Objective

A common method of optimizing a network is through the use of Quality of Service (QoS). QoS works by prioritizing certain network traffic according to the different configurable criteria. Lower priority traffic is slowed down to provide better throughput for higher priority traffic. Cisco Series Managed Switches support four queues, where queue four has the highest priority. QoS can be configured on Cisco Series Managed Switches based on different trusted modes.

The switch supports the following Trusted Modes:

• Class of Service (CoS / 802.1p) allows the user to specify priority for data packets when traffic is buffered in the switch due to congestion. CoS values ranges from 0-7, where 7 has the highest priority.

• IP Differentiated Services Code Point (DSCP) detects packets based on their DSCP values. The VLAN priority TAG remains unchanged.

This article explains how to configure QoS CoS trust mode on the 200/300 Series Managed Switches.

Default Cos to Queue mapping Table

802.1p Values

Queue

Notes

0

1

Background

1

1

Best Effort

2

2

Excellent Effort

3

3

Critical Application LSV phone SIP

4

3

Video

5

4

Voice Cisco IP phone default

6

4

Interwork Control LSV phone RTP

7

4

Network Control

Applicable Devices

• SF/SG 200 and SF/SG 300 Series Managed Switches

Software Version

• v1.2.7.76

QoS Configuration

QoS Properties

The QoS Properties page is used to enable QoS globally and configure a QoS trust mode.

Step 1. Log in to the web configuration utility and choose Quality of Service > General > QoS Properties. The QoS Properties page opens:

Step 2. Check Enable in the QoS Mode field to enable QoS on the switch.

Step 3. Click the CoS/802.1p radio button in the Trust Mode field to configure the trust mode as CoS/802.1p. The trust mode determines how network traffic will be sent to queues.

Step 4. Click Apply. The QoS trust mode is configured.

Step 5. Scroll down to the QoS Configuration Table and choose an interface from the Interface Type drop-down list.

Step 6. Click Go to bring up a list of ports or LAGs.

Step 7. Click the radio button of the port or LAG you want to edit.

Step 8. Click Edit to configure the specified interface. The Edit Interface CoS Configuration window appears.

Step 9. (Optional) Click the radio button that corresponds to the desired Interface.

• Port — From the Port drop-down list choose the port to configure. This will only affect the single port chosen.

• LAG — From the LAG drop-down list choose the LAG to configure. This will affect the group of ports defined in the LAG configuration.

Step 10. From the Default CoS drop-down list choose a default CoS value for incoming packets that do no have a VLAN tag. The 0 CoS value has the lowest priority while 7 has the highest priority.

Step 11. Click Apply. The Default CoS value for the interface is configured.

QoS Interface Settings

The QoS Interface Settings page is used to enable QoS on a per port basis.

Step 1. Log in to the web configuration utility and choose Quality of Service > General > Interface Settings. The Interface Settings page opens:

Step 2. Choose an interface from the Interface Type drop-down list.

Step 3. Click Go to bring up a list of ports or LAGs.

Step 4. Click the radio button of the port or LAG you want to edit.

Step 5. Click Edit to configure the specified interface. The Edit QoS Interface Settings window appears.

Step 6. (Optional) Click the radio button that corresponds to the desired Interface.

• Port — From the Port drop-down list choose the port to configure. This will only affect the single port chosen.

• LAG — From the LAG drop-down list choose the LAG to configure. This will affect the group of ports defined in the LAG configuration.

Step 7. Check Enable in the QoS State field. This prioritizes inbound traffic on the interface based on the configured QoS trust mode. In this case, CoS/802.1p trust mode. If QoS State is disabled, all inbound traffic on the interface is mapped to the best effort queue and no prioritization takes place.

Step 8. Click Apply. The Interface Settings are configured.

QoS Queue

The Queue page is used to configure the priority of the egress queues.

Step 1. Log in to the web configuration utility and choose Quality of Service > General > Queue. The Queue page opens:

Step 2. Click the radio button that corresponds to the desired scheduling method of each queue. This determines how traffic is handled.

• Strict Priority — Egress traffic from a higher priority queue is sent first. Traffic from a lower priority queue is processed after all the higher priority queue traffic is sent.

