o the traveler, the border crossing is
invisible: no armed guards, snarling guard
dogs, passport checks, or luggage searches.
To the signals crossing this border, it might as
well not even exist; but to your network man-
agers and technicians, it’s a critical crossing. The
border is the demarcation point, or “demarc,”
between your fiber network and that of your ser-
vice provider. On the outside, the service
provider handles maintenance; on the inside,
the responsibility is all yours.