Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 259

Dell Networking OS Behavior: A priority group consists of 802.1p priority values that are grouped for similar bandwidth allocation and scheduling, and that share latency and loss requirements. All 802.1p priorities mapped to the same queue must be in the same priority group. Configure all 802.1p priorities in priority groups associated with an ETS output policy. You can assign each dot1p priority to only one priority group. By default, all 802.1p priorities are grouped in priority group 0 and 100% of the port bandwidth is assigned to priority group 0. The complete bandwidth is equally assigned to each priority class so that each class has 12 to 13%. The maximum number of priority groups supported in ETS output policies on an interface is equal to the number of data queues (4) on the port. The 802.1p priorities in a priority group can map to multiple queues. If you configure more than one priority queue as strict priority or more than one priority group as strict priority, the higher numbered priority queue is given preference when scheduling data traffic. ETS Operation with DCBx The following section describes DCBx negotiation with peer ETS devices. In DCBx negotiation with peer ETS devices, ETS configuration is handled as follows: • ETS TLVs are supported in DCBx versions CIN, CEE, and IEEE2.5. • The DCBx port-role configurations determine the ETS operational parameters (refer to Configure a DCBx Operation). • ETS configurations received from TLVs from a peer are validated. • If there is a hardware limitation or TLV error: - DCBx operation on an ETS port goes down. - New ETS configurations are ignored and existing ETS configurations are reset to the default ETS settings. • ETS operates with legacy DCBx versions as follows: - In the CEE version, the priority group/traffic class group (TCG) ID 15 represents a non-ETS priority group. Any priority group configured with a scheduler type is treated as a strict-priority group and is given the priority-group (TCG) ID 15. - The CIN version supports two types of strict-priority scheduling: * Group strict priority: Use this to increase its bandwidth usage to the bandwidth total of the priority group and allow a single priority flow in a priority group. A single flow in a group can use all the bandwidth allocated to the group. * Link strict priority: Use this to increase to the maximum link bandwidth and allow a flow in any priority group. CIN supports only the dot1p priority-queue assignment in a priority group. To configure a dot1p priority flow in a priority group to operate with link strict priority, you configure: The dot1p priority for strict-priority scheduling (strict-priority command). The priority group for strict-priority scheduling (scheduler strict command. Configure a DCBx Operation DCB devices use data center bridging exchange protocol (DCBx) to exchange configuration information with directly connected peers using the link layer discovery protocol (LLDP) protocol. DCBx can detect the misconfiguration of a peer DCB device, and optionally, configure peer DCB devices with DCB feature settings to ensure consistent operation in a data center network. DCBx is a prerequisite for using DCB features, such as priority-based flow control (PFC) and enhanced traffic selection (ETS), to exchange link-level configurations in a converged Ethernet environment. DCBx is also deployed in topologies that support lossless operation for FCoE or iSCSI traffic. In these scenarios, all network devices are DCBx-enabled (DCBx is enabled end-toend). • Configure Enhanced Transmission Selection DCBx supports the following versions: CIN, CEE, and IEEE2.5. DCBx is not supported on PE ports and C9010 cascade ports (member ports in the C9010 LAG created to connect to an attached C1048P). Data Center Bridging (DCB) 259