draft-ietf-cdni-problem-statement-00.txt   draft-ietf-cdni-problem-statement-01.txt 
Network Working Group B. Niven-Jenkins Network Working Group B. Niven-Jenkins
Internet-Draft Velocix (Alcatel-Lucent) Internet-Draft Velocix (Alcatel-Lucent)
Intended status: Informational F. Le Faucheur Intended status: Informational F. Le Faucheur
Expires: March 12, 2012 Cisco Expires: May 3, 2012 Cisco
N. Bitar N. Bitar
Verizon Verizon
September 9, 2011 October 31, 2011
Content Distribution Network Interconnection (CDNI) Problem Statement Content Distribution Network Interconnection (CDNI) Problem Statement
draft-ietf-cdni-problem-statement-00 draft-ietf-cdni-problem-statement-01
Abstract Abstract
Content Delivery Networks (CDNs) provide numerous benefits: reduced Content Delivery Networks (CDNs) provide numerous benefits: reduced
delivery cost for cacheable content, improved quality of experience delivery cost for cacheable content, improved quality of experience
for End Users and increased robustness of delivery. For these for End Users and increased robustness of delivery. For these
reasons they are frequently used for large-scale content delivery. reasons they are frequently used for large-scale content delivery.
As a result, existing CDN providers are scaling up their As a result, existing CDN providers are scaling up their
infrastructure and many Network Service Providers (NSPs) are infrastructure and many Network Service Providers (NSPs) are
deploying their own CDNs. It is generally desirable that a given deploying their own CDNs. It is generally desirable that a given
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User's location or attachment network. This creates a requirement User's location or attachment network. This creates a requirement
for interconnecting standalone CDNs so they can interoperate as an for interconnecting standalone CDNs so they can interoperate as an
open content delivery infrastructure for the end-to-end delivery of open content delivery infrastructure for the end-to-end delivery of
content from Content Service Providers (CSPs) to End Users. However, content from Content Service Providers (CSPs) to End Users. However,
no standards or open specifications currently exist to facilitate no standards or open specifications currently exist to facilitate
such CDN interconnection. such CDN interconnection.
The goal of this document is to outline the problem area of CDN The goal of this document is to outline the problem area of CDN
interconnection (CDNI) for the IETF. interconnection (CDNI) for the IETF.
Requirements Language
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 RFC 2119 [RFC2119].
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 12, 2012. This Internet-Draft will expire on May 3, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. CDN Background . . . . . . . . . . . . . . . . . . . . . . 9 1.2. CDN Background . . . . . . . . . . . . . . . . . . . . . . 8
2. CDN Interconnect Use Cases . . . . . . . . . . . . . . . . . . 9 2. CDN Interconnect Use Cases . . . . . . . . . . . . . . . . . . 8
3. CDN Interconnect Model & Problem Area for IETF . . . . . . . . 11 3. CDN Interconnect Model & Problem Area for IETF . . . . . . . . 10
3.1. Candidate CDNI Problem Area for IETF . . . . . . . . . . . 13 4. Design Approach for Realizing the CDNI APIs . . . . . . . . . 14
4. Design Approach for Realizing the CDNI APIs . . . . . . . . . 15 4.1. CDNI Request Routing Interface . . . . . . . . . . . . . . 15
4.1. Relationship to the OSI network model . . . . . . . . . . 15 4.2. CDNI Metadata Interface . . . . . . . . . . . . . . . . . 17
4.2. "Reuse Instead of Reinvent" Principle . . . . . . . . . . 16 4.3. CDNI Logging Interface . . . . . . . . . . . . . . . . . . 18
4.3. CDNI Request Routing Interface . . . . . . . . . . . . . . 16 4.4. CDNI Control Interface . . . . . . . . . . . . . . . . . . 19
4.4. CDNI Metadata Interface . . . . . . . . . . . . . . . . . 18 5. Gap Analysis of relevant Standardization Activities . . . . . 19
4.5. CDNI Logging Interface . . . . . . . . . . . . . . . . . . 19
4.6. CDNI Control Interface . . . . . . . . . . . . . . . . . . 20
5. Gap Analysis of relevant Standardization and Research
Activities . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.1. Content Acquisition across CDNs and Delivery to End 5.1. Content Acquisition across CDNs and Delivery to End
User (Data plane) . . . . . . . . . . . . . . . . . . . . 21 User (Data plane) . . . . . . . . . . . . . . . . . . . . 20
5.2. CDNI Metadata . . . . . . . . . . . . . . . . . . . . . . 22 5.2. CDNI Metadata . . . . . . . . . . . . . . . . . . . . . . 21
6. Relationship to relevant IETF Working Groups . . . . . . . . . 23 6. Relationship to relevant IETF Working Groups . . . . . . . . . 22
6.1. ALTO . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.1. ALTO . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.2. DECADE . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.2. DECADE . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.3. PPSP . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.3. PPSP . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25 8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
10.1. Normative References . . . . . . . . . . . . . . . . . . . 26 10.1. Normative References . . . . . . . . . . . . . . . . . . . 25
10.2. Informative References . . . . . . . . . . . . . . . . . . 27 10.2. Informative References . . . . . . . . . . . . . . . . . . 25
Appendix A. Additional Material . . . . . . . . . . . . . . . . . 29 Appendix A. Additional Material . . . . . . . . . . . . . . . . . 28
A.1. Non-Goals for IETF . . . . . . . . . . . . . . . . . . . . 29 A.1. Non-Goals for IETF . . . . . . . . . . . . . . . . . . . . 28
A.2. Prioritizing the CDNI Work . . . . . . . . . . . . . . . . 30 A.2. Related standardization activities . . . . . . . . . . . . 29
A.3. Related standardization activities . . . . . . . . . . . . 31 A.2.1. IETF CDI Working Group (Concluded) . . . . . . . . . . 29
A.3.1. IETF CDI Working Group (Concluded) . . . . . . . . . . 31 A.2.2. 3GPP . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.3.2. 3GPP . . . . . . . . . . . . . . . . . . . . . . . . . 32 A.2.3. ISO MPEG . . . . . . . . . . . . . . . . . . . . . . . 30
A.3.3. ISO MPEG . . . . . . . . . . . . . . . . . . . . . . . 32 A.2.4. ATIS IIF . . . . . . . . . . . . . . . . . . . . . . . 31
A.3.4. ATIS IIF . . . . . . . . . . . . . . . . . . . . . . . 33 A.2.5. CableLabs . . . . . . . . . . . . . . . . . . . . . . 31
A.3.5. CableLabs . . . . . . . . . . . . . . . . . . . . . . 33 A.2.6. ETSI MCD . . . . . . . . . . . . . . . . . . . . . . . 32
A.3.6. ETSI MCD . . . . . . . . . . . . . . . . . . . . . . . 33 A.2.7. ETSI TISPAN . . . . . . . . . . . . . . . . . . . . . 32
A.3.7. ETSI TISPAN . . . . . . . . . . . . . . . . . . . . . 34 A.2.8. ITU-T . . . . . . . . . . . . . . . . . . . . . . . . 32
A.3.8. ITU-T . . . . . . . . . . . . . . . . . . . . . . . . 34 A.2.9. Open IPTV Forum (OIPF) . . . . . . . . . . . . . . . . 33
A.3.9. Open IPTV Forum (OIPF) . . . . . . . . . . . . . . . . 34 A.2.10. TV-Anytime Forum . . . . . . . . . . . . . . . . . . . 33
A.3.10. TV-Anytime Forum . . . . . . . . . . . . . . . . . . . 35 A.2.11. SNIA . . . . . . . . . . . . . . . . . . . . . . . . . 33
A.3.11. SNIA . . . . . . . . . . . . . . . . . . . . . . . . . 35 A.3. Related Research Projects . . . . . . . . . . . . . . . . 33
A.4. Related Research Projects . . . . . . . . . . . . . . . . 35 A.3.1. IRTF P2P Research Group . . . . . . . . . . . . . . . 34
A.4.1. IRTF P2P Research Group . . . . . . . . . . . . . . . 35 A.3.2. OCEAN . . . . . . . . . . . . . . . . . . . . . . . . 34
A.4.2. OCEAN . . . . . . . . . . . . . . . . . . . . . . . . 35 A.3.3. Eurescom P1955 . . . . . . . . . . . . . . . . . . . . 34
A.4.3. Eurescom P1955 . . . . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction 1. Introduction
The volume of video and multimedia content delivered over the The volume of video and multimedia content delivered over the
Internet is rapidly increasing and expected to continue doing so in Internet is rapidly increasing and expected to continue doing so in
the future. In the face of this growth, Content Delivery Networks the future. In the face of this growth, Content Delivery Networks
(CDNs) provide numerous benefits: reduced delivery cost for cacheable (CDNs) provide numerous benefits: reduced delivery cost for cacheable
content, improved quality of experience for End Users and increased content, improved quality of experience for End Users and increased
robustness of delivery. For these reasons CDNs are frequently used robustness of delivery. For these reasons CDNs are frequently used
for large-scale content delivery. As a result, existing CDN for large-scale content delivery. As a result, existing CDN
providers are scaling up their infrastructure and many Network providers are scaling up their infrastructure and many Network
Service Providers (NSPs) are deploying their own CDNs. It is Service Providers (NSPs) are deploying their own CDNs.
generally desirable that a given content item can be delivered to an
End User regardless of that End User's location or attachment It is generally desirable that a given content item can be delivered
to an End User regardless of that End User's location or attachment
network. However, the footprint of a given CDN in charge of network. However, the footprint of a given CDN in charge of
delivering a given content may not expand close enough to the End delivering a given content may not expand close enough to the End
User's current location or attachment network to realize the cost User's current location or attachment network to realize the cost
benefit and user experience that a more distributed CDN would benefit and user experience that a more distributed CDN would
provide. This creates a requirement for interconnecting standalone provide. This creates a requirement for interconnecting standalone
CDNs so that their collective CDN footprint can be leveraged for the CDNs so that their collective CDN footprint can be leveraged for the
end-to-end delivery of content from Content Service Providers (CSPs) end-to-end delivery of content from Content Service Providers (CSPs)
to End Users. However, no standards or open specifications currently to End Users. For example, a CSP could contract with an
exist to facilitate such CDN interconnection. "authoritative" CDN for the delivery of content and that
authoritative CDN could contract with one or more downstream CDN(s)
to distribute and deliver some or all of the content on behalf of the
authoritative CDN. The formation and details of any business
relationships between a CSP and a CDN and between one CDN and another
CDN are out of scope of this document. However, no standards or open
specifications currently exist to facilitate such CDN
interconnection.
The goal of this document is to outline the problem area of CDN The goal of this document is to outline the problem area of CDN
interconnection (CDNI) for the IETF. interconnection (CDNI) for the IETF. Section 2 discusses the use
cases for CDN interconnection. Section 3 presents the CDNI model and
Section 2 discusses the use cases for CDN interconnection. Section 3 problem area being considered by the IETF. Section 4 describes each
presents the CDNI model and problem area to be considered by the CDNI interface individually and highlights example candidate
IETF. Section 4 discusses how existing protocols can be reused to protocols that could considered for reuse or leveraging to implement
define the CDNI interfaces while Appendix A.2 proposes to focus the the CDNI interfaces. Section 5 provides a gap analysis against the
scope for the initial charter of a CDNI Working Group to the minimum work of other standards organizations. Section 6 describes the
functional elements necessary for basic CDN interconnection. relationships between the CDNI problem space and other relevant IETF
Appendix A.2 provides a gap analysis of the work of other standards Working Groups.
organizations and finally Appendix A.2 discusses the relationship
with relevant IETF Working Groups.
