HTTP/2 "Dropped Frame" Frame
draft-kerwin-http2-nak-frame-00

Abstract

This document defines an extension to the Hypertext Transfer Protocol Version 2 (HTTP/2) that allows for non-destructive signalling of unsupported extension frames.

Note to Readers

The issues list for this draft can be found at https://github.com/phluid61/internet-drafts/labels/HTTP%2F2%20NAK%20Frame

The most recent (often unpublished) draft is at http://phluid61.github.io/internet-drafts/http2-nak-frame/

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 4, 2016.

Copyright Notice

Copyright (c) 2016 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.

Table of Contents

• 1. Introduction
• 1.1. Notational Conventions
• 2. Additions to HTTP/2
• 2.1. DROPPED_FRAME
• 3. Security Considerations
• 4. IANA Considerations
• 4.1. HTTP/2 Frame Type Registry Update
• 5. Normative References
• Author's Address

1. Introduction

Out of the box, the Hypertext Transfer Protocol Version 2 (HTTP/2) [RFC7540] makes provision for extension frame types to be sent on a connection, with or without prior agreement from either or both peers, with the assertion that “implementations MUST discard frames that have unknown or unsupported types” ([RFC7540], Section 5.5). However it can be useful to explicitly notify the peer if such a frame is discarded.

This document defines an extension to HTTP/2 that allows a peer to signal that a received frame was discarded, without altering the stream or connection state ([RFC7540], Section 5.1), and in particular without triggering an error condition.

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 ([RFC7540], Section 11.2).

2.1. DROPPED_FRAME

DROPPED_FRAME frames (type code=0xTBA) can be sent on a connection at any time to indicate that a received frame was discarded without any action being taken.

  +---------------+
  |   Type (8)    |
  +---------------+

DROPPED_FRAME Frame Payload

The DROPPED_FRAME frame contains a single 8-bit integer containing the value of the Type field from the discarded frame.

The DROPPED_FRAME frame does not define any flags.

An endpoint SHOULD send a DROPPED_FRAME frame for an unknown or unsupported frame type the first time it discards such a frame.

An endpoint MAY send a DROPPED_FRAME frame for a particular incoming frame type only once, even if it discards multiple frames of that type.

An endpoint that receives a DROPPED_FRAME frame ought to take it as an indication that the extension is not supported by the peer, and MAY subsequently choose to not send further frames of that type to or to enter into extension negotiations with the peer.

DROPPED_FRAME frames are not associated with any individual stream. If a DROPPED_FRAME frame is received with a stream identifier field value other than 0x0, the recipient MUST respond with a connection error ([RFC7540], Section 5.4.1) of type PROTOCOL_ERROR.

Receipt of a DROPPED_FRAME frame with a length field value other than 1 MUST be treated as a connection error ([RFC7540], Section 5.4.1) of type FRAME_SIZE_ERROR.

3. Security Considerations

This specification does not introduce any new security considerations.

4. IANA Considerations

This document updates the registriy for frame types in the “Hypertext Transfer Protocol (HTTP) 2 Parameters” section.

4.1. HTTP/2 Frame Type Registry Update

This document updates the “HTTP/2 Frame Type” registry ([RFC7540], Section 11.2). The entries in the following table are registered by this document.

5. Normative References

Author's Address