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Real-Time Transport Object Delivery over Unidirectional Transport (ROUTE)
RFC 9223

Document Type RFC - Informational (April 2022)
Was draft-zia-route (individual)
Authors Waqar Zia , Thomas Stockhammer , Lena Chaponniere , Giridhar Mandyam , Mike Luby
Last updated 2022-04-27
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RFC 9223


Independent Submission                                            W. Zia
Request for Comments: 9223                                T. Stockhammer
Category: Informational                  Qualcomm CDMA Technologies GmbH
ISSN: 2070-1721                                           L. Chaponniere
                                                              G. Mandyam
                                              Qualcomm Technologies Inc.
                                                                 M. Luby
                                                         BitRipple, Inc.
                                                              April 2022

   Real-Time Transport Object Delivery over Unidirectional Transport
                                (ROUTE)

Abstract

   The Real-time Transport Object delivery over Unidirectional Transport
   (ROUTE) protocol is specified for robust delivery of Application
   Objects, including Application Objects with real-time delivery
   constraints, to receivers over a unidirectional transport.
   Application Objects consist of data that has meaning to applications
   that use the ROUTE protocol for delivery of data to receivers; for
   example, it can be a file, a Dynamic Adaptive Streaming over HTTP
   (DASH) or HTTP Live Streaming (HLS) segment, a WAV audio clip, etc.
   The ROUTE protocol also supports low-latency streaming applications.

   The ROUTE protocol is suitable for unicast, broadcast, and multicast
   transport.  Therefore, it can be run over UDP/IP, including multicast
   IP.  The ROUTE protocol can leverage the features of the underlying
   protocol layer, e.g., to provide security, it can leverage IP
   security protocols such as IPsec.

   This document specifies the ROUTE protocol such that it could be used
   by a variety of services for delivery of Application Objects by
   specifying their own profiles of this protocol (e.g., by adding or
   constraining some features).

   This is not an IETF specification and does not have IETF consensus.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not candidates for any level of Internet Standard;
   see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9223.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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 and restrictions with respect
   to this document.

Table of Contents

   1.  Introduction
     1.1.  Overview
     1.2.  Protocol Stack for ROUTE
     1.3.  Data Model
     1.4.  Architecture and Scope of Specification
     1.5.  Conventions Used in This Document
   2.  ROUTE Packet Format
     2.1.  Packet Structure and Header Fields
     2.2.  LCT Header Extensions
     2.3.  FEC Payload ID for Source Flows
     2.4.  FEC Payload ID for Repair Flows
   3.  Session Metadata
     3.1.  Generic Metadata
     3.2.  Session Metadata for Source Flows
     3.3.  Session Metadata for Repair Flows
   4.  Delivery Object Mode
     4.1.  File Mode
       4.1.1.  Extensions to FDT
       4.1.2.  Constraints on Extended FDT
     4.2.  Entity Mode
     4.3.  Unsigned Package Mode
     4.4.  Signed Package Mode
   5.  Sender Operation
     5.1.  Usage of ALC and LCT for Source Flow
     5.2.  ROUTE Packetization for Source Flow
       5.2.1.  Basic ROUTE Packetization
       5.2.2.  ROUTE Packetization for CMAF Chunked Content
     5.3.  Timing of Packet Emission
     5.4.  Extended FDT Encoding for File Mode Sending
     5.5.  FEC Framework Considerations
     5.6.  FEC Transport Object Construction
     5.7.  Super-Object Construction
     5.8.  Repair Packet Considerations
     5.9.  Summary FEC Information
   6.  Receiver Operation
     6.1.  Basic Application Object Recovery for Source Flows
     6.2.  Fast Stream Acquisition
     6.3.  Generating Extended FDT-Instance for File Mode
       6.3.1.  File Template Substitution for Content-Location
               Derivation
       6.3.2.  File@Transfer-Length Derivation
       6.3.3.  FDT-Instance@Expires Derivation
   7.  FEC Application
     7.1.  General FEC Application Guidelines
     7.2.  TOI Mapping
     7.3.  Delivery Object Reception Timeout
     7.4.  Example FEC Operation
   8.  Considerations for Defining ROUTE Profiles
   9.  ROUTE Concepts
     9.1.  ROUTE Modes of Delivery
     9.2.  File Mode Optimizations
     9.3.  In-Band Signaling of Object Transfer Length
     9.4.  Repair Protocol Concepts
   10. Interoperability Chart
   11. Security and Privacy Considerations
     11.1.  Security Considerations
     11.2.  Privacy Considerations
   12. IANA Considerations
   13. References
     13.1.  Normative References
     13.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

1.1.  Overview

   The Real-time Transport Object delivery over Unidirectional Transport
   (ROUTE) protocol can be used for robust delivery of Application
   Objects, including Application Objects with real-time delivery
   constraints, to receivers over a unidirectional transport.
   Unidirectional transport in this document has identical meaning to
   that in RFC 6726 [RFC6726], i.e., transport in the direction of
   receiver(s) from a sender.  The robustness is enabled by a built-in
   mechanism, e.g., signaling for loss detection, enabling loss
   recovery, and optionally integrating application-layer Forward Error
   Correction (FEC).

   Application Objects consist of data that has meaning to applications
   that use the ROUTE protocol for delivery of data to receivers, e.g.,
   an Application Object can be a file, an MPEG Dynamic Adaptive
   Streaming over HTTP (DASH) [DASH] video segment, a WAV audio clip, an
   MPEG Common Media Application Format (CMAF) [CMAF] addressable
   resource, an MPEG-4 video clip, etc.

   The ROUTE protocol is designed to enable delivery of sequences of
   related Application Objects in a timely manner to receivers, e.g., a
   sequence of DASH video segments associated to a Representation or a
   sequence of CMAF addressable resources associated to a CMAF Track.
   The applications of this protocol target services enabled on media
   consumption devices such as smartphones, tablets, television sets,
   and so on.  Most of these applications are real-time in the sense
   that they are sensitive to and rely upon such timely reception of
   data.  The ROUTE protocol also supports chunked delivery of real-time
   Application Objects to enable low-latency streaming applications
   (similar in its properties to chunked delivery using HTTP).  The
   protocol also enables low-latency delivery of DASH and Apple HTTP
   Live Streaming (HLS) content with CMAF Chunks.

   Content not intended for rendering in real time as it is received
   (e.g., a downloaded application), a file comprising continuous or
   discrete media and belonging to an app-based feature, or a file
   containing (opaque) data to be consumed by a Digital Rights
   Management (DRM) system client can also be delivered by ROUTE.

   The ROUTE protocol supports a caching model where Application Objects
   are recovered into a cache at the receiver and may be made available
   to applications via standard HTTP requests from the cache.  Many
   current day applications rely on using HTTP to access content; hence,
   this approach enables such applications in broadcast/multicast
   environments.

   ROUTE is aligned with File Delivery over Unidirectional Transport
   (FLUTE) as defined in RFC 6726 [RFC6726] as well as the extensions
   defined in Multimedia Broadcast/Multicast Service (MBMS) [MBMS], but
   it also makes use of some principles of FCAST (Object Delivery for
   the Asynchronous Layered Coding (ALC) and NACK-Oriented Reliable
   Multicast (NORM) Protocols) as defined in RFC 6968 [RFC6968]; for
   example, object metadata and the object content may be sent together
   in a compound object.

   The alignment to FLUTE is enabled since in addition to reusing
   several of the basic FLUTE protocol features, as referred to by this
   document, certain optimizations and restrictions are added that
   enable optimized support for real-time delivery of media data; hence,
   the name of the protocol.  Among others, the source ROUTE protocol
   enables or enhances the following functionalities:

   *  Real-time delivery of object-based media data

   *  Flexible packetization, including enabling media-aware
      packetization as well as transport-aware packetization of delivery
      objects

   *  Independence of Application Objects and delivery objects, i.e., a
      delivery object may be a part of a file or may be a group of
      files.

   Advanced Television Systems Committee (ATSC) 3.0 specifies the ROUTE
   protocol integrated with an ATSC 3.0 services layer.  That
   specification will be referred to as ATSC-ROUTE [ATSCA331] for the
   remainder of this document.  Digital Video Broadcasting (DVB) has
   specified a profile of ATSC-ROUTE in DVB Adaptive Media Streaming
   over IP Multicast (DVB-MABR) [DVBMABR].  This document specifies the
   Application Object delivery aspects (delivery protocol) for such
   services, as the corresponding delivery protocol could be used as a
   reference by a variety of services by specifying profiles of ROUTE in
   their respective fora, e.g., by adding new optional features atop or
   by restricting various optional features specified in this document
   in a specific service standard.  Hence, in the context of this
   document, the aforementioned ATSC-ROUTE and DVB-MABR are the services
   using ROUTE.  The definition of profiles by the services also have to
   give due consideration to compatibility issues, and some related
   guidelines are also provided in this document.

   This document is not an IETF specification and does not have IETF
   consensus.  It is provided here to aid the production of
   interoperable implementations.

1.2.  Protocol Stack for ROUTE

   ROUTE delivers Application Objects such as MPEG DASH or HLS segments
   and optionally the associated repair data, operating over UDP/IP
   networks, as depicted in Table 1.  The session metadata signaling to
   realize a ROUTE session as specified in this document MAY be
   delivered out of band or in band as well.  Since ROUTE delivers
   objects in an application cache at the receiver from where the
   application can access them using HTTP, an application like DASH may
   use its standardized unicast streaming mechanisms in conjunction with
   ROUTE over broadcast/multicast to augment the services.

