



Internet Engineering Task Force                                   A. Zhu
Internet-Draft                                                  Y. Zhang
Intended status: Experimental                                 R. Broberg
Expires: 4 April 2026                                            L. Feng
                                                               JM. Smith
    University of Pennsylvania School of Engineering and Applied Science
                                                          1 October 2025


    Quantum FWM Control Protocol (QFCP) for IP Optical Environments
                         draft-zhu-qirg-qfcp-00

Abstract

   This document specifies the Quantum Four-Wave Mixing Control Protocol
   (QFCP), a lightweight transport protocol designed to operate over UDP
   in IP optical environments.  QFCP enables the transmission of
   control- plane parameters required for quantum four-wave mixing (FWM)
   processes and associated optical configurations, including
   polarization stabilization, timestamp alignment, ROADM port
   selection, and spectral parameters.  The protocol uses a Type-Length-
   Value (TLV) structure to support versioning and extensibility.  This
   work is motivated by recent demonstrations of a classical-decisive
   quantum internet using integrated photonics.

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 4 April 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





Zhu, et al.               Expires 4 April 2026                  [Page 1]

Internet-Draft        Quantum FWM Control Protocol          October 2025


   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
   3.  QFCP Packet Format  . . . . . . . . . . . . . . . . . . . . .   3
   4.  TLV Structures  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Example Use Cases . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Dynamic ROADM Configuration . . . . . . . . . . . . . . .   4
     5.2.  Real-Time Error Mitigation  . . . . . . . . . . . . . . .   5
     5.3.  Hybrid IP Packet Orchestration  . . . . . . . . . . . . .   5
     5.4.  Timestamp Alignment . . . . . . . . . . . . . . . . . . .   5
     5.5.  WDM/TDM Extensions  . . . . . . . . . . . . . . . . . . .   5
   6.  UDP Port Assignment . . . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Hybrid quantum-classical networking is emerging as a foundation for
   distributed quantum information processing.  Recent experiments on
   commercial fiber networks have shown that quantum states can be
   dynamically routed by classical headers embedded in IP-like packets.
   To configure downstream optical switches and mitigate errors, a
   lightweight, extensible protocol is needed.  QFCP is intended to be
   that protocol, running over UDP [RFC768] and supporting modular Type-
   Length-Value (TLV) extensions.  QFCP supports applications aligned
   with scenarios defined by the IRTF Quantum Internet Research Group
   (QIRG) [RFC9583].









Zhu, et al.               Expires 4 April 2026                  [Page 2]

Internet-Draft        Quantum FWM Control Protocol          October 2025


1.1.  Requirements Language

   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.

2.  Protocol Overview

   QFCP defines a fixed header followed by TLV-encoded fields.  The
   header carries version and flag information; TLVs encode control-
   plane parameters such as quantum link layer protocol, polarization
   state, center frequency, or error-mitigation metadata.  UDP provides
   transport simplicity and compatibility with existing IP
   infrastructure.  Unknown TLVs MUST be ignored to ensure forward
   compatibility.

3.  QFCP Packet Format

   The QFCP packet consists of a fixed header followed by a sequence of
   Type-Length-Value (TLV) payloads.

   Packet Format:

    0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Version  | Flags |               Reserved                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                         TLV Payloads                         ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: QFCP Packet Header and TLV Payloads

   *  Version (4 bits): Protocol version number (currently 0x1).

   *  Flags (4 bits): Reserved for future use.

   *  Reserved (24 bits): Set to zero; ignored on receipt.

   *  TLV Payloads: Sequence of variable-length TLVs.







Zhu, et al.               Expires 4 April 2026                  [Page 3]

Internet-Draft        Quantum FWM Control Protocol          October 2025


4.  TLV Structures

   Each TLV consists of a type, a reserved field, a length (in bytes),
   and a value.  All fields are in network byte order.

   TLV Format:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Type     |    Reserved   |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Value (variable)                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 2: TLV Format

   Defined TLV Types:

    Type   Name                       Value Format
    ----   -------------------------  ------------------------------
    0x01   Quantum Protocol           32-bit float (e.g., encoding)
    0x02   Polarization State         32-bit float
    0x03   Local Timestamp            32-bit int (ns)
    0x04   ROADM Output Port ID       32-bit int
    0x05   Photon Arrival Timestamp   32-bit int (ns)
    0x06   Center Frequency (GHz)     32-bit float
    0x07   Optical Linewidth (GHz)    32-bit float
    0x08   Error Mitigation Vector    Variable (SU(2) parameters)
    0x09   Future Extension           TLV-defined

                   Figure 3: Initial TLV Type Assignments

5.  Example Use Cases

   This section illustrates how the Quantum FWM Control Protocol (QFCP)
   can be applied in practical network environments.

5.1.  Dynamic ROADM Configuration

   QFCP packets carrying TLVs for ROADM Output Port ID ([RFC4950]) allow
   classical headers to steer entangled photons through commercial
   reconfigurable optical add-drop multiplexers (ROADMs).  This enables
   dynamic path selection across metro and campus-scale optical
   networks, as demonstrated in recent hybrid IP packet experiments
   ([Zhang2025]).





