Users Guide

– ETS is enabled by default with the default ETS configuration applied (all dot1p priorities in the same
group with equal bandwidth allocation).
ETS Operation with DCBx
In DCBx negotiation with peer ETS devices, ETS configuration is handled as follows:
• ETS TLVs are supported in DCBx versions CIN, CEE, and IEEE2.5.
• ETS operational parameters are determined by the DCBX port-role configurations.
• ETS configurations received from TLVs from a peer are validated.
• In case of a hardware limitation or TLV error, the DCBx operation on an ETS port goes down.
• ETS operates with legacy DCBx versions as follows:
– 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.
Hierarchical Scheduling in ETS Output Policies
ETS supports up to three levels of hierarchical scheduling.
For example, you can apply ETS output policies with the following configurations:
Priority group 1 Assigns traffic to one priority queue with 20% of the link bandwidth and strict-
priority scheduling.
Priority group 2 Assigns traffic to one priority queue with 30% of the link bandwidth.
Priority group 3 Assigns traffic to two priority queues with 50% of the link bandwidth and strict-
priority scheduling.
In this example, the configured ETS bandwidth allocation and scheduler behavior is as follows:
Unused
bandwidth
usage:
Normally, if there is no traffic or unused bandwidth for a priority group, the
bandwidth allocated to the group is distributed to the other priority groups
according to the bandwidth percentage allocated to each group. However, when
three priority groups with different bandwidth allocations are used on an interface:
• If priority group 3 has free bandwidth, it is distributed as follows: 20% of the free
bandwidth to priority group 1 and 30% of the free bandwidth to priority group 2.
• If priority group 1 or 2 has free bandwidth, (20 + 30)% of the free bandwidth is
distributed to priority group 3. Priority groups 1 and 2 retain whatever free
bandwidth remains up to the (20+ 30)%.
Data Center Bridging (DCB)
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