Symmetric NAT Traversal

Tmedia supports passive NAT Traversal that addresses the need of peer VoIP endpoint having a private network address. This endpoint device is situated behind a NAT (Network Address Translation) device, e.g. Firewall, while the Tmedia VoIP port has a public IP address. For the passive mode, TMG detects the received RTP packet's source IP address and port. In response, Tmedia uses this source IP address and port as the packet destination for RTP.

TelcoBridges and Passive NAT Traversal

Tmedia supports passive NAT Traversal starting from Tmedia release 2.6.31.

Passive NAT traversal means the remote endpoint is behind a NAT.

This is also called Remote NAT traversal or far-end NAT traversal.

TelcoBridges and Active NAT Traversal

Tmedia supports active NAT Traversal starting from Tmedia release 2.7.

Active NAT traversal means the TMG endpoint is behind a NAT.

This is also called Local NAT traversal or near-end NAT traversal.

Typical Use Case

Important Reminders

• All devices in the path must support symmetric RTP/RTCP: RFC 4961

Configuration

• Configure NAT Traversal for version 2.9
• Configure NAT Traversal for version 2.8
• Toolpack v2.7: SIP Advance Features
• Toolpack v2.6: SIP Advance Features

External Sources

• RFC 4961 Symmetric RTP / RTP Control Protocol (RTCP)