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When a network session is transiting a firewall, the firewall may close sessions it deems idle - ones which have not sent packets for some time. At UWaterloo, the default firewall configurations have a 30 minute timeout for TCP sessions - long enough for most purposes, but people with SSH sessions People are most likely to notice this behaviour on long-lasting SSH sessions, and may find that their connection is terminated earlier than they would like. This can be fixed with a configuration change on the client side, which will cause it to send a "keepalive" packet at fixed intervals. IST recommends a 15 minute keepalive.
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