Yes, a CDR is required for skill assessment. A CDR stands for competency demonstration report, which is required to demonstrate one's (who is seeking a skilled Australian migration visa) engineering knowledge and skills in the nominated occupational category (professional engineer, engineering technologist, engineering associate, or engineering manager). 

The assessor, Engineers Australia holds the CDR Skills Assessment to assess applicants' knowledge and skills they have gained through their academic education and work experience. Based on the CDR competencies, Engineers Australia decides whom to approve or not. Call CDR Australia to know more.