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Network Working Group                                         E. Kinnear
Internet-Draft                                                  T. Pauly
Intended status: Standards Track                              Apple Inc.
Expires: March 14, 2019                               September 10, 2018


         Using HTTP/2 as a Transport for Arbitrary Bytestreams
                draft-kinnear-httpbis-http2-transport-00

Abstract

   HTTP/2 provides multiplexing of HTTP requests over a single
   underlying transport connection.  HTTP/2 Transport defines a
   transport abstraction provided by HTTP/2 framing that is separate
   from HTTP semantics.

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
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   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 March 14, 2019.

Copyright Notice

   Copyright (c) 2018 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   2
   2.  The STREAM HTTP/2 Frame . . . . . . . . . . . . . . . . . . .   2
     2.1.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Advertising Support for STREAM Frames . . . . . . . . . .   4
     2.3.  Processing STREAM Frames  . . . . . . . . . . . . . . . .   4
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   HTTP/2 [RFC7540] provides a framing layer that describes the exchange
   of HTTP messages following HTTP semantics.  This framing layer
   provides multiplexing of multiple streams on a single underlying
   transport connection, flow control, stream dependencies and
   priorities, and exchange of configuration information between
   endpoints.  HTTP/2 also defines the mapping of HTTP semantics onto
   that framing layer.

   This document defines the use of the HTTP/2 framing layer as a
   transport for arbitrary byte streams without the use of HTTP
   semantics.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  The STREAM HTTP/2 Frame

   This document defines a new HTTP/2 frame type called STREAM, that
   allows endpoints to open HTTP/2 streams without header values.
   Either endpoint can send this frame to open a stream.  STREAM frames
   are treated in all ways as HEADERS frames, including in the stream
   state machine, but are not required to contain any header values.








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2.1.  Syntax

   The STREAM frame type is 0xd (decimal 13) and contains similar fields
   to that of the HEADERS frame.

   A STREAM frame is shown below.

    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)|
   +-+-------------+-----------------------------------------------+
   |E|                 Stream Dependency? (31)                     |
   +-+-------------+-----------------------------------------------+
   |  Weight? (8)  |
   +-+-------------+-----------------------------------------------+
   |                           Padding (*)                       ...
   +---------------------------------------------------------------+

                       Figure 1: STREAM Frame Format

   The STREAM frame contains the following fields:

   Pad Length:  An 8-bit field containing the length of the frame
      padding in units of octets.  This field is only present if the
      PADDED flag is set.

   E: A single-bit flag indicating that the stream dependency is
      exclusive (see Section 5.3 of [RFC7540]).  This field is only
      present if the PRIORITY flag is set.

   Stream Dependency:  A 31-bit stream identifier for the stream that
      this stream depends on (see Section 5.3 of [RFC7540]).  This field
      is only present if the PRIORITY flag is set.

   Weight:  An unsigned 8-bit integer representing a priority weight for
      the stream (see Section 5.3 of [RFC7540]).  Add one to the value
      to obtain a weight between 1 and 256.  This field is only present
      if the PRIORITY flag is set.

   Padding:  Padding octets.

   The STREAM frame defines the following flags:

   PADDED (0x8):  When set, bit 3 indicates that the Pad Length field
      and any padding that it describes are present.





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   PRIORITY (0x20):  When set, bit 5 indicates that the Exclusive Flag
      (E), Stream Dependency, and Weight fields are present; see
      Section 5.3 of [RFC7540].

   STREAM frames MUST be associated with a stream.  If a STREAM frame is
   received whose stream identifier field is 0x0, the recipient MUST
   respond with a connection error of type PROTOCOL_ERROR.

   The STREAM frame can include padding.  Padding fields and flags are
   identical to those defined for DATA frames.

   Prioritization information in a STREAM frame is logically equivalent
   to a separate PRIORITY frame, but inclusion in a STREAM frame avoids
   the potential for churn in stream prioritization when new streams are
   created.  Prioritization fields in STREAM frames subsequent to the
   first on a stream reprioritize the stream (Section 5.3.3 of
   [RFC7540]).

2.2.  Advertising Support for STREAM Frames

   As defined in [RFC7540], both endpoints can send
   SETTINGS_MAX_CONCURRENT_STREAMS in SETTINGS frames to indicate the
   number of streams that the sender permits the receiver to create.
   This limit applies to streams created via the STREAM frame as well as
   streams created via HEADERS frames.

2.3.  Processing STREAM Frames

   The STREAM frame is a non-critical extension to HTTP/2.  Endpoints
   that do not support this frame can safely ignore it upon receipt.

   When received by a client that implements support, the STREAM frame
   behaves in the same manner as a HEADERS frame, but does not carry any
   header blocks.  This changes the connection state in the same manner
   as a HEADERS frame, described in Section 4.3 of [RFC7540].

   STREAM frames can be sent on a stream in the "idle", "reserved
   (local)", "open", or "half-closed (remote)" state.  STREAM frames can
   be sent by either endpoint on a connection.

   Streams created via a STREAM frame are multiplexed in the same manner
   on the underlying transport connection as streams created via a
   HEADERS frame.  Flow control also applies to these streams in the
   same way.  Flow control, stream dependencies, and priorities continue
   to apply to streams as defined by [RFC7540].

   Anywhere an endpoint would be permitted to send a HEADERS frame by
   [RFC7540], it is likewise permitted to send a STREAM frame.



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   A stream is closed via a RST_STREAM frame or by setting the
   END_STREAM flag on a DATA frame.

3.  IANA Considerations

   This specification adds an entry to the "HTTP/2 Frame Type" registry.

   o  Frame Type: STREAM

   o  Code: 0xd

   o  Specification: [[RFC Editor: Please fill in this value with the
      RFC number for this document.]]

4.  Security Considerations

5.  Acknowledgments

   Thanks to Anthony Chivetta, Joshua Otto, and Valentin Pistol for
   their contributions in the design and prototyping of this work.

6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/info/rfc7540>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses

   Eric Kinnear
   Apple Inc.
   One Apple Park Way
   Cupertino, California 95014
   United States of America

   Email: ekinnear@apple.com





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   Tommy Pauly
   Apple Inc.
   One Apple Park Way
   Cupertino, California 95014
   United States of America

   Email: tpauly@apple.com












































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