- From: Roberto Peon <grmocg@gmail.com>
- Date: Tue, 21 Oct 2014 00:01:19 -0700
- To: Mark Nottingham <mnot@mnot.net>
- Cc: Willy Tarreau <w@1wt.eu>, RUELLAN Herve <Herve.Ruellan@crf.canon.fr>, Amos Jeffries <squid3@treenet.co.nz>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
- Message-ID: <CAP+FsNdOHVj=YTE35Vj7mbED0OKghd-mpnFZSMcZNBM3JybJDg@mail.gmail.com>
While I prefer the indexing scheme of the previous draft, this proposal would be better than what is currently drafted. -=R On Mon, Oct 20, 2014 at 4:29 PM, Mark Nottingham <mnot@mnot.net> wrote: > Thanks for that, Willy. > > At the risk of repeating myself -- making this kind of change (one that > does not impact security or interoperability) at this stage in our process > needs to have *strong* consensus. > > What do others think? > > Regards, > > > > On 21 Oct 2014, at 3:53 am, Willy Tarreau <w@1wt.eu> wrote: > > > > Hi Mark, > > > > On Fri, Oct 17, 2014 at 10:23:35AM +1100, Mark Nottingham wrote: > >> I think we need to see a proposal here if we?re going to take this > seriously > >> ? i.e., either fairly complete text or a pull request. > > > > Here's the change I'm proposing. It's a diff against the text version > because > > it was easier for me to produce this, and it's easily readable by > everyone here. > > > > The diff looks like what's below, I think it addresses what was > discussed in > > a way that is pretty straightforward since there's no more the need to > explain > > the split between the two tables. > > > > I have not changed anything else eventhough I'm seeing room for > improvement > > (eg: swapping encoding prefix of "literal without indexing" with the one > > for "dynamic table size update" and gain one bit of encoding per header). > > > > Anyone would please review and/or comment ? > > > > Thanks, > > Willy > > > > ------------ > > > > diff --git a/compression.txt b/compression.txt > > index a4c8a40..56b2ea0 100644 > > --- a/compression.txt > > +++ b/compression.txt > > @@ -309,9 +309,6 @@ Internet-Draft HPACK > October 2014 > > (see Section 2.3.2) is dynamic and can be used by the encoder to > > index header fields repeated in the encoded header lists. > > > > - These two tables are combined into a single address space for > > - defining index values (see Section 2.3.3). > > - > > 2.3.1. Static Table > > > > The static table consists of a predefined static list of header > > @@ -348,37 +345,21 @@ Internet-Draft HPACK > October 2014 > > > > 2.3.3. Index Address Space > > > > - The static table and the dynamic table are combined into a single > > - index address space. > > - > > - Indices between 1 and the length of the static table (inclusive) > > - refer to elements in the static table (see Section 2.3.1). > > - > > + Both the static and the dynamic tables are indexed starting at 1. > > Indices strictly greater than the length of the static table refer to > > elements in the dynamic table (see Section 2.3.2). The length of the > > static table is subtracted to find the index into the dynamic table. > > > > - Indices strictly greater than the sum of the lengths of both tables > > - MUST be treated as a decoding error. > > + Static table indices strictly greater than the length of the table as > > + defined in Appendix A MUST be treated as a decoding error. Dynamic > table > > + indices strictly greater than the length of the dynamic table MUST be > > + treated as a decoding error. > > > > - For a static table size of s and a dynamic table size of k, the > > - following diagram shows the entire valid index address space. > > - > > - <---------- Index Address Space ----------> > > - <-- Static Table --> <-- Dynamic Table --> > > - +---+-----------+---+ +---+-----------+---+ > > - | 1 | ... | s | |s+1| ... |s+k| > > - +---+-----------+---+ +---+-----------+---+ > > - ^ | > > - | V > > - Insertion Point Dropping Point > > - > > - Figure 1: Index Address Space > > > > 2.4. Header Field Representation > > > > An encoded header field can be represented either as a literal or as > > - an index. > > + an index in one of the tables. > > > > A literal representation defines a header field by specifying its > > name and value. The header field name can be represented literally > > @@ -740,14 +721,15 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 1 | Index (7+) | > > - +---+---------------------------+ > > + | 1 | D | Index (6+) | > > + +---+---+---+---+---+---+---+---+ > > > > Figure 5: Indexed Header Field > > > > - An indexed header field starts with the '1' 1-bit pattern, followed > > - by the index of the matching pair, represented as an integer with a > > - 7-bit prefix (see Section 5.1). > > + An indexed header field starts with the '1' 