Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

DCB Map: Configuration Procedure

A DCB map consists of PFC and ETS parameters. By default, PFC is not enabled on any 802.1p priority and ETS allocates equal bandwidth to each priority. To configure user-defined PFC and ETS settings, you must create a DCB map.

1. Enter global configuration mode to create a DCB map or edit PFC and ETS settings.

   CONFIGURATION mode

   dcb-map name

2. Configure the PFC setting (on or off) and the ETS bandwidth percentage allocated to traffic in each priority group, or whether the priority group traffic should be handled with strict priority scheduling. You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p priorities makes the corresponding port queue lossless. The sum of all allocated bandwidth percentages in all groups in the DCB map must be 100%. Strict-priority traffic is serviced first. Afterwards, bandwidth allocated to other priority groups is made available and allocated according to the specified percentages. If a priority group does not use its allocated bandwidth, the unused bandwidth is made available to other priority groups.

   DCB MAP mode

   priority-group group_num { bandwidth percentage | strict-priority} pfc { on | off}

   Example:

                                             priority-group 0 bandwidth 60 pfc off
                                             priority-group 1 bandwidth 20 pfc on
                                             priority-group 2 bandwidth 20 pfc on
                                             priority-group 4 strict-priority pfc off
                                             
                                          

   Repeat this step to configure PFC and ETS traffic handling for each priority group.

3. Specify the dot1p priority-to-priority group mapping for each priority. Priority-group range: 0 to 7.

   DCB MAP mode

   priority-pgid dot1p0_group_num dot1p1_group_num dot1p2_group_num dot1p3_group_num dot1p4_group_num dot1p5_group_num dot1p6_group_num dot1p7_group_num

   All priorities that map to the same queue must be in the same priority group.Leave a space between each priority group number. For example: priority-pgid 0 0 0 1 2 4 4 4 in which priority group 0 maps to dot1p priorities 0, 1, and 2; priority group 1 maps to dot1p priority 3; priority group 2 maps to dot1p priority 4; priority group 4 maps to dot1p priorities 5, 6, and 7.

Important Points to Remember

• If you remove a dot1p priority-to-priority group mapping from a DCB map ( no priority pgid command), the PFC and ETS parameters revert to their default values on the interfaces on which the DCB map is applied. By default, PFC is not applied on specific 802.1p priorities; ETS assigns equal bandwidth to each 802.1p priority.

  As a result, PFC and lossless port queues are disabled on 802.1p priorities, and all priorities are mapped to the same priority queue and equally share the port bandwidth.

• To change the ETS bandwidth allocation configured for a priority group in a DCB map, do not modify the existing DCB map configuration. Instead, first create a new DCB map with the desired PFC and ETS settings, and apply the new map to the interfaces to override the previous DCB map settings. Then, delete the original dot1p priority-priority group mapping.

  If you delete the dot1p priority-priority group mapping ( no priority pgid command) before you apply the new DCB map, the default PFC and ETS parameters are applied on the interfaces. This change may create a DCB mismatch with peer DCB devices and interrupt network operation.

Applying a DCB Map on a Port

To apply a DCB map to an Ethernet port, follow these steps:

1. Enter interface configuration mode on an Ethernet port.

   CONFIGURATION mode

   interface tengigabitEthernet slot/ port

2. Apply the DCB map on the Ethernet port to configure it with the PFC and ETS settings in the map.

   INTERFACE mode

   dcb-map name

   Dell# 
                                             interface tengigabitEthernet 0/0 
                                             Dell(config-if-te-0/0)# 
                                             dcb-map SAN_A_dcb_map1
                                          

   Repeat Steps 1 and 2 to apply a DCB map to more than one port.You cannot apply a DCB map on an interface that has been already configured for PFC using the pfc priority command or which is already configured for lossless queues ( pfc no-drop queues command).

Configuring PFC without a DCB Map

In a network topology that uses the default ETS bandwidth allocation (assigns equal bandwidth to each priority), you can also enable PFC for specific dot1p-priorities on individual interfaces without using a DCB map. This type of DCB configuration is useful on interfaces that require PFC for lossless traffic, but do not transmit converged Ethernet traffic.

1. Enter interface configuration mode on an Ethernet port.

   CONFIGURATION mode

   interface tengigabitEthernet slot / port

2. Enable PFC on specified priorities. Range: 0-7. Default: None.Maximum number of lossless queues supported on an Ethernet port: 2.Separate priority values with a comma. Specify a priority range with a dash, for example: pfc priority 3,5-7.

   INTERFACE mode

   pfc priority priority-range

   You cannot configure PFC using the pfc priority command on an interface on which a DCB map has been applied or which is already configured for lossless queues ( pfc no-drop queues command).

Configuring Lossless Queues

DCB also supports the manual configuration of lossless queues on an interface after you disable PFC mode in a DCB map and apply the map on the interface. The configuration of no-drop queues provides flexibility for ports on which PFC is not needed, but lossless traffic should egress from the interface.

Lossless traffic egresses out the no-drop queues. Ingress 802.1p traffic from PFC-enabled peers is automatically mapped to the no-drop egress queues.

When configuring lossless queues on a port interface, consider the following points:

• By default, no lossless queues are configured on a port.

• A limit of two lossless queues are supported on a port. If the number of lossless queues configured exceeds the maximum supported limit per port (two), an error message is displayed. You must re-configure the value to a smaller number of queues.

• If you configure lossless queues on an interface that already has a DCB map with PFC enabled ( pfc on ), an error message is displayed.

1. Enter INTERFACE Configuration mode.

   CONFIGURATION mode

   interface tengigabitEthernet slot/ port

2. Open a DCB map and enter DCB map configuration mode.

   INTERFACE mode

   dcb-map name

3. Disable PFC.

   DCB MAP mode

   no pfc mode on

4. Return to interface configuration mode.

   DCB MAP mode

   exit

5. Apply the DCB map, created to disable the PFC operation, on the interface.

   INTERFACE mode

   dcb-map { name | default}

6. Configure the port queues that still function as no-drop queues for lossless traffic.You cannot configure PFC no-drop queues on an interface on which a DCB map with PFC enabled has been applied, or which is already configured for PFC using the pfc priority command.The maximum number of lossless queues globally supported on a port is 2.Range: 0-3. Separate queue values with a comma; specify a priority range with a dash; for example: pfc no-drop queues 1,3 or pfc no-drop queues 2-3 Default: No lossless queues are configured.

   INTERFACE mode

   pfc no-drop queues queue-range