NAT/Firewall traversal settings

Nokia Asha Java VoIP API v1.0 VoIP Settings has STUN protocol support for NAT traversal and NAT binding refresh features that comply with IETF RFC 3489. The NAT/Firewall traversal features enable VoIP functionality behind various types of NAT.

The STUN/Firewall settings cannot be edited from the phone’s UI, but must be provisioned by the service provider.

If the STUN server address is not configured, the terminal tries to find one with a SIP SRV query, using the Public User Identity domain of the SIP profile in use.

Additional dummy packet (CRLF) refresh cannot be enabled by provisioning. The CRLF refresh is enabled automatically if the STUN server is situated in a different address to the SIP proxy/registrar. The CRLF refresh is enabled if there is no STUN server is configured, and the user’s IP address is in a private address space, as it can then be assumed that the phone is behind a NAT.

The structure of the parameters in the Nat/Firewall Traversal Settings is shown in the following figure: