



Media Over QUIC                                            S. Nandakumar
Internet-Draft                                                     Cisco
Intended status: Standards Track                             C. Jennings
Expires: 20 April 2026                                     Cisco Systems
                                                         17 October 2025


      Media over QUIC Transport (MOQT) for Agent-to-Agent Protocol
                      draft-nandakumar-a2a-moqt-transport-00

Abstract

   This document specifies how the Agent-to-Agent (A2A) protocol can be
   transported over Media over QUIC Transport (MOQT).  MOQT provides a
   publish/subscribe model over QUIC that enables efficient real-time
   communication between AI agents, supporting the A2A protocol's
   requirements for discovery, negotiation, and collaboration while
   leveraging MOQT's streaming capabilities and built-in prioritization
   mechanisms.

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://ietf-wg-
   moq.github.io/draft-a2a-moqt-transport/draft-a2a-moqt-transport.html.
   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-a2a-moqt-transport/.

   Discussion of this document takes place on the Media Over QUIC
   Working Group mailing list (mailto:moq@ietf.org), which is archived
   at https://mailarchive.ietf.org/arch/browse/moq/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/moq/.

   Source for this draft and an issue tracker can be found at
   https://github.com/ietf-wg-moq/draft-a2a-moqt-transport.

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/.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  A2A Transport Requirements  . . . . . . . . . . . . . . . . .   3
   3.  MOQT Transport Mapping  . . . . . . . . . . . . . . . . . . .   4
     3.1.  Connection Establishment  . . . . . . . . . . . . . . . .   4
     3.2.  Track Organization  . . . . . . . . . . . . . . . . . . .   5
     3.3.  Message Serialization . . . . . . . . . . . . . . . . . .   5
     3.4.  Priority and Quality of Service . . . . . . . . . . . . .   6
   4.  Protocol Operations . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Agent Discovery . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Request/Response Patterns . . . . . . . . . . . . . . . .   7
     4.3.  Streaming Operations  . . . . . . . . . . . . . . . . . .   8
   5.  Benefits of MOQT for A2A  . . . . . . . . . . . . . . . . . .   9
     5.1.  Real-time Communication Benefits  . . . . . . . . . . . .   9
     5.2.  Scalability Benefits  . . . . . . . . . . . . . . . . . .  10
     5.3.  Reliability and Resilience  . . . . . . . . . . . . . . .  10
   6.  MOQT Relay Infrastructure for A2A . . . . . . . . . . . . . .  10
     6.1.  Relay Network Architecture  . . . . . . . . . . . . . . .  10
     6.2.  Message Caching Benefits  . . . . . . . . . . . . . . . .  11
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12




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1.  Introduction

   The Agent-to-Agent (A2A) protocol enables communication between AI
   agents across different platforms and frameworks.  Currently, A2A
   supports three transport protocols: JSON-RPC 2.0 over HTTP(S), gRPC,
   and HTTP+JSON/REST.  This document defines a fourth transport option
   using Media over QUIC Transport (MOQT) to provide enhanced real-time
   streaming capabilities for agent interactions.

   MOQT is designed for media streaming over QUIC and WebTransport,
   providing a publish/subscribe model with hierarchical data
   organization.  While originally intended for media applications,
   MOQT's streaming model and prioritization capabilities make it well-
   suited for real-time agent communication scenarios.

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.  A2A Transport Requirements

   According to the A2A specification, all transport protocols MUST
   provide functional equivalence and support the following
   capabilities:

   *  Secure communication over encrypted channels

   *  Request/response messaging patterns

   *  Streaming data delivery capabilities

   *  Error handling and status reporting

   *  Agent discovery and capability negotiation

   *  Support for various data types (text, JSON, files)