        +--------------------------------------------------------+
        | Application (DASH and HLS segments, CMAF Chunks, etc.) |
        +--------------------------------------------------------+
        |                         ROUTE                          |
        +--------------------------------------------------------+
        |                          UDP                           |
        +--------------------------------------------------------+
        |                           IP                           |
        +--------------------------------------------------------+

                        Table 1: Protocol Layering

1.3.  Data Model

   The ROUTE data model is constituted by the following key concepts.

   Application Object:  data that has meaning to the application that
         uses the ROUTE protocol for delivery of data to receivers,
         e.g., an Application Object can be a file, a DASH video
         segment, a WAV audio clip, an MPEG-4 video clip, etc.

   Delivery Object:  an object on course of delivery to the application
         from the ROUTE sender to ROUTE receiver.

   Transport Object:  an object identified by the Transport Object
         Identifier (TOI) in RFC 5651 [RFC5651].  It MAY be either a
         source or a repair object, depending on if it is carried by a
         Source Flow or a Repair Flow, respectively.

   Transport Session:  a Layered Coding Transport (LCT) channel, as
         defined by RFC 5651 [RFC5651].  A Transport Session SHALL be
         uniquely identified by a unique Transport Session Identifier
         (TSI) value in the LCT header.  The TSI is scoped by the IP
         address of the sender, and the IP address of the sender
         together with the TSI uniquely identify the session.  Transport
         Sessions are a subset of a ROUTE session.  For media delivery,
         a Transport Session would typically carry a media component,
         for example, a DASH Representation.  Within each Transport
         Session, one or more objects are carried, typically objects
         that are related, e.g., DASH segments associated to one
         Representation.

   ROUTE Session:  an ensemble or multiplex of one or more Transport
         Sessions.  Each ROUTE session is associated with an IP address/
         port combination.  A ROUTE session typically carries one or
         more media components of streaming media e.g., Representations
         associated with a DASH Media Presentation.

   Source Flow:  a Transport Session carrying source data.  Source Flow
         is independent of the Repair Flow, i.e., the Source Flow MAY be
         used by a ROUTE receiver without the ROUTE Repair Flows.

   Repair Flow:  a Transport Session carrying repair data for one or
         more Source Flows.

1.4.  Architecture and Scope of Specification

   The scope of the ROUTE protocol is to enable robust and real-time
   transport of delivery objects using LCT packets.  This architecture
   is depicted in Figure 1.

   The normative aspects of the ROUTE protocol focus on the following
   aspects:

   *  The format of the LCT packets that carry the transport objects.

   *  The robust transport of the delivery object using a repair
      protocol based on Forward Error Correction (FEC).

   *  The definition and possible carriage of object metadata along with
      the delivery objects.  Metadata may be conveyed in LCT packets
      and/or separate objects.

   *  The ROUTE session, LCT channel, and delivery object description
      provided as service metadata signaling to enable the reception of
      objects.

   *  The normative aspects (formats, semantics) of the delivery objects
      conveyed as a content manifest to be delivered along with the
      objects to optimize the performance for specific applications
      e.g., real-time delivery.  The objects and manifest are made
      available to the application through an Application Object cache.
      The interface of this cache to the application is not specified in
      this document; however, it will typically be enabled by the
      application acting as an HTTP client and the cache as the HTTP
      server.

                                                Application Objects
   Application                                  to application
   Objects from                                          ^
   an application    +--------------------------------------------+
        +            |  ROUTE Receiver                   |        |
        |            |                            +------+------+ |
        |            |                            | Application | |
        |            |                            | Object Cache| |
        |            |                            +------+------+ |
        |    LCT over|    +---------------+              ^        |
        v    UDP/IP  |    | Source object |  +---------+ |        |
   +----+---+        | +->+ recovery      +--+  Repair +-+        |
   | ROUTE  |        | |  +---------------+  +----+----+          |
   | Sender +----------+                          ^               |
   +----+---+        | |                          |               |
        |            | |  +---------------+       |               |
        |            | |  | Repair object |       |               |
        |            | +->+ recovery      +-------+               |
        +----------->+    +---------------+                       |
          ROUTE      |                                            |
          Metadata   +--------------------------------------------+

              Figure 1: Architecture/Functional Block Diagram

1.5.  Conventions Used in This Document

   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.  ROUTE Packet Format

2.1.  Packet Structure and Header Fields

   The packet format used by ROUTE Source Flows and Repair Flows follows
   the ALC packet format specified in RFC 5775 [RFC5775] with the UDP
   header followed by the default LCT header and the source FEC Payload
   ID followed by the packet payload.  The overall ROUTE packet format
   is as depicted in Figure 2.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           UDP Header                          |
   |                                                               |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                       Default LCT header                      |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         FEC Payload ID                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Payload Data                         |
   |                               ...                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 2: Overall ROUTE Packet Format

   The Default LCT header is as defined in the LCT building block in RFC
   5651 [RFC5651].

   The LCT packet header fields SHALL be used as defined by the LCT
   building block in RFC 5651 [RFC5651].  The semantics and usage of the
   following LCT header fields SHALL be further constrained in ROUTE as
   follows:

   Version number (V):  This 4-bit field indicates the protocol version
      number.  The version number SHALL be set to '0001', as specified
      in RFC 5651 [RFC5651].

   Congestion Control flag (C) field:  This 2-bit field, as defined in
      RFC 5651 [RFC5651], SHALL be set to '00'.

   Protocol-Specific Indication (PSI):  The most significant bit of this
      2-bit flag is called the Source Packet Indicator (SPI) and
      indicates whether the current packet is a source packet or a FEC
      repair packet.  The SPI SHALL be set to '1' to indicate a source
      packet and SHALL bet set to '0' to indicate a repair packet.

   Transport Session Identifier flag (S):  This 1-bit field SHALL be set
      to '1' to indicate a 32-bit word in the TSI field.

   Transport Object Identifier flag (O):  This 2-bit field SHALL be set
      to '01' to indicate the number of full 32-bit words in the TOI
      field.

   Half-word flag (H):  This 1-bit field SHALL be set to '0' to indicate
      that no half-word field sizes are used.

   Codepoint (CP):  This 8-bit field is used to indicate the type of the
      payload that is carried by this packet; for ROUTE, it is defined
      as shown below to indicate the type of delivery object carried in
      the payload of the associated ROUTE packet.  The remaining
      unmapped Codepoint values can be used by a service using ROUTE.
      In this case, the Codepoint values SHALL follow the semantics
      specified in the following table.  "IS" stands for Initialization
      Segment of the media content such as the DASH Initialization
      Segment [DASH].  The various modes of operation in the table
      (File/Entity/Package Mode) are specified in Section 4.  The table
      also lists a Codepoint value range that is reserved for future
      service-specific uses.

           +=================+=================================+
           | Codepoint value | Semantics                       |
           +=================+=================================+
           | 0               | Reserved (not used)             |
           +-----------------+---------------------------------+
           | 1               | Non Real Time (NRT) - File Mode |
           +-----------------+---------------------------------+
           | 2               | NRT - Entity Mode               |
           +-----------------+---------------------------------+
           | 3               | NRT - Unsigned Package Mode     |
           +-----------------+---------------------------------+
           | 4               | NRT - Signed Package Mode       |
           +-----------------+---------------------------------+
           | 5               | New IS, timeline changed        |
           +-----------------+---------------------------------+
           | 6               | New IS, timeline continued      |
           +-----------------+---------------------------------+
           | 7               | Redundant IS                    |
           +-----------------+---------------------------------+
           | 8               | Media Segment, File Mode        |
           +-----------------+---------------------------------+
           | 9               | Media Segment, Entity Mode      |
           +-----------------+---------------------------------+
           | 10              | Media Segment, File Mode with   |
           |                 | CMAF Random Access chunk        |
           +-----------------+---------------------------------+
           | 11 - 255        | Reserved, service-specific      |
           +-----------------+---------------------------------+

                         Table 2: Codepoint Values

   Congestion Control Information (CCI):  For packets carrying DASH
      segments, CCI MAY convey the 32-bit earliest presentation time
      [DASH] of the DASH segment contained in the ROUTE packet.  In this
      case, this information can be used by a ROUTE receiver for fast
      stream acquisition (details in Section 6.2).  Otherwise, this
      field SHALL be set to 0.

   Transport Session Identifier (TSI):  This 32-bit field identifies the
      Transport Session in ROUTE.  The context of the Transport Session
      is provided by signaling metadata.  The value TSI = 0 SHALL only
      be used for service-specific signaling.

   Transport Object Identifier (TOI):  This 32-bit field SHALL identify
      the object within this session to which the payload of the current
      packet belongs.  The mapping of the TOI field to the object is
      provided by the Extended File Delivery Table (FDT).

2.2.  LCT Header Extensions

   The following LCT header extensions are defined or used by ROUTE:

   EXT_FTI:  as specified in RFC 5775.

   EXT_TOL:  the length in bytes of the multicast transport object shall
      be signaled using EXT_TOL as specified by ATSC-ROUTE [ATSCA331]
      with 24 bits or, if required, 48 bits of Transfer Length.  The
      frequency of using the EXT_TOL header extension is determined by
      channel conditions that may cause the loss of the packet carrying
      the Close Object flag (B) [RFC5651].

      NOTE: The transport object length can also be determined without
      the use of EXT_TOL by examining the LCT packet with the Close
      Object flag (B).  However, if this packet is lost, then the
      EXT_TOL information can be used by the receiver to determine the
      transport object length.

   EXT_TIME Header:  as specified in RFC 5651 [RFC5651].  The Sender
      Current Time SHALL be signaled using EXT_TIME.

