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What's the difference between NAT timeout and PDP/PDN session timeout?

Once the device attaches a data connection on the network, periods of inactivity are subject to two different timeouts.

Jakub Kubinski avatar
Written by Jakub Kubinski
Updated over a week ago

Environment

  • Onomondo Core Network

Question

  • What's the difference between NAT timeout and PDP/PDN session timeout?

Answer

Once the device attaches a data connection on the network, periods of inactivity are subject to two different timeouts:

  • PDP / PDN session timeout:

    • Default: 48 hours*

    • If the device becomes idle, the mobile network tears down the device’s entire cellular data session, releasing the IP context and breaking all connections.

    • The device must reattach to regain data connectivity.

    • This timeout only applies if the device has been idle for more than 48 hours.

  • NAT timeout:

    • Default: 15 minutes

    • During an active connection, Onomondo NAT gateway translates the private IP of the SIM to one of the public IPs specified in our documentation.

    • If the device becomes idle, the NAT gateway forgets the IP/port mapping for that connection. The next time device sends data, it might use a different public IP/port.

    • This timeout only applies if the device has been idle for more than 15 minutes.

*48 hours is the default timeout on the Onomondo network. However, local operators may have shorter timeouts in place (e.g. 12 hours).

Even when NAT mapping times out, cellular data session and IP connectivity remain active.

Cause

Timeouts exist in order to preserve network resources.

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