Hi, I'm considering using Varnish in front of CalendarServer to cache iCalendar data for calendar-collections. As far as I can see the CTag is necessary because an ETag on a collection is not required by WebDAV to change when a member changes content. However... with the current calendarserver behavior returning rolled up iCalendar when doing a GET it seems that the Etag must change due to RFC4917 9,4 and RFC2616 13.3.4 (ETag must change when GET value changes). Also, it seems like this is enforced by CalendarServer storing the CTag in an attribute of the calendar collection - which in turn make Twisted update the ETag based on the modification time of the inode. So, am I right in concluding that CTag and ETag on a calendar collection will currently always be in sync. - partly because of the implementation detail of the on-disk storage that ctag is in an extended attribute. - and partly because it's an implicit requirement when GET on a calendar-collection returnes rolled up iCalendar ?? Also... Are there any special reason for not returning CTag in a HTTP header? /Peter