ISO/IEC TR 23008-13:2020

Information technology - High efficiency coding and media delivery in heterogeneous environments - Part 13: MMT implementation guidance

This document provides guidance for implementing and deploying systems based on ISO/IEC 23008‑1.

Technologies de l'information — Codage à haute efficacité et livraison des medias dans des environnements hétérogènes — Partie 13: Titre manque

General Information

• Status: Published
• Publication Date: 14-Dec-2020
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29/WG 3 - MPEG Systems
• Current Stage: 6060 - International Standard published
• Start Date: 15-Dec-2020
• Due Date: 04-May-2021
• Completion Date: 15-Dec-2020

Relations

• Revises: ISO/IEC TR 23008-13:2017 - Information technology - High efficiency coding and media delivery in heterogeneous environments - Part 13: MPEG media transport implementation guidelines
• Effective Date: 12-May-2018

Overview

ISO/IEC TR 23008-13:2020 - "MMT implementation guidance" - is a technical report that provides practical guidance for implementing and deploying systems based on ISO/IEC 23008‑1 (MPEG Media Transport, MMT). It explains system architecture, signalling, transport modes and deployment scenarios to help implementers realize high-efficiency coding and media delivery in heterogeneous networks and devices.

Key topics and requirements

The report addresses implementation concerns and operational guidance rather than new normative protocol syntax. Major technical topics include:

• System overview and tools drawn from ISO/IEC 23008‑1 (MMT/MMTP).
• Object reconstruction and recovery strategies for MPU and GFD delivery modes (recovery mechanisms and failure handling).
• MPU streaming and low‑delay live streaming workflows, including packetization, generation, and signalling for live services.
• Parallel processing considerations for MMT senders and receivers to maximize throughput and reduce latency.
• Signalling mechanisms such as HRBM (Hybrid Delivery/Resource signalling), ADC and cache manifests for session acquisition and hybrid delivery coordination.
• Hybrid delivery and interoperability: combining MMT with MPEG‑2 TS, HTTP/DASH, and other delivery methods for synchronized presentation.
• Error resilience and ARQ: delivery-time and arrival-deadline constrained ARQ strategies and AL‑FEC usage for robust delivery.
• Security and encryption: guidance on delivering encrypted MPUs and related signalling.
• Caching and middlebox architectures: MMT caching models, content‑based caching, and server‑cache synchronization.
• Conversion and integration: rules and restrictions for converting MMTP streams to MPEG‑2 TS and support for DASH delivery over MMTP.
• Specialized use cases: broadcast deployments (e.g., ATSC 3.0, DTMB/Japan), VR viewport-dependent streaming, timed text (TTML), and multi-asset signalling.

Practical applications

ISO/IEC TR 23008-13 is aimed at practical deployments where MMT is used to deliver media efficiently across diverse networks:

• Implementing low-latency live streaming and broadcast-grade over-the-air services.
• Integrating MMT with DASH and HTTP streaming for hybrid CDN/broadcast services.
• Designing caching middleboxes and MANE routers to improve bandwidth utilization.
• Enabling service providers and broadcasters to migrate legacy MPEG‑2 TS workflows to MMT.
• Supporting device manufacturers, middleware and firmware developers implementing MMTP stacks and playback logic.

Who should use this standard

• System architects and integrators designing MMT-based delivery systems
• Broadcast engineers (ATSC 3.0, DTMB) and CDN operators
• Software and hardware implementers of MMTP/MPU packetization and recovery
• Standards and interoperability test teams

Related standards

• ISO/IEC 23008‑1 (MPEG Media Transport) - primary normative specification
• MPEG and DASH-related specifications referenced for integration and conversion guidance

Keywords: ISO/IEC TR 23008-13:2020, MMT, MMTP, MPU, high efficiency coding, media delivery, DASH, ATSC 3.0, DTMB, MPEG-2 TS, AL-FEC, hybrid delivery.

