Managing Switches

Configuring Switch Features

Guidelines for Configuring CoS Priorities

Using CoS in a tagged VLAN environment controls the following:

■ Outbound port queue—The queue to which a high or normal packet will be sent

■ Outbound 802.1p priority—The new 802.1p priority setting in an outbound

 

 

 

packet or the packet’s existing 802.1p setting. This enables the packet to

 

 

 

carry an 802.1p priority to the next downstream device.

 

 

 

Using CoS without a tagged VLAN environment affects only the outbound port

 

 

 

queue to which a packet is sent. It prioritizes traffic flow only within the

 

 

 

switch. However, without a tagged VLAN environment, an outbound packet

 

 

 

cannot carry an 802.1p priority setting to a downstream device.

 

 

 

 

 

N o t e

If you use HP TopTools for Hubs & Switches to configure Quality of Service

 

 

 

(QoS) policy in a network, it overrides any CoS settings configured through

 

 

 

the console or the web browser interface in any individual HP Procurve

 

 

 

switch.

 

 

 

 

Steps for Configuring CoS Priority

 

 

 

 

 

 

The following table shows the Priority Criteria and their precedence.

 

 

 

Table 13-5. Priority Criteria and Precedence

 

 

 

 

 

 

Precedence

 

Criteria

Description

 

 

 

 

 

 

1

 

Device Priority (IP Address

You can specify a priority for any packet having a particular destination

 

 

 

 

or source IP address. It is recommended that you prioritize server

 

 

 

 

addresses instead of client addresses in order to include the widest

 

 

 

 

possible range of traffic in your device priority policy. If an outbound

 

 

 

 

packet has an IP address as the destination, it takes precedence over

 

 

 

 

another outbound packet that has the same IP address as a source.

 

 

 

 

(This can occur, for example, on an outbound port in a switch mesh

 

 

 

 

environment.) Default state: No IP address prioritization.

 

 

 

 

If a packet does not meet the criteria for device priority, then

 

 

 

 

precedence defaults to IP Type of Service (ToS) criteria, below.

 

 

 

 

 

 

2

 

IP Type-of-

Applies only to IP packets. The ToS field in an IP packet is configured

 

 

 

Service (ToS)

by an upstream device or application before the incoming packet

 

 

 

 

enters the switch, and is not altered by the switch. The switch reads

 

 

 

 

the packet’s Type of Service (ToS) field and prioritizes the packet (if

 

 

 

 

specified in the CoS configuration) for outbound transmission. The

 

 

 

 

default state is Disabled.

 

 

 

 

If a packet does not meet the criteria for ToS priority, then precedence

 

 

 

 

defaults to Protocol criteria, below.

 

 

 

 

 

13-15