Re: Call for Consensus: Remove "reference set" from HPACK (to address #552)

On Mon, Jul 14, 2014 at 4:35 PM, Kazu Yamamoto <kazu@iij.ad.jp> wrote:

> >> I think that the index for static table and one for dynamic table can
> >> be separated. If we take such a design, HPACK implementation would get
> >> simpler.
> >
> > Could you elaborate your idea?
> > I guess you have new index opcode for static table but it is not
> sufficient.
>
> What I thinking is to use two tables separately.
>
>           <-- Header  Table -->  <-- Static  Table -->
>           +---+-----------+---+  +---+-----------+---+
>           | 1 |    ...    | k |  | 1 |    ...    | 61|
>           +---+-----------+---+  +---+-----------+---+
>           ^                   |
>           |                   V
>    Insertion Point      Dropping Point
>
> Each table has its own index. Prepare necessary operations and their
> binary format.
>
>
​More binary format means we have to reduce prefix bits, which reduces
compression efficiency. Meanwhile, static table gets smaller number, so
there is a trade off.  Actually this is orthogonal to removal of reference
set.
Personally, I don't think current scheme (static table at the end of
dynamic one) is very hard to implement or tricky. So I'm not so sure this
change is worth its cost.  If dynamic header table index gets screwed up,
we still valid index in static table but it is corrupted anyway as a whole.​

​Best regards,
Tatsuhiro Tsujikawa​




> --Kazu
>
>