1-bit pattern, followed > by > > + the D bit indicating if the index references the static table (0) or > > + the dynamic table (1), and the index of the matching pair, > represented > > + as an integer with a 6-bit prefix (see Section 5.1). > > > > The index value of 0 is not used. It MUST be treated as a decoding > > error if found in an indexed header field representation. > > @@ -788,8 +770,8 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 0 | 1 | Index (6+) | > > - +---+---+-----------------------+ > > + | 0 | 1 | D | Index (5+) | > > + +---+---+---+-------------------+ > > | H | Value Length (7+) | > > +---+---------------------------+ > > | Value String (Length octets) | > > @@ -800,8 +782,8 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 0 | 1 | 0 | > > - +---+---+-----------------------+ > > + | 0 | 1 | 0 | 0 | > > + +---+---+---+-------------------+ > > | H | Name Length (7+) | > > +---+---------------------------+ > > | Name String (Length octets) | > > @@ -819,11 +801,13 @@ Internet-Draft HPACK > October 2014 > > If the header field name matches the header field name of an entry > > stored in the static table or the dynamic table, the header field > > name can be represented using the index of that entry. In this case, > > - the index of the entry is represented as an integer with a 6-bit > > - prefix (see Section 5.1). This value is always non-zero. > > + the index of the entry is represented as the D bit indicating if the > > + index references the static table (0) or the dynamic table (1), > > + followed by an integer with a 5-bit prefix (see Section 5.1). This > > + value is always non-zero. > > > > Otherwise, the header field name is represented as a literal string > > - (see Section 5.2). A value 0 is used in place of the 6-bit index, > > + (see Section 5.2). A value 0 is used in place of the 5-bit index, > > followed by the header field name. > > > > Either form of header field name representation is followed by the > > @@ -844,8 +828,8 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 0 | 0 | 0 | 0 | Index (4+) | > > - +---+---+-----------------------+ > > + | 0 | 0 | 0 | 0 | D | Index (3+)| > > + +---+---+---+---+---+-----------+ > > | H | Value Length (7+) | > > +---+---------------------------+ > > | Value String (Length octets) | > > @@ -855,8 +839,8 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 0 | 0 | 0 | 0 | 0 | > > - +---+---+-----------------------+ > > + | 0 | 0 | 0 | 0 | 0 | 0 | > > + +---+---+---+---+---+-----------+ > > | H | Name Length (7+) | > > +---+---------------------------+ > > | Name String (Length octets) | > > @@ -874,11 +858,13 @@ Internet-Draft HPACK > October 2014 > > If the header field name matches the header field name of an entry > > stored in the static table or the dynamic table, the header field > > name can be represented using the index of that entry. In this case, > > - the index of the entry is represented as an integer with a 4-bit > > - prefix (see Section 5.1). This value is always non-zero. > > + the index of the entry is represented as the D bit indicating if the > > + index references the static table (0) or the dynamic table (1), > > + followed by as an integer with a 3-bit prefix (see Section 5.1). > > + This value is always non-zero. > > > > Otherwise, the header field name is represented as a literal string > > - (see Section 5.2). A value 0 is used in place of the 4-bit index, > > + (see Section 5.2). A value 0 is used in place of the 3-bit index, > > followed by the header field name. > > > > Either form of header field name representation is followed by the > > @@ -900,8 +886,8 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 0 | 0 | 0 | 1 | Index (4+) | > > - +---+---+-----------------------+ > > + | 0 | 0 | 0 | 1 | D | Index (3+)| > > + +---+---+---+---+---+-----------+ > > | H | Value Length (7+) | > > +---+---------------------------+ > > | Value String (Length octets) | > > @@ -911,8 +897,8 @@ Internet-Draft HPACK > October 2014 > > > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > - | 0 | 0 | 0 | 1 | 0 | > > - +---+---+-----------------------+ > > + | 0 | 0 | 0 | 1 | 0 | 0 | > > + +---+---+---+---+---+-----------+ > > | H | Name Length (7+) | > > +---+---------------------------+ > > | Name String (Length octets) | > > @@ -957,7 +943,7 @@ Internet-Draft HPACK > October 2014 > > 0 1 2 3 4 5 6 7 > > +---+---+---+---+---+---+---+---+ > > | 0 | 0 | 1 | Max size (5+) | > > - +---+---------------------------+ > > + +---+---+---+-------------------+ > > > > Figure 12: Maximum Dynamic Table Size Change > > > > ------------ > > -- > Mark Nottingham https://www.mnot.net/ > > >
Received on Tuesday, 21 October 2014 07:01:48 UTC