Users Guide

PFC and ETS Configuration Examples
This section contains examples of how to configure and apply DCB policies on an interface.
Using PFC to Manage Converged Ethernet Traffic
To use PFC for managing converged Ethernet traffic, use the following command:
dcb-map stack-unit all dcb-map-name
Operations on Untagged Packets
The below is example for enabling PFC for priority 2 for tagged packets. Priority (Packet Dot1p) 2 will be mapped to PG6 on
PRIO2PG setting. All other Priorities for which PFC is not enabled are mapped to default PG – PG7.
Classification rules on ingress (Ingress FP CAM region) matches incoming packet-dot1p and assigns an internal priority (to
select queue as per Table 1 and Table 2).
The internal Priority assigned for the packet by Ingress FP is used by the memory management unit (MMU) to assign the packet
to right queue by indexing the internal-priority to queue map table (TABLE 1) in hardware.
PRIO2COS setting for honoring the PFC protocol packets from the Peer switches is as per above Packet-Dot1p->queue table
(Table 2).
The packets that come in with packet-dot1p 2 alone will be assigned to PG6 on ingress.
The packets that come in with packet-dot1p 2 alone will use Q1 (as per dot1p to Queue classification – Table 2) on the egress
port.
● When Peer sends a PFC message for Priority 2, based on above PRIO2COS table (TABLE 2), Queue 1 is halted.
● Queue 1 starts buffering the packets with Dot1p 2. This causes PG6 buffer counter to increase on the ingress, since P-dot1p
2 is mapped to PG6.
● As the PG6 watermark threshold is reached, PFC will be generated for dot1p 2.
Generation of PFC for a Priority for Untagged Packets
In order to generate PFC for a particular priority for untagged packets, and configuring PFC for that priority, you should find the
queue number associated with priority from TABLE 1 and Associate a DCB map to forward the matched DSCP packet to that
queue. PFC frames gets generated with PFC priority associated with the queue when the queue gets congested.
Configure Enhanced Transmission Selection
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 traffic with different bandwidth, latency, and best-effort needs.
For example, storage traffic is sensitive to frame loss; interprocess communication (IPC) traffic is latency-sensitive. ETS allows
different traffic types to coexist without interruption in the same converged link by:
● Allocating a guaranteed share of bandwidth to each priority group.
● Allowing each group to exceed its minimum guaranteed bandwidth if another group is not fully using its allotted bandwidth.
Data Center Bridging (DCB)
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