Network Working Group M.O. van Deventer
Internet-Draft R. van Brandenburg
Intended status: Informational TNO
Expires: January 2, 2012 July 1, 2011
Content Terminology in CDN Interconnection
draft-deventer-cdni-content-terminology-01
Abstract
This internet-draft describes how the term content might take on
various meanings in different Content Delivery Network (CDN)
interconnection scenarios. In order to solve this ambiguity, some
additional terminology to describe content in CDNs is introduced, in
alignment with terminology developed by the ETSI MCD CDN-I Working
Group.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Newspaper metaphor . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Introduction to newspaper metaphor . . . . . . . . . . . . 4
2.2. Different stages of content . . . . . . . . . . . . . . . . 5
3. Content Terminology . . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. Informative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
The goal of this document is to present some terminology to be used
when talking about content in the different stages of CDN
interconnection. The additional terminology is aligned with CDN
interconnect terminology developed by the ETSI MCD Working Group on
CDN Interconnection (MCD WG CDN-I). Documents developed by ETSI MCD
in the CDN area are publicly available from the ETSI MCD Open Area
http://docbox.etsi.org/MCD/Open/.
This document introduces a metaphor for the electronic content
delivery ecosystem to provide a better understanding of the different
phases of content in this ecosystem. The metaphor of a newspaper
distribution ecosystem was chosen, as that ecosystem is well
understood and it has many aspects in common with content delivery.
Of course, any metaphor should be used with care, as there will
always be (subtle) differences.
1.1. Terminology
This document uses the terminology defined in section 1.1 of [I-
D.jenkins-cdni-problem-statement] and [I-D.bertrand-cdni-use-cases]
and terminology used in [ETSI TS 102 990 v0.0.7].
2. Newspaper metaphor
Using the metaphor of the newspaper distribution ecosystem, this
section will describe why the term Content might have a different
meaning depending on which phase in the Content Delivery chain one is
talking about.
2.1. Introduction to newspaper metaphor
A Newspaper company can be compared to a Content Provider (or Content
Aggregator); its business is to generate and/or collect news items
and other articles, and bring those together into newspapers. The
audience for the newspapers are Newspaper Readers (End Users). Just
as Content Providers, different Newspaper Companies may have
different business models, including subscription-based, advertising-
based or other.
Getting newspapers to Newspaper Readers is essential to the Newspaper
Company, just as it essential for a Content Provider to bring content
to an End User. Some Newspapers Companies may have their own printing
press, trucks to move the printed newspapers, outlets for Readers to
pick up the newspapers and personnel to get newspapers delivered to
mailboxes of Newspaper Readers. However, Newspaper Companies may also
decide to outsource some or all of those newspaper-distribution
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activities to specialized companies.
o Printing Companies have one or more printing presses to print
newspapers.
o Postal Companies have one or more trucks and personnel to move and
deliver printed newspapers.
o Newsstand Companies have one or more newsstands where people can
pick up newspapers.
These different companies in the Newspaper delivery chain can be
compared to the different roles in the Content Delivery Network
chain. There is a role for companies to replicate, or transcode,
content. There is a role for companies to perform the large scale
distribution of content and there is a role for companies to perform
the actual delivery of content to End Users. Just as is common in the
newspaper world, companies in the Content Delivery world may take on
multiple roles.
2.2. Different stages of content
While the contents of the newspaper do not change during the
newspaper distribution path from Newspaper Company all the way to
Newspaper Reader, the form the newspaper takes during the
distribution path does change. The Newspaper Company does not
directly create the final newspaper that Readers find on their
doorstep. What the Newspaper Company creates and delivers to the
Printing Company is a printing plate, a mastercopy, of the newspaper.
The Printing Company then uses this printing plate to create a number
of replicas (mastercopy replicas) to use in all of its printing
facilities. Based on these replicas, the actual newspapers (the
consumables) are printed. These printed newspapers are then
distributed by a network of trucks to one or more distribution
centers. How the newspapers end up in the hands of to the Newspaper
Reader depends on the preferences (and location) of that Reader. Some
Readers might pick it up at a Newsstand Company, while others will
have it delivered by a Postal Company.
A path similar to the one taken by the newspaper is also taken by a
piece of Content in the Content Delivery Network chain. The Content
Provider does not necessarily create the final piece of content, or
the form it takes, that is received by the End User. Along the way
the Content might be transcoded to use a different codec, repackaged
in a different video container, and delivered using different
transport mechanisms and protocols.
In some situations, it might be useful to be able to distinguish
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between the different fases and forms content goes through in the
content delivery chain. For example, in the case of CDN
Interconnection: When talking about how an Upstream CDN ingests
content into a Downstream CDN, it is important to know what the term
'content' in this case means. Is it the content in the form as it was
first ingested into the Upstream CDN by the Content Provider? Or is
it the content in its multiple transcoded forms as stored on the
Upstream CDN?
The current terminology does not allow for distinguishing between
these different fases and forms of content in the content delivery
chain.
3. Content Terminology
As shown in the previous section, the term content might take on a
different meaning depending on which phase in the delivery chain one
is talking about. It would therefore be useful to create some
additional terminology to describe these different content phases.
What follows is a first attempt at describing the different forms of
content as found in a CDN.
Mastercopy: The content as it is delivered by the Content Provider to
the (Upstream) CDN during the Content Ingestion process.
Replica: The content as it is transferred between the Upstream CDN
and the Downstream CDN.
Consumable: The content as it is stored on a CDN delivery node
directly prior to being delivered to an End User.
Note that, depending on the agreed arrangements with the Content
Provider, a Consumable might be a repackaged or transcoded version
from the origal Mastercopy or Replica in order to make it suitable
for a specific type of end device. Furthermore, a Consumable might be
a single file or consist of multiple files/segments that are the
result of a segmentation operation having been performed on the
content, e.g. to allow for specific transport mechanisms such as HTTP
Adapative Streaming (HAS) to be used.
It should be noted that this terminology is purely meant for
indicating the role of a particular piece of content in a particular
situation; it does not mean that a Consumable and a Mastercopy cannot
be bit-for-bit equivalent.
4. IANA Considerations
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This memo includes no request to IANA.
5. Security Considerations
This memo includes no security considerations.
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6. Informative References
[I-D.bertrand-cdni-use-cases]
Bertrand, G., Stephan, E., Watson, G., Burbridge, T., and
P. Eardley, "Use Cases for Content Distribution Network
Interconnection", draft-bertrand-cdni-use-cases-01 (work
in progress), January 2011.
[I-D.jenkins-cdni-problem-statement]
Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", draft-jenkins-cdni-problem-statement-02 (work
in progress), March 2011.
[ETSI TS 102 990 v0.0.7]
ETSI MCD CDN-I Working Group, "Media Content Distribution
(MCD); Media CDN Interconnection, use cases and
requirements", http://docbox.etsi.org/MCD/Open/
Latest_Drafts/ts_102990v000007p.pdf
Authors' Addresses
M. Oskar van Deventer
TNO
Brassersplein 2
Delft,
the Netherlands
Phone: +31 6 51 914 918
Email: oskar.vandeventer@tno.nl
Ray van Brandenburg
TNO
Brassersplein 2
Delft,
the Netherlands
Phone: +31 88 86 63609
Email: ray.vanbrandenburg@tno.nl
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