CUPS 2.2rc1 is the first release candidate of CUPS 2.2.0. A detailed list of changes can be found in the change log included in the download.
CUPS 2.2rc1 is available from:
Copyright © 2007-2016 Apple Inc. All rights reserved. CUPS, the CUPS logo, and macOS are trademarks of Apple Inc. All other trademarks are the property of their respective owners.