plot explanation - Where did Tron Legacy take place?

In the movie
Tron
Legacy, Sam Flynn finds his fathers computer still running in the old arcade.
After typing on the keyboard he triggers the digitizer and is transported to the
grid.

Where is the grid?

In
the first movie the Tron universe is control by master control who states he has access
to the pentagon and wants language files for Asia. So it's clear in the first movie that
the grid is part of the world network, or at least has access to
it.

In Tron Legacy it seems very isolated. Did Keven Flynn
build a private network in the arcade where he created the grid, and if so, where in the
movie is this clarified? If it was an isolated network, then how could CLU send a
message to Alan's pager?

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class="normal">Answer

The Grid of the
original Tron was in Encom's servers. Those servers had network
access to the outside world, which is how the MCP was trying to access the Pentagon's
computers.

In Tron Legacy, Flynn setup
a server in the hidden room in his arcade. Next to the touchscreen that Sam uses to
interact with the server, are large cylinders, this is the bulk of the server. This
server must have network or phone connections, which is how CLU sent the page. At the
end of the film, Sam takes what is presumably a backup or copy of this server's storage
with him as he leaves the arcade.