Quantum Datagram Control Protocol (QDCP) for IP Optical Environments
draft-zhu-qirg-qdcp-01
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Alan Zhu , Yichi Zhang , Robert M. Broberg , Liang Feng , Jonathan M. Smith | ||
| Last updated | 2026-04-01 | ||
| Replaces | draft-zhu-qirg-qfcp | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-zhu-qirg-qdcp-01
Internet Engineering Task Force A. Zhu
Internet-Draft Y. Zhang
Intended status: Experimental R. Broberg
Expires: 3 October 2026 L. Feng
JM. Smith
University of Pennsylvania School of Engineering and Applied Science
1 April 2026
Quantum Datagram Control Protocol (QDCP) for IP Optical Environments
draft-zhu-qirg-qdcp-01
Abstract
This document specifies the Quantum Datagram protocol a lightweight
transport protocol designed to operate over UDP in IP optical
environments. QDCP (formerly QFCP) enables the transmission of
control- plane parameters required for transporting quantum
information 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 and is
prototyped for the transport of third-order nonlinear generated
quantum information on IP optical infrastructure. 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.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 3 October 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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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. QDCP Packet Format . . . . . . . . . . . . . . . . . . . . . 3
4. TLV Structures . . . . . . . . . . . . . . . . . . . . . . . 4
5. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Dynamic ROADM Configuration . . . . . . . . . . . . . . . 5
5.2. Real-Time Error Mitigation . . . . . . . . . . . . . . . 5
5.3. Hybrid IP Packet Orchestration . . . . . . . . . . . . . 5
5.4. Timestamp Alignment . . . . . . . . . . . . . . . . . . . 6
5.5. WDM/TDM Extensions . . . . . . . . . . . . . . . . . . . 6
6. Example TLV Blocks . . . . . . . . . . . . . . . . . . . . . 6
6.1. 0x08: Error Mitigation Vector . . . . . . . . . . . . . . 6
7. UDP Port Assignment . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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. QDCP is intended to be
that protocol, running over UDP [RFC768] and supporting modular Type-
Length-Value (TLV) extensions. QDCP supports applications aligned
with scenarios defined by the IRTF Quantum Internet Research Group
(QIRG) [RFC9583].
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By the no-cloning theorem, quantum information cannot be copied,
buffered, or retransmitted without disturbing the underlying state.
In the present work, where practical quantum memories and error-
corrected storage are not yet available at network scale, quantum
information is therefore transmitted as a datagram: loss is terminal,
and retransmission is physically meaningless. The accompanying
classical control header is sent without guaranteed delivery. If the
classical information is lost in transit, the associated quantum
state is presumed lost as well. Future implementations may leverage
advances in quantum memory, error correction, or entanglement-
assisted repeaters to decouple classical and quantum reliability,
potentially incorporating reliable classical transports such as QUIC
or TCP for control-plane robustness.
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
QDCP 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.
While UDP imposes a maximum datagram length (65,535 bytes), this
limitation has no impact on the amount of quantum information
conveyed. The quantum payload is not encapsulated within the UDP
packet itself but is passed through at the physical layer, with UDP
carrying only the associated classical control header. Thus the UDP
size constraint applies solely to the metadata, not to the optical or
quantum state being transported.
3. QDCP Packet Format
The QDCP packet consists of a fixed header followed by a sequence of
Type-Length-Value (TLV) payloads.
Packet Format:
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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 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLV Payloads ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: QDCP Packet Header and TLV Payloads
* Version (4 bits): Protocol version number (currently 0x1).
* Flags (4 bits): Reserved for future use.
* Length (16 bits): Specifies length of entire packet.
* Reserved (8 bits): Set to zero; ignored on receipt.
* TLV Payloads: Sequence of variable-length TLVs.
