timed global protocol ping_pong(role A, role B)
{
    rec PP
    {
        choice at A
        {
            ping(()) from A to B within [0;1] using a and resetting ();

            pong(()) from B to A within [0;1] using a and resetting ();

            continue PP within [0;1] using a and resetting ();
        }
        or
        {
            stop() from A to B within [0;1] using a and resetting ();
        }
    }
}