If that error message doesn't come down the pipe, your browser might spend a minute trying to connect in vain before giving up and switching over to IPv4 by itself.
This typically results in cleaner, smoother, less error-prone development, because programmers aren't constantly switching between a relational-mindset and an object-oriented one.
The switching function includes the integral of tracking error to avoid assuming that the derivative of desired signal must be known in conventional sliding mode variable structure control.