Subject: qpack: no need to ack refless header blocks

From: Dmitri Tikhonov <[email-masked]>
Date: Fri, 20 Jul 2018 14:33:19 -0400

There is no need to acknowledge header blocks that do not reference
the dynamic table.  These acknowledgements do not contain any
information useful to the encoder.  I propose that the draft be
modified to state that

    A Header Acknowledgement is emitted only if the header block
    references the dynamic table (only when Largest Reference in
    the Header Data Prefix is zero).

This a) saves bytes and b) allows the encoder to drop state for
such header blocks as soon as they are encoded.

  - Dmitri.