• WRR — Weighted Round Robin (WRR) sends traffic to queues in proportion to the weight of the queue. This means that more packets are sent from a queue with a higher weight. A queue is serviced until the quota of that queue is met and then the next queue is serviced.

Step 3. If the scheduling method is configured as WRR, enter the weight value for each queue in the WRR Weight field. Queues with a higher weight are given more bandwidth. The percentage of bandwidth that is given to the queue is displayed in the % of WRR Bandwidth field.

Step 4. Click Apply. The queue settings are configured.

CoS/802.1p to Queue

The CoS/802.1p to Queue page is used to map packets with 802.1p priority tags to egress queues.

Step 1. Log in to the web configuration utility and choose Quality of Service > General > CoS/802.1p to Queue. The CoS/802.1p to Queue page opens:

The following fields display information about the egress queues.

• 802.1p — The 802.1p priority tag of ingress packets. Packets with the 802.1p tag will be mapped to the corresponding egress queue.

• Output Queue — The egress queue that is mapped to the corresponding 802.1p tag.

Note: Packets without a priority tag are given a priority tag based on the configured default CoS value on the QoS Properties page.

Step 2. From the Output Queue drop-down list, choose the output queue to which packets, with the corresponding 802.1 priority tag, will be sent.

Note: Click Restore Defaults to restore the default CoS to queue configuration.

Step 3. Click Apply. The CoS to queue settings are configured.

Bandwidth

Bandwidth is the transmission rate of packets on an interface. The Bandwidth page is used to configure ingress and egress bandwidth on a per interface basis.

Step 1. Log in to the web configuration utility and choose Quality of Service > General > Bandwidth. The Bandwidth page opens:

Step 2. Choose an interface from the Interface Type drop-down list.

Step 3. Click Go to bring up a list of ports or LAGs.

Step 4. Click the radio button of the port or LAG you want to edit.

Step 5. Click Edit to configure the specified interface. The Edit QoS Interface Settings window appears.

Step 6. (Optional) Click the radio button that corresponds to the desired Interface.

• Port — From the Port drop-down list choose the port to configure. This will only affect the single port chosen.

• LAG — From the LAG drop-down list choose the LAG to configure. This will affect the group of ports defined in the LAG configuration.

Step 7. (Optional) Check Enable in the Ingress Rate Limit field to configure ingress bandwidth on the interface. This is the bandwidth for packets that are received on the interface. If this option is disabled the default value of 100 kilobits is used.

Step 8. If Ingress Rate Limit is enabled, enter the bandwidth allowed for the ingress of the interface.

Step 9. (Optional) Check Enable in the Egress Shaping Rate field to configure egress bandwidth on the interface. This is the bandwidth for packets that are transmitted from the interface. If this option is disabled the default value of 64 kilobits is used.

Step 10. If Egress Shaping Rate is enabled, enter the following fields.

• Committed Information Rate (CIR) — The bandwidth allowed for the egress of the interface.

• Committed Burst Size (CBS) — The amount of data that can be sent in a burst on the interface.

Step 11. Click Apply. The bandwidth settings are configured.

Egress Shaping Per Queue

The Egress Shaping Per Queue page is used to configure egress bandwidth on a per queue basis.

Step 1. Log in to the web configuration utility and choose Quality of Service > General > Egress Shaping Per Queue. The Egress Shaping Per Queue page opens:

Step 2. Choose an interface from the Interface Type drop-down list.

Step 3. Click Go to bring up a list of ports or LAGs.

Step 4. Click the radio button of the port or LAG you want to edit.

Step 5. Click Edit to configure the specified interface. The Edit Egress Shaping Per Queue window appears.

Step 6. (Optional) Click the radio button that corresponds to the desired Interface.

• Port — From the Port drop-down list choose the port to configure. This will only affect the single port chosen.

• LAG — From the LAG drop-down list choose the LAG to configure. This will affect the group of ports defined in the LAG configuration.

Step 7. Check Enable in the Queue field to configure the egress bandwidth of the queue.

Step 8. If the Queue field is enabled, enter the following fields.

• Committed Information Rate (CIR) — The bandwidth allowed for the egress of the interface. The default value is 64 kilobits per second.

• Committed Burst Size (CBS) — The amount of data that can be sent in a burst on the interface. The default value is 128000 bytes.

Step 9. Click Apply. The egress shaping per queue settings are configured.