Network Working Group                                        G. Fioccola
Internet-Draft                                       Huawei Technologies
Intended status: Informational                                 P. Mendes
Expires: 11 January 2024                                          Airbus
                                                                J. Burke
                                                              UCLA REMAP
                                                             D. Kutscher
                                                            10 July 2023

                     Information-Centric Metaverse


   This document aims to explore the new challenges for the transport
   network brought by the development of Metaverse.  It discusses the
   Metaverse as an Information-Centric Network (ICN).

Status of This Memo

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Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements and Gaps . . . . . . . . . . . . . . . . . . . .   3
   3.  Current and Emerging Mainstream Approaches  . . . . . . . . .   4
   4.  Opportunities and Challenges for Information-Centric
           Metaverse . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Scalable multimedia communication . . . . . . . . . . . .   7
       4.1.1.  Issues today  . . . . . . . . . . . . . . . . . . . .   7
       4.1.2.  ICN Support . . . . . . . . . . . . . . . . . . . . .   7
       4.1.3.  Research Opportunities  . . . . . . . . . . . . . . .   8
     4.2.  Interaction with applications . . . . . . . . . . . . . .   8
       4.2.1.  Issues today  . . . . . . . . . . . . . . . . . . . .   8
       4.2.2.  ICN Support . . . . . . . . . . . . . . . . . . . . .   9
       4.2.3.  Research Opportunities  . . . . . . . . . . . . . . .   9
     4.3.  In-Network Computing  . . . . . . . . . . . . . . . . . .  10
       4.3.1.  Issues today  . . . . . . . . . . . . . . . . . . . .  10
       4.3.2.  ICN Support . . . . . . . . . . . . . . . . . . . . .  10
       4.3.3.  Research Opportunities  . . . . . . . . . . . . . . .  10
     4.4.  Interoperability with existing infrastructure . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   "Metaverse" is a place-holder for a range of new technologies and
   experiences that is not particularly well-defined, but some working
   definitions include the notion of shared, interoperable, and
   persistent eXtended Reality (XR).  Whereas initial prototypes and
   blueprints suggest leveraging or extending existing Internet and Web
   protocols, we can already identify gaps with respect to performance
   and scalability, for example as reported by [socialVR-measurements].

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   Some of the observed performance problems seem to stem from
   fundamental gaps in today's Internet and Web technologies, for
   example, the lack of scalable and robust multi-destination
   communication and the lack of leveraging computing in the network
   with the required level of flexibility and trustworthiness to provide
   offloading services and to enable the ultra-low latencies that some
   Metaverse applications claim to require.

   Different remedies are being proposed, e.g., providing more (costly)
   deterministic communication services through resource reservation and
   scheduling on the Internet, requiring/enabling the network to
   understand application requirements and to provide corresponding QoS,
   extended overlay infrastructure for reducing latencies for CDN-like
   distribution etc.

   Alternatively, one might also take a more principled approach and do
   not take current design and deployment models as a given, but rather
   take Metaverse as a first candidate proposal for a future web
   infrastructure that enables fine-granular 3D content exchange, rich
   interaction between physical and virtual infrastructure, access to
   static data and dynamic computation results for individual users as
   well as for large user groups without the limitations of today's
   platform- and overlay-based system -- i.e., conceive the Metaverse
   and the future web as a fundamentally information-centric system.

   This document addresses three aspects:

   1.  the documentation of requirements and observed gaps with the
       current technology stack;

   2.  a discussion of the applicability of different networking and
       distributed computing technologies; and

   3.  an initial discussion of a more fundamental and comprehensive re-
       design of a future web that provides useful services for
       Metaverse systems and beyond.

2.  Requirements and Gaps

   [I-D.han-iccrg-arvr-transport-problem] started to analyze the
   requirements of Virtual Reality (VR) and Augmented Reality (AR) to
   networking from a transport protocol perspective.  Some of the
   requirements are:

   *  low latency and High-Speed transport to reach services in one-hop
      and for real-time user interactions;

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   *  intelligent control and SLA real-time monitoring to convey the
      traffic and manage network resources and source/route re-

   *  decentralization and Edge Services by positioning the data close
      to the user; and

   *  reducing data sizes through resolution changes, compression, and
      more efficient encodings.

   [socialVR-measurements] performed measurements with five popular
   social VR platforms.  The experimental results revealed that all
   these platforms face fundamental technical challenges considering the
   claims that are often associated with the Metaverse.  One issue was
   poor scalability with respect to the number of users in one session:
   throughput, end-to-end latency, and on-device computation resource
   utilization increase almost linearly with the number of users.  Other
   issues include noticeable load and reduced achievable video rendering
   frame rates and considerable network utilization even with smaller
   numbers of users.

