RTP Proxy

Audio is normally sent direct between your customers and your carriers' equipment without passing through DUAL Softswitch. In most cases, this causes no problems. However, if your customer's device has a private IP address behind a NAT device and your carrier do not offer a NAT Penetration service, then one way audio may result, in which your customer cannot hear the audio sent by the carrier.

DUAL Softswitch includes an RTP Proxy feature whereby audio is passed through the softswitch in each direction. RTP Proxy includes a NAT Penetration feature to overcome one way audio problems. Many carriers support NAT Penetration and so this feature is not often required.

RTP Proxy is an expensive service to offer, because it increases the data transfer and processing power required of your softswitch. Subsequently, there is an addition charge for RTP Proxy based on the maximum number of proxied calls the switch will support. The Licence box in the left sidebar of the Administration System show how many proxy channels you have purchased.

You can select whether a call should be passed through an RTP Proxy at both account level and carrier level. In this way, you can minimise the number of RTP Proxy channels required. If the account or carrier's settings determine that an RTP Proxy is required, and all channels are already in use, then the call will fail.

Account level

On each account page, there is a section called Signalling options. The first option in this section is called RTP Proxy and offers five options:

•	Do not proxy Audio will not pass through an RTP Proxy, but this choice will be overridden by the destination carrier settings.

•	Proxy on NAT DUAL Softswitch can detect if a caller's device is behind a NAT router. If this state is detected, the audio for the call will pass through an RTP Proxy.

•	Proxy on T.38 Renegotiate an RTP Proxy channel if the calling and called party start T.38 fax procedures. This can be required if the terminating equipment is a Quintum Tenor gateway.

•	Proxy on NAT and T.38 Proxy Renegotiate an RTP Proxy channel if the calling and called party start T.38 fax procedures and the caller's device is behind a NAT device.

•	Always proxy Pass all audio for calls on this account through an RTP Proxy.

Carrier level

On each carrier page, there is a section called Signalling options. The first option in this section is called RTP Proxy and offers four options:

•	Do not proxy Audio will not pass through an RTP Proxy, unless overridden by the calling account's RTP Proxy settings.

•	Proxy on NAT Audio will pass through an RTP Proxy if the caller is behind a NAT router.

•	Proxy with override Pass audio through an RTP Proxy, unless the calling account's proxy setting is "Never proxy".

•	Always proxy Proxy audio for every call, regardless of the calling accounts' settings.