HTTP/2 Encoded Data
draft-kerwin-http2-encoded-data-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
|
|
|---|---|---|---|
| Author | Matthew Kerwin | ||
| Last updated | 2014-06-19 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-kerwin-http2-encoded-data-00
Network Working Group M. Kerwin
Internet-Draft
Intended status: Informational June 20, 2014
Expires: December 22, 2014
HTTP/2 Encoded Data
draft-kerwin-http2-encoded-data-00
Abstract
This document introduces a new encoded data frame for use in HTTP/2,
and an associated setting parameter.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 22, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Kerwin Expires December 22, 2014 [Page 1]
Internet-Draft http2-encoded-data June 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Additions to HTTP/2 . . . . . . . . . . . . . . . . . . . . . 3
2.1. ENCODED_DATA Frame . . . . . . . . . . . . . . . . . . . 3
2.2. SETTINGS_ACCEPT_ENCODED_DATA Setting . . . . . . . . . . 5
3. Encoding Schemes . . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. Encoding Schemes Registry . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
Kerwin Expires December 22, 2014 [Page 2]
Internet-Draft http2-encoded-data June 2014
1. Introduction
This document describes a mechanism for applying encoding,
particularly compression, to data transported between two hops,
analogous to Transfer-Encoding in HTTP/1.1 [RFC7230].
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Additions to HTTP/2
This document introduces a new HTTP/2 frame type
([I-D.ietf-httpbis-http2], Section 11.2), and a new setting
([I-D.ietf-httpbis-http2], Section 11.3) to negotiate its use.
Note that while encoding of some or all data in a stream might affect
the total length of payload data, the "content-length" header, if
present, should continue to reflect the total length of the
_unencoded_ data. This is particularly relevant when detecting
malformed messages ([I-D.ietf-httpbis-http2], Section 8.1.2.5).
2.1. ENCODED_DATA Frame
"ENCODED_DATA" frames (type code=0x10) are semantically identical to
"DATA" frames ([I-D.ietf-httpbis-http2], Section 6.1), but have an
encoding applied to their payload. Significantly, "ENCODED_DATA"
frames are subject to flow control ([I-D.ietf-httpbis-http2],
Section 5.2). Any encoding or decoding context for an "ENCODED_DATA"
frame is unique to that frame.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Pad Length? (8)|
+---------------+
| Encoding (8) |
+---------------+-----------------------------------------------+
| Data (*) ...
+---------------------------------------------------------------+
| Padding (*) ...
+---------------------------------------------------------------+
ENCODED_DATA Frame Payload
The "ENCODED_DATA" frame contains the following fields:
Kerwin Expires December 22, 2014 [Page 3]
Internet-Draft http2-encoded-data June 2014
o Pad Length: An 8-bit field containing the length of the frame
padding in units of octets. This field is optional and is only
present if the PADDED flag is set.
o Encoding: An 8-bit identifier which describes the encoding that
has been applied to the Data field (see Section 3).
o Data: Application data. The amount of data is the remainder of
the frame payload after subtracting the length of the other fields
that are present.
o Padding: Padding octets that contain no application semantic
value. Padding octets MUST be set to zero when sending and
ignored when receiving.
The "ENCODED_DATA" frame defines the following flags:
o "END_STREAM" (0x1): Bit 1 being set indicates that this frame is
the last that the endpoint will send for the identified stream.
Setting this flag causes the stream to enter one of the "half
closed" states or the "closed" state (Section 5.1).
o "END_SEGMENT" (0x2): Bit 2 being set indicates that this frame is
the last for the current segment. Intermediaries MUST NOT
coalesce frames across a segment boundary and MUST preserve
segment boundaries when forwarding frames.
o "PADDED" (0x8): Bit 4 being set indicates that the Pad Length
field is present.
On receiving an "ENCODED_DATA" frame, an intermediary MAY decode the
data and forward it in one or more "DATA" frames. If the downstream
peer does not support the encoding scheme used in the received frame,
as advertised in a "SETTINGS_ACCEPT_ENCODED_DATA" setting, the
intermediary MUST decode the data and either: forward it in one or
more DATA frames, or encode it with a scheme supported by the
downstream peer and forward it in one or more "ENCODED_DATA" frames.
An "ENCODED_DATA" frame MUST NOT be sent on a connection before both
receiving a "SETTINGS_ACCEPT_ENCODED_DATA" setting and sending the
associated acknowledgement. A sender MUST NOT apply an encoding that
has not first been advertised by the peer in a
"SETTINGS_ACCEPT_ENCODED_DATA" setting, or was advertised with a rank
of 0. Endpoints that receive a frame with an encoding they do not
recognise or support MUST treat this is a connection error of type
"PROTOCOL_ERROR".
Kerwin Expires December 22, 2014 [Page 4]
Internet-Draft http2-encoded-data June 2014
If an endpoint detects that the payload of an "ENCODED_DATA" frame is
incorrectly encoded it MUST treat this as a stream error (see
[I-D.ietf-httpbis-http2], Section 5.4.2) of type "COMPRESSION_ERROR"
([I-D.ietf-httpbis-http2], Section 7).