1.1. Terminology 1.1. Terminology
This document uses the following terms: This document uses the following terms:
Content: Any form of digital data. One important form of Content Content: Any form of digital data. One important form of Content
with additional constraints on Distribution and Delivery is with additional constraints on Distribution and Delivery is
continuous media (i.e. where there is a timing relationship between continuous media (i.e. where there is a timing relationship between
source and sink). source and sink).
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Pre-positioned content acquisition: Content Pre-positioning is where Pre-positioned content acquisition: Content Pre-positioning is where
a CDN acquires content from the content source prior to or a CDN acquires content from the content source prior to or
independent of any End User requesting that content from the CDN. In independent of any End User requesting that content from the CDN. In
the context of CDN interconnection the Upstream CDN instructs the the context of CDN interconnection the Upstream CDN instructs the
Downstream CDN to acquire the content from content sources (including Downstream CDN to acquire the content from content sources (including
upstream CDNs) in advance of or independent of any End User upstream CDNs) in advance of or independent of any End User
requesting it. requesting it.
Pre-positioned CDNI Metadata acquisition: In the context of CDN Pre-positioned CDNI Metadata acquisition: In the context of CDN
Interconnection, Metadata pre-positioning is where the Downstream CDN Interconnection, CDNI Metadata pre-positioning is where the
acquires CDNI metadata for content prior to or independent of any End Downstream CDN acquires CDNI metadata for content prior to or
User requesting that content from the Downstream CDN. independent of any End User requesting that content from the
Downstream CDN.
End User (EU): The 'real' user of the system, typically a human but End User (EU): The 'real' user of the system, typically a human but
maybe some combination of hardware and/or software emulating a human maybe some combination of hardware and/or software emulating a human
(e.g. for automated quality monitoring etc.) (e.g. for automated quality monitoring etc.)
User Agent (UA): Software (or a combination of hardware and software) User Agent (UA): Software (or a combination of hardware and software)
through which the End User interacts with the Content Service. The through which the End User interacts with a Content Service. The
User Agent will communicate with the CSP's service for the selection User Agent will communicate with a Content Service for the selection
of content and one or more CDNs for the delivery of the Content. of content and one or more CDNs for the delivery of the Content.
Such communication is not restricted to HTTP and may be via a variety Such communication is not restricted to HTTP and may be via a variety
of protocols. Examples of User Agents (non-exhaustive) are: of protocols. Examples of User Agents (non-exhaustive) are:
Browsers, Set Top Boxes (STB), dedicated content applications (e.g. Browsers, Set Top Boxes (STBs), dedicated content applications (e.g.
media players), etc. media players), etc.
Network Service Provider (NSP): Provides network-based connectivity/ Network Service Provider (NSP): Provides network-based connectivity/
services to End Users. services to End Users.
Content Service Provider (CSP): Provides a Content Service to End Content Service Provider (CSP): Provides a Content Service to End
Users (which they access via a User Agent). A CSP may own the Users (which they access via a User Agent). A CSP may own the
Content made available as part of the Content Service, or may license Content made available as part of the Content Service, or may license
content rights from another party. content rights from another party.
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Network Service Provider and a CDN Provider. Network Service Provider and a CDN Provider.
CDN Interconnection (CDNI): The set of interfaces over which two or CDN Interconnection (CDNI): The set of interfaces over which two or
more CDNs communicate with each other in order to achieve the more CDNs communicate with each other in order to achieve the
delivery of content to User Agents by Surrogates in one CDN (the delivery of content to User Agents by Surrogates in one CDN (the
downstream CDN) on behalf of another CDN (the upstream CDN). downstream CDN) on behalf of another CDN (the upstream CDN).
Authoritative CDN: A CDN which has a direct relationship with a CSP Authoritative CDN: A CDN which has a direct relationship with a CSP
for the distribution & delivery of that CSP's content. for the distribution & delivery of that CSP's content.
Upstream CDN: For a given user request, the CDN (within a pair of Upstream CDN: For a given End User request, the CDN (within a pair of
directly interconnected CDNs) that redirects the request to the other directly interconnected CDNs) that redirects the request to the other
CDN. CDN.
Downstream CDN: For a given user request, the CDN (within a pair of Downstream CDN: For a given End User request, the CDN (within a pair
directly interconnected CDNs) to which the request is redirected by of directly interconnected CDNs) to which the request is redirected
the other CDN (the Upstream CDN). Note that in the case of by the other CDN (the Upstream CDN). Note that in the case of
successive redirections (e.g. CDN1-->CDN2-->CDN3) a given CDN (e.g. successive redirections (e.g. CDN1-->CDN2-->CDN3) a given CDN (e.g.
CDN2) may act as the Downstream CDN for a redirection (e.g. CDN2) may act as the Downstream CDN for a redirection (e.g.
CDN1-->CDN2) and as the Upstream CDN for the subsequent redirection CDN1-->CDN2) and as the Upstream CDN for the subsequent redirection
of the same request (e.g. CDN2-->CDN3). of the same request (e.g. CDN2-->CDN3).
Over-the-top (OTT): A service, e.g. a CDN, operated by a different Over-the-top (OTT): A service, e.g. a CDN, operated by a different
operator than the NSP to which the users of that service are operator than the NSP to which the users of that service are
attached. attached.
Surrogate: A device/function that interacts with other elements of Surrogate: A device/function that interacts with other elements of
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and interacts with User Agents for the delivery of the Content. and interacts with User Agents for the delivery of the Content.
Request Routing System: The function within a CDN responsible for Request Routing System: The function within a CDN responsible for
receiving a content request from a User Agent, obtaining and receiving a content request from a User Agent, obtaining and
maintaining necessary information about a set of candidate surrogates maintaining necessary information about a set of candidate surrogates
or candidate CDNs, and for selecting and redirecting the user to the or candidate CDNs, and for selecting and redirecting the user to the
appropriate surrogate or CDN. To enable CDN Interconnection, the appropriate surrogate or CDN. To enable CDN Interconnection, the
Request Routing System must also be capable of handling User Agent Request Routing System must also be capable of handling User Agent
content requests passed to it by another CDN. content requests passed to it by another CDN.
Distribution System: the function within a CDN responsible for Distribution System: The function within a CDN responsible for
distributing Content Distribution Metadata as well as content inside distributing Content Distribution Metadata as well as the Content
the CDN (e.g. down to the surrogates) itself inside the CDN (e.g. down to the surrogates).
Delivery: the function within CDN surrogates responsible for Delivery: The function within CDN surrogates responsible for
delivering a piece of content to the User Agent. For example, delivering a piece of content to the User Agent. For example,
delivery may be based on HTTP progressive download or HTTP adaptive delivery may be based on HTTP progressive download or HTTP adaptive
streaming. streaming.
Logging System: the function within a CDN responsible for collecting Logging System: The function within a CDN responsible for collecting
measurement and recording of distribution and delivery activities. the measurement and recording of distribution and delivery
The information recorded by the logging system may be used for activities. The information recorded by the logging system may be
various purposes including charging (e.g. of the CSP), analytics and used for various purposes including charging (e.g. of the CSP),
monitoring. analytics and monitoring.
1.2. CDN Background 1.2. CDN Background
Readers are assumed to be familiar with the architecture, features Readers are assumed to be familiar with the architecture, features
and operation of CDNs. For readers less familiar with the operation and operation of CDNs. For readers less familiar with the operation
of CDNs, the following resources may be useful: of CDNs, the following resources may be useful:
o RFC 3040 [RFC3040] describes many of the component technologies o RFC 3040 [RFC3040] describes many of the component technologies
that are used in the construction of a CDN that are used in the construction of a CDN.
o Taxonomy [TAXONOMY] compares the architecture of a number of CDNs o Taxonomy [TAXONOMY] compares the architecture of a number of CDNs.
o RFC 3466 [RFC3466] and RFC 3570 [RFC3570] are the output of the o RFC 3466 [RFC3466] and RFC 3570 [RFC3570] are the output of the
IETF Content Delivery Internetworking (CDI) working group which IETF Content Delivery Internetworking (CDI) working group which
was closed in 2003. was closed in 2003.
Note: Some of the terms used in this document are similar to terms Note: Some of the terms used in this document are similar to terms
used the above referenced documents. When reading this document used the above referenced documents. When reading this document
terms should be interpreted as having the definitions provided in terms should be interpreted as having the definitions provided in
Section 1.1. Section 1.1.
2. CDN Interconnect Use Cases 2. CDN Interconnect Use Cases
An increasing number of NSPs are deploying CDNs in order to deal An increasing number of NSPs are deploying CDNs in order to deal
cost-effectively with the growing usage of on-demand video services cost-effectively with the growing usage of on-demand video services
and other content delivery applications. and other content delivery applications.
CDNs allow caching of content closer to the edge so that a given item CDNs allow caching of content closer to the edge of a network so that
of content can be delivered by a CDN Surrogate (i.e. a cache) to a given item of content can be delivered by a CDN Surrogate (i.e. a
multiple User Agents (and their End Users) without transiting cache) to multiple User Agents (and their End Users) without
multiple times through the network core (i.e from the content origin transiting multiple times through the network core (i.e from the
to the surrogate). This contributes to bandwidth cost reductions for content origin to the surrogate). This contributes to bandwidth cost
the NSP and to improved quality of experience for the End Users. reductions for the NSP and to improved quality of experience for the
CDNs also enable replication of popular content across many End Users. CDNs also enable replication of popular content across
surrogates, which enables content to be served to large numbers of many surrogates, which enables content to be served to large numbers
User Agents concurrently. This also helps dealing with situations of User Agents concurrently. This also helps dealing with situations
such as flash crowds and denial of service attacks. such as flash crowds and denial of service attacks.
The CDNs deployed by NSPs are not just restricted to the delivery of The CDNs deployed by NSPs are not just restricted to the delivery of
content to support the Network Service Provider's own 'walled garden' content to support the Network Service Provider's own 'walled garden'
services, such as IP delivery of television services to Set Top services, such as IP delivery of television services to Set Top
Boxes, but are also used for delivery of content to other devices Boxes, but are also used for delivery of content to other devices
including PCs, tablets, mobile phones etc. including PCs, tablets, mobile phones etc.
