Posts Tagged ‘DSCP’

04.3
14

Congestion Management

by como ·

QoS involves many components and features, but the component that is most typically associated with the term QoS is congestion management. Congestion management is the key component for QoS on Catalyst switches. routing and switching The congestion management component of QoS itself is made up of many different features in Cisco IOS and CatOS. All Catalyst switches that support QoS features support congestion management or congestion avoidance. The next section looks at these features in detail, but the purpose of this section in general. As the name implies, congestion management enables you to manage the congestion that is experienced by packets at a given point in the network. Congestion management involves three main steps: 1?Queues are created at the interface where congestion is expected. Depending on the specific feature or mechanism being used to provide QoS ccie workbooks and the platform on which the QoS is being configured, there could be only two queues or there could be several hundred (although there is currently no practical application for this many queues on any Catalyst platform). 2 Packets (this could also be frames, but for the sake of simplicity, the word packets is used) are then assigned to these queues, based on classification characteristics such as DiffServ codepoint (DSCP) value. The classification CCIE of packets by characteristics is typically user-defined, and packets are placed into queues by these predetermined characteristics. Some examples of packet characteristics that are typically used in classification are the values in the packet for IP precedence, DSCP, and Layer 2 class of service . It is also common to use extended access lists to match packets based on more complex criteria, such as port numbers.

QoS involves many components and features, but the component that is most typically associated with the term QoS is congestion management. Congestion management is the key component for QoS on Catalyst switches. routing and switching The congestion management component of QoS itself is made up of many different features in Cisco IOS and CatOS. All Catalyst switches that support QoS features support congestion management or congestion avoidance. The next section looks at these features in detail, but the purpose of this section in general. As the name implies, congestion management enables you to manage the congestion that is experienced by packets at a given point in the network. Congestion management involves three main steps: 1?Queues are created at the interface where congestion is expected. Depending on the specific feature or mechanism being used to provide QoS ccie workbooks and the platform on which the QoS is being configured, there could be only two queues or there could be several hundred (although there is currently no practical application for this many queues on any Catalyst platform). 2 Packets (this could also be frames, but for the sake of simplicity, the word packets is used) are then assigned to these queues, based on classification characteristics such as DiffServ codepoint (DSCP) value. The classification CCIE of packets by characteristics is typically user-defined, and packets are placed into queues by these predetermined characteristics. Some examples of packet characteristics that are typically used in classification are the values in the packet for IP precedence, DSCP, and Layer 2 class of service . It is also common to use extended access lists to match packets based on more complex criteria, such as port numbers.