3.  Current and Emerging Mainstream Approaches

   Different IETF technologies have been proposed to address some of the
   above-mentioned issues and to provider a better service for Metaverse
   applications.  In the following, we list a few of them and will
   discuss them in more detail in a future version of this document.
   For example, on the network and transport layer, there are elaborate
   solutions for dealing with bandwidth limitations, network congestion,
   lossy transport protocols, and the ever growing size of video data,
   to address the above requirements, for instance:

   *  MPTCP[RFC8684] and MPQUIC[I-D.ietf-quic-multipath] are the
      expansions of TCP[RFC9293] and QUIC[RFC9000] in order to dispatch
      packets over multiple paths to maximize throughput.

   *  Dynamic Adaptive Streaming over HTTP (DASH) aim to improve the
      viewport quality of immersive videos by refining the tiles
      delivery.  But client-driven nature of DASH introduces less
      control on the server side.

   *  Media over QUIC (MoQ) ([I-D.ietf-moq-requirements]) and extensions
      such as QuicR ([I-D.jennings-moq-proto]) use similar concepts and
      delivery mechanisms to those used by CDN and named objects.  There
      are fundamental characteristics that QuicR provides for ultra low
      latency delivery, by leveraging the characteristics of QUIC

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   *  The APplication-aware Networking (APN) aims to develop a framework
      to enable fine-granularity network service provisioning (traffic
      operations) within the network domain(s) that supports APN
      ([]).  APN aims to use the ability to apply
      policies to traffic flows entering into the infrastructure.  In
      modern networks, where things such as deterministic networking and
      networking slicing are required, there is a requirement for more
      functionality than QoS can provide.

   *  The Computing-Aware Traffic Steering (CATS) aims to analyze the
      problem on the edge node, which makes a decision based on the
      metrics of interest, and then steers the traffic to a node that
      serves a service instance.  Indeed, for AR/VR services, the
      performance experienced by the end users depends on both network
      metrics such as bandwidth and latency, and compute metrics such as
      processing, storage capabilities, and capacity.

   In all of these approaches, the Metaverse is considered as an overlay
   application with corresponding infrastructure dependencies, but this
   potentially increases the current gaps (and resulting costs and
   technical complexity) between distributed applications and the
   underlying network architecture.

   In the 3D hypermedia space, one proposal for a new "Spatial Web"
   Framework is the HyperSpace Transaction Protocol (HSTP), as described
   by [IEEE-P2874], intended to "enable interoperable, semantically
   compatible connections between connected hardware (e.g. autonomous
   drones, sensors, smart devices, robots) and software (e.g. services,
   platforms, applications, artificial intelligence systems)".  The
   specification, which is not accessible publically, is supposed to

   1.  a spatial range query format and response language for requesting
       data about objects within a dimensional range (spatial,
       temperature, pressure, motion) and their content.

   2.  a semantic data ontology schema for describing objects,
       relations, and actions in a standardized way

   3.  a verifiable credentialing and certification method for
       permissioning create, retrieve, update, and delete (CRUD) access
       to devices, locations, users, and data; and

   4.  a human and machine-readable contracting language that enables
       the expression and automated execution of legal, financial and
       physical activities.

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   We cannot review the technical specification, but the feature
   description seems to suggest an application layer protocol that would
   enable more expressiveness and functionality in the "web" (i.e.,
   application and presentation) layer, however based on the assumption
   of existing networking technology and overlay approaches.

4.  Opportunities and Challenges for Information-Centric Metaverse

   Considering the gaps and perceived requirements from applications and
   proposed application layer protocols, we can reason about a holistic
   design that can address the afore-mentioned problems _and_ provide a
   more useful foundations for future hypermedia communication.

   Information-Centric Networking (ICN) introduces named information
   objects, e.g. media contents, as the central concept as opposed to a
   physical computer, or node ([RFC7927]).  In ICN approaches, the
   principal paradigm is not host-to-host communication as in the
   current Internet architecture.  The increasing demand for highly
   scalable and efficient distribution of content has motivated the
   development of architectures that focus on information objects, their
   properties, and receiver interest in the network to achieve efficient
   and reliable distribution of such objects.

   Therefore, we can conceive the Metaverse as an information-centric
   system where most applications participate in granular 3D content
   exchange, context-aware integration with the physical world, and
   other Metaverse-relevant services.  The assumption is that the
   Metaverse is an information-centric concept that will become
   synonymous with the network itself.

   Many applications already work with data-oriented paradigms.  Mapping
   them to a host-centric network model creates complexities and
   robustness issues, which can be addressed with an ICN oriented

   The overlay approach to deal with real-time interactive media adds
   significant complexity.  It is needed a fine-grained, hierarchical
   media exchange for low-latency interactive communication that enables
   scalable multi-destination distribution, and in-network replication
   and transformation that exposes object hierarchy for fine grained
   access and security.

