3.7.2.3 KeepAlive Timer

HTTP Encapsulation protocols do not support a native KeepAlive timer, but rather rely on the encapsulated protocol to provide a KeepAlive mechanism. Encapsulated protocols SHOULD implement their own KeepAlive mechanisms. The SSTP protocol provides its own KeepAlive mechanism using the SSTP_NOOP command<54>. The default client KeepAlive timeout value is 45 seconds. KeepAlive timers with short intervals SHOULD be used to interoperate with firewalls and proxies. The maximum KeepAlive value is limited by proxy implementations. The KeepAlive timer event processing is handled as specified in section 3.7.6.3.