Users Guide

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.
ETS Prerequisites and Restrictions
The following prerequisites and restrictions apply when you configure ETS bandwidth allocation or queue
scheduling.
• Configuring ETS bandwidth allocation or a queue scheduler for dot1p priorities in a priority group is
applicable if the DCBx version used on a port is CIN (refer to Configuring DCBx).
• When allocating bandwidth or configuring a queue scheduler for dot1p priorities in a priority group on a
DCBx CIN interface, take into account the CIN bandwidth allocation (refer to
Configuring Bandwidth Allocation for DCBx CIN) and dot1p-queue mapping.
NOTE: The IEEE 802.1Qaz, CEE, and CIN versions of ETS are supported.
Data Center Bridging (DCB) 275