   Since the Metaverse is an extension of the Web into immersive XR
   modalities that are often aligned with physical space, leveraging ICN
   concepts provides support for decentralized publishing, content
   interoperability and co-existence, based on general building blocks
   and not within separated application silos as today’s initial

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   In the following, we discuss issues with today's technologies, ICN
   support that could be leveraged, and research opportunities for the
   ICN community for four topics:

   1.  Scalable multimedia communication;

   2.  Interaction with applications;

   3.  In-network computing; and

   4.  Interoperability with existing infrastructure.

4.1.  Scalable multimedia communication

4.1.1.  Issues today

   *  Low-latency live streaming is not easy and not efficient in the
      Internet today.  CDN-based DASH incurs high latencies.

   *  Current trends: blending of real-time interactive (WebRTC with
      RTP) and streaming (DASH), for example: Amazon Twitch, Meta Rush,
      IETF Media-over-QUIC, QuicR

   *  What is needed:

      -  fine-granular media distribution that supports both interactive
         and streaming;

      -  scalable multi-destination distribution, i.e., some kind of in-
         network replication;

      -  ability to leverage wireless broadcast such as 5G Broadcast;

      -  support for hetergeneous devices and edge networks, i.e.,
         different quality layers, possibly dynamic transcoding.

4.1.2.  ICN Support

   ICN is generally supporting most of these requirements: * multi-
   destination distribution can be achieved through automatic in-network
   replication and interest aggregation, further supported by
   opportunistic caching. * ICN provides a uniform interface for unicast
   and "multicast" (i.e., there is no difference for consumers). * IP-
   Multicast issues (inter-domain, routing scalability) do not apply *
   Wireless broadcast could be leveraged where available, without
   requiring application-aware in edge routers. * Receiver-driven
   operation conducive to supporting different quality levels, like in

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   DASH today: receiver has all the knowledge directly (current
   performance) and can make timely decisions. * Consumer mobility is an
   efficient operation in ICN (a non-operation).

4.1.3.  Research Opportunities

   *  Based on ICN's basic capabilities, actual systems would need
      specific approaches for quality adaptation, e.g.,

      -  use of layered coding; and

      -  role of in-network transcoding.

   *  In order to achieve low-latency and QoS, more work is needed for

      -  fine-tuning with respect to interest aggregation, caching; and

      -  prioritizing "flows", e.g., audio over video.

   *  Sender mobility has seen some proposals in research that need to
      be validated.

   *  More experiments are needed with large-scale interactive
      multimedia communication and low-latency transport.

   *  Actual application development and deployment is needed to
      gradually develop best practices, software stacks, and re-usable
      application components.

      -  For initial deployments, some kind of overlay topology over the
         current Internet might be needed.

      -  Whereas the technology (different faces and underlay protocols)
         is essentially ready, there are other issues the deployment and
         efficient operation of such overlays (shortest path
         communication, routing, reliability).

4.2.  Interaction with applications

4.2.1.  Issues today

   Many applications, not only the Metaverse, work inherently with data-
   oriented paradigms when they are accessing named data, objects etc.
   Mapping this to a connection-based communication model creates
   complexities and robustness issues and would not result in good
   abstractions for systems.

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   In Metaverse applications, data can potentially be shared efficiently
   between nodes and within one node/process.  Connection-based
   communication models make it hard/impossible to do so.

   Application layer data structures in VR (3D models, scene
   descriptions) are based on object hierarchies, connection-based
   systems may not be able to take advantage of it.

4.2.2.  ICN Support

   ICN generally enables direct data-oriented communication: just names
   and objects so that location, storage contexts (files etc.) become
   less relevant.  In addition ICN provides

   *  named-based APIs to applications;

   *  support for object collections through manifests;

   *  additional "middleware" such as dataset synchronization; and

   *  data-sharing is generally supported, which has benefits beyond
      networking, e.g., zero-copy sharing in processes etc.

4.2.3.  Research Opportunities

   *  Work should be started on the development of information-centric
      hypermedia concepts, i.e., linking from object collections to
      other objects/collections.

   *  Manifest technologies such as FLIC should be extended to support
      dynamically created objects.

   *  Concepts for dealing with "mutable objects" (or mutable
      "information") should be developed, i.e., how to deal with updates
      without giving up data immutability.

   *  The relationship between application-layer data-oriented operation
      and network-layer needs to be explored further, e.g.,

      -  Would there be any differences?

      -  Would it be needed to think about robust namespace mappings

   *  Concepts and mechanisms for privacy, selective attention, content
      filtering, and autonomous interactions, as well as ownership and
      control on the publishing side are needed.

