This article explains how the SRX device processes new packets after an existing session has timed out.

The behavior depends on the type of traffic and the firewall settings. For instance, with UDP traffic, new packets will initiate a new session after the current session expires. In the case of TCP traffic, the outcome depends on the status of SYN-check and SEQ-check settings. If these checks are enabled, the traffic will be dropped. If they are disabled, a new session will be established.