This read-write INTEGER flag, with no source description but named identically to swanPPPActive, most likely indicates or controls whether PPP (Point-to-Point Protocol) is active on this UART serial port. An admin toggles this to enable PPP encapsulation for IP traffic over the serial connection rather than a raw or other framing. Setting suartPPPActive to true(1) would be done when connecting this serial port to a peer via a PPP link rather than a simple async terminal connection.