ISO/IEC 21558-1:2022

Telecommunications and information exchange between systems - Future network architecture - Part 1: Switching and routing

This document specifies the switching and routing architecture of the Future Network (FN).

Télécommunications et échange d'informations entre systèmes — Architecture du réseau du futur — Partie 1: Commutation et routage

General Information

• Status: Published
• Publication Date: 28-Feb-2022
• ICS: 35.100.30 - Network layer
• Technical Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Drafting Committee: ISO/IEC JTC 1/SC 6/WG 7 - Network, transport and future network
• Current Stage: 6060 - International Standard published
• Start Date: 01-Mar-2022
• Due Date: 06-May-2022
• Completion Date: 01-Mar-2022

Overview

ISO/IEC 21558-1:2022 defines the switching and routing architecture of the Future Network (FN). It specifies how FN handles packet delivery, separates forwarding metadata from packet payloads, and supports both real‑time audiovisual (AV) and traditional information‑technology (IT) traffic. The standard is part of the FN series and works with protocol definitions in ISO/IEC 21559‑1 and requirements in ISO/IEC TR 29181.

Key topics and requirements

• Two main services: an ultra‑low‑latency AV service for regular-interval media traffic (audio/video) and a best‑effort IT service for general data.
• Flows: FN defines three flow types - AV flows (single source, multicast destinations), connection‑oriented IT flows (single source/destination), and connectionless IT flows (multiple sources, single destination).
• Encapsulation and payload rules: each packet contains an encapsulation (forwarding information) and an opaque payload (octet string) that intermediate elements do not process.
• Forwarding model: routing/forwarding information is carried separately from packet headers, reducing encapsulation size and simplifying switch forwarding; flow identifiers appear in signalling, not in packet headers.
• Service levels: three levels - best‑effort, asynchronous (bounded latency with resource reservation), and synchronous (well‑defined latency with tight synchronisation and timeslots).
• Links and topology:
  • Physical links implement tight synchronisation and can support synchronous service.
  • Virtual links are carried over non‑FN technologies and do not meet tight synchronisation requirements.
  • Network composition uses islands (elements connected by physical links) and clouds (islands connected by virtual links).
• Lower‑layer requirements: physical point‑to‑point links must provide a stream of octets with formatting that allows octet positioning; virtual link behaviour is defined in ISO/IEC 21559‑1.
• QoS and AV considerations: Clauses address packet formats, QoS implications, synchronisation domains, slots/allocations and virtual links for AV traffic.

Practical applications and users

Who uses ISO/IEC 21558‑1:

• Network architects and systems designers planning low‑latency media networks (live audio/video production, broadcast, AV-over-IP).
• Vendors building FN‑compliant switches, routers and signalling systems.
• Service providers and enterprises migrating from IP to Future Network architectures that require deterministic latency and improved mobility handling.
• Standards bodies and implementers referencing FN flow, timing and encapsulation models for interoperability.

Benefits for implementers:

• Enables ultra‑low‑latency AV transport, simpler forwarding logic, smaller encapsulation overhead, and support for mobility without IP‑in‑IP tunnels.

Related standards

• ISO/IEC 21559‑1 - Future network protocols and mechanisms (switching and routing)
• ISO/IEC TR 29181‑1 and TR 29181‑3 - FN problem statement and requirements
• IEC 62379‑5‑2 - Signalling for networked digital audio/video (flow identifiers and setup)

