Reference Guide

Data Center Bridging (DCB) | 287
ETS Prerequisites and Restrictions
On an S5000 switch, ETS is enabled by default on Ethernet ports; equal bandwidth is assigned to each
802.1p priority. You can change the default ETS configuration only by using a DCB map. For more
information, see DCB Map: Configuration Procedure.
The following prerequisites and restrictions apply when you configure ETS bandwidth allocation or
strict-priority queuing in a DCB map:
• When allocating bandwidth or configuring strict-priority queuing for dot1p priorities in a priority
group on a DCBx CIN interface, take into account the CIN bandwidth allocation (see Configuring
Bandwidth Allocation for DCBx CIN) and dot1p-queue mapping (Table 13-1).
• Although ETS bandwidth allocation or strict-priority queuing does not support weighted random early
detection (WRED), explicit congestion notification (ECN), rate shaping, and rate limiting because
these parameters are not negotiated by DCBx with peer devices, you can apply a QoS output policy
with WRED and/or rate shaping on a DCBx CIN-enabled interface (see Configuring Port-based Rate
Shaping and Weighted Random Early Detection). In this case, the WRED or rate shaping configuration
in the QoS output policy must take into account the bandwidth allocation or queue scheduler
configured in the DCB map.
Priority-Group Configuration Notes
When you configure priority groups in a DCB map:
• A priority group consists of 802.1p priority values that are grouped together for similar bandwidth
allocation and scheduling, and that share the same latency and loss requirements. All 802.1p priorities
mapped to the same queue must be in the same priority group.
• In a DCB map, each 802.1p priority must map to a priority group.
• The maximum number of priority groups supported in a DCB map on an interface is equal to the
number of data queues (4) on the port. Each priority group can support more than one data queue.
• You can enable PFC on a maximum of two priority queues on an interface.
• If you configure more than one priority group as strict priority, the higher numbered priority queue is
given preference when scheduling data traffic.
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.
Step Task Command Command Mode
1 Enter global configuration mode to create a DCB map
or edit PFC and ETS settings.
dcb-map name
CONFIGURATION