JDK 6 comes bundled with JAX-WS RI. GlassFish Metro is a web services stack that includes JAX-WS RI among other components like JAXB RI or StAX, but it's a separate project. So you would have to download the Metro jars if you want to use it.
JDK 6 started including JAX-WS RI 2.0 and since update 4 it includes JAX-WS RI 2.1.
You can find the JAX-WS RI version your JDK is using with the wsimport command: wsimport -version
.