4. TLV Structures
Each TLV consists of a type, a reserved field, a length (in bytes),
and a value. The length specifies the length of the value, not the
entire TLV. 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:
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Type Name Value Format
---- ------------------------- ------------------------------
0x01 Quantum Protocol 32-bit int (e.g., encoding)
0x02 Polarization State 32-bit float
0x03 Timestamp of Origination 128-bit int (ps)
0x04 ROADM Output Port ID 32-bit int
0x05 Quantum Packet Delay 128-bit int (ps)
0x06 Duration of quantum 128-bit int (ps)
information
0x07 Center Frequency (GHz) 32-bit float
0x08 Optical Linewidth (GHz) 32-bit float
0x09 Polarization Correction Variable Polarizations
Figure 3: Initial TLV Type Assignments
5. Example Use Cases
This section illustrates how the Quantum Datagram Control Protocol
(QDCP) can be applied in practical network environments.
5.1. Dynamic ROADM Configuration
QDCP 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]).
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 QDCP 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.
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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.
The mechanisms to achieve such precision for distributed-clock
synchronization (e.g. NTP, PTP, White Rabbit) are out of scope for
this document.
TLVs carrying "Duration of Quantum Information" specify the period
during which the optical bypass must remain active to support quantum
information transport. After the indicated duration expires, the
bypass is automatically reverted back to its normal state to resume
classical control-plane processing.
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. Example TLV Blocks
This section specifies the TLV structure for specific TLV types.
6.1. 0x08: Error Mitigation Vector
Error mitigation can be done by sending different known polarization
states with respect to the output of the chip and identifying the
SU(2) transformation applied to these states by the fiber once they
reach the receiver ([ZhangSM2025]).
The value of the Error Mitigation TLV will be composed of a sequence
of 64 bit structures, where each structure corresponds to a specific
polarization state that is transmitted. The structure of each 64 bit
block is as follows:
Error Mitigation Value Structure:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Polarization | Duration (ns) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Arrival Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 4: Error Mitigation Value Structure
The first eight bits specify which polarization is being sent. For
simplicity, assume transmitted states must be in a horizontal,
vertical, diagonal, anti-diagonal, right-circular, or left-circular
polarization. The polarization section for each of these 64-bit
structures can then be specified using the following mapping table.
Polarization to Reserved Bit Mapping:
Value Polarization
----- ------------------
0 Horizontal
1 Vertical
2 Diagonal
3 Anti-Diagonal
4 Right-Circular
5 Left-Circular
Figure 5: Polarization to Reserved Bit Mappings
The duration in nanoseconds specifies how long the the specific
polarization will be transmitted for. The arrival time specifies how
long after the reception of the QDCP packet this specific
polarization will arrive with nanosecond precision.
To accurately identify the SU(2) transformation, at least two non-
orthogonal polarizations are required to be sent. Zhang et al.
experimentally used Horizontal and Right-Circular polarizations for
error mitigation, both other combinations are also valid.
For concreteness, consider the example where Horizontal and Right-
Circular polarizations are transmitted for error correction.
Example Error Mitigation TLV Structure:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x08 | 0x00 | 0x10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 | 0x400 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x400 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x04 | 0x400 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x800 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Error Mitigation TLV including Right-Circular and
Horizontal Polarizations. 0x08 is the TLV type. 0x00 is the
reserved field. 0x10 is the length of the value, which is 16
bytes in this case. The next 0x00 represents horizontal
polarization according to Figure 5. The first 0x400 represents
the duration of the horizontal polarization in nanoseconds and
the second represents the arrival time of the horizontal
polarization in nanoseconds. The next 0x04 represents right-
circular polarization, with the following 0x400 representing the
duration of the right-circular polarization and the 0x800
representing the arrival time of the right-circular polarization.
7. UDP Port Assignment
Implementations SHOULD use a configurable default port. IANA is
requested to allocate a well-known port for QDCP.
8. IANA Considerations
- Allocate a UDP port for QDCP.
- IANA is also requested to establish a QDCP TLV Types Registry with
initial assignments as defined in Section 4.
9. Security Considerations
QDCP 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 MUST be protected if
confidentiality is required.
Use of DTLS/IPsec and reliable classical transport mechanisms are
reserved for future work.
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10. Acknowledgements
The authors would like to thank Steve Schwartz and Wes Harding for
their constructive feedback and detailed comments. Their suggestions
helped broaden the scope of this document beyond the initial
implementation and guided refinements to the protocol design and
terminology.
11. References
11.1. 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>.
11.2. 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>.
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[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>.
[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
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