6-8
Quality of Service (QoS): Managing Bandwidth More Effectively
Introduction
If a packet is not in a VLAN-tagged port environment, then the QoS settings in
table 6-2 control only to which outbound queue the packet goes. Without VLAN
tagging, no 802.1p priority is added to the packet for downstream device use.
But if the packet is in a VLAN-tagged environment, then the above setting is
also added to the packet as an 802.1p priority for use by downstream devices
and applications (shown in table 6-3). In either case, an IP packet can also
carry a priority policy to downstream devices by using DSCP-marking in the
ToS byte.
Table 6-3. Mapping Switch QoS Priority Settings to Device Queues
QoS Types for Prioritizing Outbound Packets
The QoS types used in the switches covered in this chapter are a subset of the
types used in full-featured switches.
Note On Using
Multiple
Criteria
ProCurve recommends that you configure a minimum number of the available
QoS types for prioritizing any given packet type. Increasing the number of
active type options for a packet type increases the complexity of the possible
outcomes and consumes switch resources.
Priority Setting Outbound Port
Queues in the
Switch
802.1p Priority Setting Added
to Tagged VLAN Packets
Leaving the Switch
Queue Assignment in Downstream Devices With:
8 Queues 3 Queues 2 Queues
1 Queue 1 1 (low priority) Queue 1 Queue 1
2 2 Queue 2 Queue 1
0 Queue 2 0 (normal priority) Queue 3 Queue 2
3 3 Queue 4
4 Queue 3 4 (medium priority) Queue 5 Queue 3
5 5 Queue 6 Queue 2
6 Queue 4 6 (high priority) Queue 7
7 7 Queue 8