Some service providers operate over multiple geographies and federate Some service providers operate over multiple geographies and federate
multiple affiliate NSPs. These NSPs typically operate independent multiple affiliate NSPs. These NSPs typically operate independent
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direct business relationships with many different CDN providers (or direct business relationships with many different CDN providers (or
having to extend their own CDN to a large number of locations). Some having to extend their own CDN to a large number of locations). Some
NSPs are considering interconnecting their respective CDNs (as well NSPs are considering interconnecting their respective CDNs (as well
as possibly over-the-top CDNs) so that this collective infrastructure as possibly over-the-top CDNs) so that this collective infrastructure
can address the requirements of CSPs in a cost effective manner. In can address the requirements of CSPs in a cost effective manner. In
particular, this would enable the CSPs to benefit from on-net particular, this would enable the CSPs to benefit from on-net
delivery (i.e. within the Network Service Provider's own network/CDN delivery (i.e. within the Network Service Provider's own network/CDN
footprint) whenever possible and off-net delivery otherwise, without footprint) whenever possible and off-net delivery otherwise, without
requiring the CSPs to maintain direct business relationships with all requiring the CSPs to maintain direct business relationships with all
the CDNs involved in the delivery. Again, for this requirement, CDN the CDNs involved in the delivery. Again, for this requirement, CDN
operators (NSPs or over-the-top CDN operators) are faced with a lack providers (NSPs or over-the-top CDN operators) are faced with a lack
of open specifications and best practices. of open specifications and best practices.
NSPs have often deployed CDNs as specialized cost-reduction projects NSPs have often deployed CDNs as specialized cost-reduction projects
within the context of a particular service or environment, some NSPs within the context of a particular service or environment, some NSPs
operate separate CDNs for separate services. For example, there may operate separate CDNs for separate services. For example, there may
be a CDN for managed IPTV service delivery, a CDN for web-TV delivery be a CDN for managed IPTV service delivery, a CDN for web-TV delivery
and a CDN for video delivery to Mobile terminals. As NSPs integrate and a CDN for video delivery to Mobile terminals. As NSPs integrate
their service portfolio, there is a need for interconnecting these their service portfolio, there is a need for interconnecting these
CDNs. Again, NSPs face the problem of lack of open interfaces for CDNs. Again, NSPs face the problem of lack of open interfaces for
CDN interconnection. CDN interconnection.
For operational reasons (e.g. disaster, flash crowd) or commercial For operational reasons (e.g. disaster, flash crowd) or commercial
reasons, an over-the-top CDN may elect to make use of another CDN reasons, an over-the-top CDN may elect to make use of another CDN
(e.g. an NSP CDN with on-net Surrogates for a given footprint) for (e.g. an NSP CDN with on-net Surrogates for a given footprint) for
serving a subset of the user requests (e.g. requests from users serving a subset of the user requests (e.g. requests from users
attached to that NSP). Again, for this requirement, CDN operators attached to that NSP). Again, for this requirement, CDN providers
(over-the-top CDN operators or NSPs) are faced with a lack of open (over-the-top CDN providers or NSPs) are faced with a lack of open
specifications and best practices. specifications and best practices.
Use cases for CDN Interconnection are further discussed in Use cases for CDN Interconnection are further discussed in
[I-D.bertrand-cdni-use-cases] (which contains a merged set of use [I-D.ietf-cdni-use-cases].
cases previously presented in [I-D.watson-cdni-use-cases] and
[I-D.bertrand-cdni-use-cases-00]).
3. CDN Interconnect Model & Problem Area for IETF 3. CDN Interconnect Model & Problem Area for IETF
Interconnecting CDNs involves interactions among multiple different Interconnecting CDNs involves interactions among multiple different
functions and components that form each CDN. Only some of those functions and components that form each CDN. Only some of those
require standardization. The CDNI model and problem area proposed require standardization. This section discusses the problem area for
for IETF work is illustrated in Figure 1. The candidate problem area the IETF work on CDN Interconnection. The CDNI model and problem
(and respectively the non-goals) for IETF work on CDN Interconnection area defined for IETF work is illustrated in Figure 1.
are discussed in Section 3.1 (and respectively Appendix A.1 ).
-------- --------
/ \ / \
| CSP | | CSP |
\ / \ /
-------- --------
* *
* *
* /\ * /\
* / \ * / \
skipping to change at page 12, line 47 skipping to change at page 11, line 47
. ---------------------- ---------*------------ . . ---------------------- ---------*------------ .
. * . . * .
. * Delivery . . * Delivery .
. * . . * .
. +--*---+ . . +--*---+ .
...............Request.............................| User |..Request.. ...............Request.............................| User |..Request..
| Agent| | Agent|
+------+ +------+
<==> interfaces inside the scope of CDNI <==> interfaces inside the scope of CDNI
**** interfaces outside the scope of CDNI **** interfaces outside the scope of CDNI
.... interfaces outside the scope of CDNI .... interfaces outside the scope of CDNI
Figure 1: CDNI Problem Area Figure 1: CDNI Problem Area
3.1. Candidate CDNI Problem Area for IETF
Listed below are the four interfaces required to interconnect a pair Listed below are the four interfaces required to interconnect a pair
of CDNs and that constitute the problem space that is proposed to be of CDNs and that constitute the problem space that is proposed to be
addressed by a potential CDNI working group in the IETF. The use of addressed by a potential CDNI working group in the IETF. The use of
the term "interface" is meant to encompass the protocol over which the term "interface" is meant to encompass the protocol over which
CDNI data representations (e.g. CDNI Metadata records) are exchanged CDNI data representations (e.g. CDNI Metadata records) are exchanged
as well as the specification of the data representations themselves as well as the specification of the data representations themselves
(i.e. what properties/fields each record contains, its structure, (i.e. what properties/fields each record contains, its structure,
etc.). etc.).
o CDNI Control interface: This interface allows the "CDNI Control" o CDNI Control interface: This interface allows the "CDNI Control"
skipping to change at page 13, line 35 skipping to change at page 12, line 31
* Allow the downstream CDN to communicate static (or fairly * Allow the downstream CDN to communicate static (or fairly
static) information about its delivery capabilities and static) information about its delivery capabilities and
policies. policies.
* Allow bootstrapping of the interface between CDNs for content * Allow bootstrapping of the interface between CDNs for content
acquisition (even if that interface itself is outside the scope acquisition (even if that interface itself is outside the scope
of the CDNI work). of the CDNI work).
* Allow upstream CDN to initiate or request specific actions to * Allow upstream CDN to initiate or request specific actions to
be undertaken in the downstream CDN. For example, this may be undertaken in the downstream CDN. For example, this may
include the following capabilities: include the following capabilities:
+ Allow an upstream CDN to request that content files and/or + Allow an upstream CDN to request that content files and/or
CDNI Metadata that it shared, be purged from, or invalidated CDNI Metadata that it previously shared, be purged from, or
in, a downstream CDN. Support for content deletion or invalidated in, a downstream CDN. Support for content
invalidation from a CDN is a key requirement for some deletion or invalidation from a CDN is a key requirement for
Content Service Providers in order, amongst other use cases some Content Service Providers in order, amongst other use
for content deletion, to support the content rights cases for content deletion, to support the content rights
agreements they have negotiated. Today's CDNs use agreements they have negotiated. Today's CDNs use
proprietary control interfaces to enable CSPs to remove proprietary control interfaces to enable CSPs to remove
content cached in the CDN and therefore there is a need to content cached in the CDN and therefore there is a need to
have a similar but standardized content deletion capability have a similar but standardized content deletion capability
between interconnected CDNs. between interconnected CDNs.
+ Allow an upstream CDN to initiate Pre-positioned content + Allow an upstream CDN to initiate Pre-positioned content
acquisition and/or Pre-positioned CDN Metadata acquisition acquisition and/or Pre-positioned CDNI Metadata acquisition
in a downstream CDN. in a downstream CDN.
o CDNI Request Routing interface: This interface allows the Request o CDNI Request Routing interface: This interface allows the Request
Routing system in interconnected CDNs to communicate to ensure Routing systems in interconnected CDNs to communicate to ensure
that an End User request can be (re)directed from an upstream CDN that an End User request can be (re)directed from an upstream CDN
to a surrogate in the downstream CDN, in particular where to a surrogate in the downstream CDN, in particular where
selection responsibilities may be split across CDNs (for example selection responsibilities may be split across CDNs (for example
the upstream CDN may be responsible for selecting the downstream the upstream CDN may be responsible for selecting the downstream
CDN while the downstream CDN may be responsible for selecting the CDN while the downstream CDN may be responsible for selecting the
actual surrogate within that CDN). In particular, the CDN Request actual surrogate within that downstream CDN). In particular, the
Routing interface, may support the following: CDN Request Routing interface, may support the following:
* allow the upstream CDN to query the downstream CDN at request- * Allow the upstream CDN to query the downstream CDN at request
routing time before redirecting the request to the downstream routing time before redirecting the request to the downstream
CDN CDN.
* allow the downstream CDN to provide to the upstream CDN (static * Allow the downstream CDN to provide to the upstream CDN (static
or dynamic) information (e.g. resources, footprint, load) to or dynamic) information (e.g. resources, footprint, load) to
facilitate selection of the downstream CDN by the upstream CDN facilitate selection of the downstream CDN by the upstream CDN
request routing system when processing subsequent content request routing system when processing subsequent content
requests from User Agents. requests from User Agents.
o CDNI Metadata distribution interface: This interface allows the o CDNI Metadata distribution interface: This interface allows the
Distribution system in interconnected CDNs to communicate to Distribution system in interconnected CDNs to communicate to
ensure CDNI Metadata can be exchanged across CDNs. See ensure CDNI Metadata can be exchanged across CDNs. See
Section 1.1 for definition and examples of CDNI Metadata. Section 1.1 for definition and examples of CDNI Metadata.
o CDNI Logging interface: This interface allows the Logging system o CDNI Logging interface: This interface allows the Logging system
in interconnected CDNs to communicate the relevant activity logs in interconnected CDNs to communicate the relevant activity logs
skipping to change at page 14, line 42 skipping to change at page 13, line 39
after further study (e.g. some subset of functionality be moved from after further study (e.g. some subset of functionality be moved from
one interface into another). one interface into another).
The above list covers a significant potential problem space, in part The above list covers a significant potential problem space, in part
because in order to interconnect two CDNs there are several 'touch because in order to interconnect two CDNs there are several 'touch
points' that require standardization. However, it is expected that points' that require standardization. However, it is expected that
the CDNI interfaces need not be defined from scratch and instead can the CDNI interfaces need not be defined from scratch and instead can
very significantly reuse or leverage existing protocols: this is very significantly reuse or leverage existing protocols: this is
discussed further in Section 4. Also, it is expected that the items discussed further in Section 4. Also, it is expected that the items
above will be prioritized so that the CDNI Working Group can focus above will be prioritized so that the CDNI Working Group can focus
(at least initially) on the most essential and urgent work: this is (at least initially) on the most essential and urgent work.
discussed further in Appendix A.2.
As part of the development of the CDNI interfaces and solutions it As part of the development of the CDNI interfaces and solutions it
will also be necessary to agree on common mechanisms for how to will also be necessary to agree on common mechanisms for how to
identify and name the data objects that are to be interchanged identify and name the data objects that are to be interchanged
between interconnected CDNs, as well as how to describe which policy between interconnected CDNs, as well as how to describe which policy
should be used when doing so. [I-D.jenkins-cdni-names] presents one should be used when doing so.
view on how CDN data types/objects could be classified such that the
problem space of their naming and referencing is not as large as it
might at first appear because there is significant commonality
between the different data types/objects required for CDNI.
