Linksys SLM248P QoS CoS Settings, CoS Default, Chapter, Configuration Using the Web-based Utility

Chapter 4 Configuration Using the Web-based Utility

QoS

Network traffic is usually unpredictable, and the only basic assurance that can be offered is best effort traffic delivery. To overcome this challenge, Quality of Service (QoS) is applied throughout the network. This ensures that network traffic is prioritized according to specified criteria, and that specific traffic receives preferential treatment. QoS in the network optimizes network performance and entails two basic facilities:

Classifying incoming traffic into handling classes, based on an attribute, including:

•The ingress interface

•Packet content

•A combination of these attributes

Providing various mechanisms for determining the allocation of network resources to different handling classes, including:

•The assignment of network traffic to a particular hardware queue

•The assignment of internal resources

•Traffic shaping

The terms Class of Service (CoS) and QoS are used in the following context:

•CoS provides varying Layer 2 traffic services. CoS refers to classifying traffic into traffic classes, where each class is handled as an aggregate whole, with no per-flow settings. CoS is usually related to the 802.1p service that classifies flows according to their Layer 2 priority, as set in the VLAN header.

•QoS refers to Layer 2 traffic and above. QoS handles per-flow settings, even within a single traffic class.

The QoS facility involves the following elements:

•Traffic Classification—Classifies each incoming packet as belonging to a given traffic class, based on the packet contents and/or the context.

•Assignment to Hardware Queues—Assigns incoming packets to forwarding queues. Packets are sent to a particular queue for handling as a function of the traffic class to which they belong, as defined by the classification mechanism.

•Traffic Class-Handling Attributes—Applies QoS/CoS mechanisms to different classes, including Bandwidth Management.

The QoS configuration options are as follows:

•CoS Settings

•Queue Settings

•DSCP Setting

•Basic Mode

QoS > CoS Settings

The CoS Settings screen contains fields for enabling or disabling CoS. This screen contains two sections, CoS Settings and CoS Default.

QoS > CoS Settings

CoS Settings

QoS Mode  Indicates if QoS is enabled. The possible values are:

•Disable  Disables QoS.

•Basic  Enables QoS. This is the default value.

Class of Service  Specifies the CoS priority tag values, where 0 is the lowest and 7 is the highest.

Queue  Defines the traffic forwarding queue to which the CoS priority is mapped. Four traffic priority queues are supported.

Click Restore Defaults to restore the device factory defaults for mapping CoS values to a forwarding queue.

CoS Default

Interface  The interface to which the CoS configuration applies.

Default CoS  Determines the default CoS value for incoming packets for which a VLAN tag is not defined. The possible field values are 0-7. The default CoS is 0.

LAG  The LAG to which the port belongs, if relevant. If the port is a member of a LAG, the LAG settings override the port settings.

Click Save Settings to save the changes, or Cancel Changes to cancel the changes.

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