2.2. SETTINGS_ACCEPT_ENCODED_DATA Setting
This document defines a new "SETTINGS" parameter:
"SETTINGS_ACCEPT_ENCODED_DATA" (code=0x5): Indicates the sender's
ability and willingness to receive "ENCODED_DATA" frames that are
encoded using the scheme identified in the Value.
The Value field is further divided into three sub-fields: an unsigned
8-bit encoding identifier, an unsigned 8-bit rank, and 16 bits of
padding.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoding (8) | Rank (8) | Padding (16) |
+---------------+-------------------+---------------------------+
The rank fulfils the same role as in the HTTP/1.1 TE header
([RFC7230] Section 4.3). The rank value is an integer in the range 0
through 255, where 1 is the least preferred and 255 is the most
preferred; a value of 0 means "not acceptable".
An endpoint that receives a "SETTINGS_ACCEPT_ENCODED_DATA" setting
with any unknown or unsupported encoding identifier MUST ignore that
setting.
An endpoint may advertise support for an encoding scheme and later
decide that it no longer supports that scheme. After sending a
"SETTINGS_ACCEPT_ENCODED_DATA" setting with a rank of 0, the endpoint
SHOULD continue to accept "ENCODED_DATA" frames using that scheme for
a reasonable amount of time, until the acknowledgement arrives. (See
[I-D.ietf-httpbis-http2], Section 6.5.3)
Note that subsequent "SETTINGS_ACCEPT_ENCODED_DATA" parameters _do
not_ replace existing values for the parameter unless they contain
the same encoding identifier. Effectively, one may consider this
specification to introduce 256 new settings parameters, each having a
24-bit identifier (the 16-bit "SETTINGS" identifier plaus the 8-bit
encoding parameter) and an 8-bit value (the encoding rank); however,
as support for any given encoding is entirely optional, an endpoint
only need track rankings for those encodings it supports for sending
encoded data.
Kerwin Expires December 22, 2014 [Page 5]
Internet-Draft http2-encoded-data June 2014
3. Encoding Schemes
The following encoding schemes are defined:
o "ENCODING_COMPRESS" (1): The "compress" coding is an adaptive
Lempel-Ziv-Welch (LZW) coding [Welch] that is commonly produced by
the UNIX file compression program "compress".
o "ENCODING_DEFLATE" (2): The "deflate" coding is a "zlib" data
format [RFC1950] containing a "deflate" compressed data stream
[RFC1951] that uses a combination of the Lempel-Ziv (LZ77)
compression algorithm and Huffman coding.
o "ENCODING_GZIP" (3): The "gzip" coding is an LZ77 coding with a 32
bit CRC that is commonly produced by the gzip file compression
program [RFC1952].
4. Security Considerations
Further to the Use of Compression in HTTP/2
([I-D.ietf-httpbis-http2], Section 10.6), intermediaries MUST NOT
apply compression to DATA frames, or alter the compression of
"ENCODED_DATA" frames other than decompressing, unless additional
information is available that allows the intermediary to identify the
source of data. In particular, frames that are not compressed cannot
be compressed, and frames that are separately compressed cannot be
merged into a single compressed frame.
5. IANA Considerations
This document establishes a registry for encoding schemes. This new
registries is entered into the "Hypertext Transfer Protocol (HTTP) 2
Parameters" section.
5.1. Encoding Schemes Registry
This document establishes a registry for encoding scheme codes. The
"HTTP/2 Encoding Scheme" registry manages an 8-bit space. The "HTTP/
2 Encoding Scheme" registry operates under either of the "IETF
Review" or "IESG Approval" policies [RFC5226] for values between 0x00
and 0xef, with values between 0xf0 and 0xff being reserved for
experimental use.
New entries in this registry require the following information:
o Frame Type: A name or label for the encoding scheme.
o Code: The 8-bit code assigned to the encoding scheme.
Kerwin Expires December 22, 2014 [Page 6]
Internet-Draft http2-encoded-data June 2014
o Specification: A reference to a specification that includes a
description of the encoding scheme.
An initial set of encoding scheme code registrations can be found in
Section 3.
6. References
6.1. Normative References
[I-D.ietf-httpbis-http2]
Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer
Protocol version 2", draft-ietf-httpbis-http2-13 (work in
progress), June 2014.
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
Specification version 3.3", RFC 1950, May 1996.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
version 1.3", RFC 1951, May 1996.
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G.
Randers-Pehrson, "GZIP file format specification version
4.3", RFC 1952, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[Welch] Welch, T., "A Technique for High-Performance Data
Compression", IEEE Computer 17(6), June 1984.
6.2. Informative References
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June
2014.
Author's Address
Matthew Kerwin
Email: matthew@kerwin.net.au
URI: http://matthew.kerwin.net.au/
Kerwin Expires December 22, 2014 [Page 7]