Zhu, et al.               Expires 4 April 2026                  [Page 4]

Internet-Draft        Quantum FWM Control Protocol          October 2025


5.2.  Real-Time Error Mitigation

   TLVs containing polarization parameters and error-mitigation vectors
   (Type 0x08) allow active compensation of SU(2) rotations induced by
   deployed fiber ([ZhangSM2025]).  Classical light encodes detection
   signals in the header, enabling dynamic updates to the error
   mitigator without disturbing quantum states.

5.3.  Hybrid IP Packet Orchestration

   The QFCP framework aligns with the IRTF QIRG goals and use-cases
   ([RFC9583]).  By transporting control-plane metadata in TLVs,
   classical headers and quantum payloads can be synchronized and routed
   through existing IP infrastructure.

5.4.  Timestamp Alignment

   TLVs carrying local and photon arrival timestamps can provide
   synchronization similar to RTP ([RFC3550]).  This enables sub-
   nanosecond correlation of entangled photon arrivals across nodes.

5.5.  WDM/TDM Extensions

   Additional TLVs may specify per-wavelength parameters, enabling
   wavelength-division multiplexing (WDM) or time-division multiplexing
   (TDM) of entangled states ([ZhangSM2025]).  This supports scaling of
   quantum internet bandwidth across multiple frequency channels while
   preserving compatibility with ITU-T DWDM grids ([ITU-T.G694.1]).

6.  UDP Port Assignment

   Implementations SHOULD use a configurable default port.  IANA is
   requested to allocate a well-known port for QFCP.

7.  IANA Considerations

   - Allocate a UDP port for QFCP.

   - IANA is also requested to establish a QFCP TLV Types Registry with
   initial assignments as defined in Section 4.

8.  Security Considerations

   QFCP inherits the risks of UDP: spoofing, injection, replay.  It MUST
   be run in trusted environments or protected by DTLS/IPsec.  TLVs may
   reveal network state information and SHOULD be protected if
   confidentiality is required.




Zhu, et al.               Expires 4 April 2026                  [Page 5]

Internet-Draft        Quantum FWM Control Protocol          October 2025


9.  References

9.1.  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,
              <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>.

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [RFC4950]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro, "ICMP
              Extensions for Multiprotocol Label Switching", RFC 4950,
              DOI 10.17487/RFC4950, August 2007,
              <https://www.rfc-editor.org/info/rfc4950>.

9.2.  Informative References

   [RFC9583]  Wang, C., Rahman, A., Li, R., Aelmans, M., and K.
              Chakraborty, "Application Scenarios for the Quantum
              Internet", RFC 9583, DOI 10.17487/RFC9583, June 2024,
              <https://www.rfc-editor.org/info/rfc9583>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <https://www.rfc-editor.org/info/rfc3550>.

   [ITU-T.G694.1]
              International Telecommunication Union (ITU-T), "Spectral
              grids for WDM applications: DWDM frequency grid",
              Recommendation G.694.1, February 2012,
              <https://www.itu.int/rec/T-REC-G.694.1/en>.

   [Zhang2025]
              Zhang, Y., Broberg, R., Zhu, A., Li, G., Ge, L., Smith,
              J.M., and L. Feng, "Classical-decisive quantum internet by
              integrated photonics", DOI: 10.1126/science.adx6176,
              Science Vol. 389, pp. 940-944, August 2025,
              <https://doi.org/10.1126/science.adx6176>.





Zhu, et al.               Expires 4 April 2026                  [Page 6]

Internet-Draft        Quantum FWM Control Protocol          October 2025


   [ZhangSM2025]
              Zhang, Y., Broberg, R., Zhu, A., Li, G., Ge, L., Smith,
              J.M., and L. Feng, "Supplementary Materials for Classical-
              decisive quantum internet by integrated photonics",
              Science Supplementary Materials, August 2025.

Authors' Addresses

   Alan Zhu
   University of Pennsylvania School of Engineering and Applied Science
   Philadelphia, PA 19104
   United States
   Email: alzhu@seas.upenn.edu


   Yichi Zhang
   University of Pennsylvania School of Engineering and Applied Science
   Philadelphia, PA 19104
   United States
   Email: zyc@seas.upenn.edu


   Robert Broberg
   University of Pennsylvania School of Engineering and Applied Science
   Philadelphia, PA 19104
   United States
   Email: rbroberg@seas.upenn.edu


   Liang Feng
   University of Pennsylvania School of Engineering and Applied Science
   Philadelphia, PA 19104
   United States
   Email: fenglia@seas.upenn.edu


   Jonathan M. Smith
   University of Pennsylvania School of Engineering and Applied Science
   Philadelphia, PA 19104
   United States
   Email: jms@seas.upenn.edu










Zhu, et al.               Expires 4 April 2026                  [Page 7]
