Compatible Version Negotiation for QUIC
draft-schinazi-quic-version-negotiation-01

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QUIC Working Group                                           D. Schinazi
Internet-Draft                                                Google LLC
Intended status: Informational                               E. Rescorla
Expires: March 13, 2020                                          Mozilla
                                                      September 10, 2019

                Compatible Version Negotiation for QUIC
               draft-schinazi-quic-version-negotiation-01

Abstract

   QUIC does not provide a complete version negotiation mechanism but
   instead only provides a way for the server to indicate that the
   version the client offered is unacceptable.  This document describes
   a version negotiation mechanism that allows a client and server to
   select from a set of QUIC versions which share a compatible Initial
   format without incurring an extra round trip.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on March 13, 2020.

Copyright Notice

   Copyright (c) 2019 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  Version Negotiation Mechanism . . . . . . . . . . . . . . . .   3
   4.  Compatible Versions Transport Parameter . . . . . . . . . . .   3
   5.  Compatible Versions . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   QUIC [I-D.ietf-quic-transport] does not provide a complete version
   negotiation (VN) mechanism; the VN packet only allows the server to
   indicate that the version the client offered is unacceptable, but
   doesn't allow the client to safely make use of that information.  In
   principle the VN packet could be part of a mechanism to allow two
   QUIC implementations to negotiate between two totally disjoint
   versions of QUIC (at the cost of an extra round trip).  However,
   experience with negotiation of previous IETF protocols indicates that
   this is probably not the most common scenario:

   1.  Implementations do not generally want to incur an extra round
       trip to negotiate versions.

   2.  Most incremental versions are broadly similar to the the previous
       version, and so the version negotiation mechanism can be built on
       the assumption that the version advertisement and selection is
       common to the versions to be negotiated.

   This specification describes a simple version negotiation mechanism
   which exploits property (2) and can negotiate between the set of
   "compatible" versions in a single round trip.  Negotiation between
   totally disjoint versions - if it ever proves to be necessary - is
   left as a topic for future work.

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.

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3.  Version Negotiation Mechanism

   The mechanism defined in this document is straightforward: the client
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