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RFC 9287 - Greasing the QUIC Bit

Abstract​

This document describes a method for negotiating the ability to send an arbitrary value for the second-most significant bit in QUIC packets.

Status of This Memo​

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9287.

Copyright (c) 2022 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.

Table of Contents​

    1. Introduction
    1. Conventions and Definitions
    1. The Grease QUIC Bit Transport Parameter
    1. Security Considerations
    1. IANA Considerations
    1. References
  • Author's Address

1. Introduction​

The version-independent definition of QUIC [QUIC-INVARIANTS] intentionally describes a very narrow set of fields that are visible to entities other than endpoints. Beyond those characteristics that are invariant, very little about the "wire image" [RFC8546] of QUIC is visible.

The second-most significant bit of the first byte in every QUIC packet is defined as having a fixed value in QUIC version 1 [QUIC]. The purpose of having a fixed value is to allow endpoints to efficiently distinguish QUIC from other protocols; see [DEMUX] for a description of a system that might use this property. As this bit can identify a packet as QUIC, it is sometimes referred to as the "QUIC Bit".

Where endpoints and the intermediaries that support them do not depend on the QUIC Bit having a fixed value, sending the same value in every packet is more of a liability than an asset. If systems come to depend on a fixed value, then it might become infeasible to define a version of QUIC that attributes semantics to this bit.

In order to safeguard future use of this bit, this document defines a QUIC transport parameter that indicates that an endpoint is willing to receive QUIC packets containing any value for this bit. By sending different values for this bit, the hope is that the value will remain available for future use [USE-IT].

2. Conventions and Definitions​

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.

This document uses terms and notational conventions from [QUIC].

3. The Grease QUIC Bit Transport Parameter​

The grease_quic_bit transport parameter (0x2ab2) is defined for QUIC version 1 [QUIC]. This transport parameter can be sent by both client and server. The transport parameter is sent with an empty value; an endpoint that understands this transport parameter MUST treat receipt of a non-empty value of the transport parameter as a connection error of type TRANSPORT_PARAMETER_ERROR.

An endpoint that advertises the grease_quic_bit transport parameter MUST accept packets with the QUIC Bit set to a value of 0. The QUIC Bit is defined as the second-most significant bit of the first byte of QUIC packets (that is, the value 0x40).

3.1. Clearing the QUIC Bit​

Endpoints that receive the grease_quic_bit transport parameter from a peer SHOULD set the QUIC Bit to an unpredictable value unless another extension assigns specific meaning to the value of the bit.

Endpoints can set the QUIC Bit to 0 on all packets that are sent after receiving and processing transport parameters. This could include Initial, Handshake, and Retry packets.

A client MAY also set the QUIC Bit to 0 in Initial, Handshake, or 0-RTT packets that are sent prior to receiving transport parameters from the server. However, a client MUST NOT set the QUIC Bit to 0 if it also sends a token provided in a Retry packet or in a NEW_TOKEN frame (Section 19.7 of [QUIC]).

3.2. Using the QUIC Bit​

This document describes a use of the QUIC Bit that is compatible with the definition in [QUIC].

4. Security Considerations​

Greasing the QUIC Bit is intended to safeguard the future use of the bit. It does not provide any security properties.

5. IANA Considerations​

This document registers the grease_quic_bit transport parameter in the "QUIC Transport Parameters" registry established in Section 22.3 of [QUIC].

The following fields are registered:

  • Value: 0x2ab2
  • Parameter Name: grease_quic_bit
  • Status: Permanent
  • Specification: RFC 9287

6. References​

6.1. Normative References​

[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, https://www.rfc-editor.org/info/rfc9000.

[QUIC-INVARIANTS] Thomson, M., "Version-Independent Properties of QUIC", RFC 8999, DOI 10.17487/RFC8999, May 2021, https://www.rfc-editor.org/info/rfc8999.

[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.

[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.

6.2. Informative References​

[DEMUX] Kühlewind, M. and C. Huitema, "Multiplexing Scheme Updates for QUIC", Work in Progress, Internet-Draft, draft-ietf-quic-multiplexing-02, 22 October 2020, https://datatracker.ietf.org/doc/html/draft-ietf-quic-multiplexing-02.

[RFC8546] Trammell, B. and M. Kühlewind, "The Wire Image of a Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April 2019, https://www.rfc-editor.org/info/rfc8546.

[USE-IT] Thomson, M., "Use It or Lose It", RFC 9170, DOI 10.17487/RFC9170, December 2021, https://www.rfc-editor.org/info/rfc9170.

Author's Address​

Martin Thomson Mozilla Email: [email protected]

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