[core] Strictness of RFC7959

[Christian Amsüss <[e-mail]>]

Hello block-wise authors,
hello CoRE,

I am uncertain about the behavior RFC7959 actually prescribes to
servers: How liberal is it for servers about which blocks can be acted
on together (or when to send 4.08 Request Entity Incomplete)?

The last paragraph of section 2.4 implies that the Cache-Key[1] is what
messages are grouped by (which makes sense and would make the
specification of Request-Tag much shorter), but nowhere else is the
cache key mentioned in the document.

What is the expected behavior of a server (or let's say proxy, as the
proxy needs to do block-wise too but doesn't need to know elective
options) in presence of similar-but-not-quite-alike messages from the
same source that could be a blockwise operation? Group by URI? By
Cach-Key? By all options unless it knows it's irrelevant from the
option's description? May the server choose depending on the
application?

And can I rely on that behavior in echo-request-tag?

Best regards
Christian

[1]: Actually Cache-Key without request body after RFC7252 errata, as
that body is not represented in Block2 phase when combining.

-- 
Reflection. Surprise. Terror. For the future.
  -- Kosh