Reference Guide

• ETS-assigned bandwidth allocation and scheduling apply only to data queues, not to control queues.
• Dell Networking OS supports hierarchical scheduling on an interface. Dell Networking OS control trac is redirected to control
queues as higher priority trac with strict priority scheduling. After control queues drain out, the remaining data trac is
scheduled to queues according to the bandwidth and scheduler conguration in the dcb-map. The available bandwidth calculated
by the ETS algorithm is equal to the link bandwidth after scheduling non-ETS higher-priority trac.
• By default, equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.
• By default, equal bandwidth is assigned to each priority group in the dcb-map applied to an egress port. The sum of auto-
congured bandwidth allocation to dot1p priority trac in all ETS priority groups is 100%.
• dot1p priority trac on the switch is scheduled according to the default dot1p-queue mapping. dot1p priorities within the same
queue should have the same trac properties and scheduling method.
• 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 should be in the same priority
group.
– By default:
* All 802.1p priorities are grouped in priority group 0.
* 100% of the port bandwidth is assigned to priority group 0. The complete bandwidth is equally assigned to each priority
class so that each class has 12 to 13%.
– The maximum number of priority groups supported in ETS output policies on an interface is equal to the number of data
queues (4) on the port. The 802.1p priorities in a priority group can map to multiple queues.
• A dcb-map is created to associate a priority group with a dcb-map with scheduling and bandwidth conguration, and applied on
egress ports.
– The ETS conguration associated with 802.1p priority trac in a dcb-map is used in DCBx negotiation with ETS peers.
– When a dcb-map is applied to an interface, ETS-congured scheduling and bandwidth allocation take precedence over any
auto-congured settings in the QoS output policies.
– ETS is enabled by default with the default ETS conguration applied (all dot1p priorities in the same group with equal
bandwidth allocation).
ETS Operation with DCBx
In DCBx negotiation with peer ETS devices, ETS conguration 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 congurations.
• ETS congurations 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/trac class group (TCG) ID 15 represents a non-ETS priority group. Any priority group
congured 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 ow in a priority group to increase its bandwidth usage to the bandwidth total
of the priority group. A single ow in a group can use all the bandwidth allocated to the group.
* Link strict priority: Allows a ow 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 congurations:
Priority group 1
Assigns trac to one priority queue with 20% of the link bandwidth and strict-priority scheduling.
Data Center Bridging (DCB)
35