2.3.  FEC Payload ID for Source Flows

   The syntax of the FEC Payload ID for the Compact No-Code FEC Scheme
   used in ROUTE Source Flows is a 32-bit unsigned integer value that
   SHALL express the start_offset as an octet number corresponding to
   the first octet of the fragment of the delivery object carried in
   this packet.  The start_offset value for the first fragment of any
   delivery object SHALL be set to 0.  Figure 3 shows the 32-bit
   start_offset field.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         start_offset                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 3: FEC Payload ID for Source Flows

2.4.  FEC Payload ID for Repair Flows

   FEC Payload ID for Repair Flows is specified in RFC 6330 [RFC6330].

3.  Session Metadata

   The required session metadata for Source and Repair Flows is
   specified in the following sections.  The list specified here is not
   exhaustive; a service MAY signal more metadata to meet its needs.
   The data format is also not specified beyond its cardinality; the
   exact format of specifying the data is left for the service, e.g., by
   using XML encoding format, as has been done by [DVBMABR] and
   [ATSCA331].  It is specified in the following if an attribute is
   mandatory (m), conditional mandatory (cm) or optional (o) to realize
   a basic ROUTE session.  A mandatory field SHALL always be present in
   the session metadata, and a conditional mandatory field SHALL be
   present if the specified condition is true.  The delivery of the
   session metadata to the ROUTE receiver is beyond the scope of this
   document.

3.1.  Generic Metadata

   Generic metadata is applicable to both Source and Repair Flows as
   follows.  Before a receiver can join a ROUTE session, the receiver
   needs to obtain this generic metadata that contains at least the
   following information:

   ROUTE version number (m):  the version number of ROUTE used in this
      session.  The version number conforming to this document SHALL be
      1.

   Connection ID (m):  the unique identifier of a Connection, usually
      consisting of the following 4-tuple: source IP address/source port
      number, destination IP address/destination port number.  The IP
      addresses can be IPv4 or IPv6 addresses depending upon which IP
      version is used by the deployment.

3.2.  Session Metadata for Source Flows

   stsi (m): The LCT TSI value corresponding to the Transport Session
   for the Source Flow.

   rt (o):  A Boolean flag that SHALL indicate whether the content
      component carried by this Source Flow corresponds to real-time
      streaming media or non-real-time content.  When set to "true", it
      SHALL be an indication of real-time content, and when absent or
      set to "false", it SHALL be an indication of non-real-time (NRT)
      content.

   minBufferSize (o):  A 32-bit unsigned integer that SHALL represent,
      in kilobytes, the minimum required storage size of the receiver
      transport buffer for the parent LCT channel of this Source Flow.
      The buffer holds the data belonging to a source object until its
      complete reception.  This attribute is only applicable when rt =
      "true".

      A service that chooses not to signal this attribute relies on the
      receiver implementation, which must discard the received data
      beyond its buffering capability.  Such discarding of data will
      impact the service quality.

   EFDT (cm):  When present, SHALL contain a single instance of an FDT-
      Instance element per RFC 6726 FLUTE [RFC6726], which MAY contain
      the optional FDT extensions as defined in Section 4.1.  The
      optional EFDT element MAY only be present for File Mode of
      delivery.  In File Mode, it SHALL be present if this Source Flow
      transports streaming media segments.

   contentType (o):  A string that SHALL represent the media type for
      the media content.  It SHALL obey the semantics of the Content-
      Type header as specified by the HTTP/1.1 protocol in RFC 7231
      [RFC7231].  This document does not define any new contentType
      strings.  In its absence, the signaling of media type for the
      media content is beyond the scope of this document.

   applicationMapping (m):  A set of identifiers that provide an
      application-specific mapping of the received Application Objects
      to the Source Flows.  For example, for DASH, this would provide
      the mapping of a Source Flow to a specific DASH Representation
      from a Media Presentation Description (MPD), the latter identified
      by its Representation and corresponding Adaptation Set and Period
      IDs.

3.3.  Session Metadata for Repair Flows

   minBuffSize (o):  A 32-bit unsigned integer whose value SHALL
      represent a required size of the receiver transport buffer for
      AL-FEC decoding processing.  When present, this attribute SHALL
      indicate the minimum buffer size that is required to handle all
      associated objects that are assigned to a super-object, i.e., a
      delivery object formed by the concatenation of multiple FEC
      transport objects in order to bundle these FEC transport objects
      for AL-FEC protection.

      A service that chooses not to signal this attribute relies on the
      receiver implementation, which must discard the received repair
      data beyond its buffering capability.  Such discarding of data
      will impact the service quality.

   fecOTI (m):  A parameter consisting of the concatenation of Common
      and Scheme-Specific FEC Object Transmission Information (FEC OTI)
      as defined in Sections 3.3.2 and 3.3.3 of [RFC6330] and that
      corresponds to the delivery objects carried in the Source Flow to
      which this Repair Flow is associated, with the following
      qualification: the 40-bit Transfer Length (F) field may either
      represent the actual size of the object, or it is encoded as all
      zeroes.  In the latter case, the FEC transport object size either
      is unknown or cannot be represented by this attribute.  In other
      words, for the all-zeroes format, the delivery objects in the
      Source Flow correspond to streaming content, either a live Service
      whereby content encoding has not yet occurred at the time this
      session data was generated or pre-recorded streaming content whose
      delivery object sizes, albeit known at the time of session data
      generation, are variable and cannot be represented as a single
      value by the fecOTI attribute.

   ptsi (m):  TSI value(s) of each Source Flow protected by this Repair
      Flow.

   mappingTOIx (o):  Values of the constant X for use in deriving the
      TOI of the delivery object of each protected Source Flow from the
      TOI of the FEC (super-)object.  The default value is "1".
      Multiple mappingTOIx values MAY be provided for each protected
      Source Flow depending upon the usage of FEC (super-)object.

   mappingTOIy (o):  The corresponding constant Y to each mappingTOIx,
      when present, for use in deriving the parent SourceTOI value from
      the above equation.  The default value is "0".

4.  Delivery Object Mode

   ROUTE provides several different delivery object modes, and one of
   these modes may suit the application needs better for a given
   Transport Session.  A delivery object is self contained for the
   application, typically associated with certain properties, metadata,
   and timing-related information relevant to the application.  The
   signaling of the delivery object mode is done on an object basis
   using Codepoint as specified in Section 2.1.

4.1.  File Mode

   File Mode uses an out-of-band Extended FDT (EFDT) signaling for
   recovery of delivery objects with the following extensions and
   considerations.

4.1.1.  Extensions to FDT

   The following extensions are specified to FDT, as specified in RFC
   6726 [RFC6726].  An Extended FDT-Instance is an instance of FLUTE
   FDT, as specified in [RFC6726], plus optionally one or more of the
   following extensions:

   efdtVersion:  A value that SHALL represent the version of this
      Extended FDT-Instance.

   maxExpiresDelta:  Let "tp" represent the wall clock time at the
      receiver when the receiver acquires the first ROUTE packet
      carrying data of the object described by this Extended FDT-
      Instance.  maxExpiresDelta, when present, SHALL represent a time
      interval that when added to "tp" SHALL represent the expiration
      time of the associated Extended FDT-Instance "te".  The time
      interval is expressed in number of seconds.  When maxExpiresDelta
      is not present, the expiration time of the Extended FDT-Instance
      SHALL be given by the sum of a) the value of the ERT field in the
      EXT_TIME LCT header extension in the first ROUTE packet carrying
      data of that file, and b) the current receiver time when parsing
      the packet header of that ROUTE packet.  See Sections 5.4 and
      6.3.3 on additional rules for deriving the Extended FDT-Instance
      expiration time.  Hence, te = tp + maxExpiresDelta

   maxTransportSize:  An attribute that SHALL represent the maximum
      transport size in bytes of any delivery object described by this
      Extended FDT-Instance.  This attribute SHALL be present if a) the
      fileTemplate is present in Extended FDT-Instance, or b) one or
      more File elements, if present in this Extended FDT-Instance, do
      not include the Transfer-Length attribute.  When maxTransportSize
      is not present, the maximum transport size is not signaled, while
      other signaling such as the Transfer-Length attribute signal the
      exact Transfer Length of the object.

   fileTemplate:  A string value, which when present and in conjunction
      with parameter substitution, is used in deriving the Content-
      Location attribute for the delivery object described by this
      Extended FDT-Instance.  It SHALL include the "$TOI$" identifier.
      Each identifier MAY be suffixed as needed by specific file names
      within the enclosing '$' characters following this prototype:
      %0[width]d

   The width parameter is an unsigned integer that provides the minimum
   number of characters to be printed.  If the value to be printed is
   shorter than this number, the result SHALL be padded with leading
   zeroes.  The value is not truncated even if the result is larger.
   When no format tag is present, a default format tag with width=1
   SHALL be used.

   Strings other than identifiers SHALL only contain characters that are
   permitted within URIs according to RFC 3986 [RFC3986].

   $$ is an escape sequence in fileTemplate value, i.e., "$$" is non-
   recursively replaced with a single "$".

   The usage of fileTemplate is described in Sender and Receiver
   operations in Sections 5.4 and 6.3, respectively.

4.1.2.  Constraints on Extended FDT

   The Extended FDT-Instance SHALL conform to an FDT-Instance according
   to RFC 6726 [RFC6726] with the following constraints: at least one
   File element and the @Expires attribute SHALL be present.

   Content encoding MAY be used for delivery of any file described by an
   FDT-Instance.File element in the Extended FDT-Instance.  The content
   encoding defined in the present document is gzip [RFC1952].  When
   content encoding is used, the File@Content-Encoding and File@Content-
   Length attributes SHALL be present in the Extended FDT-Instance.

