Re: [quicwg/base-drafts] Use "Insert Count" rather than "Largest Reference" (#2111)

Mike Bishop <> Mon, 07 January 2019 23:42 UTC

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From: Mike Bishop <>
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Subject: Re: [quicwg/base-drafts] Use "Insert Count" rather than "Largest Reference" (#2111)
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MikeBishop approved this pull request.

In general, I think this is a good improvement.  You seem to switch from using "Base" to using "the Base" part-way through, so I'd pick one and switch the others.

> @@ -444,33 +452,40 @@ referenced by a given relative index will change while interpreting instructions
 on the encoder stream.
 ~~~~~ drawing
-    +---+---------------+-----------+
-    | n |      ...      |   d + 1   |  Absolute Index
-    + - +---------------+ - - - - - +
-    | 0 |      ...      | n - d - 1 |  Relative Index
-    +---+---------------+-----------+
-      ^                       |
-      |                       V
-Insertion Point         Dropping Point
+      +---+---------------+-----------+
+      | n |      ...      |     d     |  Absolute Index

If Absolute Index is zero-based, then the Absolute Index of the most recently inserted item would be n-1.

-Header data is prefixed with two integers, `Largest Reference` and `Base Index`.
+Each header block is prefixed with two integers.  The Required Insert Count
+encoded as an integer with an 8-bit prefix after the encoding described in

**is** encoded, presumably.

>  ~~~
-TotalNumberOfInserts is the total number of inserts into the decoder's
-dynamic table.  This encoding limits the length of the prefix on
-long-lived connections.
+Where TotalNumberOfInserts is the total number of inserts into the decoder's

I know that the actual intent is to continue the previous sentence (...using the following algorithm, where....), but this reads as a dangling phrase.  If you want the "where," maybe move the whole thing above the algorithm?

 A header block that does not reference the dynamic table can use any value for
-Base Index; setting both Largest Reference and Base Index to zero is the most
+Base; setting both Required Insert Count and Delta Base to zero is the most
 efficient encoding.

NYT but isn't it required to set a correct RIC?

> -Because frames from request streams can be delivered out of order with
-instructions on the encoder stream, relative indices are relative to the Base
-Index at the beginning of the header block (see {{header-prefix}}). The Base
-Index is an absolute index. When interpreting the rest of the frame, the entry
-identified by Base Index has a relative index of zero.  The relative indices of
-entries do not change while interpreting headers on a request or push stream.
+Unlike on the encoder stream, relative indices on push and request streams are
+relative to the Base at the beginning of the header block (see
+{{header-prefix}}). This ensures that references are stable even if the dynamic
+table is updated while decoding a header block.
+The Base is encoded as a value relative to the Required Insert Count. The Base
+identifies which dynamic table entries can be referenced using relative
+indexing, starting with 0 at the last entry added.
+Post-base references are used for entries inserted after base, starting at 0 for

"Base" is capitalized elsewhere

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