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

Priority Setting

Outbound Port

802.1p Priority Setting Added

Queue Assignment in Downstream Devices With:

 

Queues in the

to Tagged VLAN Packets

8 Queues

3 Queues

2 Queues

 

Switch

 

Leaving the Switch

 

 

 

 

 

1

Queue 1

1

(low priority)

Queue 1

Queue 1

 

2

 

2

 

Queue 2

 

Queue 1

0

 

 

 

Queue 3

 

 

Queue 2

0

(normal priority)

Queue 2

 

3

 

3

 

Queue 4

 

 

4

 

 

 

Queue 5

 

 

Queue 3

4

(medium priority)

Queue 3

 

5

 

5

 

Queue 6

 

Queue 2

6

 

 

 

Queue 7

 

 

Queue 4

6

(high priority)

 

 

7

 

7

 

Queue 8

 

 

 

 

 

 

 

 

 

 

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.

 

 

N o t e O n U s i n g

ProCurve recommends that you configure a minimum number of the available

M u l t i p l e

QoS types for prioritizing any given packet type. Increasing the number of

C r i t e r i a

active type options for a packet type increases the complexity of the possible

 

outcomes and consumes switch resources.

 

 

6-8