Qos Priority Mapping With And Without Qos Pass-Through Mode - HP Switch 2800 Series Management And Configuration Manual

Port Status and Basic Configuration
QoS Pass-Through Mode on the Series 2800 Switches
10-26
cant performance improvement for high-bandwidth traffic flows through the
2800 switches, particularly when running traffic flows from 1000Base to either
100Base or 10Base connections.
QoS Pass-Through mode is OFF by default, and must be enabled via the
"config" context of the CLI by entering the CLI command qos-passthrough­
mode, followed by write memory and rebooting the switch.
QoS Pass-Through mode, when enabled, results in the following general
changes to switch operation:
Alters the switch's default outbound priority queue scheme from four
queues (low, normal, medium, and high), to two queues (normal &
high).
Optimizes outbound port buffers for a two-queue scheme.
All packets received with an 802.1p priority tag of 0 to 5 (low, normal,
or medium priorities), or tagged by the switch's QOS feature, will be
serviced by the (now larger) "normal" priority queue.
All packets received with an 802.1p priority tag of 6 or 7 (high priority),
or tagged by the switch's QoS feature, will be serviced by the "high"
priority queue.
High priority packets sourced by the switch itself, such as Spanning
Tree packets, will be serviced in the "high" priority queue.
Any 802.1p tagging on a received packet, or any tag added to a
received frame by the switch via its QoS configuration, will be
preserved as it is transmitted from the switch.
NOTE: As stated earlier, use of this QoS-Passthrough-Mode feature
generally assumes that QoS tagged packets are not being sent through
the 2800 Switch. The receipt of priority 6 or 7 packets may in fact
suffer packet drops depending on the traffic load of non-priority 6 or
7 packets.

QoS Priority Mapping With and Without QoS Pass-Through Mode

The switch supports 802.1p VLAN tagging, which is used in conjunction with
the outbound port
priority queues to prioritize outbound traffic.