ISSUE-11 (Duration-header): How the UA knows the full media duration when only a fragment is served?

ISSUE-11 (Duration-header): How the UA knows the full media duration when only a fragment is served?

http://www.w3.org/2008/WebVideo/Fragments/tracker/issues/11

Raised by: Silvia Pfeiffer
On product: 

An issue with any of our existing specs with fragments (#) that just occurred to me is: if the retrieval action only retrieves the specified segment, the browser has no way to figure out the length (start/duration) of the original resource. Maybe we need to introduce additional headers that would provide for that?