Tag :: Shaping

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.

This document describes the introduction and use of the global knob which facilitates the txQueue percentage-based allocations based on the available bandwidth of the parent interface.

L2 protocol frames - LLDP, LACP and STP are trapped to the CPU by default. This feature allows for disabling the per protocol trap on a given set of interfaces. Starting from 4.32.1F, forwarding of MACsec EAPoL frames is also supported on a per interface basis on certain platforms. Starting from 4.35.0F, specific platforms support forwarding LLDP VXLAN encapsulated frames while continuing to trap regular/local LLDP frames to the CPU per interface.

Subinterfaces divide a single ethernet or port channel interface into multiple logical L3 interfaces based on the 802.1q tag (VLAN ID) of incoming traffic. Subinterfaces are commonly used in the L2/L3 boundary device, but they can also be used to isolate traffic with 802.1q tags between L3 peers by assigning each subinterface to a different VRF. L3 subinterface shaping + VRF is also supported.

Forwarding destination prediction allows users to determine which interface a given packet will egress out. This feature is enhanced to identify the TCAM bank and rule offset for the matched ACL rule responsible for the forwarding decision. This allows network operators to trace the egress result back to the exact rule that triggered the action.

Subinterfaces divide a single ethernet or port channel interface into multiple logical L2 or L3 interfaces based on the 802.1q or 802.1ad tags of incoming traffic. Subinterfaces are commonly used in the L2/L3 boundary device, but they can also be used to isolate traffic with 802.1q tags between L3 peers by assigning subinterfaces to different VRFs or different L2 bridging domains.

This feature is only applicable to shaped port-channel subinterfaces. Traffic destined to a shaped port-channel subinterface would be load-balanced across all members of the port-channel. Shaping configured on the port-channel subinterface will be directly used across all the members of port-channel. Load-balancing criterion for flows destined to a shaped port-channel subinterface is the same as parent port-channel load-balancing criterion. Each shaped port-channel subinterface consumes as many SPPID (System physical port identifier) as the number of members added to the port-channel along with one extra port-channel resource (LAG ID) to combine all these SPPID. Anchor based approach is default behavior and we explicitly need to enable and reload the system for this feature to work.

TX queue precision shaping allows improving accuracy of observed shape rates on interfaces relative to configured values, in particular when the configured rate is low.

Tx-Queues are usually assigned to subinterfaces only when explicit shaping or scheduling is configured. Without this feature, unshaped or unscheduled subinterfaces might continue to use the parent interface's Tx-Queues. This capability enables the allocation of a set of Tx-Queues to the subinterface, with the Tx-Queues operating at the maximum shaping rate derived from the parent interface. This feature is only supported in conjunction with Priority Aware Subinterface Scheduling.