Tests that fail due to server problems

We have some tests (for encrypted-media) which rely on a 3rd party server.
Presently, if that server fails then the tests report TIMEOUT, which is
then indistinguishable (for some of the tests) from certain kinds of test
failure (for example, video was expected to start but never did).

What is the appropriate result when the inability to complete the test is
due to such a 3rd party dependency, rather than a problem with the
implementation under test ? Should this be NOTRUN ? How do we trigger this ?

...Mark