Standards Content (Sample)

TECHNICAL ISO/IEC TR
REPORT 23008-13
Third edition
2020-12
Information technology — High
efficiency coding and media delivery
in heterogeneous environments —
Part 13:
MMT implementation guidance
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved

Contents Page
Foreword .vii
Introduction .ix
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General overview of MPEG media transport . 1
4.1 System overview . 1
4.2 Tools specified in ISO/IEC 23008-1 . 2
5 MMT function deployments . 3
5.1 General . 3
5.2 Object reconstruction . 3
5.2.1 General. 3
5.2.2 Recovery in MPU mode . 4
5.2.3 Recovery in GFD mode . 6
5.3 Default assets . 6
5.4 Low-delay live streaming . 7
5.5 Parallel processing in MMT sending and receiving entities . 9
5.5.1 Processing in MMT sending entity . 9
5.5.2 Processing in MMT receiving entity .11
5.6 MPU streaming for live services .13
5.6.1 MPU packetization.13
5.6.2 Sending of MPU and signalling message .16
5.6.3 MPU generation for SHVC-encoded video in real-time streaming .17
5.7 Fast MMT session acquisition .19
5.8 Referencing and processing non-timed data .20
5.8.1 General.20
5.8.2 Resource grouping and referencing .20
5.8.3 Receiver handling .21
5.9 Media adaptation for quality control in MMTP .21
5.9.1 General.21
5.9.2 Parameters for media adaptation .21
5.9.3 Adaptation operation of MMT entity .21
5.10 Hybrid delivery in MMT .22
5.10.1 General.22
5.10.2 Classification of hybrid delivery .22
5.10.3 Technical elements for hybrid delivery .23
5.11 Example of detailed implementation of MMT .24
5.11.1 Use case: Combination of MMT and MPEG-2 TS for synchronized presentation .24
5.11.2 Use case: Combination of MMT and HTTP streaming for synchronized
decoding .24
5.11.3 Use case: Content request in advance for synchronized play-out .25
5.12 HRBM signalling for hybrid delivery .26
5.12.1 Hybrid delivery from the single MMT sending entity .26
5.12.2 Hybrid delivery from the multiple MMT sending entities .27
5.13 Error resilience in MMT protocol .29
5.14 Delay constrained ARQ .30
5.14.1 General.30
5.14.2 Delivery-time constrained ARQ.30
5.14.3 Arrival-deadline constrained ARQ .31
5.15 Delivery of encrypted MPUs .33
5.16 HRBM message updating .33
5.16.1 General.33
© ISO/IEC 2020 – All rights reserved iii

5.16.2 HRBM message sending schedule .34
5.16.3 Use case.34
5.16.4 HRBM buffer operation in unicast environment .35
5.17 MMTP packet with padded data .37
5.18 Constraints on signalling splicing points .39
5.18.1 General.39
5.18.2 Constraints on Case 1 – Asset change at the start of MPU .39
5.18.3 Constraints on Case 2 – Asset change at a point in MPU .39
5.18.4 Signal the splicing point for target assets in Case 1 and Case 2 .40
6 Use cases for MMT deployment .40
6.1 General .40
6.2 Delivery of DASH presentations using MMT .40
6.2.1 General.40
6.2.2 Delivery of the MPD . .41
6.2.3 Delivery of the data segments .41
6.3 Client operation for DASH service delivered through MMT protocol .42
6.3.1 Delivery of MPD with MMTP .42
6.3.2 Delivery and consumption of DASH segments with MMTP .42
6.4 Hybrid of MMT and DASH over heterogeneous network .44
6.5 MMT caching for effective bandwidth utilization .45
6.5.1 Overview of MMT caching middlebox architecture .45
6.5.2 Content-based caching of MMT media .46
6.5.3 MPU sync protocol between server and caching middlebox .48
6.5.4 MMT cache manifest .53
6.6 Usage of ADC signalling message .55
6.6.1 General.55
6.6.2 Operation in MMT sending entity .55
6.6.3 Operation in MANE router .55
6.6.4 Example operation in MMT-receiving entities .55
6.6.5 QoE multiplexing gain and bottleneck coordination .55
6.7 MMT deployment in Japanese broadcasting systems .58
6.7.1 General.58
6.7.2 Broadcasting systems using MMT .59
6.7.3 Media transport protocol .61
6.7.4 Signalling information.66
6.7.5 Start-up procedure of broadcasting service . .74
6.7.6 Actual packet structure .77
6.8 MMT deployment in ATSC 3.0 systems .79
6.9 Implementation of MMT based on D-TMB in China .81
6.9.1 Background.81
6.9.2 MMT over legacy DTMB infrastructure .81
6.9.3 Use cases .81
6.10 Conversion of MMTP stream to MPEG-2 TS .83
6.10.1 Overview of conversion operation .83
6.10.2 Restrictions to MMTP packets .83
6.10.3 Calculation of PTS, DTS .83
6.10.4 Restriction related to MPEG-2 T-STD .84
6.10.5 Packet field conversion rule .85
6.10.6 PSI Conversion rule .86
6.11 MMT service provisioning at conventional broadcast environment .87
6.12 Usage of multimedia configuration for interface switching management .89
6.13 MMT signalling for multiple timed text assets .89
6.13.1 Multiple timed text assets within an MMT presentation .89
6.13.2 Selective spatial assignment for multiple timed text assets .90
6.13.3 Example of multiple timed text assets signalling in MMT . .92
6.13.4 Carriage of TTML based timed text in MMT .92
6.14 Viewport-dependent baseline media profile with packed streaming for VR .94
iv © ISO/IEC 2020 – All rights reserved

