QUIC                                                           M. KozukaInternet-Draft                                        Okayama UniversityIntended status: Standards Track                         26 January 2026Expires: 30 July 2026        QUIC Extension for Server-Initiated Connection Migration                 draft-kozuka-quic-server-migration-00Abstract   This document specifies an extension of QUIC that allows the server   to initiate connection migration.About This Document   This note is to be removed before publishing as an RFC.   The latest revision of this draft can be found at https://masa-   koz.github.io/draft-kozuka-quic-server-migration/draft-kozuka-quic-   server-migration.html.  Status information for this document may be   found at https://datatracker.ietf.org/doc/draft-kozuka-quic-server-   migration/.   Discussion of this document takes place on the QUIC Working Group   mailing list (mailto:quic@ietf.org), which is archived at   https://mailarchive.ietf.org/arch/browse/quic/.  Subscribe at   https://www.ietf.org/mailman/listinfo/quic/.   Source for this draft and an issue tracker can be found at   https://github.com/masa-koz/draft-kozuka-quic-server-migration.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 30 July 2026.Kozuka                    Expires 30 July 2026                  [Page 1]Internet-Draft            QUIC Server Migration             January 2026Copyright Notice   Copyright (c) 2026 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 . . . . . . . . . . . . . . . . .   2   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3   4.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3   5.  Negotiating Extension Use . . . . . . . . . . . . . . . . . .   3   6.  Connection Migration Procedure  . . . . . . . . . . . . . . .   4   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4     8.1.  QUIC Transport Parameter  . . . . . . . . . . . . . . . .   4   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   4   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5   Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . .   5   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   51.  Introduction   RFC 9000 defines connection migration as a mechanism initiated by the   client to change its IP address or network path without disrupting   the QUIC connection.  This mechanism is based on the assumption that   a client may be behind a NAT and a server has a public address.   However, there is a reversed situation where a client has a public   address and a server is behind a NAT.  This document specifies an   extension that reverses this role: the server initiates migration.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.Kozuka                    Expires 30 July 2026                  [Page 2]Internet-Draft            QUIC Server Migration             January 20263.  Motivation   A key scenario is:   *  The server is initially behind a NAT and cannot accept direct      connections.   *  The client has a public IP address.   *  The server first establishes the QUIC connection via a relay      server.   *  Immediately after the handshake, the server migrates the      connection to the client’s public address, reducing latency.   This specification does not define how the server obtains the public   address of the client.  Possible methods include application-level   signaling or external mechanisms, but these are out of scope.4.  Scope   *  Reverse migration roles defined in RFC 9000.   *  Maintain QUIC security guarantees.   *  No new NAT traversal mechanism.5.  Negotiating Extension Use   allow_server_migration (0x3e764478):   Clients advertise their support of this extension by sending the   allow_server_migration (0x3e764478) transport parameter (Section 7.4   of [QUIC-TRANSPORT]) with an empty value.  Sending this transport   parameter signals to the server that the client will accept the   server-initiated migration.   Servers also send this parameter with an empty value.  The server   informs the client that it will initiate the connection migration by   sending this parameter.   When this extension is negotiated, the server-initiated migration is   only permitted and the client-initiated migration is prohibited.   An implementation that understands this transport parameter MUST   treat the receipt of a non-empty value as a connection error of type   TRANSPORT_PARAMETER_ERROR.Kozuka                    Expires 30 July 2026                  [Page 3]Internet-Draft            QUIC Server Migration             January 2026   Endpoints MUST NOT remember the value of this extension for 0-RTT.6.  Connection Migration Procedure   The connection migration procedure is the same as (Section 9 of   [QUIC-TRANSPORT]) except that the roles between the client and the   server are reversed.7.  Security Considerations   TODO Security8.  IANA Considerations8.1.  QUIC Transport Parameter   This document registers the allow_server_migration transport   parameter in the "QUIC Transport Parameters" registry established in   Section 22.3 of [QUIC-TRANSPORT].  The following fields are   registered:   Value:  0x3e764478   Parameter Name:  allow_server_migration   Status:  Provisional   Specification:  This document   Change Controller:  IETF (iesg@ietf.org)   Contact:  Masahiro Kozuka (kozuka@okayama-u.ac.jp)9.  Normative References   [QUIC-TRANSPORT]              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/rfc/rfc9000>.   [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/rfc/rfc2119>.Kozuka                    Expires 30 July 2026                  [Page 4]Internet-Draft            QUIC Server Migration             January 2026   [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>.Acknowledgments   TODO acknowledge.Questions   *  Sould we extend this extension to allow both clients and servers      to initiate connection migration?   *  Any new security conserations from allowing servers to initiate      connection migration?Author's Address   Masahiro Kozuka   Okayama University   Email: kozuka@okayama-u.ac.jpKozuka                    Expires 30 July 2026                  [Page 5]