Network Working Group M. Kerwin
Internet-Draft June 2, 2016
Intended status: Standards Track
Expires: December 4, 2016

HTTP/2 "Dropped Frame" Frame


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

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Table of Contents

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).


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)    |


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.

Frame Type Code Section

5. 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.
[RFC7540] Belshe, M., Peon, R. and M. Thomson, "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI 10.17487/RFC7540, May 2015.

Author's Address

Matthew Kerwin EMail: URI: