SGOS 5.x by default will only send a keep-alive notice at a longer interval. This may caused some application to break due to timing out, or the firewall dropping the connection due to a time out.
SGOS 22.214.171.124 and above has the ability to overwrite this through the following CLI command:
ProxySG# config t
ProxySG#(config) tcp-ip tcp-keepalive-timeout N
Replace N with the preferred timeout value in second