Users Guide

If an error occurs when a port receives a peer’s ETS configuration, the port’s configuration resets to the ETS configuration in the
previously configured DCB map. If no DCB map was previously applied, the port resets to the default ETS parameters.
ETS Prerequisites and Restrictions
On the switch, ETS is enabled by default on Ethernet ports with equal bandwidth assigned to each 802.1p priority, when DCB is enabled.
You can change the default ETS configuration only by using a DCB map.
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 and dot1p-queue mapping.
• 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. 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.
• ETS is not supported on PE ports and C9010 cascade ports (member ports in the C9010 LAG created to connect to an attached
C1048P).
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 3. Each priority group can support more
than one data queue.
• If you configure more than one priority group as strict priority, the higher numbered priority queue is given preference when scheduling
data traffic.
Configuring Priority-Based Flow Control
Priority-Based Flow Control (PFC) provides a flow control mechanism based on the 802.1p priorities in converged Ethernet traffic received
on an interface and is enabled by default when you enable DCB.
As an enhancement to the existing Ethernet pause mechanism, PFC stops traffic transmission for specified priorities (Class of Service
(CoS) values) without impacting other priority classes. Different traffic types are assigned to different priority classes.
When traffic congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of the traffic that is to be stopped.
Data Center Bridging Exchange protocol (DCBx) provides the link-level exchange of PFC parameters between peer devices. PFC allows
network administrators to create zero-loss links for Storage Area Network (SAN) traffic that requires no-drop service, while retaining
packet-drop congestion management for Local Area Network (LAN) traffic.
To configure PFC, follow these steps.
1 Create a DCB Map.
CONFIGURATION mode
dcb-map dcb-map-name
The dcb-map-name variable can have a maximum of 32 characters.
2 Create a priority group.
CONFIGURATION mode
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Data Center Bridging (DCB)