7 Application layer forward error correction (AL-FEC) .97
7.1 FEC decoding method for ssbg_mode2 .97
7.1.1 General.97
7.1.2 Source symbol block format for ssbg_mode2 .97
7.1.3 Regionalization of source symbol Block for FEC decoding .98
7.1.4 How to choose a proper unit of data for FEC decoding .102
7.2 Usage of two stage FEC coding structure .102
7.2.1 General.102
7.2.2 Use case: Hybrid content delivery .103
7.2.3 Use case: Streaming multicasting (or broadcasting) to two different end-
user groups which is under two different channel conditions each other .104
7.3 Usage of layer-aware FEC coding structure .104
7.3.1 General.104
7.3.2 Use case 1: Layered multicast streaming .105
7.3.3 Use case 2: Hybrid delivery .106
7.3.4 Use case 3: Fast zapping with long time interleaving (LA-FEC UI) .107
7.3.5 Use case 4: Prioritized transmission .107
7.4 MPU mapping to source packet block .108
7.4.1 General.108
7.4.2 Aligned MPU mapping method to source packet block .108
7.5 FEC for hybrid service .109
7.6 Usage of rate-adaptive AL-FEC .111
7.6.1 General.111
7.6.2 AL-FEC rate control .112
7.7 FEC scheme for interleaved source symbol block .115
7.7.1 General.115
7.7.2 Re-order buffer for interleaved source symbol block .115
8 MMT developments in mobile environments .115
8.1 True realtime video streaming over a lossy channel .115
8.1.1 General.115
8.1.2 Main features .115
8.1.3 Ring buffer in the client.116
8.1.4 FEC/deFEC performance and delay .116
8.1.5 Characteristics of UDP based multi-path and multi-session transmitting
for true real-time video streaming .116
8.2 Dynamic asset change .119
8.3 Media adaptation for quality control .121
8.3.1 Use cases of QoS management for adaptive video service .121
8.3.2 Advanced adaptation operation of MMT entity: selective transmission .125
8.4 Transition time decision using MTR and MTN .129
8.5 Usage of DRI and DSI message .130
8.5.1 Overview .130
8.5.2 Operation in MMT sending entity or MANE .130
8.5.3 Operation in MMT receiving entity .131
8.6 Usage of dynamic media resource identification information update .131
8.6.1 General.131
8.6.2 Classification of dynamic media resource allocation .131
8.6.3 Operation in MMT sending entity .131
8.6.4 Operation in MMT receiving entity .132
8.6.5 Example operation in MANE proxy .132
8.7 MMT service list .134
8.8 Usage of DNS message for MMT URL resolution .135
8.8.1 General.135
8.8.2 Example on DNS resolution procedure .135
8.9 Usage of guide information for dynamic media resource allocation .137
8.9.1 General.137
8.9.2 Classification of guide information .137
8.9.3 Classification of dynamic media resource allocation .137
© ISO/IEC 2020 – All rights reserved v

8.9.4 Operation in MANEs .138
8.9.5 Operation in MMT sending entity .138
8.9.6 Example of dynamic media resource allocation using guide information .138
8.10 Usage of DARI for supporting DNS in MMT .139
8.10.1 General.139
8.10.2 Classification of DARI proxy .139
8.10.3 Operation in MANE DNS or DNS.140
8.10.4 Operation in DARI proxy .140
8.10.5 Relation between the media resource identification in MMT and DNS
message .140
Bibliography .142
vi © ISO/IEC 2020 – 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 activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also
take part in the 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).
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 http:// patents .iec .ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This third edition cancels and replaces the second edition (ISO/IEC 23008-13:2017), which has been
technically revised. The main changes compared to the previous edition are as follows:
— Guidance added to show how the MMT protocol can transmit media streams adaptively to
environment changes such as network congestions, while also minimizing service quality
degradation.
— Guidance added to describe the scenario in which MMT and MPEG-2 TS are used as transport
schemes in broadband networks and broadcast channels, respectively.
— Guidance added for constraints on signalling splicing points that are specified for changing points
or splicing points on MMT assets.
— Application Layer Forward Error Correction (AL-FEC) guidance added to describe the usage of Rate-
Adaptive AL-FEC, Layer-Aware (LA) FEC coding structure and FEC scheme for interleaved source
symbol block.
— Broadcasting MMT deployment guidance added to describe the implementation of MMT based on
D-TMB in China and MMT Deployment in ATSC 3.0 systems.
— MMT deployment guidance added to show the usage of MMT signalling for multiple timed text assets
and for the viewport-dependent baseline media profile with packed streaming for VR.
— MMT developments in mobile environments guidance added to describe the usage of true real
time video streaming over lossy channels, dynamic asset change, and media adaptation for quality
control.
— MMT developments in mobile environments guidance added to describe the usage of signalling
messages for supporting Package retransmission and dynamic media resource allocation.
© ISO/IEC 2020 – All rights reserved vii

