Each section can be a separate file, or even split to separate files.
The only issue seems to be that it's not supported in epub2.
It is supported in AZW/KF8 according to Amazon's HTML tag guide for Kindle generation.
I have a suspicion that it is possible in epub2 by having all the files in the TOC but messing with the playorder? Possibly actual epub renderers would baulk
Code:
<navPoint id="u5As8H7DXtuyEsfIbRU5kJ5" playOrder="18">
<navLabel>
<text>Chapter 18: Recognition</text>
</navLabel>
<content src="index_split_021.html"/>
</navPoint>
Typically Calibre breaks the source into separate HTML files by Chapter or Heading or source TOC.
There is no link at all between the chapters in the files. So next & prior page are within a file except when it's the next TOC or previous TOC entry.
So the epub renderer uses the TOC to get to the next page at the end of a chapter. There is also the Manifest, but it's just a link of files.
Presumably the Playorder and/or the order of TOC entries decides what happens with page next at the end of a chapter?