Option A: PCP/VLAN PFC: UP to TC Mapping

To configure how Ethernet Priority Code Point (PCP) values map to Traffic Classes (TCs) using Enhanced Transmission Selection (ETS), you can use the lldptool utility on Linux. The up2tc option allows you to define which traffic class each priority level (0-7) should be assigned to.

For example, this command assigns packets marked with prio=2 to TC1, packets with prio=0 to TC2, and all other packet priorities to TC0.

Option B: DSCP Based PFC: UP to TC Mapping

In the case of the 800 Series Adapter implementation of DSCP, UP has a one to one mapping to TC. This means that an UP value of 0 is mapped to TC 0, an UP value of 1 is mapped to TC 1, and so on.

Linux traffic shaping utilities like tc or cgroups do not work for RDMA applications because RDMA applications bypass the kernel. If running a combination of LAN and RDMA traffic, you can still use Linux traffic shaping for LAN traffic, but you must use the PCP or DSCP based mappings described in this section for RDMA traffic.

To enable DSCP mode on an 800 Series Adapter, you must define at least one DSCP-to-priority mapping using DCB APP values. This can be done using the dcb utility from the iproute2 package. For example:

dcb app add dev eth0 dscp-prio 14:0

This command maps DSCP value 14 to priority 0. Even though the adapter has default mappings, at least one manual mapping must be applied to activate DSCP mode.

By default, DSCP values are grouped and mapped to priorities as follows:

Even if you want to keep the default behavior, you still need to apply at least one mapping manually to switch the adapter into DSCP mode.