A list of all parts in the ISO/IEC 23008 series can be found on the ISO website.
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.
viii © ISO/IEC 2020 – All rights reserved

Introduction
This document provides guidance for implementation and deployment of multimedia systems based on
ISO/IEC 23008-1. These document include the following:
— Guidance on usage of MMT functions;
— Guidance on deployment use cases designed based on ISO/IEC 23008-1.
© ISO/IEC 2020 – All rights reserved ix

TECHNICAL REPORT ISO/IEC TR 23008-13:2020(E)
Information technology — High efficiency coding and
media delivery in heterogeneous environments —
Part 13:
MMT implementation guidance
1 Scope
This document provides guidance for implementing and deploying systems based on ISO/IEC 23008-1.
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 23008-1:2017, Information technology — High efficiency coding and media delivery in
heterogeneous environments — Part 1: MPEG media transport (MMT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 23008-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 General overview of MPEG media transport
4.1 System overview
This clause describes the exemplary but typical system overview of MPEG media transport (MMT) as
shown in Figure 1.
The media origin provides A/V media or generic files to MMT sending entity in the form of packages or
assets which are defined in ISO/IEC 23008-1. A package is comprised of assets, presentation information
and transparent characteristics, etc. physically, an asset is a group of MPUs or generic files.
The MMT sending entity fragments MPU/generic files and generates MMTP packets to deliver A/V
media data itself. Concurrently, it also generates signalling message for the successful delivery and
presentation of A/V media included on that MMTP packet flow.
© ISO/IEC 2020 – All rights reserved 1

Figure 1 — Example of MMT-based media distribution chain
The MMT aware network element (MANE) may be any network element, such as, media caches and
routers, that aware of MMTP and has augmented functions for its own purposes to utilize tools from MMT.
Then, MMTP packets can be transmitted through either or both of broadcast channel and broadband
channel at its own environment and scenarios.
The CI information provides presentation information, such as the location of media objects as well
as the timing and relation of the media objects that the MMT receiving entity has to follow. This
information is provided by the MMT sending entity and also pushes related MMTP packet flow to the
MMT receiving entity. It means it fully controls the media streaming session, i.e., it manages the on-time
delivery, playback and temporal/spatial presentation information of the media.
4.2 Tools specified in ISO/IEC 23008-1
ISO/IEC 23008-1 specifies a set of tools to enable advanced media transport and delivery services.
Figure 2 depicts the end-to-end architecture and illustrates the different functional tools and
their relationships. Moreover, it shows interfaces between existing protocols and standards
defined by ISO/IEC 23008-1 and those defined in other specifications. The tools spread over three
different functional areas: media processing unit (MPU) format; delivery; and signalling defined in
ISO/IEC 23008-1 as follows:
— The media processing unit (MPU) defines the logical structure of media content format of the data
units to be processed by an MMT entity and their instantiation with ISO base media file format as
specified in ISO/IEC 14496-12.
— The delivery function defines an application layer transport protocol and a payload format. The
MMTP transport protocol provides enhanced features for delivery of multimedia data, e.g.,
multiplexing and support of mixed use of streaming and download delivery in a single packet flow.
The payload format is defined to enable the carriage of encoded media data which is agnostic to
media types and encoding methods.
— The signalling function defines formats of signalling messages to manage delivery and consumption
of media data.
2 © ISO/IEC 2020 – All rights reserved