Some NSPs have started to perform experiments to explore whether Some NSPs have started to perform experiments to explore whether
their CDN use cases can already be addressed with existing CDN their CDN use cases can already be addressed with existing CDN
implementations. One set of such experiments is documented in implementations. One set of such experiments is documented in
[I-D.bertrand-cdni-experiments]. The conclusions of those [I-D.bertrand-cdni-experiments]. The conclusions of those
experiments are that while some basic limited CDN Interconnection experiments are that while some basic limited CDN Interconnection
functionality can be achieved with existing CDN technology, the functionality can be achieved with existing CDN technology, the
current lack of any standardized CDNI interfaces/protocols such as current lack of any standardized CDNI interfaces/protocols such as
those discussed in this document is preventing the deployment of those discussed in this document is preventing the deployment of
production CDN Interconnection solutions with the necessary level of production CDN Interconnection solutions with the necessary level of
functionality. functionality.
The acquisition of content between interconnected CDNs is out of The acquisition of content between interconnected CDNs is out of
scope for CDNI and deserves some additional explanation. The scope for CDNI and deserves some additional explanation. The
consequence of such a decision is that the CDNI WG is focussed on consequence of such a decision is that the CDNI WG is focussed on
only defining the control plane for CDNI; and the CDNI data plane only defining the control plane for CDNI; and the CDNI data plane
(i.e. the acquisition & distribution of the actual content objects) (i.e. the acquisition & distribution of the actual content objects)
will not be addressed by a CDNI WG. The rationale for such a will not be addressed by the CDNI WG. The rationale for such a
decision is that CDNs today typically already use standardized decision is that CDNs today typically already use standardized
protocols such as HTTP, FTP, rsync, etc. to acquire content from protocols such as HTTP, FTP, rsync, etc. to acquire content from
their CSP customers and it is expected that the same protocols could their CSP customers and it is expected that the same protocols could
be used for acquisition between interconnected CDNs. Therefore the be used for acquisition between interconnected CDNs. Therefore the
problem of content acquisition is considered already solved and all problem of content acquisition is considered already solved and all
that is required from specifications developed by the CDNI WG is to that is required from specifications developed by the CDNI WG is to
describe within the CDNI Metadata where to go and which protocol to describe within the CDNI Metadata where to go and which protocol to
use to retrieve the content. use to retrieve the content.
4. Design Approach for Realizing the CDNI APIs 4. Design Approach for Realizing the CDNI APIs
This section expands on how CDNI interfaces can reuse and leverage This section expands on how CDNI interfaces can reuse and leverage
existing protocols. First the "reuse instead of reinvent" design existing protocols before describing each CDNI interface individually
principle is restated, then each inetrface is discussed individually and highlighting example candidate protocols that could considered
with example candidate protocols that can be considered for reuse or for reuse or leveraging to implement the CDNI interfaces. This
leverage. This discussion is not intended to pre-empt any WG discussion is not intended to pre-empt any WG decision as to the most
decision as to the most appropriate protocols, technologies and appropriate protocols, technologies and solutions to select to solve
solutions to select to solve CDNI but is intended as an illustration CDNI but is intended as an illustration of the fact that the CDNI
of the fact that the CDNI interfaces need not be created in a vacuum interfaces need not be created in a vacuum and that reuse or leverage
and that reuse or leverage of existing protocols is likely possible. of existing protocols is likely possible.
4.1. Relationship to the OSI network model
The four CDNI interfaces (CDNI Control interface, CDNI Request The four CDNI interfaces (CDNI Control interface, CDNI Request
Routing interface, CDNI Metadata interface, CDNI Logging interface) Routing interface, CDNI Metadata interface, CDNI Logging interface)
described in Section 3.1 within the CDNI problem area are all control described in Section 3 within the CDNI problem area are all control
plane interfaces operating at the application layer (Layer 7 in the plane interfaces operating at the application layer (Layer 7 in the
OSI network model). Since it is not expected that these interfaces OSI network model). Since it is not expected that these interfaces
would exhibit unique session, transport or network requirements as would exhibit unique session, transport or network requirements as
compared to the many other existing applications in the Internet, it compared to the many other existing applications in the Internet, it
is expected that the CDNI interfaces will be defined on top of is expected that the CDNI interfaces will be defined on top of
existing session, transport and network protocols. existing session, transport and network protocols.
4.2. "Reuse Instead of Reinvent" Principle
Although a new application protocol could be designed specifically Although a new application protocol could be designed specifically
for CDNI we assume that this is unnecessary and it is recommended for CDNI we assume that this is unnecessary and it is recommended
that existing application protocols be reused or leveraged (HTTP that existing application protocols be reused or leveraged (HTTP
[RFC2616], Atom Publishing Protocol [RFC5023], XMPP [RFC6120], for [RFC2616], Atom Publishing Protocol [RFC5023], XMPP [RFC6120], for
example) to realize the CDNI interfaces. example) to realize the CDNI interfaces.
4.3. CDNI Request Routing Interface 4.1. CDNI Request Routing Interface
The CDNI Request Routing interface enables a Request Routing function The CDNI Request Routing interface enables a Request Routing function
in an upstream CDN to query a Request Routing function in a in an upstream CDN to query a Request Routing function in a
downstream CDN to determine if the downstream CDN is able (and downstream CDN to determine if the downstream CDN is able (and
willing) to accept the delegated content request and to allow the willing) to accept the delegated content request and to allow the
downstream CDN to control what the upstream Request Routing function downstream CDN to control what the upstream Request Routing function
should return to the User Agent in the redirection message. should return to the User Agent in the redirection message.
The CDNI Request Routing interface needs to offer a mechanism for an The CDNI Request Routing interface needs to offer a mechanism for an
upstream CDN to issue a "Redirection Request" to a downstream CDN. upstream CDN to issue a "Redirection Request" to a downstream CDN.
The Request Routing interface needs to be able to support scenarios The Request Routing interface needs to be able to support scenarios
where the initial User Agent request to the upstream CDN is received where the initial User Agent request to the upstream CDN is received
over DNS as well as over a content specific application protocol over DNS as well as over a content specific application protocol
(e.g. HTTP, RTSP, RTMP, etc.). (e.g. HTTP, RTSP, RTMP, etc.).
Therefore a Redirection Request needs to contain information such as: Therefore a Redirection Request needs to contain information such as:
o The protocol (e.g. DNS, HTTP) over which the upstream CDN o The protocol (e.g. DNS, HTTP) over which the upstream CDN
received the initial User Agent request received the initial User Agent request.
o Additional details of the User Agent request that are required to o Additional details of the User Agent request that are required to
perform effective Request Routing by the Downstream CDN. For DNS perform effective Request Routing by the Downstream CDN. For DNS
this would typically be the IP address of the DNS resolver making this would typically be the IP address of the DNS resolver making
the request on behalf of the User Agent. For requests received the request on behalf of the User Agent. For requests received
over content specific application protocols the Redirection over content specific application protocols the Redirection
Request could contain significantly more information related to Request could contain significantly more information related to
the original User Agent request but at a minimum would need to the original User Agent request but at a minimum would need to
contain the User Agent's IP address, the equivalent of the HTTP contain the User Agent's IP address, the equivalent of the HTTP
Host header and the equivalent of the HTTP abs_path defined in Host header and the equivalent of the HTTP abs_path defined in
[RFC2616]. [RFC2616].
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application specific redirection response(s) to return to the application specific redirection response(s) to return to the
requesting User Agent. For HTTP requests from User Agents this requesting User Agent. For HTTP requests from User Agents this
could be in the form of a URI that the upstream CDN could return could be in the form of a URI that the upstream CDN could return
in a HTTP 302 response. in a HTTP 302 response.
The CDNI Request Routing interface is therefore a fairly The CDNI Request Routing interface is therefore a fairly
straightforward request/response interface and could be implemented straightforward request/response interface and could be implemented
over any number of request/response protocols. For example, it may over any number of request/response protocols. For example, it may
be implemented as a WebService using one of the common WebServices be implemented as a WebService using one of the common WebServices
methodologies (XML-RPC, HTTP query to a known URI, etc.). This methodologies (XML-RPC, HTTP query to a known URI, etc.). This
removes the need for a CDNI WG to define a new protocol for the removes the need for the CDNI WG to define a new protocol for the
request/response element of the CDNI Request Routing interface. request/response element of the CDNI Request Routing interface.
Thus, a CDNI WG would be left only with the task of specifying: Thus, the CDNI WG would be left only with the task of specifying:
o The recommended request/response protocol to use along with any o The recommended request/response protocol to use along with any
additional semantics and procedures that are specific to the CDNI additional semantics and procedures that are specific to the CDNI
Request Routing interface (e.g. handling of malformed requests/ Request Routing interface (e.g. handling of malformed requests/
responses). responses).
o The syntax (i.e representation/encoding) of the redirection o The syntax (i.e representation/encoding) of the redirection
requests and responses. requests and responses.
o The semantics (i.e. meaning and expected contents) of the o The semantics (i.e. meaning and expected contents) of the
redirection requests and responses. redirection requests and responses.
4.4. CDNI Metadata Interface Additionally, as discussed in Section 3, the CDNI Request Routing
interface is also expected to enable a downstream CDN to provide to
the upstream CDN (static or dynamic) information (e.g. resources,
footprint, load) to facilitate selection of the downstream CDN by the
upstream CDN request routing system when processing subsequent
content requests from User Agents. It is expected that such
functionality of the CDNI request Routing could be specified by the
CDNI WG with significant leveraging of existing IETF protocols
supporting the dynamic distribution of reachability information (for
example by leveraging existing routing protocols) or supporting
application level queries for topological information (for example by
leveraging ALTO).
4.2. CDNI Metadata Interface
The CDNI Metadata interface enables the Metadata function in a The CDNI Metadata interface enables the Metadata function in a
downstream CDN to obtain CDNI Metadata from an upstream CDN so that downstream CDN to obtain CDNI Metadata from an upstream CDN so that
the downstream CDN can properly process and respond to: the downstream CDN can properly process and respond to:
o Redirection Requests received over the CDNI Request Routing o Redirection Requests received over the CDNI Request Routing
interface. interface.
o Content Requests received directly from User Agents. o Content Requests received directly from User Agents.
The CDNI Metadata interface needs to offer a mechanism for an The CDNI Metadata interface needs to offer a mechanism for an
Upstream CDN to: Upstream CDN to:
o distribute/update/remove CDNI Metadata to a Downstream CDN o Distribute/update/remove CDNI Metadata to a Downstream CDN.
and/or to allow a downstream CDN to: and/or to allow a downstream CDN to:
o Make direct requests for CDNI Metadata records where the o Make direct requests for CDNI Metadata records where the
downstream CDN knows the identity of the Metadata record(s) it downstream CDN knows the identity of the Metadata record(s) it
requires. requires.
o Search for CDNI Metadata records where the downstream CDN does not o Search for CDNI Metadata records where the downstream CDN does not
know the specific Metadata record(s) it requires but does know know the specific Metadata record(s) it requires but does know
some property of the record it is searching for. For example, it some property of the record it is searching for. For example, it
may know the value of the HTTP Host header received in a HTTP may know the value of the HTTP Host header received in a HTTP
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request. request.
