Quality of Service (QoS): Managing Bandwidth More Effectively

Preparation for Configuring QoS

How the Switch Uses Resources in DSCP Configurations. In the default configuration, the DSCP map is configured with one DSCP policy (Expedited Forwarding; 101110 with a “7” priority) but, because no ToS Diff- Services options are configured, no rules are used. If ToS Diff-Services mode is enabled, then one rule is immediately used for this codepoint. Adding a new DSCP policy (for example, 001111 with a “5” priority) and then configuring ToS Diff-Services to assign inbound packets with a codepoint of 001010 to the 001111 policy implements all policies configured in the DSCP map and, in this case, uses three rules; that is, one rule for each codepoint invoked in the switch’s current DSCP configuration (101110—the default, 001111, and 001010). Adding another Diff-Services assignment, such as assigning inbound packets with a codepoint of 000111 to the Expedited Forwarding policy (101110), would use one more rule on all ports.

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