The type of physical devices that this session is attached
to for the local end of the tunnel. The meaning of each
device type is explained below:
other: Any device that has not been
defined.
asyncInternalModem: Modem Pool device of an access
server.
async: A regular asynchronous serial
interface.
sync: A regular synchronous serial
interface.
bchan: An ISDN call.
xdsl: xDSL interface.
cable: cable modem interface.