Subject: Issue #171: ACK Frame Proposal (Low Priority)

From: James M Snell <[email-masked]>
Date: Tue, 9 Jul 2013 09:42:01 -0700

https://github.com/http2/http2-spec/issues/171

This one is low priority, just getting the proposal documented for
later discussion once we're past the August interop...

Essentially: Introduces a new ACK frame with a two step flow...

Sender: Sends initial ACK frame, followed by a sequence of Frames,
followed by a final ACK frame that includes a hash. Peer would respond
with an ACK frame with it's own hash of the same sequence of frames.

This would serve several use cases:

1. Sending a SETTINGS frame bookmarked by ACK frames allows
acknowledgement of new SETTINGS (e.g. for header table resizing as
discussed at the face to face)

2. Sending a WINDOW_UPDATE frame bookmarked by ACK frames allows
acknowledge of flow control changes

3. Sending a sequence of DATA frames bookmarked by ACK frames allows
reliable, fail-fast check of data (a particularly important
application use case for me personally but not a major priority just
yet)

Anyway, not a major priority at this point so feel free to file this
one away for later :-)