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      A2A Protocol Layer
      ┌─────────────────────────────────────────────────────────────┐
      │  Agent Discovery │ Capability Exchange │ Task Collaboration │
      └─────────────────────────────────────────────────────────────┘
                                    │
      ┌─────────────────────────────────────────────────────────────┐
      │                    MOQT Transport Layer                     │
      │  ┌─────────────┐  ┌─────────────┐  ┌─────────────────────┐  │
      │  │ PUB/SUB     │  │ Streaming   │  │ Priority/QoS        │  │
      │  │ Model       │  │ Support     │  │ Management          │  │
      │  └─────────────┘  └─────────────┘  └─────────────────────┘  │
      └─────────────────────────────────────────────────────────────┘
                                    │
      ┌─────────────────────────────────────────────────────────────┐
      │                    QUIC/WebTransport                        │
      │        ┌─────────────┐              ┌─────────────┐         │
      │        │ Encryption  │              │ Multiplexing│         │
      │        │ (TLS 1.3)   │              │ & Flow Ctrl │         │
      │        └─────────────┘              └─────────────┘         │
      └─────────────────────────────────────────────────────────────┘

3.  MOQT Transport Mapping

3.1.  Connection Establishment

   A2A agents using MOQT transport MUST establish a QUIC or WebTransport
   connection with the ALPN value "moq-00" as defined in the MOQT
   specification.  The connection setup follows this sequence:

   Agent A                                                   Agent B
      |                                                        |
      |──── QUIC Connection (ALPN: "moq-00") ────────────────▶ |
      |◄─── QUIC Connection Established ───────────────────────|
      |                                                        |
      |──── MOQT CLIENT_SETUP ────────────────────────────────▶|
      |◄─── MOQT SERVER_SETUP ─────────────────────────────────|
      |                                                        |
      |──── A2A Agent Registration ───────────────────────────▶|
      |◄─── A2A Capability Exchange ───────────────────────────|
      |                                                        |
      |◄═══ A2A Protocol Exchang ═════════════════════════════▶|

   During the MOQT setup phase, agents MUST negotiate the following A2A-
   specific extensions:

   *  a2a-version: Supported A2A protocol version

   *  a2a-capabilities: Agent capabilities and supported operations



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   *  a2a-auth: Authentication and authorization tokens

3.2.  Track Organization

   A2A protocol messages are mapped to MOQT tracks using a hierarchical
   namespace structure.  Each agent creates tracks for different message
   categories: Tracks are organized as follows:

   Request Tracks:  Used for A2A request messages, organized by category
      and action (e.g., discovery/capabilities, tasks/execute).

   Response Tracks:  Used for A2A response messages, organized by
      request ID for correlation.

   Stream Tracks:  Used for long-running streaming operations like task
      execution updates or file transfers.

   Notification Tracks:  Used for asynchronous notifications and events.

3.3.  Message Serialization

   A2A protocol messages are serialized as JSON and encapsulated within
   MOQT objects.  Each MOQT object contains:

   MOQT Object Structure for A2A:

   ┌─────────────────────────────────────────────────────────┐
   │                 MOQT Object Header                      │
   │  Track ID │ Group ID │ Object ID │ Priority │ ....      │
   └─────────────────────────────────────────────────────────┘
   ┌─────────────────────────────────────────────────────────┐
   │                 A2A Message Payload                     │
   │  ┌─────────────────────────────────────────────────────┐│
   │  │              JSON A2A Message                       ││
   │  │  {                                                  ││
   │  │    "jsonrpc": "2.0",                                ││
   │  │    "method": "category/action",                     ││
   │  │    "params": { ... },                               ││
   │  │    "id": "request-id"                               ││
   │  │  }                                                  ││
   │  └─────────────────────────────────────────────────────┘│
   └─────────────────────────────────────────────────────────┘

   The A2A message format remains unchanged from the JSON-RPC 2.0
   specification, ensuring compatibility with existing A2A
   implementations.





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3.4.  Priority and Quality of Service

   MOQT's built-in priority system is mapped to A2A message urgency:

   Priority 1 (Highest):  Emergency and critical error responses

   Priority 2:  Real-time interaction responses and notifications

   Priority 3:  Standard request/response messages

   Priority 4:  Discovery and capability exchange messages

   Priority 5 (Lowest):  Background updates and non-critical
      notifications

4.  Protocol Operations

4.1.  Agent Discovery

   Agent discovery over MOQT uses a Subscribe Namespace pattern where
   agents subscribe to the <session_context_id>/discovery namespace
   prefix and publish their agent announcements using the
   <session_context_id>/discovery/agent-{id} pattern to reach all
   subscribers.