Figure 2 — MMT functions deployment
Other aspects, such as client implementations for media reconstruction and presentation itself are not
defined in ISO/IEC 23008-1.
5 MMT function deployments
5.1 General
This clause gives implementation guidance on general MMT deployment based on basic functionalities
provided by ISO/IEC 23008-1. In particular, it provides guidance on how to make best use of
ISO/IEC 23008-1 for the basic topics such as, but not limited to;
— low delay media consumption;
— media adaptation;
— hybrid delivery;
— error recovery.
5.2 Object reconstruction
5.2.1 General
MMTP is designed to deliver object flows that may be multiplexed together in the same MMTP flow.
The objects of an object flow are usually related to each other, meaning that the application is likely to
consume all objects of an object flow, if the flow or one of its objects is of interest to that application.
Depending on the delivery mode, the recovery of the object may differ. The GFD mode usually requires
that the full object is recovered prior to its delivery to the application. However, the application may
request that correctly received contiguous byte ranges of the object are forwarded to the application.
© ISO/IEC 2020 – All rights reserved 3

The MPU mode is used to deliver MPUs and usually operates on movie fragments. Alternatively, the
application may request that each received MFU is forwarded to the application without additional
delay. It may also require that the complete MPU be reconstructed prior to forwarding it to the
application.
5.2.2 Recovery in MPU mode
When operating in the MPU mode, the object flow consists of MPUs of the same asset. Each MPU is a
single object in the object flow and shares the same packet_id as all MPUs of the same asset.
The MMT receiving entity performs the following steps:
1) Receive MMTP packet.
2) Check if packet_id is equal to the packet_id of the object flow of interest, discard packet and go to
step 1 if it does not belong to an object flow of interest.
3) Assert that type of the MMTP packet is MPU.
4) If fragmentation flags are set (different than ‘00’).
a) If fragmentation flag is equal to ‘11’, attempt to recover packet and if successful go to step 6.
b) Else add packet to the list of packet fragments based on the MMTP sequence number and
goto step 1.
5) If aggregation flag A is set, extract all aggregated data units and proceed to step 7 for each extracted
data unit.
6) If object map with same MPU_sequence_number does not exist, create new object map for the MPU
with that sequence number.
7) Check fragment type (FT) of the MPU payload header.
a) If FT is MPU metadata:
i) Check if MPU metadata is already received:
1) If yes, discard the MPU metadata as being a duplicate;
2) Else insert MPU metadata at the beginning of the object map:
a.  Optionally, forward MPU metadata to application.
ii  Go to step 1.
b) If FT is fragment metadata:
i) Check if movie fragment with the same movie_fragment_sequence_number already exists:
1) If no, create a placeholder for the movie fragment in the object map.
2) Else, check if fragment metadata has already been received:
a)  If yes, discard fragment metadata as being a duplicate;
b) Otherwise, insert fragment metadata at the beginning of the fragment placeholder.
3)  Go to step 1.
4 © ISO/IEC 2020 – All rights reserved

c) If FT is MFU:
i) If fragment placeholder with sequence number movie_fragment_sequence_number does
not exist in the object map of the MPU with sequence number MPU_sequence_number, then
create movie fragment placeholder in the object map of the MPU.
ii) If timed metadata flag is set:
1) Insert payload in the fragment placeholder in the correct order based on the sample_
number and offset values.
2) Check if movie fragment is complete.
a)  If yes, forward fragment to the application.
3)  Go to step 1.
iii)  If timed metadata flag is not set:
1)  Insert payload in the item in the object map based on the item item_ID.
2)  Recover item information from MPU metadata for the recovered item and forward the
item to the application.
3)  Go to step 1.
The sender may send the movie fragment out of order, i.e., sending the movie fragment header after
sending all the media units that are contained in that movie fragment. At the receiver side, step 7)c)
i) ensures that the movie fragment is recovered appropriately by reordering the received data using
the MPU_sequence_number and the movie_fragment_sequence_number. This is necessary if the receiver
is operating in the fragment mode or MPU mode, where only complete movie fragments or complete
MPUs are forwarded to the application. When operating in the very low delay mode, the receiver will
forward every single MFU to the application. In this case, it has to make sure that the content supports
this operation, so that MFUs will be self-describing and self-contained. In particular, the receiver should
be able to recover the presentation timestamp of that MFU payload using the sample number, fragment_
sequence_number, and MPU_sequence_number.
For fragments and items that cannot be recovered correctly by the time the fixed end to end delivery
delay passes, error concealment is performed on the movie fragment or the partially recovered item.
An MFU may be fragmented by multiple fragments and the total number of fragments can be larger
than the range which the fragment counter can present. It can be recognized by using the fragmentation
indicator and the fragment counter. In this case, the fragmentation indicator (f_i) indicates that the
received payload is neither the first nor the last fragment (wh
...