How does the Session Director detects if one registered endpoint is behind NAT and triggers HNT

Hi guys,

 

As per previous posts I've made I'm posting this as I still see this question from partners and customers in some deployments. Although for the experience users in the community this may be not new... Hopefully it will be useful for someone.

 

I'm talking about Access-Scenario where Remote EPs register into the core PBX(Registrar) through Acme Packet SBC. Not all the EPs are behind NAT, but those who are need a "special" treatment by our SD.

 

Extracted from Net-Net 4000 ACLI Configuration Guide:

 

SIP HNT is a technique the Net-Net SBC uses to provide persistent reachability for SIP UAs located in private Local Area Networks (LANs) behind Nat/firewall devices. It relies on frequent, persistent messaging to ensure that the binding on the intermediary NAT device is not torn down because of inactivity. HNT does not require support for the NAT in the SIP endpoint.