Enhanced QoS mode is an advanced priority-based routing algorithm where VLAN P-bit, IP DSCP or the EMAC port-based default priority is used to determine the destination QoS queue and CPPI flow. This routing algorithm is required to support egress L2 shaper and is described in details here.
For each EMAC interface, PASS will be configured for:
- Base queue (egress only)
- Base flow (egress only
- DSCP_MAP[] {one entry (= flow offset /queue offset) for each DSCP value, 64 total}
- VLAN_PRIORITY_MAP[] { one entry (= flow offset/queue offset) for each P-bit value, 8 total}
- Default priority to use per the ingress interface
- Routing mode: P-bit or DSCP
- PriorityOverride: True/False
Routing algorithm supports two modes and is described as below:
- DP-bit mode:
- If frame has VLAN tag, use p-bits to lookup shaper input queue # from the VLAN_PRIORITY_MAP[] for the frame's egress port
- If frame is un-tagged, but is an IP packet, use the DSCP value to lookup the shaper input queue # from the DSCP_MAP[] for the frame's egress port unless priority override is set for the egress port (see last bullet below).
- If frame is un-tagged, and non-ip , then use the default priority for the frame's ingress port to look up the shaper input queue from the egress port's VLAN_PRIORITY_MAP[]. For SOC-generated traffic, the default priority is a separate global configuration item.
- If priority override is set and the packet is IP then do as in un-tagged/non-ip (above bullet).
- DSCP mode:
- If frame is an IP packet, use the DSCP value and the DSCP_MAP [] for the egress port as above to determine the L2 shaper queue to use
- For non-ip packets, use the default priority for the frame's ingress port to look up the shaper input queue from the egress port's VLAN_PRIORITY_MAP[]. For SOC-generated traffic, the default priority is a separate global configuration item.
- Priority override setting is not applicable in this mode.