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. 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 February 20, 2015. 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 February 20, 2015 [Page 1] Internet-Draft http2-segments August 2014 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: Kerwin Expires February 20, 2015 [Page 2] Internet-Draft http2-segments August 2014 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. Kerwin Expires February 20, 2015 [Page 3] Internet-Draft http2-segments August 2014 Author's Address Matthew Kerwin Email: matthew@kerwin.net.au URI: http://matthew.kerwin.net.au/ Kerwin Expires February 20, 2015 [Page 4]