Serialization of MoQ Objects to Files
draft-jennings-moq-file-05

moq                                                          C. Jennings
Internet-Draft                                                     Cisco
Intended status: Standards Track                         18 October 2025
Expires: 21 April 2026

                 Serialization of MoQ Objects to Files
                       draft-jennings-moq-file-05

Abstract

   This specification provides a way to save the metadata about each MoQ
   Object in one or more files as well as pointers to other files that
   contain the contents of the object.  Separating of the metadata and
   payload data allows the payload data to remain in files that are used
   for other purposes such as serving HLS/DASH video.  This format makes
   it easier to test and develop caching relays and create test data
   they can serve to clients.

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   This Internet-Draft will expire on 21 April 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  JSON Meta Object  . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Base64 Encoding . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  File Name Encoding  . . . . . . . . . . . . . . . . . . .   4
   4.  MoQT Track DataFile . . . . . . . . . . . . . . . . . . . . .   4
   5.  Playback  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Time Object Example . . . . . . . . . . . . . . . . . . .   5
   7.  IANA  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This specification defines a way of serializing the MoQ Objects
   defined in [MoQT] into files.  The payload data and the metadata are
   separated into separate files to allows reuse of existing files with
   the payload data.

2.  JSON Meta Object

   The .moq files consist of an array of one or more JSON objects.  Each
   JSON object contains information about the MoQT object as well as
   pointers to the where the original data can be found.

   The following fields are defined for each JSON object:

   *  trackNamespace: Array of strings that have a Base64 encoded
      version of the data in each tuple of MoQT Track Namespace as
      defined in [MoQT].

   *  trackName: string with Base64 encoded version of the MoQT
      Trackname as defined in [MoQT].

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   *  objectID: integer corresponding to the MoQT Object ID as defined
      in [MoQT].

   *  groupID: integer corresponding to the MoQT Group ID as defined in
      [MoQT].

   *  subgroupID: integer corresponding to the MoQT Subgroup as defined
      in [MoQT].

   *  forwardingPref: String with value of "Subgroup" or "Datagram" to
      represent the Object Forwarding Preference as defined in [MoQT].
      Open Issue: string or use the binary values used in spec?

   *  objectStatus: Numeric value representing Object Status enum as
      defined in [MoQT].

   *  publisherPriority: integer corresponding to the MoQT Publisher
      Priority as defined in [MoQT].

   *  maxCacheDuration: integer corresponding to the MoQT publisher MAX
      CACHE DURATION Parameter as defined in [MoQT].

   *  publisherDeliveryTimeout: integer corresponding to the MoQT
      DELIVERY TIMEOUT Parameter sent by the publisher as defined in
      [MoQT].

   *  receiveTime: time original object was created (if known) or time
      object was received by the relay.  This is saved as an integer in
      milliseconds since the unix epoch which is 00:00:00 UTC on January
      first, 1970.

   *  dataFile: string with relative path name to the file that stores
      the MoQT Object, including header and its payload data.

   *  dataOffset: number of bytes into file where the objects starts ( 0
      is first byte of file )

   *  dataLength: number of bytes of data in the object

   Any Object Extension Headers, as defined in [MoQT], should also be
   saved using a field name formed by the string "ext" then the base 10
   integer representation of the extension type with a value that is the
   Base64 encoded version of the extension header data.

   Open Issue: this will not preserve the order of the extension
   headers.  Is that a problem?

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3.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This specification uses the terminology defined in [MoQT].

3.1.  Base64 Encoding

   The Base64 encoding used in this specification is the "Base64
   Encoding with URL and Filename Safe Alphabet" as defined in
   [RFC4648], Section 5.  Additionally, the encoding is performed
   without any padding or extra blank space characters

3.2.  File Name Encoding

   The filename SHOULD be formed by percent encoding each tuple of the
   namespace and track.  Each tuple of the namespace is separated with a
   period and the last tuple is separated from the track name with a
   dash.  The percent encoding users a percent symbol followed by two
   lower case hex digits for any characters outside the range of 0 to 9,
   a to z, or A to Z.

   For example, a names of of ( Foo, b+r ) with track name of ex1 would
   be encoded as: Foo.b%2br-ex1

   If the filename only has data for a subset of the track, a plus sign
   followed by number of first group ID represented by the file SHOULD
   be appended.

4.  MoQT Track DataFile

   When saving a whole MoQT Track to a file, a common way to do this
   would be to make one ".dat" file with all the object data and another
   ".moq" file with all the array of JSON object for each MoQT Object.
   An implementation can choose to have one file per MoQT group.  In
   such a case, it does so by creating one metadata (".moq") file and
   one datafile (".dat") containing data for each object in the MoQT
   group.

5.  Playback

   Some use cases will want to just load a file into the relay as
   quickly as possible.  Others may decide to rename the track name to a
   new track name and publish the objects at a rate based on differences
   of the receiveTime of the JSON objects.

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6.  Example

   TODO More complete example

6.1.  Time Object Example

   Data file named time1.dat contains:

   {"time":17294570764566}

   Metadata file contains:

   [
     {
       "namesSpace": [ "bW9xLXRpbWUuYXJwYQo=" , "dGltZS12MQo=" ],
       "trackName": "bWFjOjcyOjVjOmYwOjdjOmJmOmIw",
       "objectID": 0,
       "groupID": 123,
       "subGroup": 0,
       "publisherPriority": 0,
       "maxCacheDuration": 3600000,
       "publisherDeliveryTimeout": 60000,
       "receiveTime": 1729457464000,
       "dataFile": "time1.dat",
       "dataOffset": 0,
       "dataLength": 25
     }
   ]

7.  IANA

   This document has no IANA actions.

8.  Security Considerations

   An application that subscribes to a set of tracks and records objects
   to files SHOULD NOT store any authorization tokens that it receives.

   An application that reads MOQ files must ensure it properly controls
   which data files are accessed.  A corrupt or malicious input MOQ file
   could cause the application to attempt to read unauthorized data
   files, such as an SSH private key, and potentially transmit the data
   over MoQT.

9.  Acknowledgements

   Thank you to Suhas Nandakumar, Tomas Rigaux, Carsten Bormann and
   Gwendal Simon for their reviews and suggestions.

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10.  Normative References

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

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <https://www.rfc-editor.org/rfc/rfc4648>.

Author's Address

   Cullen Jennings
   Cisco
   Canada
   Email: fluffy@iii.ca

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