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QPACK Blocking Setting #1143

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merged 12 commits into from May 14, 2018
Merged

QPACK Blocking Setting #1143

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0b2ea4e
SETTINGS_BLOCKING_HEADER_REFERENCES
MikeBishop Feb 27, 2018
dfb3198
Index variable is sufficient
MikeBishop Feb 27, 2018
aabe254
Setting is a number, not a boolean
MikeBishop Mar 19, 2018
6a39ef6
Martin's feedback
MikeBishop Apr 24, 2018
348c473
Re-add lost definition
MikeBishop Apr 26, 2018
e606615
blocking => blocked
MikeBishop Apr 26, 2018
6009451
ack'd
MikeBishop Apr 26, 2018
7b81097
Merge remote-tracking branch 'origin/master' into qcram_blocking
MikeBishop Apr 26, 2018
c2b3fe8
Martin's feedback
MikeBishop May 9, 2018
f10d1cc
Adapting Martin's text
MikeBishop May 10, 2018
e19cd23
Martin's rewords
MikeBishop May 11, 2018
0779dbc
Describe unblocking
MikeBishop May 14, 2018
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17 changes: 8 additions & 9 deletions draft-ietf-quic-qpack.md
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Expand Up @@ -102,9 +102,9 @@ received.
Each header block contains a Largest Reference (see {{absolute-index}}) which
identifies the table state necessary for decoding. If the greatest absolute
index in the dynamic table is less than the value of the Largest Reference, the
stream is considered "blocked." While blocked, header field data MUST remain in
the blocked stream's flow control window. When the Largest Reference is zero,
the frame contains no references to the dynamic table and can always be
stream is considered "blocked." While blocked, header field data should remain
in the blocked stream's flow control window. When the Largest Reference is
zero, the frame contains no references to the dynamic table and can always be
processed immediately.
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We probably need to explain when a stream becomes unblocked.


A decoder can permit the possibility of blocked streams by setting
Expand All @@ -115,17 +115,16 @@ An encoder can decide whether to risk having a stream become blocked. If
permitted by the value of SETTINGS_QPACK_BLOCKED_STREAMS, compression efficiency
can be improved by referencing dynamic table entries that are still in transit,
but if there is loss or reordering the stream can become blocked at the decoder.
An encoder avoids the rist of blocking by only referencing dynamic table entries
An encoder avoids the risk of blocking by only referencing dynamic table entries
which have been acknowledged, but this means using literals. Since literals make
the header block larger, this can result in the encoder becoming blocked on
congestion or flow control limits.

An encoder MUST limit the number of streams which could become blocked to the
value of SETTINGS_QPACK_BLOCKED_STREAMS at all times. Note that the decoder's
count of streams which are actually blocked will be at most the encoder's count
of streams which could become blocked. If the decoder encounters more blocked
streams than it promised to support, it SHOULD treat this as a stream error of
type HTTP_QPACK_DECOMPRESSION_FAILED.
value of SETTINGS_QPACK_BLOCKED_STREAMS at all times. Note that the decoder
might not actually become blocked on every stream which risks becoming blocked.
If the decoder encounters more blocked streams than it promised to support, it
SHOULD treat this as a stream error of type HTTP_QPACK_DECOMPRESSION_FAILED.

# Wire Format

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