Configuration manual

Quality of Service Overview
Fixed Switch Configuration Guide 17-3
There are up to four areas of CoS configuration depending on what type of hardware resource you
want to configure. The terminology associated with CoS configuration is introduced in Table 17-1.
CoS Settings
Use the CoS settings configuration when mapping the priority of the ingressing packet to a
hardware resource reference, flood control state, or 802.1 priority or ToS remarking.
CoS Hardware Resource Reference
The CoS hardware resource reference can be an inbound rate limiter reference.
CoS Flood Control State
CoS flood control state enables or disables flood control for the CoS setting.
CoS Priority and ToS Rewrite
The two parameters configurable for CoS priority are 802.1p and Type of Service (ToS). Each CoS
can be mapped to an 802.1p priority and a ToS rewrite value. 802.1p and ToS are specified in the
CoS settings configuration layer.
The 802.1p parameter is:
• A subset of ToS with values 0–7 (upper 3 bits of the 8 bit ToS field)
• Supported in both layer 2 and layer 3
The ToS parameter is:
• An 8-bit field with values 0–255
• Supported in layer 3 only
• Also referred to as the Differentiated Services Code Point (DSCP) when limited to the lower 5
bits of the field
Figure 17-1 on page 17-4 displays the relationship between your application, priority level, 802.1p,
and ToS assignments (shown here using DSCP terminology).
QoS priority/ToS configuration:
• Derives its characteristic requirements from the end-system application.
• Is configured on the edge device the application is connected to
Table 17-1 CoS Configuration Terminology
Term Description
CoS Setting Maps configured resources to a CoS index. When a packet is received, the
packet is mapped to a CoS index based on the packet 802.1 priority, port,
and policy role, if a policy role is present. The CoS index translates into
available hardware resources through indirect mappings to IRL or the
administrative state of flood control.
CoS Reference Provides a means of mapping a CoS setting to a specific hardware resource,
such as an IRL.
CoS Port Resource Specifies the IRL or flood control rate limiter threshold value that the CoS
reference is mapped to.
CoS Port Configuration Specifies the ports to which CoS resource configuration should be applied.