Information About Qos - Cisco Catalyst 2960 series Configuration Manual

Information About QoS

• The switch must be running the LAN Base image to use the following QoS features:
Information About QoS
QoS Implementation
Typically, networks operate on a best-effort delivery basis, which means that all traffic has equal priority and
an equal chance of being delivered in a timely manner. When congestion occurs, all traffic has an equal chance
of being dropped.
When you configure the QoS feature, you can select specific network traffic, prioritize it according to its
relative importance, and use congestion-management and congestion-avoidance techniques to provide
preferential treatment. Implementing QoS in your network makes network performance more predictable and
bandwidth utilization more effective.
The QoS implementation is based on the Differentiated Services (Diff-Serv) architecture, a standard from the
Internet Engineering Task Force (IETF). This architecture specifies that each packet is classified upon entry
into the network.
The classification is carried in the IP packet header, using 6 bits from the deprecated IP type of service (ToS)
field to carry the classification (class) information. Classification can also be carried in the Layer 2 frame.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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◦ Enable Priority queueing at interface level.
◦ Enable or disable mls qos rewrite ip dscp.
◦ Policy maps
◦ Policing and marking
◦ Mapping tables
◦ WTD