Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 255

• For PFC to be applied, the configured priority traffic 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 flow control on the interface using the flowcontrol rx on tx on command. To delete the DCB map, first disable link-level flow control. PFC is then automatically enabled on the interface because an interface is PFC-enabled by default, when DCB is enabled. • To ensure no-drop handling of lossless traffic, PFC allows you to configure lossless queues on a port (see Configuring Lossless Queues). • When you configure a DCB map with more than the maximum lossless queues configured, 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 flow control is already enabled on an interface. You cannot enable PFC and link-level flow control at the same time on an interface. • Configure all the backplane ports of the linecards and RPM0 and RPM1 with same dcb-map configuration. dcb-map linecard 0 backplane all name dcb-map linecard all backplane all name • Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the change satisfies the following requirements in DCB maps already applied to the interfaces: - All 802.1p priorities mapped to the same queue must be in the same priority group. - A maximum of four PFC-enabled, lossless queues are supported on an interface. Otherwise, the reconfiguration of a default dot1p-queue assignment is rejected. • To ensure complete no-drop service, apply the same PFC parameters on all PFC-enabled peers. ETS Configuration Notes ETS provides a way to optimize bandwidth allocation to outbound 802.1p classes of converged Ethernet traffic. Different traffic types have different service needs. Using ETS, you can create groups within an 802.1p priority class to configure different treatment for traffics with different bandwidth, latency, and best-effort needs. When you configure ETS in a DCB map: • The DCB map associates a priority group with a PFC operational mode (on or off) and an ETS scheduling and bandwidth allocation. You can apply a DCB map on multiple egress ports. • Use the ETS configuration associated with 802.1p priority traffic in a DCB map in DCBx negotiation with ETS peers. • Traffic in priority groups is assigned to strict-queue or weighted round-robin (WRR) scheduling in an ETS configuration and is managed using the ETS bandwidth-assignment algorithm. Dell Networking OS de-queues all frames of strict-priority traffic before servicing any other queues. A queue with strict-priority traffic can starve other queues in the same port. • ETS-assigned bandwidth allocation and strict-priority scheduling apply only to data queues, not to control queues. • Dell Networking OS supports hierarchical scheduling on an interface. The control traffic on Dell Networking OS is redirected to control queues as higher priority traffic with strict priority scheduling. After the control queues drain out, the remaining data traffic is scheduled to queues according to the bandwidth and scheduler configuration in the DCB map. The available bandwidth calculated by the ETS algorithm is equal to the link bandwidth after scheduling non-ETS higher-priority traffic. • The configuration of bandwidth allocation and strict-queue scheduling is not supported at the same time for a priority group. • Bandwidth assignment: By default, equal bandwidth is assigned to each dot1p priority in a priority group. To configure the bandwidth assigned to the port queues associated with dot1p priorities in a priority group, use the bandwidth percentage parameter. The sum of the bandwidth allocated to all priority groups in a DCB map must be 100% of the bandwidth on the link. You must allocate at least 1% of the total bandwidth to each priority group. • Scheduling of priority traffic: dot1p priority traffic on the switch is scheduled to the current queue mapping. dot1p priorities within the same queue must have the same traffic properties and scheduling method. • ETS configuration error: If an error occurs in an ETS configuration, the configuration is ignored and the scheduler and bandwidth allocation settings are reset to the ETS default value: 100% of available bandwidth is allocated to priority group 0 and the bandwidth is equally assigned to each dot1p priority. If an error occurs when a port receives a peer's ETS configuration, the port's configuration resets to the ETS configuration in the previously configured DCB map. If no DCB map was previously applied, the port resets to the default ETS parameters. Data Center Bridging (DCB) 255