Earths motion through the CMB

If there is no universal reference frame (according to Special Relativity)
how can we measure the motion of the earth relative to the Cosmic Background Radiation (CMB) which would seem to act as a universal frame of reference.

Three comments (off the top of my head) -

I don't see how the CMB can act as a reference frame. Where is its north pole, for instance?

As far as relativity is concerned, being stationary with respect to the CMB is no more special than being stationary with respect to the Earth.

There is a difference between a universal reference frame (which cannot exist), and a reference frame that is universally accessible (which, I think, could exist).

I'm not an astrophysicist, but I think the above three comments are consistent with the science.

Chris.

I remember some years ago reading a book by one of the original gurus on CMB, he was also involved in the COBE project. Maybe some one can remember the title of the book?

Afterglow of creation by Marcus Chown perhaps?

Albert,
Thanks but I think it may have been 'Wrinkles in Time'

By the way for anyone interested the original problem leading to the discovery was excess noise in a radio dish receiver. At the time the problem was thought to originate from pidgeon droppings on the dish. Hence the saying 'S*** Happens!'