QoS and QoS Policies
56
Quality of Service Guide
3HE 11014 AAAC TQZZA Edition: 01
3.1.11.1 6-port SAR-M Ethernet Module
The egress datapath shapers on a 6-port SAR-M Ethernet module operate on the
same frame size as any other shaper. These egress datapath shapers are:
• per-queue shapers
• per-SAP aggregate shapers
• per-customer aggregate (MSS) shapers
The egress port shaper on a 6-port SAR-M Ethernet module does not account for the
4-byte FCS. Packet byte offset can be used to make adjustments to match the
desired operational rate or eliminate the implications of FCS. See Packet Byte Offset
(PBO) for more information.
3.1.11.2 4-Priority Scheduling Behavior on Gen-3 Hardware
For access ingress, access egress, and network ingress traffic, the behavior of
4-priority scheduling on Gen-3 hardware is similar to 4-priority scheduling on Gen-1
and Gen-2 hardware. See Figure 9 (access ingress), Figure 10 (access egress),
Figure 11 (network ingress, destination mode), and Figure 12 (network ingress,
aggregate mode).
For network egress traffic through a network port on Gen-3 hardware, the behavior
of 4-priority scheduling is as follows: traffic priority is determined at the queue-level
scheduler, which is based on the queue PIR and CIR and the queue type. The
queue-level priority is carried through the various shaping stages and is used by the
4-priority Gen-3 VLAN scheduler at network egress. See Figure 13 and its
accompanying description.
For hybrid ports, both access and network egress traffic use 4-priority scheduling that
is similar to 4-priority scheduling on Gen-1 and Gen-2 hardware. See Figure 14 and
its accompanying description.
Note: For network egress traffic when the port is in network mode, there is no change to
CIR-based shaping for per-VLAN shapers (that is, PIR-based shaping only, CIR-based
shaping is not enabled), and backpressure to the FC queues based on the relative priority
among all VLAN-bound IP interfaces is still enabled.
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