Not to disagree, or even to try to expound a sense of what the universe "is," the word "infinite" can be applied to mass as well as to length/distance. I don't think a measurement of the background microwave radiation allows one to conclude the mass of the universe is infinite.
Just because the boundaries are beyond our ability to perceive doesn't make them infinite.
Speaking of perception, our perception of time is RULED like an iron fist by merely the earth's shadow. That is our ruler. A shadow.