4.2.  Entity Mode

   For Entity Mode, the following applies:

   *  Delivery object metadata SHALL be expressed in the form of entity
      headers as defined in HTTP/1.1, which correspond to one or more of
      the representation header fields, payload header fields, and
      response header fields as defined in Sections 3.1, 3.3, and 7,
      respectively, of [RFC7231].

   *  The entity headers sent along with the delivery object provide all
      information about that multicast transport object.

   *  Sending a media object (if the object is chunked) in Entity Mode
      may result in one of the following options:

      -  If the length of the chunked object is known at the sender, the
         ROUTE Entity Mode delivery object MAY be sent without using
         HTTP/1.1 chunked transfer coding, i.e., the object starts with
         an HTTP header containing the Content Length field followed by
         the concatenation of CMAF Chunks:

         |HTTP Header+Length||---chunk ----||---chunk ----||---chunk --
         --||---chunk ----|

      -  If the length of the chunked object is unknown at the sender
         when starting to send the object, HTTP/1.1 chunked transfer
         coding format SHALL be used:

         |HTTP Header||Separator+Length||---chunk ----
         ||Separator+Length||---chunk ----||Separator+Length||---chunk
         ----||Separator+Length||---chunk ----||Separator+Length=0|

         Note, however, that it is not required to send a CMAF Chunk in
         exactly one HTTP chunk.

4.3.  Unsigned Package Mode

   In this delivery mode, the delivery object consists of a group of
   files that are packaged for delivery only.  If applied, the client is
   expected to unpack the package and provide each file as an
   independent object to the application.  Packaging is supported by
   Multipart Multipurpose Internet Mail Extensions (MIME) [RFC2557],
   where objects are packaged into one document for transport, with
   Content-Type set to multipart/related.  When binary files are
   included in the package, Content-Transfer-Encoding of "binary" should
   be used for those files.

4.4.  Signed Package Mode

   In Signed Package Mode delivery, the delivery object consists of a
   group of files that are packaged for delivery, and the package
   includes one or more signatures for validation.  Signed packaging is
   supported by RFC 8551 Secure MIME (S/MIME) [RFC8551], where objects
   are packaged into one document for transport and the package includes
   objects necessary for validation of the package.

5.  Sender Operation

5.1.  Usage of ALC and LCT for Source Flow

   ROUTE Source Flow carries the source data as specified in RFC 5775
   [RFC5775].  There are several special considerations that ROUTE
   introduces to the usage of the LCT building block as outlined in the
   following:

   *  ROUTE limits the usage of the LCT building block to a single
      channel per session.  Congestion control is thus sender driven in
      ROUTE.  It also signifies that there is no specific congestion-
      control-related signaling from the sender to the receiver; the CCI
      field is either set to 0 or used for other purposes as specified
      in Section 2.1.  The functionality of receiver-driven layered
      multicast may still be offered by the application, allowing the
      receiver application to select the appropriate delivery session
      based on the bandwidth requirement of that session.

   Further, the following details apply to LCT:

   *  The Layered Coding Transport (LCT) Building Block as defined in
      RFC 5651 [RFC5651] is used with the following constraints:

      -  The TSI in the LCT header SHALL be set equal to the value of
         the stsi attribute in Section 3.2.

      -  The Codepoint (CP) in the LCT header SHALL be used to signal
         the applied formatting as defined in the signaling metadata.

      -  In accordance with ALC, a source FEC Payload ID header is used
         to identify, for FEC purposes, the encoding symbols of the
         delivery object, or a portion thereof, carried by the
         associated ROUTE packet.  This information may be sent in
         several ways:

         o  As a simple new null FEC scheme with the following usage:

            +  The value of the source FEC Payload ID header SHALL be
               set to 0 in case the ROUTE packet contains the entire
               delivery object, or

            +  The value of the source FEC Payload ID header SHALL be
               set as a direct address (start offset) corresponding to
               the starting byte position of the portion of the object
               carried in this packet using a 32-bit field.

         o  In a compatible manner to RFC 6330 [RFC6330] where the SBN
            and ESI defines the start offset together with the symbol
            size T.

         o  The signaling metadata provides the appropriate parameters
            to indicate any of the above modes using the srcFecPayloadId
            attribute.

   *  The LCT Header EXT_TIME extension as defined in RFC 5651 [RFC5651]
      MAY be used by the sender in the following manner:

      -  The Sender Current Time (SCT), depending on the application,
         MAY be used to occasionally or frequently signal the sender
         current time possibly for reliever time synchronization.

      -  The Expected Residual Time (ERT) MAY be used to indicate the
         expected remaining time for transmission of the current object
         in order to optimize detection of a lost delivery object.

      -  The Sender Last Changed (SLC) flag is typically not utilized
         but MAY be used to indicate the addition/removal of Segments.

   Additional extension headers MAY be used to support real-time
   delivery.  Such extension headers are defined in Section 2.1.

5.2.  ROUTE Packetization for Source Flow

   The following description of the ROUTE sender operation on the
   mapping of the Application Object to the ROUTE packet payloads
   logically represents an extension of RFC 5445 [RFC5445], which in
   turn inherits the context, language, declarations, and restrictions
   of the FEC building block in RFC 5052 [RFC5052].

   The data carried in the payload of a given ROUTE packet constitutes a
   contiguous portion of the Application Object.  ROUTE source delivery
   can be considered as a special case of the use of the Compact No-Code
   Scheme associated with FEC Encoding ID = 0 according to Sections
   3.4.1 and 3.4.2 of [RFC5445], in which the encoding symbol size is
   exactly one byte.  As specified in Section 2.1, for ROUTE Source
   Flows, the FEC Payload ID SHALL deliver the 32-bit start_offset.  All
   receivers are expected to support, at minimum, operation with this
   special case of the Compact No-Code FEC.

   Note that in the event the source object size is greater than 2^32
   bytes (approximately 4.3 GB), the applications (in the broadcaster
   server and the receiver) are expected to perform segmentation/
   reassembly using methods beyond the scope of this document.

   Finally, in some special cases, a ROUTE sender MAY need to produce
   ROUTE packets that do not contain any payload.  This may be required,
   for example, to signal the end of a session.  These dataless packets
   do not contain FEC Payload ID or payload data, but only the LCT
   header fields.  The total datagram length, conveyed by outer protocol
   headers (e.g., the IP or UDP header), enables receivers to detect the
   absence of the LCT header, FEC Payload ID, and payload data.

5.2.1.  Basic ROUTE Packetization

   In the basic operation, it is assumed that the Application Object is
   fully available at the ROUTE sender.

   1.  The amount of data to be sent in a single ROUTE packet is limited
       by the maximum transfer unit of the data packets or the size of
       the remaining data of the Application Object being sent,
       whichever is smaller.  The transfer unit is determined either by
       knowledge of underlying transport block sizes or by other
       constraints.

   2.  The start_offset field in the LCT header of the ROUTE packet
       indicates the byte offset of the carried data in the Application
       Object being sent.

   3.  The Close Object flag (B) is set to 1 if this is the last ROUTE
       packet carrying the data of the Application Object.

   The order of packet delivery is arbitrary, but in the absence of
   other constraints, delivery with increasing start_offset value is
   recommended.

5.2.2.  ROUTE Packetization for CMAF Chunked Content

   The following additional guidelines should be followed for ROUTE
   packetization of CMAF Chunked Content in addition to the guidelines
   of Section 5.2.1:

   1.  If it is the first ROUTE packet carrying a CMAF Random Access
       chunk, except for the first CMAF Chunk in the segment, the
       Codepoint value MAY be set to 10, as specified in the Codepoint
       value table in Section 2.1.  The receiver MAY use this
       information for optimization of random access.

   2.  As soon as the total length of the media object is known,
       potentially with the packaging of the last CMAF Chunk of a
       segment, the EXT_TOL extension header MAY be added to the LCT
       header to signal the Transfer Length, so that the receiver may
       know this information in a timely fashion.

5.3.  Timing of Packet Emission

   The sender SHALL use the timing information provided by the
   application to time the emission of packets for a timely reception.
   This information may be contained in the Application Objects e.g.,
   DASH segments and/or the presentation manifest.  Hence, such packets
   of streaming media with real-time constraints SHALL be sent in such a
   way as to enable their timely reception with respect to the
   presentation timeline.

5.4.  Extended FDT Encoding for File Mode Sending

   For File Mode sending:

   *  The TOI field in the ROUTE packet header SHALL be set such that
      Content-Location can be derived at the receiver according to File
      Template substitution specified in Section 6.3.1.

   *  After sending the first packet with a given TOI value, none of the
      packets pertaining to this TOI SHALL be sent later than the wall
      clock time as derived from maxExpiresDelta.  The EXT_TIME header
      with Expected Residual Time (ERT) MAY be used in order to convey
      more accurate expiry time.

5.5.  FEC Framework Considerations

   The FEC framework uses concepts of the FECFRAME work as defined in
   RFC 6363 [RFC6363], as well as the FEC building block, RFC 5052
   [RFC5052], which is adopted in the existing FLUTE/ALC/LCT
   specifications.

   The FEC design adheres to the following principles:

   *  FEC-related information is provided only where needed.

   *  Receivers not capable of this framework can ignore repair packets.

   *  The FEC is symbol based with fixed symbol size per protected
      Source Flow.  The ALC protocol and existing FEC schemes are
      reused.

   *  A FEC Repair Flow provides protection of delivery objects from one
      or more Source Flows.

   The FEC-specific components of the FEC framework are:

   *  FEC Repair Flow declaration including all FEC-specific
      information.

   *  A FEC transport object that is the concatenation of a delivery
      object, padding octets, and size information in order to form a
      chunk of data that has a size in symbols of N, where N >= 1.

