1. A method in a first wireless station of establishing a connection with a second wireless station, comprising:generating a frame including a capabilities element having:
a capabilities element length field appended to a capabilities identifier field, the capabilities element length field containing an element length value indicating the length of the capabilities element;
a core capabilities field having a fixed length, the core capabilities field appended after the capabilities element length field and containing a predefined sequence of core subfields having respective predefined lengths; the core subfields containing respective first core values defining core capabilities of the first wireless station; and
at least one extended capability field having a variable length, the at least one extended capability field containing:
an extended capability identifier subfield containing an identifier of one of a plurality of predefined extended capabilities;
an extended capability length subfield containing an extended capability length value; and
an extended capability payload subfield having a length equal to the extended capability length value; the payload subfield containing a first extended value defining an extended capability of the first wireless station; and
responsive to generating the frame, transmitting the frame.