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The SIP standard defines the payload range for DTMF tones. Some call
managers do not accept all of the payload types, select the supported payload
type in this setting.
Lastly, some call managers require RFC 2543 for on-hold media. For these call
managers, change the Media on-hold message to that value.
Transport
The Transport section of the management interface allows configuring specific
transport methods based on call manager settings and network and firewall
configurations.
If QoS is enabled, SIP and media packages are tagged to indicate QoS
requirements.
Typically SIP messages are sent using UDP (if available). By checking Enable
TCP transport protocol these messages are sent using TCP instead.