Network Working Group M. Kerwin
Internet-Draft
Intended status: Standards Track August 19, 2014
Expires: February 20, 2015
HTTP/2 Segments
draft-kerwin-http2-segments-01
Abstract
This document introduces the concept of "segments" to HTTP/2, and
adds a flag to the DATA frame type to allow the expression segments.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 2
2. Segments . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. SETTINGS_USE_SEGMENTS Setting . . . . . . . . . . . . . . . . 2
4. SEGMENT_CONTINUES Flag . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 3
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
6.1. HTTP/2 Settings Registry Update . . . . . . . . . . . . . 3
7. Normative References . . . . . . . . . . . . . . . . . . . . 3
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
This document extends HTTP/2 [I-D.ietf-httpbis-http2] by introducing
the concept of "segments" to HTTP/2, as a mechanism to combat the
effects of fragmentation within a stream. It does this by adding a
new flag to the DATA frame type ([I-D.ietf-httpbis-http2],
Section 6.1).
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. Segments
A "segment" is a contiguous region of a HTTP/2 message's payload data
which can be freely fragmented and recombined. A segment is
expressed by marking all but the final frame in the segment with the
SEGMENT_CONTINUES flag (Section 4). Any data-bearing frame that does
not have the SEGMENT_CONTINUES flag set, and does not follow one that
does, comprises a single segment.
Segments can be used to mitigate the effects of fragmentation within
a stream. For example, an endpoint may have a large chunk of data
which it has to transmit via multiple DATA frames in order to comply
with frame size limits. It can mark those frames as a single segment
so that any downstream peer without the same frame size restrictions
knows that it can safely coalesce the frames.
3. SETTINGS_USE_SEGMENTS Setting
The following new SETTINGS parameter ([I-D.ietf-httpbis-http2],
Section 6.5.2) is defined:
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o "SETTINGS_USE_SEGMENTS" (0xTBA): Informs the remote endpoint of
whether or not the sender supports the SEGMENT_CONTINUES flag
(Section 4). A value of 1 indicates that the sender supports the
flag. Any other value MUST be treated as a connection error
([I-D.ietf-httpbis-http2], Section 5.4.1) of type PROTOCOL_ERROR.
4. SEGMENT_CONTINUES Flag
The following new flag is defined for the DATA frame
([I-D.ietf-httpbis-http2], Section 6.1):
o "SEGMENT_CONTINUES" (0x10): Bit 5 being set indicates that the
current segment continues after the current frame (see Section 2).
Intermediaries MUST NOT coalesce frames across a segment boundary
and MUST preserve segment boundaries when forwarding frames.
The SEGMENT_CONTINUES flag MUST NOT be set on any frames unless
the remote endpoint has indicated support by sending a
SETTINGS_USE_SEGMENTS setting (Section 3) with a value of 1.
5. Security Considerations
6. IANA Considerations
This document updates the registry for settings in the "Hypertext
Transfer Protocol (HTTP) 2 Parameters" section.
6.1. HTTP/2 Settings Registry Update
This document updates the "HTTP/2 Settings" registry
([I-D.ietf-httpbis-http2], Section 11.3). The entries in the
following table are registered by this document.
+-----------------------+------+---------------+---------------+
| Name | Code | Initial Value | Specification |
+-----------------------+------+---------------+---------------+
| SETTINGS_USE_SEGMENTS | TBD | N/A | Section 3 |
+-----------------------+------+---------------+---------------+
7. Normative References
[I-D.ietf-httpbis-http2]
Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer
Protocol version 2", draft-ietf-httpbis-http2-14 (work in
progress), July 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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Author's Address
Matthew Kerwin
Email: matthew@kerwin.net.au
URI: http://matthew.kerwin.net.au/
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