   *  A FEC super-object that is the concatenation of one or more FEC
      transport objects in order to bundle FEC transport objects for FEC
      protection.

   *  A FEC protocol and packet structure.

   A receiver needs to be able to recover delivery objects from repair
   packets based on available FEC information.

5.6.  FEC Transport Object Construction

   In order to identify a delivery object in the context of the repair
   protocol, the following information is needed:

   *  TSI and TOI of the delivery object.  In this case, the FEC object
      corresponds to the (entire) delivery object.

   *  Octet range of the delivery object, i.e., start offset within the
      delivery object and number of subsequent and contiguous octets of
      delivery object that constitutes the FEC object (i.e., the FEC-
      protected portion of the source object).  In this case, the FEC
      object corresponds to a contiguous byte range portion of the
      delivery object.

   Typically, for real-time object delivery with smaller delivery object
   sizes, the first mapping is applied, i.e., the delivery object is a
   FEC object.

   Assuming that the FEC object is the delivery object, for each
   delivery object, the associated FEC transport object is comprised of
   the concatenation of the delivery object, padding octets (P), and the
   FEC object size (F) in octets, where F is carried in a 4-octet field.

   The FEC transport object size S, in FEC encoding symbols, SHALL be an
   integer multiple of the symbol size Y.  S is determined from the
   session information and/or the repair packet headers.

   F is carried in the last 4 octets of the FEC transport object.
   Specifically, let:

   *  F be the size of the delivery object in octets,

   *  F' be the F octets of data of the delivery object,

   *  f' denote the four octets of data carrying the value of F in
      network octet order (high-order octet first),

   *  S be the size of the FEC transport object with S=ceil((F+4)/Y),
      where the ceil() function rounds the result upward to its nearest
      integer,

   *  P' be S*Y-4-F octets of data, i.e., padding placed between the
      delivery object and the 4-byte field conveying the value of F and
      located at the end of the FEC transport object, and

   *  O' be the concatenation of F', P', and f'.

   O' then constitutes the FEC transport object of size S*Y octets.
   Note that padding octets and the object size F are not sent in source
   packets of the delivery object but are only part of a FEC transport
   object that FEC decoding recovers in order to extract the FEC object
   and thus the delivery object or portion of the delivery object that
   constitutes the FEC object.  In the above context, the FEC transport
   object size in symbols is S.

   The general information about a FEC transport object that is conveyed
   to a FEC-enabled receiver is the source TSI, source TOI, and the
   associated octet range within the delivery object comprising the
   associated FEC object.  However, as the size in octets of the FEC
   object is provided in the appended field within the FEC transport
   object, the remaining information can be conveyed as:

   *  The TSI and TOI of the delivery object from which the FEC object
      associated with the FEC transport object is generated

   *  The start octet within the delivery object for the associated FEC
      object

   *  The size in symbols of the FEC transport object, S

5.7.  Super-Object Construction

   From the FEC Repair Flow declaration, the construction of a FEC
   super-object as the concatenation of one or more FEC transport
   objects can be determined.  The FEC super-object includes the general
   information about the FEC transport objects as described in the
   previous sections, as well as the placement order of FEC transport
   objects within the FEC super-object.

   Let:

   *  N be the total number of FEC transport objects for the FEC super-
      object construction.

   *  For i = 0, ..., N-1, let S[i] be the size in symbols of FEC
      transport object i.

   *  B' be the FEC super-object that is the concatenation of the FEC
      transport objects in numerical order, comprised of K = Sum of N
      source symbols, each symbol denoted as S[i].

   For each FEC super-object, the remaining general information that
   needs to be conveyed to a FEC-enabled receiver, beyond what is
   already carried in the FEC transport objects that constitute the FEC
   super-object, comprises:

   *  The total number of FEC transport objects N.

   *  For each FEC transport object:

      -  The TSI and TOI of the delivery object from which the FEC
         object associated with the FEC transport object is generated,

      -  The start octet within the delivery object for the associated
         FEC object, and

      -  The size in symbols of the FEC transport object.

   The carriage of the FEC repair information is discussed below.

5.8.  Repair Packet Considerations

   The repair protocol is based on Asynchronous Layered Coding (ALC) as
   defined in RFC 5775 [RFC5775] and the Layered Coding Transport (LCT)
   Building Block as defined in RFC 5651 [RFC5651] with the following
   details:

   *  The Layered Coding Transport (LCT) Building Block as defined in
      RFC 5651 [RFC5651] is used as defined in Asynchronous Layered
      Coding (ALC), Section 2.1.  In addition, the following constraint
      applies:

      -  The TSI in the LCT header SHALL identify the Repair Flow to
         which this packet applies by the matching the value of the ptsi
         attribute in the signaling metadata among the LCT channels
         carrying Repair Flows.

   *  The FEC building block is used according to RFC 6330 [RFC6330],
      but only repair packets are delivered.

      -  Each repair packet within the scope of the Repair Flow (as
         indicated by the TSI field in the LCT header) SHALL carry the
         repair symbols for a corresponding FEC transport object/super-
         object as identified by its TOI.  The repair object/super-
         object TOI SHALL be unique for each FEC super-object that is
         created within the scope of the TSI.

5.9.  Summary FEC Information

   For each super-object (identified by a unique TOI within a Repair
   Flow that is in turn identified by the TSI in the LCT header) that is
   generated, the following information needs to be communicated to the
   receiver:

   *  The FEC configuration consisting of:

      -  FEC Object Transmission Information (OTI) per RFC 5052
         [RFC5052].

      -  Additional FEC information (see Section 3.3).

      -  The total number of FEC objects included in the FEC super-
         object, N.

   *  For each FEC transport object:

      -  TSI and TOI of the delivery object used to generate the FEC
         object associated with the FEC transport object,

      -  The start octet within the delivery object of the associated
         FEC object, if applicable, and

      -  The size in symbols of the FEC transport object, S.

   The above information is delivered:

   *  Statically in the session metadata as defined in Section 3.3, and

   *  Dynamically in an LCT extension header.

6.  Receiver Operation

   The receiver receives packets and filters those packets according to
   the following.  From the ROUTE session and each contained LCT
   channel, the receiver regenerates delivery objects from the ROUTE
   session and each contained LCT channel.

   In the event that the receiver receives data that does not conform to
   the ROUTE protocol specified in this document, the receiver SHOULD
   attempt to recover gracefully by e.g., informing the application
   about the issues using means beyond the scope of this document.  The
   ROUTE packetization specified in Section 5.2.1 implies that the
   receiver SHALL NOT receive overlapping data; if such a condition is
   encountered at the receiver, the packet SHALL be assumed to be
   corrupted.

   The basic receiver operation is provided below (it assumes an error-
   free scenario), while repair considerations are provided in
   Section 7.

6.1.  Basic Application Object Recovery for Source Flows

   Upon receipt of each ROUTE packet of a Source Flow, the receiver
   proceeds with the following steps in the order listed.

   1)  The ROUTE receiver is expected to parse the LCT and FEC Payload
       ID to verify that it is a valid header.  If it is not valid, then
       the payload is discarded without further processing.

   2)  All ROUTE packets used to recover a specific delivery object
       carry the same TOI value in the LCT header.

   3)  The ROUTE receiver is expected to assert that the TSI and the
       Codepoint represent valid operation points in the signaling
       metadata, i.e., the signaling contains a matching entry to the
       TSI value provided in the packet header, as well as for this TSI,
       and the Codepoint field in the LCT header has a valid Codepoint
       mapping.

   4)  The ROUTE receiver should process the remainder of the payload,
       including the appropriate interpretation of the other payload
       header fields, using the source FEC Payload ID (to determine the
       start_offset) and the payload data to reconstruct the
       corresponding object as follows:

       a.  For File Mode, upon receipt of the first ROUTE packet payload
           for an object, the ROUTE receiver uses the File@Transfer-
           Length attribute of the associated Extended FDT-Instance,
           when present, to determine the length T of the object.  When
           the File@Transfer-Length attribute is not present in the
           Extended FDT-Instance, the receiver uses the maxTransportSize
           attribute of the associated Extended FDT-Instance to
           determine the maximum length T' of the object.
           Alternatively, and specifically for delivery modes other than
           File Mode, the EXT_TOL header can be used to determine the
           length T of the object.

       b.  The ROUTE receiver allocates buffer space for the T or T'
           bytes that the object will or may occupy.

       c.  The ROUTE receiver computes the length of the payload, Y, by
           subtracting the payload header length from the total length
           of the received payload.

       d.  The ROUTE receiver allocates a Boolean array RECEIVED[0..T-1]
           or RECEIVED[0..T'-1], as appropriate, with all entries
           initialized to false to track received object symbols.  The
           ROUTE receiver continuously acquires packet payloads for the
           object as long as all of the following conditions are
           satisfied:

           i.    there is at least one entry in RECEIVED still set to
                 false,

           ii.   the object has not yet expired, and

           iii.  the application has not given up on reception of this
                 object.

                 More details are provided below.

       e.  For each received ROUTE packet payload for the object
           (including the first payload), the steps to be taken to help
           recover the object are as follows:

           i.    If the packet includes an EXT_TOL or EXT_FTI header,
                 modify the Boolean array RECEIVED[0..T'-1] to become
                 RECEIVED[0..T-1].

           ii.   Let X be the value of the start_offset field in the
                 ROUTE packet header and let Y be the length of the
                 payload, Y, computed by subtracting the LCT header size
                 and the FEC Payload ID size from the total length of
                 the received packet.

           iii.  The ROUTE receiver copies the data into the appropriate
                 place within the space reserved for the object and sets
                 RECEIVED[X ... X+Y-1] = true.

           iv.   If all T entries of RECEIVED are true, then the
                 receiver has recovered the entire object.

