Far End NAT Traversal (FENT)

The Internet Gate can enable SIP connectivity for remote users that use NAT devices without SIP support. It can adapt to characteristics of remote NAT devices.

Using FENT you can allow people behind non-SIP-capable NAT firewalls to register on your Internet Gate's SIP server.

:!: You might need to purchase a license to be able to use FENT in your unit.

You configure FENT on the Advanced SIP Settings page.

FENT sends keep-alive packets to remote SIP clients behind non-SIP-capable firewalls to keep the SIP communications channel open to them. The keep-alive packets are SIP messages that are sent more often than the remote firewall's timeout.

Far End NAT Traversal

There are two methods used for keep-alive:

  • REGISTER: by lowering the REGISTER expiration timeout the SIP client behind the remote NAT will REGISTER often enough for keeping the connection open.
  • OPTIONS: the Internet Gate will send SIP OPTIONS messages at regular intervals to the client behind the remote NAT, keeping the connection open.

You can enable both methods, then the REGISTER method is tried first and if it does not work properly the OPTIONS method is used.

Shortest media path

By enabling Detect endpoints behind same NAT you allow SIP clients behind the same remote NAT making local calls to each other to send media locally between them on that LAN.

media on remote LAN

sip/fent.txt · Last modified: 2010/11/09 11:49 by tibor
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