   Discovery Flow:

   Agent A                       MOQT Network                    Agent B
      |                              |                             |
      |─ SUBSCRIBE_NAMESPACE────────▶|                             |
      |  (<..>/discovery)            |◄─ SUBSCRIBE_NAMESPACE───────┤
      |                              |   (<..>/discovery)          |
      |                              |                             |
      |─ PUBLISH(/discovery/         |                             |
      |   agent-a) ─────────────────▶|─ PUBLISH(/discovery/        |
      |                              |agent-a) ───────────────────▶|
      |                              |                             |
      |                              |◄─ PUBLISH(/discovery/       |
      |                              |    agent-b) ────────────────┤
      |◄─ PUBLISH(/discovery/        |                             |
      |   agent-b) ──────────────────|                             |
      |                              |                             |
      |                              |                             |
      |◄── Object(Agent B caps) ─────|── Object(Agent A caps) ────▶|







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4.2.  Request/Response Patterns

   A2A request/response interactions are implemented using coordinated
   PUBLISH/SUBSCRIBE operations:

   1.  Server agent uses SUBSCRIBE_NAMESPACE to subscribe to
       <..>/server-agent-{id} Namespace prefix

   2.  Client agent sends PUBLISH message on <..>/server-
       agent-{id}/request track

   3.  Client agent subscribes to <..>/server-agent-{id}/response track

   4.  Client agent publishes OBJECT on <..>/server-agent-{id}/request
       track

   5.  Server agent receives OBJECT via its namespace subscription

   6.  Server agent publishes OBJECT on <..>/server-agent-{id}/response
       track

   7.  Client agent receives response OBJECT via its subscription





























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   Request/Response Flow:

   Client Agent                MOQT                   Server Agent
        |                        |                        |
        |                        |◄(1) SUBSCRIBE_NAMESPACE|
        |                        | (<..>/server-agent-{id})
        |─(2) PUBLISH(           |                        |
        |  /server-agent-{id}/   |                        |
        |  request) ────────────▶|                        |
        |                        |─(2) PUBLISH(           |
        |                        |  /server-agent-{id}/   |
        |                        |  request) ────────────▶|
        |─(3) SUBSCRIBE(         |                        |
        |  /server-agent-{id}/   |                        |
        |  response) ───────────▶|                        |
        |                        |─(3) SUBSCRIBE(         |
        |                        |  /server-agent-{id}/   |
        |                        |  response) ───────────▶|
        |─(4) OBJECT(            |                        |
        |  /server-agent-{id}/   |                        |
        |  request) ────────────▶|───────────────────────▶|
        |                        |                        |
        |                        |◄(5) OBJECT(            |
        |                        |  /server-agent-{id}/   |
        |                        |  response) ────────────|
        |◄(6) OBJECT(            |◄───────────────────────|
        |  /server-agent-{id}/   |                        |
        |  response) ────────────|                        |
        |                        |                        |

4.3.  Streaming Operations

   Long-running A2A operations like task execution or file transfer
   utilize MOQT's streaming capabilities.  Stream tracks carry
   incremental updates as separate MOQT objects.
















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   Streaming Task Execution:

   Client                     MOQT Stream                  Server
     |                           |                           |
     |─ SUBSCRIBE(               |                           |
     |  /server-agent-{id}/      |                           |
     |  task_{id}) ─────────────▶|                           |
     |                           |─ SUBSCRIBE(               |
     |                           |  /server-agent-{id}/      |
     |                           |  task_{id}) ─────────────▶|
     |                           |◄─ OBJECT(                 |
     |                           |  /server-agent-{id}/      |
     |                           |  task_{id}, progress-1) ──|
     |◄─ Progress Update 1 ──────|                           |
     |                           |◄─ OBJECT(                 |
     |                           |  /server-agent-{id}/      |
     |                           |  task_{id}, progress-2) ──|
     |◄─ Progress Update 2 ──────|                           |
     |                           |◄─ OBJECT(                 |
     |                           |  /server-agent-{id}/      |
     |                           |  task_{id}, result) ──────|
     |◄─ Final Result ───────────|                           |
     |                           |◄─ OBJECT(                 |
     |                           |  /server-agent-{id}/      |
     |                           |  task_{id}, complete) ────|
     |◄─ Stream Complete ────────|                           |

