It has some advantages in that derivatives of the BSD networking code turns up all over the place, so it can be useful to know your way around it - and the Rich

It has some advantages in that derivatives of the BSD networking code turns up all over the place, so it can be useful to know your way around it - and the Richard Stevens TCP/IP illustrated books are a very helpful guide. But I wouldn’t deliberately specialize: get a job working with BSD or Linux, and learn by doing; but keep an eye on the other kernels to see how they do it, and to get a broader basis for your skills.