JAX-WS is indeed part of Java SE 6. Its classes can be found along with all the other JRE classes; in my Java installation it's all in a file called "classes.jar", but I suppose that could be different for other JREs.
If you intend to use those classes independently of the JRE they're distributed with you're probably better off downloading the JAX-WS RI - which has those jar files you mentioned. Be aware that the JAX-WS RI is most likely newer than what's distributed with the JRE, so using them together may be problematic.