Cisco Systems Configuring a Service Rule for Standard Priority Queuing and Policing

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Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter58 Configuring QoS
Configuring QoS
Detailed Steps
Step1 Go to Configuration> Device Management > Advanced > Priority Queue, and click Add.
The Add Priority Queue dialog box displays.
Step2 From the Interface drop-down list, choose the physical interface name on which you want to enable the
priority queue, or for the ASA 5505 or ASASM, the VLAN interface name.
Step3 To change the size of the priority queues, in the Queue Limit field, enter the number of average, 256-byte
packets that the specified interface can transmit in a 500-ms interval.
A packet that stays more than 500 ms in a network node might trigger a timeout in the end-to-end
application. Such a packet can be discarded in each network node.
Because queues are not of infinite size, they can fill and overflow. When a queue is full, any additional
packets cannot get into the queue and are dropped (called tail drop). To avoid having the queue fill up,
you can use this option to increase the queue buffer size.
The upper limit of the range of values for this option is determined dynamically at run time. The key
determinants are the memory needed to support the queues and the memory available on the device.
The Queue Limit that you specify affects both the higher priority low-latency queue and the best effort
queue.
Step4 To specify the depth of the priority queues, in the Transmission Ring Limit field, enter the number of
maximum 1550-byte packets that the specified interface can transmit in a 10-ms interval.
This setting guarantees that the hardware-based transmit ring imposes no more than 10-ms of extra
latency for a high-priority packet.
This option sets the maximum number of low-latency or normal priority packets allowed into the
Ethernet transmit driver before the driver pushes back to the queues on the interface to let them buffer
packets until the congestion clears.
The upper limit of the range of values is determined dynamically at run time. The key determinants are
the memory needed to support the queues and the memory available on the device.
The Transmission Ring Limit that you specify affects both the higher priority low-latency queue and the
best-effort queue.
Configuring a Service Rule for Standard Priority Queuing and Policing
You can configure standard priority queuing and policing for different class maps within the same policy
map. See the “How QoS Features Interact” section on page 58-4 for information about valid QoS
configurations.
To create a policy map, perform the following steps.
Restrictions
•You cannot use the class-default class map for priority traffic.
•You cannot configure traffic shaping and standard priority queuing for the same interface; only
hierarchical priority queuing is allowed.
•(ASASM) The ASASM only supports policing.