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 21558-1
First edition
2022-03
Telecommunications and information
exchange between systems — Future
network architecture —
Part 1:
Switching and routing
Télécommunications et échange d'informations entre systèmes —
Architecture du réseau du futur —
Partie 1: Commutation et routage
Reference number
© ISO/IEC 2022
© ISO/IEC 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
© ISO/IEC 2022 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
5 Network elements and links . 2
5.1 Levels of service . 2
5.2 Links . 2
5.3 Topology . 2
6 Service interfaces . 2
6.1 Service provided to the layers above . 2
6.2 Service required from the layers below. 3
7 Flows . 3
7.1 General . 3
7.2 AV flows . 3
7.3 Connection-oriented IT flows . 3
7.4 Connectionless IT flows . 3
8 IT services . 4
8.1 Packet format . 4
8.2 QoS considerations . 4
8.3 Carriage over other technologies . 4
9 AV services . 4
9.1 Synchronisation domains . 4
9.2 Packet format . 5
9.3 QoS considerations . 5
9.3.1 Flows within an island . 5
9.3.2 AV flows not within an island . 5
9.3.3 All AV flows . 5
9.4 Slots and allocations . 5
9.5 Virtual links . 6
10 Signalling service .6
Bibliography . 7
iii
© ISO/IEC 2022 – All rights reserved

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
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work.
The procedures used to develop this document and those intended for its further maintenance
are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria
needed for the different types of document should be noted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs). International Standards are drafted in accordance with the
rules given in the ISO/IEC Directives, Part 2.
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see patents.iec.ch). The main task of the joint technical committee
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the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 6, Telecommunications and information exchange between systems.
A list of all parts in the ISO/IEC 21558 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
iv
© ISO/IEC 2022 – All rights reserved

Introduction
ISO/IEC TR 29181-1 describes the definition, general concept, problems and requirements for the
Future Network (FN).
ISO/IEC TR 29181-3 examines the requirements for carrying data over digital networks and
identifies the requirements that are not satisfied by the current Internet. It also notes some expected
characteristics of new systems that are better able to satisfy the requirements and specifies a model
which supports both the existing system and the new systems. This will enable a migration to the new
systems; it is also intended to make networks of all sizes easier to manage.
This document specifies the FN architecture which is designed to meet the requirements identified in
ISO/IEC TR 29181-3. Protocols to support this architecture are specified in ISO/IEC 21559-1.
FN is a packet network which, as well as carrying data between computers, also meets the rather
different requirements of live digital audio and video, which form an increasing proportion of the traffic
on today's networks.
Whereas in IP all addressing information needs to be present in the packet headers, in FN the
information needed to route packets is carried separately from the packets themselves. This reduces
the size of the encapsulation by an order of magnitude and simplifies the process of forwarding the
packets in switches.
Most importantly, it allows different addressing mechanisms to be used without changing the packet
format and supports mobility without needing artificial devices such as IP-in-IP tunnels.
FN offers two main services: an ultra-low-latency “AV” service tailored to the needs of constant-bit-
rate traffic such as audio and video, and a best-effort “IT” service suitable for the kind of unpredictable
demand for which IP was intended. The AV service can also be used for file transfer, where it eliminates
the need for the kind of empirical throughput testing that is a feature of TCP.
Some details of the services (particularly the slot size for the AV service, which was originally envisaged
as being much more flexible) are a result of experimentation with a prototype implementation.
v
© ISO/IEC 2022 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 21558-1:2022(E)
Telecommunications and information exchange between
systems — Future network architecture —
Part 1:
Switching and routing
1 Scope
This document specifies the switching and routing architecture of the Future Network (FN).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 21559-1, Telecommunications and information exchange between systems — Future network
protocols and mechanisms — Part 1: Switching and routing
ISO/IEC/TR 29181-1, Information technology — Future Network — Problem statement and requirements
— Part 1: Overall aspects
ISO/IEC/TR 29181-3, Information technology — Future Network — Problem statement and requirements
— Part 3: Switching and routing
IEC 62379-5-2, Common control interface for networked digital audio and video products - Part 5-2:
Transmission over networks – Signalling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC TR 29181-1,
ISO/IEC TR 29181-3 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org
3.1
AV flow
flow in which packets are expected to be transmitted at regular intervals, suitable for carrying live
audio, video, and other media
3.2
IT flow
flow in which packets are not e
...