QoS

Quality of service (QoS) provides the ability to set particular priorities for different applications, users, or data flows.

QoS involves the following elements:

• Classification is the process of determining the priority of a packet. This can be as simple as trusting the QoS markings in the packet header when it is received and so accept the packet. Alternatively, it can hinge on criteria (such as incoming port, VLAN, or service) that are defined by the network administrator.
• Marking involves setting bits in the packet header to indicate the priority of this packet.
• Queuing involves defining priority queues to ensure that packets marked as high priority take precedence over those marked as lower priority. If network congestion becomes so severe that packet drops are inevitable, the queuing process will also select the packets to drop.

The FortiSwitch unit supports the following QoS configuration capabilities:

• Mapping the IEEE 802.1p and layer-3 QoS values (Differentiated Services and IP Precedence) to an outbound QoS queue number.
• Providing eight egress queues on each port.
• Policing the maximum data rate of egress traffic on the interface.

NOTE: There are some differences in QoS configuration on the FS-108E, FS-108E-POE, FS-108E-FPOE, FS-124E, FS-124E-POE, FS-124E-FPOE, FS-148E, FS-148E-POE, FS-124F, FS-124F-POE, FS-124F-FPOE, FS-148F, FS-148F-POE, and FS-148F-FPOE models:

• You can configure only one dot1p-map per switch.
• You can configure only one ip-dscp-map per switch.
• You cannot set min-rate, min-rate-percent, drop-policy, or wred-slope under the config switch qos qos-policy command.
• Under the config switch qos qos-policy command, the switch rounds the max-rate value to the nearest multiple of 16 internally. If the rounding result is 0, max-rate is disabled internally.
• You cannot configure priority tagging on outgoing frames (egress-pri-tagging) under the config switch qos dot1p-map command.
• You can configure only one QoS drop policy per switch. You can configure the QoS drop policy under the config switch global command. You can specify random early detection (RED) with the set qos-drop-policy random-early-detection command on the FS-108E, FS-124E, FS-148E, FS-124F, and FS-148F models.
• You can set the QoS RED/WRED drop probability (qos-red-probability) under the config switch global command. The FS-108E, FS-108E-POE, FS-108E-FPOE, FS-124E, FS-124E-POE, and FS-124E-FPOE models support 0-100 percent. The FS-148E, FS-148E-POE, FS-148E-FPOE, FS-124F, FS-124F-POE, FS-124F-FPOE, FS-148F, FS-148F-POE, and FS-148F-FPOE models support 0-25 percent.
• Adaptive or active RED (ARED) and robust RED (RRED) are not supported.

This section covers the following topics:

• Classification
• Marking
• Queuing
• Determining the egress queue
• Configuring FortiSwitch QoS
• Checking the QoS statistics
• Resetting and restoring QoS counters
• Configuring security checks
• Cut-through switching mode
• Enabling packet forwarding
• Configuring auto topology