Technical Tip: Enabling Quality of Service (QoS) for VoIP Traffic

Quality of Service (QoS) is an essential networking feature that prioritizes and efficiently manages network resources for specific applications and services. VoIP (Voice over Internet Protocol) services, such as communication using SIP (Session Initiation Protocol), depend on low latency and consistent network performance. FortiGate firewalls offer robust QoS capabilities to optimize network traffic and deliver a seamless VoIP experience.

Configure the QoS profile for VoIP traffic:

config firewall shaper traffic-shaper
    edit "VoIP QoS"
        set guaranteed-bandwidth 200
        set maximum-bandwidth 200
        set bandwidth-unit mbps
        set diffserv enable
        set diffservcode 101110

    next
end

The details of Telephony Differentiated Services Code Point (DSCP) are explained in RFC3246.

More about DSCP in Wikipedia. Also refer to this Technical Tip: Differentiated Services Code Point (DSCP) marking.

Applying QoS policy in the firewall policy can be done only on CLI.

config firewall policy
    edit 1
        set name "VOIP_QoS"
        set srcintf "port1"
        set dstintf "port2"
        set action accept
        set srcaddr "all"
        set dstaddr "all"
        set schedule "always"
        set service "SIP"
        set logtraffic all
        set nat enable
        set traffic-shaper "VoIP QoS"
        set traffic-shaper-reverse "VoIP QoS"
    next
end

Once it is configured it can be modified in the GUI.

Related document:

Admin Guide: Configuring traffic class IDs