quic                                                          M. Thomson
Internet-Draft                                                   Mozilla
Intended status: Standards Track                             9 June 2022
Expires: 11 December 2022

                         Greasing the QUIC Bit


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

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the QUIC Working Group
   mailing list (quic@ietf.org), which is archived at

   Source for this draft and an issue tracker can be found at
   https://github.com/quicwg/quic-bit-grease (https://github.com/quicwg/

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 https://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 11 December 2022.

Thomson                 Expires 11 December 2022                [Page 1]

Internet-Draft            Greasing the QUIC Bit                June 2022

Copyright Notice

   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  The Grease QUIC Bit Transport Parameter . . . . . . . . . . .   3
     3.1.  Clearing the QUIC Bit . . . . . . . . . . . . . . . . . .   3
     3.2.  Using the QUIC Bit  . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

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

   The second-to-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 QUIC to be
   efficiently distinguished 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 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.

Thomson                 Expires 11 December 2022                [Page 2]

Internet-Draft            Greasing the QUIC Bit                June 2022

   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",
   "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) 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-to-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
   unless the Initial packets it sends include a token provided by the
   server in a NEW_TOKEN frame (Section 19.7 of [QUIC]), received less
   than 604800 seconds (7 days) prior on a connection where the server
   also included the grease_quic_bit transport parameter.

Thomson                 Expires 11 December 2022                [Page 3]

Internet-Draft            Greasing the QUIC Bit                June 2022

      |  This 7 day limit allows for changes in server configuration.
      |  If server configuration changes and a client does not set the
      |  QUIC Bit, then it is possible that a server will drop packets,
      |  resulting in connection failures.

   A server MUST set the QUIC bit to 0 only after processing transport
   parameters from a client.  A server MUST NOT remember that a client
   negotiated the extension in a previous connection and set the QUIC
   Bit to 0 based on that information.

   An endpoint MUST NOT set the QUIC Bit to 0 without knowing whether
   the peer supports the extension.  As Stateless Reset packets
   (Section 10.3 of [QUIC]) are only used after a loss of connection
   state, endpoints are unlikely to be able to set the QUIC Bit to 0 on
   Stateless Reset packets.

3.2.  Using the QUIC Bit

   The purpose of this extension is to allow for the use of the QUIC Bit
   by later extensions.

   Extensions to QUIC that define semantics for the QUIC Bit can be
   negotiated at the same time as the grease_quic_bit transport
   parameter.  In this case, a recipient needs to be able to distinguish
   a randomized value from a value carrying information according to the
   extension.  Extensions that use the QUIC Bit MUST negotiate their use
   prior to acting on any semantic.

   For example, an extension might define a transport parameter that is
   sent in addition to the grease_quic_bit transport parameter.  Though
   the value of the QUIC Bit in packets received by a peer might be set
   according to rules defined by the extension, they might also be
   randomized as specified in this document.

   Receiving a transport parameter for an extension that uses the QUIC
   Bit could be used to confirm that a peer supports the semantic
   defined in the extension.  To avoid acting on a randomized signal,
   the extension can require that endpoints set the QUIC Bit according
   to the rules of the extension, but defer acting on the information
   conveyed until the transport parameter for the extension is received.

   Extensions that define semantics for the QUIC Bit can be negotiated
   without using the grease_quic_bit transport parameter.  However,
   including both extensions allows for the QUIC Bit to be greased even
   if the alternative use is not supported.

Thomson                 Expires 11 December 2022                [Page 4]

Internet-Draft            Greasing the QUIC Bit                June 2022

4.  Security Considerations

   This document introduces no new security considerations for endpoints
   or entities that can rely on endpoint cooperation.  However, this
   change makes the task of identifying QUIC more difficult without
   cooperation of endpoints.  This sometimes works counter to the
   security goals of network operators who rely on network
   classification to identify threats.

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:  This document.

   Date:  Date of registration.

   Contact:  QUIC Working Group (quic@ietf.org)

   Change Controller:  IETF (iesg@ietf.org)

   Notes:  (none)

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,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [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/rfc/rfc8174>.

Thomson                 Expires 11 December 2022                [Page 5]

Internet-Draft            Greasing the QUIC Bit                June 2022

6.2.  Informative References

   [DEMUX]    Aboba, B., Salgueiro, G., and C. Perkins, "Multiplexing
              Scheme Updates for QUIC", Work in Progress, Internet-
              Draft, draft-ietf-avtcore-rfc7983bis-04, 12 May 2022,

              Thomson, M., "Version-Independent Properties of QUIC",
              RFC 8999, DOI 10.17487/RFC8999, May 2021,

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

   [USE-IT]   Thomson, M. and T. Pauly, "Long-Term Viability of Protocol
              Extension Mechanisms", RFC 9170, DOI 10.17487/RFC9170,
              December 2021, <https://www.rfc-editor.org/rfc/rfc9170>.

Author's Address

   Martin Thomson
   Email: mt@lowentropy.net

Thomson                 Expires 11 December 2022                [Page 6]