Tag :: VoQ

Transmit queues are logical partitions of an Ethernet port’s egress bandwidth. Data streams are assigned to queues based on their traffic class, then sent as scheduled by port and transmit settings. Sand platform switches have eight queues, 0 through 7, and all queues are exposed through the CLI. However, queue 7 is not user-configurable. Queue 7 is always mapped to traffic class 7, which is reserved for control plane traffic. This feature allows tx-queue 7 to be configurable. As of 4.33.0F, a limited set of features are configurable on tx-queue 7.

Configurable Voq Tail Drop Thresholds provides flexibility to change default voq tail drop based on speed of the

Fair Adaptive Dynamic thresholds (FADT) provides efficient allocation of shared packet buffer resources amongst various virtual output queues. FADT is useful when queues are getting congested and buffer resources should be allocated in a way tdat prioritizes certain queues while avoiding starvation of lower priority queues. the scheme works on each incoming packet by calculating instantaneous queue threshold based on available free resources. Queue buffer threshold is calculated as:

This feature allows setting the desired maximum VOQ latency. Drop probabilities are adjusted in hardware to meet this limit.

Temporal Tail Drop Thresholds enables the configuration of interface TX queue tail drops thresholds in units of time. The system dynamically computes the maximum allowable queue occupancy by considering the current interface speed and the Weighted Round Robin (WRR) bandwidth allocation. This feature simplifies configuration in environments with mixed link speeds. The calculated threshold represents the maximum bytes queued to hold packets for the specified duration.