• To ensure complete no-drop service, apply the same PFC parameters on all PFC-enabled peers.
PFC Prerequisites and Restrictions
On an S6000 switch, PFC is globally enabled by default, but not applied on specic 802.1p priorities. To enable PFC on 802.1p
priorities, create a DCB map.
The following prerequisites and restrictions apply when you congure PFC in a DCB map:
• You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p priorities congures the
corresponding port queue as lossless.
• You cannot enable PFC and link-level ow control at the same time on an interface.
ETS Conguration Notes
ETS provides a way to optimize bandwidth allocation to outbound 802.1p classes of converged Ethernet trac. Dierent trac types
have dierent service needs. Using ETS, you can create groups within an 802.1p priority class to congure dierent treatment for
tracs with dierent bandwidth, latency, and best-eort needs.
When you congure ETS in a DCB map:
• The DCB map associates a priority group with a PFC operational mode (on or o) and an ETS scheduling and bandwidth
allocation. You can apply a DCB map on multiple egress ports.
• Use the ETS conguration associated with 802.1p priority trac in a DCB map in DCBx negotiation with ETS peers.
Data Center Bridging (DCB)
217