The image is protected by copyright. Unless it has been released under a license which permits reuse, or you have permission from the copyright holder (normally the artist), you cannot reproduce it without violating copyright, unless one of the exceptions to copyright applies. These vary in different countries.
Of course if you obtain permission there is no problem.
In the US "fair use" is the most common exception. Whether fair use applies is determined on a case-by-case basis, in a way highly dependent on the specific facts of the situation. Somewhat similar laws in other countries (e.g. "fair dealing") have quite different provisions.
A redrawing modeled on this image would be a derivative work of the image, and creating it would be just as much an infringement of copyright as a straight photocopy.
However, copyright does not protect facts, as opposed to words and images. If a new diagram is created, based on a factual description of Alexnet, but NOT based on this image, that would not be an infringement. (Edit A "factual description" would include facts conveyed by the original diagram.)
At least in the US, if the diagram is a 'natural and obvious" way of representing the facts, and there are no or few other ways to represent them, it would not be protected. The laws of other countries are different on this point.