   Upon recovery of both the complete set of packet payloads for the
   delivery object associated with a given TOI value, and the metadata
   for that delivery object, the reception of the delivery object, now a
   fully received Application Object, is complete.

   Given the timely reception of ROUTE packets belonging to an
   Application Object, the receiver SHALL make the Application Objects
   available to the application in a timely fashion using the
   application-provided timing data (e.g., the timing data signaled via
   the presentation manifest file).  For example, HTTP/1.1 chunked
   transfer may need to be enabled to transfer the Application Objects
   if MPD@availabilityTimeOffset is signaled in the DASH presentation
   manifest in order to allow for the timely sending of segment data to
   the application.

6.2.  Fast Stream Acquisition

   When the receiver initially starts reception of ROUTE packets, it is
   likely that the reception does not start from the very first packet
   carrying the data of a multicast transport object; in this case, such
   a partially received object is normally discarded.  However, the
   channel acquisition or "tune-in" times can be improved if the
   partially received object is usable by the application.  One example
   realization for this is as follows:

   *  The receiver checks for the first received packet with the
      Codepoint value set to 10, indicating the start of a CMAF Random
      Access chunk.

   *  The receiver MAY make the partially received object (a partial
      DASH segment starting from the packet above) available to the
      application for fast stream acquisition.

   *  It MAY recover the earliest presentation time of this CMAF Random
      Access chunk from the ROUTE packet LCT Congestion Control
      Information (CCI) field as specified in Section 2.1 to be able to
      add a new Period element in the MPD exposed to the application
      containing just the partially received DASH segment with period
      continuity signaling.

6.3.  Generating Extended FDT-Instance for File Mode

   An Extended FDT-Instance conforming to RFC 6726 [RFC6726], is
   produced at the receiver using the service metadata and in-band
   signaling in the following steps:

6.3.1.  File Template Substitution for Content-Location Derivation

   The Content-Location element of the Extended FDT for a specific
   Application Object is derived as follows:

   "$TOI$" is substituted with the unique TOI value in the LCT header of
   the ROUTE packets used to recover the given delivery object (as
   specified in Section 6.1).

   After the substitution, the fileTemplate SHALL be a valid URL
   corresponding to the Content-Location attribute of the associated
   Application Object.

   An example @fileTemplate using a width of 5 is:
   fileTemplate="myVideo$TOI%05d$.mps", resulting in file names with
   exactly five digits in the number portion.  The Media Segment file
   name for TOI=33 using this template is myVideo00033.mps.

6.3.2.  File@Transfer-Length Derivation

   Either the EXT_FTI header (per RFC 5775 [RFC5775]) or the EXT_TOL
   header, when present, is used to derive the Transport Object Length
   (TOL) of the File.  If the File@Transfer-Length parameter in the
   Extended FDT-Instance is not present, then the EXT_TOL header or the
   or EXT_FTI header SHALL be present.  Note that a header containing
   the transport object length (EXT_TOL or EXT_FTI) need not be present
   in each packet header.  If the broadcaster does not know the length
   of the transport object at the beginning of the transfer, an EXT_TOL
   or EXT_FTI header SHALL be included in at least the last packet of
   the file and should be included in the last few packets of the
   transfer.

6.3.3.  FDT-Instance@Expires Derivation

   When present, the maxExpiresDelta attribute SHALL be used to generate
   the value of the FDT-Instance@Expires attribute.  The receiver is
   expected to add this value to its wall clock time when acquiring the
   first ROUTE packet carrying the data of a given delivery object to
   obtain the value for @Expires.

   When maxExpiresDelta is not present, the EXT_TIME header with
   Expected Residual Time (ERT) SHALL be used to derive the expiry time
   of the Extended FDT-Instance.  When both maxExpiresDelta and the ERT
   of EXT_TIME are present, the smaller of the two values should be used
   as the incremental time interval to be added to the receiver's
   current time to generate the effective value for @Expires.  When
   neither maxExpiresDelta nor the ERT field of the EXT_TIME header is
   present, then the expiration time of the Extended FDT-Instance is
   given by its @Expires attribute.

7.  FEC Application

7.1.  General FEC Application Guidelines

   It is up to the receiver to decide to use zero, one, or more of the
   FEC streams.  Hence, the application assigns a recovery property to
   each flow, which defines aspects such as the delay and the required
   memory if one or the other is chosen.  The receiver MAY decide
   whether or not to utilize Repair Flows based on the following
   considerations:

   *  The desired start-up and end-to-end latency.  If a Repair Flow
      requires a significant amount of buffering time to be effective,
      such Repair Flow might only be used in time-shift operations or in
      poor reception conditions, since use of such Repair Flow trades
      off end-to-end latency against DASH Media Presentation quality.

   *  FEC capabilities, i.e., the receiver MAY pick only the FEC
      algorithm that it supports.

   *  Which Source Flows are being protected; for example, if the Repair
      Flow protects Source Flows that are not selected by the receiver,
      then the receiver may not select the Repair Flow.

   *  Other considerations such as available buffer size, reception
      conditions, etc.

   If a receiver decides to acquire a certain Repair Flow, then the
   receiver must receive data on all Source Flows that are protected by
   that Repair Flow to collect the relevant packets.

7.2.  TOI Mapping

   When mappingTOIx/mappingTOIy are used to signal X and Y values, the
   TOI value(s) of the one or more source objects (sourceTOI) protected
   by a given FEC transport object or FEC super-object with a TOI value
   rTOI is derived through an equation sourceTOI = X*rTOI + Y.

   When neither mappingTOIx nor mappingTOIy is present, there is a 1:1
   relationship between each delivery object carried in the Source Flow
   as identified by ptsi to a FEC object carried in this Repair Flow.
   In this case, the TOI of each of those delivery objects SHALL be
   identical to the TOI of the corresponding FEC object.

7.3.  Delivery Object Reception Timeout

   The permitted start and end times for the receiver to perform the
   file repair procedure, in case of unsuccessful broadcast file
   reception, and associated rules and parameters are as follows:

   *  The latest time that the file repair procedure may start is bound
      by the @Expires attribute of the FDT-Instance.

   *  The receiver may choose to start the file repair procedure earlier
      if it detects the occurrence of any of the following events:

      -  Presence of the Close Object flag (B) in the LCT header
         [RFC5651] for the file of interest;

      -  Presence of the Close Session flag (A) in the LCT header
         [RFC5651] before the nominal expiration of the Extended FDT-
         Instance as defined by the @Expires attribute.

7.4.  Example FEC Operation

   To be able to recover the delivery objects that are protected by a
   Repair Flow, a receiver needs to obtain the necessary Service
   signaling metadata fragments that describe the corresponding
   collection of delivery objects that are covered by this Repair Flow.
   A Repair Flow is characterized by the combination of an LCT channel,
   a unique TSI number, as well as the corresponding protected Source
   Flows.

   If a receiver acquires data of a Repair Flow, the receiver is
   expected to collect all packets of all protected Transport Sessions.
   Upon receipt of each packet, whether it is a source or repair packet,
   the receiver proceeds with the following steps in the order listed.

   1.  The receiver is expected to parse the packet header and verify
       that it is a valid header.  If it is not valid, then the packet
       SHALL be discarded without further processing.

   2.  The receiver is expected to parse the TSI field of the packet
       header and verify that a matching value exists in the Service
       signaling for the Repair Flow or the associated Protected Source
       Flow.  If no match is found, the packet SHALL be discarded
       without further processing.

   3.  The receiver processes the remainder of the packet, including
       interpretation of the other header fields, and using the source
       FEC Payload ID (to determine the start_offset byte position
       within the source object), the Repair FEC Payload ID, as well as
       the payload data, reconstructs the decoding blocks corresponding
       to a FEC super-object as follows:

       a.  For a source packet, the receiver identifies the delivery
           object to which the received packet is associated using the
           session information and the TOI carried in the payload
           header.  Similarly, for a repair object, the receiver
           identifies the FEC super-object to which the received packet
           is associated using the session information and the TOI
           carried in the payload header.

       b.  For source packets, the receiver collects the data for each
           FEC super-object and recovers FEC super-objects in the same
           way as a Source Flow in Section 6.1.  The received FEC super-
           object is then mapped to a source block and the corresponding
           encoding symbols are generated.

       c.  With the reception of the repair packets, the FEC super-
           object can be recovered.

       d.  Once the FEC super-object is recovered, the individual
           delivery objects can be extracted.

8.  Considerations for Defining ROUTE Profiles

   Services (e.g., ATSC-ROUTE [ATSCA331], DVB-MABR [DVBMABR], etc.) may
   define specific ROUTE "profiles" based on this document in their
   respective standards organizations.  An example is noted in the
   overview section: DVB has specified a profile of ATSC-ROUTE in DVB
   Adaptive Media Streaming over IP Multicast (DVB-MABR) [DVBMABR].  The
   definition has the following considerations.  Services MAY

   *  Restrict the signaling of certain values signaled in the LCT
      header and/or provision unused fields in the LCT header.

   *  Restrict using certain LCT header extensions and/or add new LCT
      header extensions.

   *  Restrict or limit usage of some Codepoints and/or assign semantics
      to service-specific Codepoints marked as reserved in this
      document.

   *  Restrict usage of certain Service signaling attributes and/or add
      their own service metadata.

   Services SHALL NOT redefine the semantics of any of the ROUTE
   attributes in LCT headers and extensions, as well as Service
   signaling attributes already specified in this document.

   By following these guidelines, services can define profiles that are
   interoperable.

