Disable SIP ALG
Improve the Quality of Service on your VoIP calls by disabling the SIP Application Layer Gateway.
One way to ensure Quality of Service (QoS) is to enable QoS settings.
Quality of Service (QoS) settings allow you to prioritize the voice calls made through your data network and prevent other applications from interfering with sound quality.
This function allows you to prioritize your internet connection’s data, and set it so it makes sure you always have space for VoIP calls. In this case, QoS slows other applications in use at the same time.
Disable SIP Application Layer Gateway (ALG)
SIP Application Layer Gateway (ALG) is there for preventing and modifying some of the issues that are caused by router firewalls via the inspection of VoIP traffic.
Most routers will have SIP ALG turned on by default. The problem with SIP ALG is that it sometimes modifies SIP packets in ways that corrupt them. This creates SIP packets that are unreadable and can cause issues in regard to registering incoming calls. If your business is experiencing such problems, try disabling SIP ALG in your router.