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   *  In general more applications should be developed to enable more

4.3.  In-Network Computing

   In-network computing can support Metaverse systems in different ways:

   *  transcoding (to support heterogeneous receiver groups and networks

   *  coding for better communication robustness & efficiency;

   *  rendering for offloading clients and servers;

   *  compression and decompression on various levels, including
      semantic communication;

   *  ad insertion; and

   *  potentially for future decomposed Metaverse systems.

4.3.1.  Issues today

   *  In-network computing today is typically limited to coarse-grained
      CDN-style computing, include Multi-Access Edge Computing.

   *  Current trust and security frameworks require TLS connection
      termination, i.e., represent an overlay approach, which is not
      conducive to low latency communication.

   *  Dynamic, just-in-time, instantiation of computing function on
      application-agnostic platforms is not available.

4.3.2.  ICN Support

   *  The named-data approach is generally useful for distributed
      computing (NFN, RICE, CFN).

   *  ICN's security model makes it possible to do on-path computing /
      data transformation securely

   *  discovery of functions and request forwarding can be punted on
      regular ICN mechanisms (name-based forwarding).

4.3.3.  Research Opportunities

   *  Robust distributed computing interaction models (RMI, Dataflow,
      REST) should be further developed and tested.

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   *  Specific approaches such as in-network media transcoding should be

   *  In general, more experiments for different types of applications
      are needed.

4.4.  Interoperability with existing infrastructure

   In addition, the interoperability aspects also need to be
   investigated, and, for example, Hybrid Information-Centric Networking
   (hICN), which implements information-networking functionalities into
   IPv6 ([I-D.muscariello-intarea-hicn], can provide a solution.

   It would be theoretically possible to leverage the solutions
   mentioned in the previous section in order to reach the above ICN
   oriented capabilities.  But a systemic approach would be highly
   desirable in the longer term.

5.  Security Considerations


6.  IANA Considerations

   This document makes no request of IANA.

7.  Contributors


8.  Acknowledgements


9.  Informative References

              Han, L. and K. Smith, "Problem Statement: Transport
              Support for Augmented and Virtual Reality Applications",
              Work in Progress, Internet-Draft, draft-han-iccrg-arvr-
              transport-problem-01, 12 March 2017,

              Gruessing, J. and S. Dawkins, "Media Over QUIC - Use Cases
              and Requirements for Media Transport Protocol Design",
              Work in Progress, Internet-Draft, draft-ietf-moq-

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              requirements-01, 10 July 2023,

              Liu, Y., Ma, Y., De Coninck, Q., Bonaventure, O., Huitema,
              C., and M. Kühlewind, "Multipath Extension for QUIC", Work
              in Progress, Internet-Draft, draft-ietf-quic-multipath-05,
              10 July 2023, <

              Jennings, C. F. and S. Nandakumar, "QuicR - Media Delivery
              Protocol over QUIC", Work in Progress, Internet-Draft,
              draft-jennings-moq-proto-00, 13 March 2023,

              Li, Z., Peng, S., Voyer, D., Li, C., Liu, P., Cao, C., and
              G. S. Mishra, "Application-aware Networking (APN)
              Framework", Work in Progress, Internet-Draft, draft-li-
              apn-framework-07, 3 April 2023,

              Muscariello, L., Carofiglio, G., Auge, J., Papalini, M.,
              and M. Sardara, "Hybrid Information-Centric Networking",
              Work in Progress, Internet-Draft, draft-muscariello-
              intarea-hicn-04, 20 May 2020,

              "IEEE SA P2874 Standard for Spatial Web Protocol,
              Architecture and Governance", n.d.,

   [RFC7927]  Kutscher, D., Ed., Eum, S., Pentikousis, K., Psaras, I.,
              Corujo, D., Saucez, D., Schmidt, T., and M. Waehlisch,
              "Information-Centric Networking (ICN) Research
              Challenges", RFC 7927, DOI 10.17487/RFC7927, July 2016,

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   [RFC8684]  Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
              Paasch, "TCP Extensions for Multipath Operation with
              Multiple Addresses", RFC 8684, DOI 10.17487/RFC8684, March
              2020, <>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,

   [RFC9293]  Eddy, W., Ed., "Transmission Control Protocol (TCP)",
              STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022,

              Cheng, R., Wu, N., Varvello, M., Chen, S., and B. Han,
              "Are we ready for metaverse?: a measurement study of
              social virtual reality platforms", ACM, Proceedings of the
              22nd ACM Internet Measurement Conference,
              DOI 10.1145/3517745.3561417, October 2022,

Authors' Addresses

   Giuseppe Fioccola
   Huawei Technologies
   Palazzo Verrocchio, Centro Direzionale Milano 2
   20054 Segrate (Milan)

   Paulo Mendes
   82024 Taufkirchen

   Jeff Burke
   102 East Melnitz Hall
   Los Angeles,  CA 90095
   United States of America

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   Dirk Kutscher

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