The CDNI Metadata interface is therefore similar to the CDNI Request The CDNI Metadata interface is therefore similar to the CDNI Request
Routing interface because it is a request/response interface with the Routing interface because it is a request/response interface with the
potential addition that CDNI Metadata search may have more complex potential addition that CDNI Metadata search may have more complex
semantics than a straightforward Request Routing redirection request. semantics than a straightforward Request Routing redirection request.
Therefore, like the CDNI Request Routing interface, the CDNI Metadata Therefore, like the CDNI Request Routing interface, the CDNI Metadata
interface may be implemented as a WebService using one of the common interface may be implemented as a WebService using one of the common
WebServices methodologies (XML-RPC, HTTP query to a known URI, etc.) WebServices methodologies (XML-RPC, HTTP query to a known URI, etc.)
or possibly using other existing protocols such as XMPP [RFC6120]. or possibly using other existing protocols such as XMPP [RFC6120].
This removes the need for a CDNI WG to define a new protocol for the This removes the need for the CDNI WG to define a new protocol for
request/response element of the CDNI Metadata interface. the request/response element of the CDNI Metadata interface.
Thus, a CDNI WG would be left only with the task of specifying: Thus, the CDNI WG would be left only with the task of specifying:
o The recommended request/response protocol to use along with any o The recommended request/response protocol to use along with any
additional semantics that are specific to the CDNI Metadata additional semantics that are specific to the CDNI Metadata
interface (e.g. handling of malformed requests/responses). interface (e.g. handling of malformed requests/responses).
o The syntax (i.e representation/encoding) of the CDNI Metadata o The syntax (i.e representation/encoding) of the CDNI Metadata
records that will be exchanged over the interface. records that will be exchanged over the interface.
o The semantics (i.e. meaning and expected contents) of the o The semantics (i.e. meaning and expected contents) of the
individual properties of a Metadata record. individual properties of a Metadata record.
o How the relationships between different CDNI Metadata records are o How the relationships between different CDNI Metadata records are
represented. represented.
4.5. CDNI Logging Interface 4.3. CDNI Logging Interface
The CDNI Logging interface enables details of logs or events to be The CDNI Logging interface enables details of logs or events to be
exchanged between interconnected CDNs, where events could be: exchanged between interconnected CDNs, where events could be:
o Log lines related to the delivery of content (similar to the log o Log lines related to the delivery of content (similar to the log
lines recorded in a web server's access log). lines recorded in a web server's access log).
o Real-time or near-real time events before, during or after content o Real-time or near-real time events before, during or after content
delivery, e.g. content Start/Pause/Stop events, etc. delivery, e.g. content Start/Pause/Stop events, etc.
o Operations and diagnostic messages. o Operations and diagnostic messages.
Within CDNs today, logs and events are used for a variety of purposes Within CDNs today, logs and events are used for a variety of purposes
in addition to real-time and non real-time diagnostics and auditing in addition to real-time and non real-time diagnostics and auditing
by the CDN Operator and its customers. Specifically CDNs use logs to by the CDN Provider and its customers. Specifically CDNs use logs to
generate Call Data Records (CDRs) for passing to billing and payment generate Call Data Records (CDRs) for passing to billing and payment
systems and to real-time (and near real-time) analytics systems. systems and to real-time (and near real-time) analytics systems.
Such use cases place requirements on the CDNI Logging interface to Such use cases place requirements on the CDNI Logging interface to
support guaranteed and timely delivery of log messages between support guaranteed and timely delivery of log messages between
interconnected CDNs. It may also be necessary to be able to prove interconnected CDNs. It may also be necessary to be able to prove
the integrity of received log messages. the integrity of received log messages.
Several protocols already exist that could potentially be used to Several protocols already exist that could potentially be used to
exchange CDNI logs between interconnected CDNs including SNMP Traps, exchange CDNI logs between interconnected CDNs including SNMP Traps,
syslog, ftp, HTTP POST, etc. although it is likely that some of the syslog, ftp, HTTP POST, etc. although it is likely that some of the
candidate protocols may not be well suited to meet all the candidate protocols may not be well suited to meet all the
requirements of CDNI. For example SNMP traps pose scalability requirements of CDNI. For example SNMP traps pose scalability
concerns and SNMP does not support guaranteed delivery of Traps and concerns and SNMP does not support guaranteed delivery of Traps and
therefore could result in log records being lost and the consequent therefore could result in log records being lost and the consequent
CDRs and billing records for that content delivery not being produced CDRs and billing records for that content delivery not being produced
as well as that content delivery being invisible to any analytics as well as that content delivery being invisible to any analytics
platforms. platforms.
Although it is not necessary to define a new protocol for exchanging Although it is not necessary to define a new protocol for exchanging
logs across the CDNI Logging interface, a CDNI WG would still need to logs across the CDNI Logging interface, the CDNI WG would still need
specify: to specify:
o The recommended protocol to use. o The recommended protocol to use.
o A default set of log fields and their syntax & semantics. Today o A default set of log fields and their syntax & semantics. Today
there is no standard set of common log fields across different there is no standard set of common log fields across different
content delivery protocols and in some cases there is not even a content delivery protocols and in some cases there is not even a
standard set of log field names and values for different standard set of log field names and values for different
implementations of the same delivery protocol. implementations of the same delivery protocol.
o A default set of events that trigger logs to be generated. o A default set of events that trigger logs to be generated.
4.6. CDNI Control Interface 4.4. CDNI Control Interface
The CDNI Control interface allows the "CDNI Control" system in The CDNI Control interface allows the "CDNI Control" system in
interconnected CDNs to communicate. The exact inter-CDN control interconnected CDNs to communicate. The exact inter-CDN control
functionality required to be supported by the CDNI Control interface functionality required to be supported by the CDNI Control interface
is less well defined than the other three CDNI interfaces at this is less well defined than the other three CDNI interfaces at this
time. time.
However, as discussed in Section 3.1, the CDNI Control interface may However, as discussed in Section 3, the CDNI Control interface may be
be required to support functionality similar to the following: required to support functionality similar to the following:
o Allow an upstream CDN and downstream CDN to establish, update or o Allow an upstream CDN and downstream CDN to establish, update or
terminate their CDNI interconnection. terminate their CDNI interconnection.
o Allow bootstrapping of the other CDNI interfaces (e.g. protocol o Allow bootstrapping of the other CDNI interfaces (e.g. protocol
address discovery and establishment of security associations). address discovery and establishment of security associations).
o Allow configuration of the other CDNI interfaces (e.g. Upstream o Allow configuration of the other CDNI interfaces (e.g. Upstream
CDN specifies information to be reported through the CDNI Logging CDN specifies information to be reported through the CDNI Logging
interface). interface).
o Allow the downstream CDN to communicate static information about o Allow the downstream CDN to communicate static information about
its delivery capabilities, resources and policies. its delivery capabilities, resources and policies.
o Allow bootstrapping of the interface between CDNs for content o Allow bootstrapping of the interface between CDNs for content
acquisition (even if that interface itself is outside the scope of acquisition (even if that interface itself is outside the scope of
the CDNI work). the CDNI work).
It is expected that for the Control inetrface also, existing It is expected that for the Control interface also, existing
protocols can be reused or leveraged. Those will be considered once protocols can be reused or leveraged. Those will be considered once
the requirements for the Control interface have been refined. the requirements for the Control interface have been refined.
5. Gap Analysis of relevant Standardization and Research Activities 5. Gap Analysis of relevant Standardization Activities
There are a number of other standards bodies and industry forums that There are a number of other standards bodies and industry forums that
are working in areas related to CDNs, and in some cases related to are working in areas related to CDNs, and in some cases related to
CDNI. This section outlines any potential overlap with the work of CDNI. This section outlines any potential overlap with the work of
the CDNI WG and any component that could potentially be reused by the CDNI WG and any component that could potentially be reused by
CDNI. CDNI.
A number of standards bodies have produced specifications related to A number of standards bodies have produced specifications related to
CDNs, namely: CDNs, for example:
o TISPAN has a dedicated specification for CDN. o TISPAN has a dedicated specification for CDN.
o OIPF and ATIS specify the architecture and the protocols of an o OIPF and ATIS specify the architecture and the protocols of an
IPTV solution. Although OIPF and ATIS specifications include the IPTV solution. Although OIPF and ATIS specifications include the
interaction with a CDN, the CDN specifications are coupled with interaction with a CDN, the CDN specifications are coupled with
their IPTV specifications. their IPTV specifications.
o CableLabs, SNIA and ITU have defined (or are working on)
o <TODO: Add a sentence on ITU> definitions for content related metadata definitions and
o IETF CDN WG (now concluded) touched on the same problem space as specification for its distribution. However, they do not include
metadata specific to the distribution of content within a CDN or
between interconnected CDNs.
o IETF CDI WG (now concluded) touched on the same problem space as
the present document. However, in accordance with its initial the present document. However, in accordance with its initial
charter, the CDI WG did not define any protocols or interfaces to charter, the CDI WG did not define any protocols or interfaces to
actually enable CDN Interconnection and at that time (2003) there actually enable CDN Interconnection and at that time (2003) there
was not enough industry interest and real life requirements to was not enough industry interest and real life requirements to
justify rechartering the WG to conduct the corresponding protocol justify rechartering the WG to conduct the corresponding protocol
work. work.
Although some of the specifications describe multi-CDN cooperation or Although some of the specifications describe multi-CDN cooperation or
include reference points for interconnecting CDNs, none of them include reference points for interconnecting CDNs, none of them
specify in sufficient detail all the CDNI interfaces and CDNI specify in sufficient detail all the CDNI interfaces and CDNI
Metadata representations required to enable even a base level of CDN Metadata representations required to enable even a base level of CDN
Interconnection functionality to be implemented. Interconnection functionality to be implemented.
The following sections will summarize the existing work of the The following sections will summarize the existing work of the
standard bodies above against the CDNI problem space. standard bodies listed earlier against the CDNI problem space.
Section 5.1 summarises existing interfaces that could be leveraged
for content acquisition between CDNs and Section 5.2 summarises
existing metadata specifications that may be applicable to CDNI. To
date we are not aware of any standardisation activities in the areas
of the remaining CDNI interfaces (CDNI Request Routing, CDNI Control
and CDNI Logging).
5.1. Content Acquisition across CDNs and Delivery to End User (Data 5.1. Content Acquisition across CDNs and Delivery to End User (Data
plane) plane)
A number of standards bodies have completed work in the areas of A number of standards bodies have completed work in the areas of
content acquisition interface between a CSP and a CDN, as well as as content acquisition interface between a CSP and a CDN, as well as as
on the delivery interface between the surrogate and the User Agent. on the delivery interface between the surrogate and the User Agent.
Some of this work is summarized below. Some of this work is summarized below.
