We feel your pain, which is why we created NAT Assistant. NAT Assistant is a product that enables users of Dialogic's HMP software to traverse NATs and firewalls. By intercepting SIP packets generated by HMP locally, NAT Assistant is able to correct relevant port and IP address information before it is sent out over the internet. By doing so, the remote party is able to correctly establish audio with the HMP software across the NAT.

As many users and developers would prefer to leave HMP behind a NAT for security reasons, NAT Assistant resolves a security issue that troubles many Dialogic HMP customers. Regrettably, until NAT Assistant, many developers were forced to place a computer on the open Internet with a public IP address.

Problem

When a SIP based call is initiated, critical information about the call needs to be revealed to the called party (such as the IP address and port for the RTP data stream).

Unfortunately, when the HMP software sits behind a NAT or firewall, HMP is only aware of its local LAN's IP address. It is not aware of its public IP address which is critical information needed by the called party.

Accordingly, when HMP tries to send the call related information to the called party, it incorrectly uses its local LAN address. Since the called party has no notion of HMP’s local LAN address, it cannot send RTP (voice) traffic back to HMP.

Solution

NAT Assistant intercepts the SIP packets generated by HMP. It makes appropriate corrections to the SIP message and then transmits the corrected packet to the called party. This allows the remote caller to establish its data stream with HMP!

> NAT Assistant runs between Dialogic HMP and the NAT router.

> Packaged as a Windows application that runs alongside HMP.

> Supports most NAT Routers or firewalls.