9.  ROUTE Concepts

9.1.  ROUTE Modes of Delivery

   Different ROUTE delivery modes specified in Section 4 are optimized
   for delivery of different types of media data.  For example, File
   Mode is specifically optimized for delivering DASH content using
   Segment Template with number substitution.  Using File Template in
   EFDT avoids the need for the repeated sending of metadata as outlined
   in the following section.  Same optimizations, however, cannot be
   used for time substitution and segment timeline where the addressing
   of each segment is time dependent and in general does not follow a
   fixed or repeated pattern.  In this case, Entity Mode is more
   optimized since it carries the file location in band.  Also, Entity
   Mode can be used to deliver a file or part of the file using HTTP
   Partial Content response headers.

9.2.  File Mode Optimizations

   In File Mode, the delivery object represents an Application Object.
   This mode replicates FLUTE as defined in RFC 6726 [RFC6726] but with
   the ability to send static and pre-known file metadata out of band.

   In FLUTE, FDT-Instances are delivered in band and need to be
   generated and delivered in real time if objects are generated in real
   time at the sender.  These FDT-Instances have some differences as
   compared to the FDT specified in Section 3.4.2 of [RFC6726] and
   Section 7.2.10 of MBMS [MBMS].  The key difference is that besides
   separated delivery of file metadata from the delivery object it
   describes, the FDT functionality in ROUTE may be extended by
   additional file metadata and rules that enable the receiver to
   generate the Content-Location attribute of the File element of the
   FDT, on the fly.  This is done by using information in both the
   extensions to the FDT and the LCT header.  The combination of pre-
   delivery of static file metadata and receiver self generation of
   dynamic file metadata avoids the necessity of continuously sending
   the FDT-Instances for real-time objects.  Such modified FDT
   functionality in ROUTE is referred to as the Extended FDT.

9.3.  In-Band Signaling of Object Transfer Length

   As an extension to FLUTE, ROUTE allows for using EXT_TOL LCT header
   extension with 24 bits or, if required, 48 bits to signal the
   Transfer Length directly within the ROUTE packet.

   The transport object length can also be determined without the use of
   EXT_TOL by examining the LCT packet with the Close Object flag (B).
   However, if this packet is lost, then the EXT_TOL information can be
   used by the receiver to determine the transport object length.

   Applications using ROUTE for delivery of low-latency streaming
   content may make use of this feature for sender-end latency
   optimizations: the sender does not have to wait for the completion of
   the packaging of a whole Application Object to find its Transfer
   Length to be included in the FDT before the sending can start.
   Rather, partially encoded data can already be started to be sent via
   the ROUTE sender.  As the time approaches when the encoding of the
   Application Object is nearing completion, and the length of the
   object becomes known (e.g., the time of writing the last CMAF Chunk
   of a DASH segment), only then the sender can signal the object length
   using the EXT TOL LCT header.  For example, for a 2-second DASH
   segment with 100-millisecond chunks, it may result in saving up to
   1.9 second latency at the sending end.

9.4.  Repair Protocol Concepts

   The ROUTE repair protocol is FEC-based and is enabled as an
   additional layer between the transport layer (e.g., UDP) and the
   object delivery layer protocol.  The FEC reuses concepts of the FEC
   Framework defined in RFC 6363 [RFC6363], but in contrast to the FEC
   Framework in RFC 6363 [RFC6363], the ROUTE repair protocol does not
   protect packets but instead protects delivery objects as delivered in
   the source protocol.  In addition, as an extension to FLUTE, it
   supports the protection of multiple objects in one source block which
   is in alignment with the FEC Framework as defined in RFC 6363
   [RFC6363].  Each FEC source block may consist of parts of a delivery
   object, as a single delivery object (similar to FLUTE) or multiple
   delivery objects that are bundled prior to FEC protection.  ROUTE FEC
   makes use of FEC schemes in a similar way as those defined in RFC
   5052 [RFC5052] and uses the terminology of that document.  The FEC
   scheme defines the FEC encoding and decoding as well as the protocol
   fields and procedures used to identify packet payload data in the
   context of the FEC scheme.

   In ROUTE, all packets are LCT packets as defined in RFC 5651
   [RFC5651].  Source and repair packets may be distinguished by:

   *  Different ROUTE sessions, i.e., they are carried on different UDP/
      IP port combinations.

   *  Different LCT channels, i.e., they use different TSI values in the
      LCT header.

   *  The most significant PSI bit in the LCT, if carried in the same
      LCT channel.  This mode of operation is mostly suitable for FLUTE-
      compatible deployments.

10.  Interoperability Chart

   As noted in prevision sections, ATSC-ROUTE [ATSCA331] and DVB-MABR
   [DVBMABR] are considered services using this document that constrain
   specific features as well as add new ones.  In this context, the
   following table is an informative comparison of the interoperability
   of ROUTE as specified in this document with ATSC-ROUTE [ATSCA331] and
   DVB-MABR [DVBMABR]:

   +===============+===================+==================+============+
   | Element       | ATSC-ROUTE        | This Document    | DVB-MABR   |
   +===============+===================+==================+============+
   | LCT header    | PSI LSB set to 0  | Not defined      | Set to 1   |
   | field         | for Source Flow   |                  | for Source |
   |               |                   |                  | Flow for   |
   |               |                   |                  | CMAF       |
   |               |                   |                  | Random     |
   |               |                   |                  | Access     |
   |               |                   |                  | chunk      |
   |               +-------------------+------------------+------------+
   |               | CCI may be set to | CCI may be set to EPT for     |
   |               | 0                 | Source Flow                   |
   +---------------+-------------------+------------------+------------+
   | LCT header    | EXT_ROUTE_        | Not defined;     | Shall not  |
   | extensions    | PRESENTATION_TIME | may be added by  | be used.   |
   |               | Header used for   | a profile.       |            |
   |               | Media Delivery    |                  |            |
   |               | Event (MDE) mode  |                  |            |
   |               +-------------------+------------------+------------+
   |               | EXT_TIME Header   | EXT_TIME Header may be used   |
   |               | linked to MDE     | regardless (for FDT-          |
   |               | mode in Annex     | Instance@Expires              |
   |               | A.3.7.2           | calculation)                  |
   |               | [ATSCA331]        |                               |
   +---------------+-------------------+------------------+------------+
   | Codepoints    | Full set          | Does not         | Restricted |
   |               |                   | specify range    | to 5 - 9   |
   |               |                   | 11 - 255         |            |
   |               |                   | (leaves to       |            |
   |               |                   | profiles)        |            |
   +---------------+-------------------+------------------+------------+
   | Session       | Full set          | Only defines a   | Reuses     |
   | metadata      |                   | small subset of  | A/331      |
   |               |                   | data necessary   | metadata,  |
   |               |                   | for setting up   | duplicated |
   |               |                   | Source and       | from its   |
   |               |                   | Repair Flows.    | own        |
   |               |                   | Does not define  | Service    |
   |               |                   | format or        | signaling. |
   |               |                   | encoding of      |            |
   |               |                   | data except if   |            |
   |               |                   | data is          |            |
   |               |                   | integral/        |            |
   |               |                   | alphanumerical.  |            |
   |               |                   | Leaves rest to   |            |
   |               |                   | profiles.        |            |
   +---------------+-------------------+------------------+------------+
   | Extended FDT  | Instance shall    | Not restricted,  | Instance   |
   |               | not be sent with  | may be           | shall not  |
   |               | Source Flow       | restricted by a  | be sent    |
   |               |                   | profile.         | with       |
   |               |                   |                  | Source     |
   |               |                   |                  | Flow       |
   |               +-------------------+------------------+------------+
   |               | No restriction    |   Only allowed in File Mode   |
   +---------------+-------------------+------------------+------------+
   | Delivery      |    File, Entity, Signed/unsigned     | Signed/    |
   | Object Mode   |               package                | unsigned   |
   |               |                                      | package    |
   |               |                                      | not        |
   |               |                                      | allowed    |
   +---------------+-------------------+------------------+------------+
   | Sender        | Defined for DASH  |  Defined for DASH segment and |
   | operation:    | segment           |          CMAF Chunks          |
   | Packetization |                   |                               |
   +---------------+-------------------+-------------------------------+
   | Receiver      | Object handed to  |  Object may be handed before  |
   | object        | application upon  |         completion if         |
   | recovery      | complete          |   MPD@availabilityTimeOffset  |
   |               | reception         |            signaled           |
   |               +-------------------+-------------------------------+
   |               |         -         |    Fast Stream acquisition    |
   |               |                   |      guidelines provided      |
   +---------------+-------------------+-------------------------------+

                      Table 3: Interoperability Chart

11.  Security and Privacy Considerations

11.1.  Security Considerations

   As noted in Section 9, ROUTE is aligned with FLUTE as specified in
   RFC 6726 [RFC6726] and only diverges in certain signaling
   optimizations, especially for the real-time object delivery case.
   Hence, most of the security considerations documented in RFC 6726
   [RFC6726] for the data flow itself, the session metadata (session
   control parameters in RFC 6726 [RFC6726]), and the associated
   building blocks apply directly to ROUTE as elaborated in the
   following along with some additional considerations.

   Both encryption and integrity protection applied either on file or
   packet level, as recommended in the file corruption considerations of
   RFC 6726 [RFC6726], SHOULD be used for ROUTE.  Additionally, RFC 3740
   [RFC3740] documents multicast security architecture in great detail
   with clear security recommendations that SHOULD be followed.

   When ROUTE is carried over UDP and a reverse channel from receiver to
   sender is available, the security mechanisms provided in RFC 9147
   [RFC9147] SHOULD be applied.