TISPAN, OIPF and ATIS have specified IPTV and/or CoD services, TISPAN, OIPF and ATIS have specified IPTV and/or CoD services,
including the data plane aspects (typically different flavors of RTP/ including the data plane aspects (typically different flavors of RTP/
RTCP and HTTP) to obtain content and deliver it to User Agents. For RTCP and HTTP) to obtain content and deliver it to User Agents. For
example, : example, :
o The OIPF data plane includes both RTP and HTTP flavors (HTTP o The OIPF data plane includes both RTP and HTTP flavors (HTTP
progressive download, HTTP Adaptive streaming [_3GP-DASH],...). progressive download, HTTP Adaptive streaming [_3GP-DASH]).
o ATIS specification "IPTV Content on Demand (CoD) Service" o The ATIS specification "IPTV Content on Demand (CoD) Service"
[ATIS-COD] defines a reference point (C2) and the corresponding [ATIS-COD] defines a reference point (C2) and the corresponding
HTTP-based data plane protocol for content acquisition between an HTTP-based data plane protocol for content acquisition between an
authoritative origin server and the CDN. authoritative origin server and the CDN.
While these protocols have not been explicitly specified for content While these protocols have not been explicitly specified for content
acquisition across CDNs, they are suitable (in addition to others acquisition across CDNs, they are suitable (in addition to others
such as standard HTTP) for content acquisition between CDNs in a CDN such as standard HTTP) for content acquisition between CDNs in a CDN
Interconnection environment. Therefore for the purpose of a CDNI WG Interconnection environment. Therefore for the purpose of the CDNI
there are already multiple existing data plane protocols that can be WG there are already multiple existing data plane protocols that can
used for content acquisition across CDNs. be used for content acquisition across CDNs.
Similarly, there are multiple existing standards (e.g. OIPF data Similarly, there are multiple existing standards (e.g. the OIPF data
plane mentioned above, HTTP adaptive streaming [_3GP-DASH]) or public plane mentioned above, HTTP adaptive streaming [_3GP-DASH]) or public
specifications (e.g. vendor specific HTTP Adaptive streaming specifications (e.g. vendor specific HTTP Adaptive streaming
specification) so that content delivery is considered already solved specifications) so that content delivery can be considered already
(or at least sufficiently addressed in other forums). solved (or at least sufficiently addressed in other forums
Thus, specification of the content acquisition interface between CDNs Thus, specification of the content acquisition interface between CDNs
and the delivery interface between the surrogate and the User Agent and the delivery interface between the surrogate and the User Agent
are out of scope for CDNI. CDNI may only concern itself with the are out of scope for CDNI. CDNI may only concern itself with the
negotiation/selection aspects of the acquisition protocol to be used negotiation/selection aspects of the acquisition protocol to be used
in a CDN interonnect scenario. in a CDN interonnect scenario.
5.2. CDNI Metadata 5.2. CDNI Metadata
CableLabs, ITU, OIPF and TV-Anytime have work items dedicated to the CableLabs, ITU, OIPF and TV-Anytime have work items dedicated to the
skipping to change at page 23, line 23 skipping to change at page 22, line 29
with information to perform better-than-random initial peer with information to perform better-than-random initial peer
selection. ALTO services may take different approaches at balancing selection. ALTO services may take different approaches at balancing
factors such as maximum bandwidth, minimum cross-domain traffic, factors such as maximum bandwidth, minimum cross-domain traffic,
lowest cost to the user, etc. The WG will consider the needs of lowest cost to the user, etc. The WG will consider the needs of
BitTorrent, tracker-less P2P, and other applications, such as content BitTorrent, tracker-less P2P, and other applications, such as content
delivery networks (CDN) and mirror selection." delivery networks (CDN) and mirror selection."
In particular, the ALTO service can be used by a CDN Request Routing In particular, the ALTO service can be used by a CDN Request Routing
system to improve its selection of a CDN surrogate to serve a system to improve its selection of a CDN surrogate to serve a
particular User Agent request (or to serve a request from another particular User Agent request (or to serve a request from another
surrogate). See [I-D.penno-alto-cdn] for a detailed discussion on surrogate). [I-D.jenkins-alto-cdn-use-cases] describes a number of
how CDN Request Routing can be used as an integration point of ALTO use cases for a CDN to be able to obtain network topology and cost
information from an ALTO server(s) and [I-D.penno-alto-cdn] discusses
how CDN Request Routing could be used as an integration point of ALTO
into CDNs. It is possible that the ALTO service could be used in the into CDNs. It is possible that the ALTO service could be used in the
same manner in a multi-CDN environment based on CDN Interconnection. same manner in a multi-CDN environment based on CDN Interconnection.
For example, an upstream CDN may take advantage of the ALTO service For example, an upstream CDN may take advantage of the ALTO service
in its decision for selecting a downstream CDN to which a user in its decision for selecting a downstream CDN to which a user
request should be delegated. request should be delegated.
However, the work of ALTO is complementary to and does not overlap However, the work of ALTO is complementary to and does not overlap
with the work proposed in this document because the integration with the work described in this document because the integration
between ALTO and a CDN would fall under "algorithms for selection of between ALTO and a CDN is an internal decision for a specific CDN and
CDN or Surrogate by Request-Routing systems" in Appendix A.1 and is is therefore out of scope for the CDNI WG. One area for further
therefore out of scope for a CDNI WG. One area for further study is study is whether additional information should be provided by an ALTO
whether additional information should be provided by an ALTO service service to facilitate CDNI CDN selection.
to facilitate CDNI CDN selection.
6.2. DECADE 6.2. DECADE
The DECADE Working Group [DECADE-Charter] is addressing the problem The DECADE Working Group [DECADE-Charter] is addressing the problem
of reducing traffic on the last-mile uplink, as well as backbone and of reducing traffic on the last-mile uplink, as well as backbone and
transit links caused by P2P streaming and file sharing applications. transit links caused by P2P streaming and file sharing applications.
It addresses the problem by enabling an application endpoint to make It addresses the problem by enabling an application endpoint to make
content available from an in-network storage service and by enabling content available from an in-network storage service and by enabling
other application endpoints to retrieve the content from there. other application endpoints to retrieve the content from there.
Exchanging data through the in-network storage service in this Exchanging data through the in-network storage service in this
manner, instead of through direct communication, provides significant manner, instead of through direct communication, provides significant
gain where: gain where:
o The network capacity/bandwidth from in-network storage service to o The network capacity/bandwidth from in-network storage service to
application endpoint significantly exceeds the capacity/bandwidth application endpoint significantly exceeds the capacity/bandwidth
skipping to change at page 24, line 52 skipping to change at page 24, line 12
acquisition protocol between CDNs is outside the scope of the CDNI acquisition protocol between CDNs is outside the scope of the CDNI
work, this question is left for further study. work, this question is left for further study.
The DECADE in-network storage architecture and mechanisms may The DECADE in-network storage architecture and mechanisms may
potentially also be used within a given CDN for the distribution of potentially also be used within a given CDN for the distribution of
the content objects themselves among surrogates of that CDN. Since the content objects themselves among surrogates of that CDN. Since
the CDNI work does not concern itself with operation within a CDN, the CDNI work does not concern itself with operation within a CDN,
this question is left for further study. this question is left for further study.
Therefore, the work of DECADE may be complementary to but does not Therefore, the work of DECADE may be complementary to but does not
overlap with the CDNI work proposed in this document. overlap with the CDNI work described in this document.
6.3. PPSP 6.3. PPSP
As stated in the PPSP Working Group charter [PPSP-Charter]: As stated in the PPSP Working Group charter [PPSP-Charter]:
"The Peer-to-Peer Streaming Protocol (PPSP) working group develops "The Peer-to-Peer Streaming Protocol (PPSP) working group develops
two signaling and control protocols for a peer-to-peer (P2P) two signaling and control protocols for a peer-to-peer (P2P)
streaming system for transmitting live and time-shifted media content streaming system for transmitting live and time-shifted media content
with near real-time delivery requirements." and "The PPSP WG designs with near real-time delivery requirements." and "The PPSP WG designs
a protocol for signaling and control between trackers and peers (the a protocol for signaling and control between trackers and peers (the
skipping to change at page 25, line 30 skipping to change at page 24, line 39
content itself along with the necessary signaling and control content itself along with the necessary signaling and control
required to distribute the content. As such, it could potentially be required to distribute the content. As such, it could potentially be
used for the acquisition of streamed content across interconnected used for the acquisition of streamed content across interconnected
CDNs. But since the acquisition protocol is outside the scope of the CDNs. But since the acquisition protocol is outside the scope of the
work proposed for CDNI, we leave this for further study. Also, work proposed for CDNI, we leave this for further study. Also,
because of its streaming nature, PPSP is not seen as applicable to because of its streaming nature, PPSP is not seen as applicable to
the distribution and control of the CDNI control plane and CDNI data the distribution and control of the CDNI control plane and CDNI data
representations. representations.
Therefore, the work of PPSP may be complementary to but does not Therefore, the work of PPSP may be complementary to but does not
overlap with the work proposed in this document for CDNI. overlap with the work described in this document for CDNI.
7. IANA Considerations 7. IANA Considerations
This document makes no request of IANA. This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an Note to RFC Editor: this section may be removed on publication as an
RFC. RFC.
8. Security Considerations 8. Security Considerations
skipping to change at page 26, line 13 skipping to change at page 25, line 22
metadata (including distribution and delivery policies) and the CDNs metadata (including distribution and delivery policies) and the CDNs
distributing and delivering it, are critical requirements for both distributing and delivering it, are critical requirements for both
CDN Providers and CSPs and any work on CDN Interconnection must CDN Providers and CSPs and any work on CDN Interconnection must
provide sufficient mechanisms to maintain the security of the overall provide sufficient mechanisms to maintain the security of the overall
system of interconnected CDNs as well as the information (content, system of interconnected CDNs as well as the information (content,
metadata, logs, etc) distributed and delivered through any CDN metadata, logs, etc) distributed and delivered through any CDN
interconnects. interconnects.
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Andre Beck, Mark Carlson, Bruce The authors would like to thank Andre Beck, Gilles Bertrand, Mark
Davie, David Ferguson, Yiu Lee, Kent Leung, Kevin Ma, Julien Carlson, Bruce Davie, David Ferguson, Yiu Lee, Kent Leung, Will Li,
Maisonneuve, Guy Meador, Emile Stephan, Oskar van Deventer and Mahesh Kevin Ma, Julien Maisonneuve, Guy Meador, Emile Stephan, Oskar van
Viveganandhan for their review comments and contributions to the Deventer and Mahesh Viveganandhan for their review comments and
text. contributions to the text.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.bertrand-cdni-experiments]
Bertrand, G., Faucheur, F., and L. Peterson, "Content
Distribution Network Interconnection (CDNI) Experiments",
draft-bertrand-cdni-experiments-01 (work in progress),
August 2011.
[I-D.bertrand-cdni-use-cases]
Bertrand, G., Stephan, E., Watson, G., Burbridge, T.,
Eardley, P., and K. Ma, "Use Cases for Content Delivery
Network Interconnection", draft-bertrand-cdni-use-cases-02
(work in progress), July 2011.
[I-D.bertrand-cdni-use-cases-00]
Bertrand, G. and E. Stephan, "Use Cases for Content
Distribution Network Interconnection -
draft-bertrand-cdni-use-cases-00 (superseded)",
January 2011.
[I-D.jenkins-cdni-names]
Niven-Jenkins, B., "Thoughts on Naming and Referencing of
Data Objects within Content Distribution Network
Interconnection (CDNI) solutions",
draft-jenkins-cdni-names-00 (work in progress),
February 2011.
