Configuration manual

– In the CEE version, the priority group/traffic class group (TCG) ID 15 represents a non-ETS priority

group. Any priority group configured with a scheduler type is treated as a strict-priority group and

is given the priority-group (TCG) ID 15.

– The CIN version supports two types of strict-priority scheduling:

* Group strict priority: Allows a single priority flow in a priority group to increase its bandwidth

usage to the bandwidth total of the priority group. A single flow in a group can use all the

bandwidth allocated to the group.

* Link strict priority: Allows a flow in any priority group to increase to the maximum link

bandwidth.

CIN supports only the default dot1p priority-queue assignment in a priority group.

Bandwidth Allocation for DCBX CIN

After an ETS output policy is applied to an interface, if the DCBX version used in your data center network

is CIN, a QoS output policy is automatically configured to overwrite the default CIN bandwidth allocation.

This default setting divides the bandwidth allocated to each port queue equally between the dot1p

priority traffic assigned to the queue.

DCBX Operation

The data center bridging exchange protocol (DCBX) is used by DCB devices to exchange configuration

information with directly connected peers using the link layer discovery protocol (LLDP) protocol. DCBX

can detect the misconfiguration of a peer DCB device, and optionally, configure peer DCB devices with

DCB feature settings to ensure consistent operation in a data center network.

DCBX is a prerequisite for using DCB features, such as priority-based flow control (PFC) and enhanced

traffic selection (ETS), to exchange link-level configurations in a converged Ethernet environment. DCBX

is also deployed in topologies that support lossless operation for FCoE or iSCSI traffic. In these scenarios,

all network devices are DCBX-enabled (DCBX is enabled end-to-end).

The following versions of DCBX are supported on an Aggregator: CIN, CEE, and IEEE2.5.

DCBX requires the LLDP to be enabled on all DCB devices.

DCBx Operation

DCBx performs the following operations:

• Discovers DCB configuration (such as PFC and ETS) in a peer device.

• Detects DCB mis-configuration in a peer device; that is, when DCB features are not compatibly

configured on a peer device and the local switch. Mis-configuration detection is feature-specific

because some DCB features support asymmetric configuration.

• Reconfigures a peer device with the DCB configuration from its configuration source if the peer

device is willing to accept configuration.

• Accepts the DCB configuration from a peer if a DCBx port is in “willing” mode to accept a peer’s DCB

settings and then internally propagates the received DCB configuration to its peer ports.

Data Center Bridging (DCB)