   In regard to considerations for attacks against session description,
   this document does not specify the semantics or mechanism of delivery
   of session metadata, though the same threats apply for service using
   ROUTE as well.  Hence, a service using ROUTE SHOULD take these
   threats into consideration and address them appropriately following
   the guidelines provided by RFC 6726 [RFC6726].  Additionally, to the
   recommendations of RFC 6726 [RFC6726], for Internet connected
   devices, services SHOULD enable clients to access the session
   description information using HTTPS with customary authentication/
   authorization, instead of sending this data via multicast/broadcast,
   since considerable security work has been done already in this
   unicast domain, which can enable highly secure access of session
   description data.  Accessing via unicast, however, will have
   different privacy considerations, noted in Section 11.2.  Note that
   in general the multicast/broadcast stream is delayed with respect to
   the unicast stream.  Therefore, the session description protocol
   SHOULD be time synchronized with the broadcast stream, particularly
   if the session description contains security-related information.

   In regard to FDT, there is one key difference for File Mode when
   using File Template in EFDT, which avoids repeated sending of FDT-
   Instances and hence, the corresponding threats noted in RFC 6726
   [RFC6726] do not apply directly to ROUTE in this case.  The threat,
   however, is shifted to the ALC/LCT headers, since they carry the
   additional signaling that enables determining Content-Location and
   File@Transfer-Length in this case.  Hence, integrity protection
   recommendations of ALC/LCT header SHOULD be considered with higher
   emphasis in this case for ROUTE.

   Finally, attacks against the congestion control building block for
   the case of ROUTE can impact the optional fast stream acquisition
   specified in Section 6.2.  Receivers SHOULD have robustness against
   timestamp values that are suspicious, e.g., by comparing the signaled
   time in the LCT headers with the approximate time signaled by the
   MPD, and SHOULD discard outlying values.  Additionally, receivers
   MUST adhere to the expiry timelines as specified in Section 6.
   Integrity protection mechanisms documented in RFC 6726 [RFC6726]
   SHOULD be used to address this threat.

11.2.  Privacy Considerations

   Encryption mechanisms recommended for security considerations in
   Section 11.1 SHOULD also be applied to enable privacy and protection
   from snooping attacks.

   Since this protocol is primarily targeted for IP multicast/broadcast
   environments where the end user is mostly listening, identity
   protection and user data retention considerations are more protected
   than in the unicast case.  Best practices for enabling privacy on IP
   multicast/broadcast SHOULD be applied by the operators, e.g.,
   "Recommendations for DNS Privacy Service Operators" in RFC 8932
   [RFC8932].

   However, if clients access session description information via HTTPS,
   the same privacy considerations and solutions SHALL apply to this
   access as for regular HTTPS communication, an area that is very well
   studied and the concepts of which are being integrated directly into
   newer transport protocols such as IETF QUIC [RFC9000] enabling HTTP/3
   [HTTP3].  Hence, such newer protocols SHOULD be used to foster
   privacy.

   Note that streaming services MAY contain content that may only be
   accessed via DRM (digital rights management) systems.  DRM systems
   can prevent unauthorized access to content delivered via ROUTE.

12.  IANA Considerations

   This document has no IANA actions.

13.  References

13.1.  Normative References

   [ATSCA331] Advanced Television Systems Committee, "Signaling,
              Delivery, Synchronization, and Error Protection", ATSC
              Standard A/331:2022-03, March 2022.

   [RFC1952]  Deutsch, P., "GZIP file format specification version 4.3",
              RFC 1952, DOI 10.17487/RFC1952, May 1996,
              <https://www.rfc-editor.org/info/rfc1952>.

   [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>.

   [RFC2557]  Palme, J., Hopmann, A., and N. Shelness, "MIME
              Encapsulation of Aggregate Documents, such as HTML
              (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
              <https://www.rfc-editor.org/info/rfc2557>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5052]  Watson, M., Luby, M., and L. Vicisano, "Forward Error
              Correction (FEC) Building Block", RFC 5052,
              DOI 10.17487/RFC5052, August 2007,
              <https://www.rfc-editor.org/info/rfc5052>.

   [RFC5445]  Watson, M., "Basic Forward Error Correction (FEC)
              Schemes", RFC 5445, DOI 10.17487/RFC5445, March 2009,
              <https://www.rfc-editor.org/info/rfc5445>.

   [RFC5651]  Luby, M., Watson, M., and L. Vicisano, "Layered Coding
              Transport (LCT) Building Block", RFC 5651,
              DOI 10.17487/RFC5651, October 2009,
              <https://www.rfc-editor.org/info/rfc5651>.

   [RFC5775]  Luby, M., Watson, M., and L. Vicisano, "Asynchronous
              Layered Coding (ALC) Protocol Instantiation", RFC 5775,
              DOI 10.17487/RFC5775, April 2010,
              <https://www.rfc-editor.org/info/rfc5775>.

   [RFC6330]  Luby, M., Shokrollahi, A., Watson, M., Stockhammer, T.,
              and L. Minder, "RaptorQ Forward Error Correction Scheme
              for Object Delivery", RFC 6330, DOI 10.17487/RFC6330,
              August 2011, <https://www.rfc-editor.org/info/rfc6330>.

   [RFC6363]  Watson, M., Begen, A., and V. Roca, "Forward Error
              Correction (FEC) Framework", RFC 6363,
              DOI 10.17487/RFC6363, October 2011,
              <https://www.rfc-editor.org/info/rfc6363>.

   [RFC6726]  Paila, T., Walsh, R., Luby, M., Roca, V., and R. Lehtonen,
              "FLUTE - File Delivery over Unidirectional Transport",
              RFC 6726, DOI 10.17487/RFC6726, November 2012,
              <https://www.rfc-editor.org/info/rfc6726>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [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>.

   [RFC8551]  Schaad, J., Ramsdell, B., and S. Turner, "Secure/
              Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
              Message Specification", RFC 8551, DOI 10.17487/RFC8551,
              April 2019, <https://www.rfc-editor.org/info/rfc8551>.

13.2.  Informative References

   [CMAF]     International Organization for Standardization,
              "Information technology -- Multimedia application format
              (MPEG-A) -- Part 19: Common media application format
              (CMAF) for segmented media", First edition, ISO/IEC
              FDIS 23000-19, January 2018,
              <https://www.iso.org/standard/71975.html>.

   [DASH]     International Organization for Standardization,
              "Information technology - Dynamic adaptive streaming over
              HTTP (DASH) - Part 1: Media presentation description and
              segment formats", Fourth edition, ISO/IEC 23009-1:2019,
              December 2019, <https://www.iso.org/standard/79329.html>.

   [DVBMABR]  ETSI, "Digital Video Broadcasting (DVB); Adaptive media
              streaming over IP multicast", version 1.1.1, ETSI TS 103
              769, November 2020.

   [HTTP3]    Bishop, M., Ed., "Hypertext Transfer Protocol Version 3
              (HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
              quic-http-34, 2 February 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
              http-34>.

   [MBMS]     ETSI, "Universal Mobile Telecommunications Systems (UMTS);
              LTE; 5G; Multimedia Broadcast/Multicast Service (MBMS);
              Protocols and codecs", version 16.9.1, ETSI TS 126 346,
              May 2021.

   [RFC3740]  Hardjono, T. and B. Weis, "The Multicast Group Security
              Architecture", RFC 3740, DOI 10.17487/RFC3740, March 2004,
              <https://www.rfc-editor.org/info/rfc3740>.

   [RFC6968]  Roca, V. and B. Adamson, "FCAST: Object Delivery for the
              Asynchronous Layered Coding (ALC) and NACK-Oriented
              Reliable Multicast (NORM) Protocols", RFC 6968,
              DOI 10.17487/RFC6968, July 2013,
              <https://www.rfc-editor.org/info/rfc6968>.

   [RFC8932]  Dickinson, S., Overeinder, B., van Rijswijk-Deij, R., and
              A. Mankin, "Recommendations for DNS Privacy Service
              Operators", BCP 232, RFC 8932, DOI 10.17487/RFC8932,
              October 2020, <https://www.rfc-editor.org/info/rfc8932>.

   [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>.

   [RFC9147]  Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
              <https://www.rfc-editor.org/info/rfc9147>.

Acknowledgments

   As outlined in the introduction and in ROUTE concepts in Section 9,
   the concepts specified in this document are the culmination of the
   collaborative work of several experts and organizations over the
   years.  The authors would especially like to acknowledge the work and
   efforts of the following people and organizations to help realize the
   technologies described in this document (in no specific order): Mike
   Luby, Kent Walker, Charles Lo, and other colleagues from Qualcomm
   Incorporated, LG Electronics, Nomor Research, Sony, and BBC R&D.

Authors' Addresses

   Waqar Zia
   Qualcomm CDMA Technologies GmbH
   Anzinger Str. 13
   81671 Munich
   Germany
   Email: wzia@qti.qualcomm.com

   Thomas Stockhammer
   Qualcomm CDMA Technologies GmbH
   Anzinger Str. 13
   81671 Munich
   Germany
   Email: tsto@qti.qualcomm.com

   Lenaig Chaponniere
   Qualcomm Technologies Inc.
   5775 Morehouse Drive
   San Diego, CA 92121
   United States of America
   Email: lguellec@qti.qualcomm.com

   Giridhar Mandyam
   Qualcomm Technologies Inc.
   5775 Morehouse Drive
   San Diego, CA 92121
   United States of America
   Email: mandyam@qti.qualcomm.com

   Michael Luby
   BitRipple, Inc.
   1133 Miller Ave
   Berkeley, CA 94708
   United States of America
   Email: luby@bitripple.com