[I-D.watson-cdni-use-cases]
Watson, G., "CDN Interconnect Use Cases",
draft-watson-cdni-use-cases-00 (work in progress),
January 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References 10.2. Informative References
[ALTO-Charter] [ALTO-Charter]
"IETF ALTO WG Charter "IETF ALTO WG Charter
(http://datatracker.ietf.org/wg/alto/charter/)". (http://datatracker.ietf.org/wg/alto/charter/)".
[ATIS] "ATIS (http://www.atis.org/)". [ATIS] "ATIS (http://www.atis.org/)".
[ATIS-COD] [ATIS-COD]
"ATIS IIF: IPTV Content on Demand Service, January 2011 (h "ATIS IIF: IPTV Content on Demand Service, January 2011 (h
skipping to change at page 27, line 38 skipping to change at page 26, line 14
"CableLabs (http://www.cablelabs.com/about/)". "CableLabs (http://www.cablelabs.com/about/)".
[CableLabs-Metadata] [CableLabs-Metadata]
"CableLabs VoD Metadata Project Primer "CableLabs VoD Metadata Project Primer
(http://www.cablelabs.com/projects/metadata/primer/)". (http://www.cablelabs.com/projects/metadata/primer/)".
[DECADE-Charter] [DECADE-Charter]
"IETF DECADE WG Charter "IETF DECADE WG Charter
(http://datatracker.ietf.org/wg/decade/charter/)". (http://datatracker.ietf.org/wg/decade/charter/)".
[I-D.bertrand-cdni-experiments]
Bertrand, G., Faucheur, F., and L. Peterson, "Content
Distribution Network Interconnection (CDNI) Experiments",
draft-bertrand-cdni-experiments-01 (work in progress),
August 2011.
[I-D.ietf-cdni-use-cases]
Bertrand, G., Emile, S., Watson, G., Burbridge, T.,
Eardley, P., and K. Ma, "Use Cases for Content Delivery
Network Interconnection", draft-ietf-cdni-use-cases-00
(work in progress), September 2011.
[I-D.jenkins-alto-cdn-use-cases]
Niven-Jenkins, B., Watson, G., Bitar, N., Medved, J., and
S. Previdi, "Use Cases for ALTO within CDNs",
draft-jenkins-alto-cdn-use-cases-01 (work in progress),
June 2011.
[I-D.penno-alto-cdn] [I-D.penno-alto-cdn]
Penno, R., Medved, J., Alimi, R., Yang, R., and S. Penno, R., Medved, J., Alimi, R., Yang, R., and S.
Previdi, "ALTO and Content Delivery Networks", Previdi, "ALTO and Content Delivery Networks",
draft-penno-alto-cdn-03 (work in progress), March 2011. draft-penno-alto-cdn-03 (work in progress), March 2011.
[MPEG-DASH] [MPEG-DASH]
"Information technology - MPEG systems technologies - Part "Information technology - MPEG systems technologies - Part
6: Dynamic adaptive streaming over HTTP (DASH), (DIS 6: Dynamic adaptive streaming over HTTP (DASH), (DIS
version), February 2011 version), February 2011
http://mpeg.chiariglione.org/ http://mpeg.chiariglione.org/
skipping to change at page 30, line 31 skipping to change at page 29, line 27
acquisition methods are outside the scope of the CDNI work. acquisition methods are outside the scope of the CDNI work.
Content management (e.g. Content Deletion) as it relates to CDNI Content management (e.g. Content Deletion) as it relates to CDNI
content management policies, is in scope but the internal content management policies, is in scope but the internal
algorithms used by a cache to determine when to no longer cache an algorithms used by a cache to determine when to no longer cache an
item of Content (in the absence of any specific metadata to the item of Content (in the absence of any specific metadata to the
contrary) is out of scope. contrary) is out of scope.
o Element management interfaces. o Element management interfaces.
o Commercial, business and legal aspects related to the o Commercial, business and legal aspects related to the
interconnections of CDNs. interconnections of CDNs.
A.2. Prioritizing the CDNI Work A.2. Related standardization activities
In order to manage the potential workload of a CDNI WG, it is
recommended that the work be prioritized in a "walk before you run"
approach.
The CDNI problem area can be categorized into different solution
scopes as follows:
o "Base CDNI" Scope: This solution scope comprises the solution
elements that can be considered as the 'minimum' needed to
actually deliver any content using interconnected CDNs. For
example, a base CDNI Request Routing interface and a base CDNI
Metadata interface belong to this scope because without them the
upstream CDN is unable to redirect User Agents to the downstream
CDN and the downstream CDN is unable to obtain the delivery
policies and other CDNI Metadata required to ingest and deliver
the content.
o "Operationalized CDNI" Scope: This solution scope comprises the
solution elements that can be considered as the 'minimum' needed
to 'operationalize' CDN Interconnection. For example, the CDNI
Logging interface and the base capabilities of the CDNI Control
interface (e.g. content file/metadata deletion) belong to this
scope because without them CDN operators are required to
substitute for them either with manual processes or proprietary
interfaces.
o "Enhanced CDNI" Scope: This solution scope comprises the solution
elements that can be classed as 'enhanced features'. For example,
the aspects of the CDNI Control interface related to automatic
bootstrapping and configuration belong to this scope.
It is proposed that these solution scopes be addressed primarily
sequentially by a CDNI WG and that the initial charter be centered
around the "Base CDNI" scope. However there is obvious benefit from
having a solution for the "Base CDNI" scope that is amenable to
extension for support of the "Operational" scope and "Enhanced"
scope. Therefore it is proposed that the initial CDNI WG charter
also includes definition of (at least) the main requirements for the
"Operationalized CDNI" scope and "Enhanced CDNI" Scope, so those can
be kept in mind when defining the solution for the "Base CDNI" scope.
A.3. Related standardization activities
A.3.1. IETF CDI Working Group (Concluded) A.2.1. IETF CDI Working Group (Concluded)
The Content Distribution Internetworking (CDI) Working Group was The Content Distribution Internetworking (CDI) Working Group was
formed in the IETF following a BoF in December 2000 and closed in mid formed in the IETF following a BoF in December 2000 and closed in mid
2003. 2003.
For convenience, here is an extract from the CDI WG charter For convenience, here is an extract from the CDI WG charter
[CDI-Charter]: [CDI-Charter]:
" "
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Thus, the CDI WG touched on the same problem space as the present Thus, the CDI WG touched on the same problem space as the present
document. document.
The CDI WG published 3 Informational RFCs: The CDI WG published 3 Informational RFCs:
o RFC 3466 [RFC3466] - "A Model for Content Internetworking (CDI)". o RFC 3466 [RFC3466] - "A Model for Content Internetworking (CDI)".
o RFC 3568 [RFC3568] - "Known Content Network (CN) Request-Routing o RFC 3568 [RFC3568] - "Known Content Network (CN) Request-Routing
Mechanisms". Mechanisms".
o RFC 3570 [RFC3570] - "Content Internetworking (CDI) Scenarios". o RFC 3570 [RFC3570] - "Content Internetworking (CDI) Scenarios".
A.3.2. 3GPP A.2.2. 3GPP
3GPP was the first organization that released a specification related 3GPP was the first organization that released a specification related
to adaptive streaming over HTTP. 3GPP Release 9 specification on to adaptive streaming over HTTP. 3GPP Release 9 specification on
adaptive HTTP streaming was published in March 2010, and there have adaptive HTTP streaming was published in March 2010, and there have
been some bug fixes on this specification since the publication. In been some bug fixes on this specification since the publication. In
addition, 3GPP is preparing an extended version for Release 10, which addition, 3GPP is preparing an extended version for Release 10, which
is scheduled to be published later in 2011. This release will is scheduled to be published later in 2011. This release will
include a number of clarifications, improvements and new features. include a number of clarifications, improvements and new features.
[_3GP-DASH] is defined as a general framework independent of the data [_3GP-DASH] is defined as a general framework independent of the data
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The content retrieved by a client using [_3GP-DASH] adaptive The content retrieved by a client using [_3GP-DASH] adaptive
streaming could be obtained from a CDN but this is not discussed or streaming could be obtained from a CDN but this is not discussed or
specified in the 3GPP specifications as it is transparent to specified in the 3GPP specifications as it is transparent to
[_3GP-DASH] operations. Similarly, it is expected that [_3GP-DASH] [_3GP-DASH] operations. Similarly, it is expected that [_3GP-DASH]
can be used transparently from the CDNs as a delivery protocol can be used transparently from the CDNs as a delivery protocol
(between the delivering CDN surrogate and the User Agent) in a CDN (between the delivering CDN surrogate and the User Agent) in a CDN
Interconnection environment. [_3GP-DASH] could also be a candidate Interconnection environment. [_3GP-DASH] could also be a candidate
for content acquisition between CDNs in a CDN Interconnection for content acquisition between CDNs in a CDN Interconnection
environment. environment.
A.3.3. ISO MPEG A.2.3. ISO MPEG
Within ISO MPEG, the Dynamic Adaptive Streaming over HTTP (DASH) ad- Within ISO MPEG, the Dynamic Adaptive Streaming over HTTP (DASH) ad-
hoc group adopted the 3GPP Release 9 [_3GP-DASH] specification as a hoc group adopted the 3GPP Release 9 [_3GP-DASH] specification as a
starting point and has made some improvements and extensions. starting point and has made some improvements and extensions.
Similar to 3GPP SA4, the MPEG DASH ad-hoc group has been working on Similar to 3GPP SA4, the MPEG DASH ad-hoc group has been working on
standardizing the manifest file and the delivery format. standardizing the manifest file and the delivery format.
Additionally, the MPEG DASH ad-hoc group has also been working on the Additionally, the MPEG DASH ad-hoc group has also been working on the
use of MPEG-2 Transport Streams as a media format, conversion from/to use of MPEG-2 Transport Streams as a media format, conversion from/to
existing file formats, common encryption, and so on. The MPEG DASH existing file formats, common encryption, and so on. The MPEG DASH
specification could also be a candidate for delivery to the User specification could also be a candidate for delivery to the User
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February 2011. February 2011.
In the 95th MPEG meeting in January 2011, the DASH ad-hoc group In the 95th MPEG meeting in January 2011, the DASH ad-hoc group
decided to start a new evaluation experiment called "CDN-EE". The decided to start a new evaluation experiment called "CDN-EE". The
goals are to understand the requirements for MPEG DASH to better goals are to understand the requirements for MPEG DASH to better
support CDN-based delivery, and to provide a guidelines document for support CDN-based delivery, and to provide a guidelines document for
CDN operators to better support MPEG DASH streaming services. The CDN operators to better support MPEG DASH streaming services. The
ongoing work is still very preliminary and does not currently target ongoing work is still very preliminary and does not currently target
looking into CDN Interconnection use cases. looking into CDN Interconnection use cases.
A.3.4. ATIS IIF A.2.4. ATIS IIF
ATIS ([ATIS]) IIF is the IPTV Interoperability Forum (within ATIS) ATIS ([ATIS]) IIF is the IPTV Interoperability Forum (within ATIS)
that develops requirements, standards, and specifications for IPTV. that develops requirements, standards, and specifications for IPTV.
