If you have not taken CS 571 (or its equivalent at another university), you cannot take CS 707.
If you have taken CS 571 (or its equivalent) and a class on computer networks (CS 656 or its equivalent) but have not taken CS 706 AND you have a strong background in concurrent programming AND are a strong C/C++/Java programmer, please attend the first lecture of CS 707 in January. I may allow additional students into the class depending on the usual factors - background in concurrent programming, classroom size, etc.