Cisco CiscoWork QoS Policy Manager 4.1.2 User Guide
![Cisco](https://files.manualsbrain.com/attachments/7380d0050044647c30f5c24bbbf5d0c0b6d9bb84/common/fit/150/50/faa183d287233c52228cfea3dbc2a127fe780f60564fcb0955d9c3d1cd23/brand_logo.png)
2-19
User Guide for QoS Policy Manager 3.0
78-12542-01
Chapter 2 Planning for Quality of Service
What Types of Quality of Service Does QPM Handle?
Managing Congestion on Switch Ports
Queuing methods on switch ports use a packet’s precedence setting to determine
how that packet is serviced on the port. The queuing methods use multiple queues
of different priority, with one or more thresholds for each queue, to determine the
bandwidth allowed for traffic based on each Class of Service (CoS) value.
how that packet is serviced on the port. The queuing methods use multiple queues
of different priority, with one or more thresholds for each queue, to determine the
bandwidth allowed for traffic based on each Class of Service (CoS) value.
These queues and thresholds are serviced using weighted round robin (WRR)
techniques to ensure a fair chance of transmission to each class of traffic. These
queuing methods favor high-priority traffic without starving low-priority traffic.
techniques to ensure a fair chance of transmission to each class of traffic. These
queuing methods favor high-priority traffic without starving low-priority traffic.
QPM supports the following queuing methods for switch ports:
•
•
•
•
•
2 Queues, 2 Thresholds (2Q2T)
2Q2T queuing uses two queues, one high priority, the other low priority, with two
thresholds for each queue, to determine the bandwidth allowed for traffic based
on each Class of Service (CoS) value. 2Q2T assigns each precedence to a specific
queue and threshold on that queue.
thresholds for each queue, to determine the bandwidth allowed for traffic based
on each Class of Service (CoS) value. 2Q2T assigns each precedence to a specific
queue and threshold on that queue.
For example, packets with CoS value of 0 (the lowest priority) are placed in the
low priority queue and use the lower threshold by default. This ensures that the
least important traffic gets less service than any other traffic.
low priority queue and use the lower threshold by default. This ensures that the
least important traffic gets less service than any other traffic.
2Q2T queuing comes with a default configuration for the queues, thresholds, and
traffic assignments based on CoS settings. You can change this configuration if it
does not suit your requirements. You can change the size of the queues, their
relative WRR weights, the sizes of their thresholds, and the assignment of
precedence values to the appropriate queue and threshold. You do not need to
define queuing policies for ports with 2Q2T queuing.
traffic assignments based on CoS settings. You can change this configuration if it
does not suit your requirements. You can change the size of the queues, their
relative WRR weights, the sizes of their thresholds, and the assignment of
precedence values to the appropriate queue and threshold. You do not need to
define queuing policies for ports with 2Q2T queuing.