Using the migrate_d2d_ui module to migrate Drupal 6 cck content to Drupal 7, I previously asked "Do I need to create CCK content types before migrate_d2d_ui?" and presume the answer is "Yes" based on my personal experience.
This follow-up question is whether it is necessary to also build out all the cck fields for content types containing cck fields. I am hoping the answer is "No" as this would imply a lot of work.
It would seem that migrate_d2d_ should be smart enough to recognize the D6 cck fields and create the corresponding D7 fields.