ATIS IIF is developing the "IPTV Content on Demand (CoD) Service" ATIS IIF is developing the "IPTV Content on Demand (CoD) Service"
specification. This includes use of a CDN (referred to in ATIS IIF specification. This includes use of a CDN (referred to in ATIS IIF
CoD as the "Content Distribution and Delivery Functions") for support CoD as the "Content Distribution and Delivery Functions") for support
of a Content on Demand (CoD) Service as part of a broader IPTV of a Content on Demand (CoD) Service as part of a broader IPTV
service. However, this only covers the case of a managed IPTV service. However, this only covers the case of a managed IPTV
service (in particular where the CDN is administered by the service service (in particular where the CDN is administered by the service
provider) and does not cover the use, or interconnection, of multiple provider) and does not cover the use, or interconnection, of multiple
CDNs. CDNs.
A.3.5. CableLabs A.2.5. CableLabs
"Founded in 1988 by cable operating companies, Cable Television "Founded in 1988 by cable operating companies, Cable Television
Laboratories, Inc. (CableLabs) is a non-profit research and Laboratories, Inc. (CableLabs) is a non-profit research and
development consortium that is dedicated to pursuing new cable development consortium that is dedicated to pursuing new cable
telecommunications technologies and to helping its cable operator telecommunications technologies and to helping its cable operator
members integrate those technical advancements into their business members integrate those technical advancements into their business
objectives." [CableLabs] objectives." [CableLabs]
CableLabs has defined specifications for CoD Content Metadata as part CableLabs has defined specifications for CoD Content Metadata as part
of its VOD Metadata project. of its VOD Metadata project.
A.3.6. ETSI MCD A.2.6. ETSI MCD
ETSI MCD (Media Content Distribution) is the ETSI technical committee ETSI MCD (Media Content Distribution) is the ETSI technical committee
"in charge of guiding and coordinating standardization work aiming at "in charge of guiding and coordinating standardization work aiming at
the successful overall development of multimedia systems (television the successful overall development of multimedia systems (television
and communication) responding to the present and future market and communication) responding to the present and future market
requests on media content distribution". requests on media content distribution".
MCD created a specific work item on interconnection of heterogeneous MCD created a specific work item on interconnection of heterogeneous
CDNs ("CDN Interconnection, use cases and requirements") in March CDNs ("CDN Interconnection, use cases and requirements") in March
2010. MCD very recently created a working group to progress this 2010. MCD very recently created a working group to progress this
work item. However, no protocol level work has yet started in MCD work item. However, no protocol level work has yet started in MCD
for CDN Interconnection. for CDN Interconnection.
A.3.7. ETSI TISPAN A.2.7. ETSI TISPAN
ETSI TISPAN has published two sets of IPTV specifications, one of ETSI TISPAN has published two sets of IPTV specifications, one of
which is based on IMS. In addition, TISPAN is about to complete the which is based on IMS. In addition, TISPAN is about to complete the
specifications of a CDN architecture supporting delivery of various specifications of a CDN architecture supporting delivery of various
content services such as time-shifted TV and VoD to TISPAN devices content services such as time-shifted TV and VoD to TISPAN devices
(UEs) or regular PCs. The use cases allow for hierarchically and (UEs) or regular PCs. The use cases allow for hierarchically and
geographically distributed CDN scenarios, along with multi-CDN geographically distributed CDN scenarios, along with multi-CDN
cooperation. As a result, the architecture contains reference points cooperation. As a result, the architecture contains reference points
to support interconnection of other TISPAN CDNs. The protocol to support interconnection of other TISPAN CDNs. The protocol
definition phase for the corresponding CDN architecture was kicked- definition phase for the corresponding CDN architecture was kicked-
off at the end of 2010. In line with its long history of leveraging off at the end of 2010. In line with its long history of leveraging
IETF protocols, ETSI could potentially leverage CDNI interfaces IETF protocols, ETSI could potentially leverage CDNI interfaces
developed in the IETF for their related protocol level work on developed in the IETF for their related protocol level work on
interconnections of CDNs. interconnections of CDNs.
A.3.8. ITU-T A.2.8. ITU-T
SG13 is developing standards related to the support of IPTV services SG13 is developing standards related to the support of IPTV services
(i.e.. multimedia services such as television/VoD/audio/text/ (i.e.. multimedia services such as television/VoD/audio/text/
graphics/data delivered over IP-based managed networks). graphics/data delivered over IP-based managed networks).
ITU-T Recommendation Y.1910 [Y.1910] provides the description of the ITU-T Recommendation Y.1910 [Y.1910] provides the description of the
IPTV functional architecture. This architecture includes functions IPTV functional architecture. This architecture includes functions
and interfaces for the distribution and delivery of content. This and interfaces for the distribution and delivery of content. This
architecture is aligned with the ATIS IIF architecture. architecture is aligned with the ATIS IIF architecture.
Based upon ITU-T Rec. Y.1910, ITU-T Rec. Y.2019 [Y.2019] describes in Based upon ITU-T Rec. Y.1910, ITU-T Rec. Y.2019 [Y.2019] describes in
more detail the content delivery functional architecture. This more detail the content delivery functional architecture. This
architecture allows CDN Interconnection: some interfaces (such as D3, architecture allows CDN Interconnection: some interfaces (such as D3,
D4) at the control level allow relationships between different CDNs, D4) at the control level allow relationships between different CDNs,
in the same domain or in different domains. Generic procedures are in the same domain or in different domains. Generic procedures are
described, but the choice of the protocols is open. described, but the choice of the protocols is open.
A.3.9. Open IPTV Forum (OIPF) A.2.9. Open IPTV Forum (OIPF)
The Open IPTV Forum has developed an end-to-end solution to allow any The Open IPTV Forum has developed an end-to-end solution to allow any
OIPF terminal to access enriched and personalized IPTV services OIPF terminal to access enriched and personalized IPTV services
either in a managed or a non-managed network[OIPF-Overview]. Some either in a managed or a non-managed network[OIPF-Overview]. Some
OIPF services (such as Network PVR) may be hosted in a CDN. OIPF services (such as Network PVR) may be hosted in a CDN.
To that end, the Open IPTV Forum specification is made of 5 parts: To that end, the Open IPTV Forum specification is made of 5 parts:
o Media Formats including HTTP Adaptive Streaming o Media Formats including HTTP Adaptive Streaming
o Content Metadata o Content Metadata
o Protocols o Protocols
o Terminal (Declarative or Procedural Application Environment) o Terminal (Declarative or Procedural Application Environment)
o Authentication, Content Protection and Service Protection o Authentication, Content Protection and Service Protection
A.3.10. TV-Anytime Forum A.2.10. TV-Anytime Forum
Version 1 of the TV-Anytime Forum specifications were published as Version 1 of the TV-Anytime Forum specifications were published as
ETSI TS 102 822-1 through ETSI TS 102 822-7 "Broadcast and On-line ETSI TS 102 822-1 through ETSI TS 102 822-7 "Broadcast and On-line
Services: Search, select, and rightful use of content on personal Services: Search, select, and rightful use of content on personal
storage systems ("TV-Anytime")". It includes the specification of storage systems ("TV-Anytime")". It includes the specification of
content metadata in XML schemas (ETSI TS 102 822-3) which define content metadata in XML schemas (ETSI TS 102 822-3) which define
technical parameters for the description of CoD and Live contents. technical parameters for the description of CoD and Live contents.
The specification is referenced by DVB and OIPF. The specification is referenced by DVB and OIPF.
The TV-anytime Forum was closed in 2005. The TV-anytime Forum was closed in 2005.
A.3.11. SNIA A.2.11. SNIA
The Storage Networking Industry Association (SNIA) is an association The Storage Networking Industry Association (SNIA) is an association
of producers and consumers of storage networking products whose goal of producers and consumers of storage networking products whose goal
is to further storage networking technology and applications. is to further storage networking technology and applications.
SNIA has published the Cloud Data Management Interface (CDMI) SNIA has published the Cloud Data Management Interface (CDMI)
standard ([SNIA-CDMI]). standard ([SNIA-CDMI]).
"The Cloud Data Management Interface defines the functional interface "The Cloud Data Management Interface defines the functional interface
that applications will use to create, retrieve, update and delete that applications will use to create, retrieve, update and delete
data elements from the Cloud. As part of this interface the client data elements from the Cloud. As part of this interface the client
will be able to discover the capabilities of the cloud storage will be able to discover the capabilities of the cloud storage
offering and use this interface to manage containers and the data offering and use this interface to manage containers and the data
that is placed in them. In addition, metadata can be set on that is placed in them. In addition, metadata can be set on
containers and their contained data elements through this interface." containers and their contained data elements through this interface."
A.4. Related Research Projects A.3. Related Research Projects
A.3.1. IRTF P2P Research Group
A.4.1. IRTF P2P Research Group
Some information on CDN interconnection motivations and technical Some information on CDN interconnection motivations and technical
issues were presented in the P2P RG at IETF 77. The presentation can issues were presented in the P2P RG at IETF 77. The presentation can
be found in [P2PRG-CDNI]. be found in [P2PRG-CDNI].
A.4.2. OCEAN A.3.2. OCEAN
OCEAN (http://www.ict-ocean.eu/) is an EU funded research project OCEAN (http://www.ict-ocean.eu/) is an EU funded research project
that started in February 2010 for 3 years. Some of its objectives that started in February 2010 for 3 years. Some of its objectives
are relevant to CDNI. It aims, among other things, at designing a are relevant to CDNI. It aims, among other things, at designing a
new architectural framework for audiovisual content delivery over the new architectural framework for audiovisual content delivery over the
Internet, defining public interfaces between its major building Internet, defining public interfaces between its major building
blocks in order to foster multi-vendor solutions and interconnection blocks in order to foster multi-vendor solutions and interconnection
between Content Networks (the term "Content Networks" corresponds between Content Networks (the term "Content Networks" corresponds
here to the definition introduced in [RFC3466], which encompasses here to the definition introduced in [RFC3466], which encompasses
CDNs). CDNs).
OCEAN has not yet published any open specifications, nor common best OCEAN has not yet published any open specifications, nor common best
practices, defining how to achieve such CDN interconnection. practices, defining how to achieve such CDN interconnection.
A.4.3. Eurescom P1955 A.3.3. Eurescom P1955
Eurescom P1955 was a 2010 research project involving a four European Eurescom P1955 was a 2010 research project involving a four European
Network operators, which studied the interests and feasibility of Network operators, which studied the interests and feasibility of
interconnecting CDNs by firstly elaborating the main service models interconnecting CDNs by firstly elaborating the main service models
around CDN interconnection, as well as analyzing an adequate CDN around CDN interconnection, as well as analyzing an adequate CDN
interconnection technical architecture and framework, and finally by interconnection technical architecture and framework, and finally by
providing recommendations for telcos to implement CDN providing recommendations for telcos to implement CDN
interconnection. The Eurescom P1955 project ended in July 2010. interconnection. The Eurescom P1955 project ended in July 2010.
The authors are not aware of material discussing CDN interconnection The authors are not aware of material discussing CDN interconnection
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