5.  Benefits of MOQT for A2A

   MOQT provides significant advantages over traditional A2A transports,
   particularly for real-time agent collaboration and large-scale
   deployments:

5.1.  Real-time Communication Benefits

   *  Low-latency streaming enables immediate agent response to changing
      conditions

   *  Priority-based message delivery ensures critical communications
      are not delayed

   *  Streaming object delivery allows agents to act on incomplete data
      when appropriate

   *  Built-in flow control prevents agent overload during high-volume
      interactions





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5.2.  Scalability Benefits

   MOQT's publish/subscribe model creates powerful network effects for
   multi-agent environments:

   *  One-to-many broadcasts enable efficient agent coordination

   *  Subscription-based interest management reduces unnecessary traffic

   *  Dynamic agent discovery scales to thousands of participants

   *  Relay-based distribution prevents connection explosion in mesh
      networks

5.3.  Reliability and Resilience

   MOQT provides enhanced reliability features critical for production
   agent deployments:

   *  Connection migration maintains agent sessions during network
      changes

   *  Automatic retry and recovery mechanisms handle transient failures

   *  Graceful degradation allows agents to continue operating with
      reduced capabilities

   *  Quality of Service controls prevent cascade failures in agent
      networks

6.  MOQT Relay Infrastructure for A2A

   MOQT relays provide critical infrastructure benefits for large-scale
   A2A deployments, enabling efficient message distribution and caching.

6.1.  Relay Network Architecture

   MOQT relays form a hierarchical distribution network that optimizes
   A2A message delivery across geographic and organizational boundaries:

   This hierarchical structure provides:

   *  Regional optimization with local agent clusters

   *  Global connectivity for cross-region agent collaboration

   *  Load distribution to prevent single points of failure




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   *  Configurable routing policies based on agent requirements

6.2.  Message Caching Benefits

   MOQT relays can implement intelligent caching strategies optimized
   for A2A communication patterns.

   The most frequently accessed and time-sensitive data with time-to-
   live values are measured in seconds.  This includes real-time agent
   responses, live data streams, and status updates that require
   immediate availability.  These messages are kept in high-speed memory
   to ensure minimal latency for active agent interactions.

   Another layer can serve as an intermediate storage tier with time-to-
   live values measured in minutes.  This layer contains agent
   capability profiles, metadata about agent configurations, and results
   from common queries that are accessed regularly.  The caching layer
   can provide a balance between accessibility and resource utilization.

   Also for archives of historical data with extended retention periods
   measured in hours or days, can employ a different storage strategy.
   Examples data might include historical logs, archived computation
   results, compliance audit data, and debug traces that may be needed
   for analysis or regulatory purposes but are accessed infrequently.

7.  References

7.1.  Normative References

   [A2A]      A2A Project, "Agent-to-Agent Protocol Specification",
              2025, <https://a2a-protocol.org/latest/specification/>.

   [MoQ-TRANSPORT]
              Nandakumar, S., Vasiliev, V., Swett, I., and A. Frindell,
              "Media over QUIC Transport", Work in Progress, Internet-
              Draft, draft-ietf-moq-transport-14, 2 September 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-moq-
              transport-14>.

   [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>.




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   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC9000]  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/info/rfc9000>.

7.2.  Informative References

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/info/rfc7540>.

   [WebTransport]
              Vasiliev, V., "The WebTransport Protocol Framework",
              RFC 9297, August 2023,
              <https://www.rfc-editor.org/rfc/rfc9297>.

Appendix A.  Acknowledgments

Authors' Addresses

   Suhas Nandakumar
   Cisco
   Email: snandaku@cisco.com


   Cullen Jennings
   Cisco Systems
   Email: fluffy@cisco.com


















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