ETSI TS 182 019 V3.1.1 (2011-06)

Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); Content Delivery Network (CDN) Architecture

DTS/TISPAN-02076-NGN-R3

General Information

• Status: Published
• Publication Date: 26-Jun-2011
• Technical Committee: TISPAN 2 - TISPAN Architecture
• Current Stage: 12 - Completion
• Due Date: 21-Jul-2011
• Completion Date: 27-Jun-2011

Standards Content (Sample)

Technical Specification
Telecommunications and Internet converged Services and
Protocols for Advanced Networking (TISPAN);
Content Delivery Network (CDN) Architecture

2 ETSI TS 182 019 V3.1.1 (2011-06)

Reference
DTS/TISPAN-02076-NGN-R3
Keywords
IPTV, CDN
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3 ETSI TS 182 019 V3.1.1 (2011-06)
Contents
Intellectual Property Rights . 6
Foreword . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 7
3 Definitions and abbreviations . 7
3.1 Definitions . 7
3.2 Abbreviations . 8
4 General description of CDN . 8
4.1 Functional roles and CDN Relationships . 9
4.2 High Level functional overview . 9
4.3 Requirements . 11
4.3.1 CDN Functional Requirements . 11
4.3.2 Functional Requirements for interconnecting a CDN with an IPTV subsystem . 12
4.3.3 CDN Non-Functional Requirements . 13
5 Content Delivery Network (CDN) Functional Architecture . 14
5.1 General Description . 14
5.2 Functional entities . 15
5.2.1 Content Delivery Network Controller Function (CDNCF). 15
5.2.2 Cluster Controller Function (CCF) . 16
5.2.3 Content Delivery Function (CDF) . 17
5.2.4 Asset Location Function (ALF) . 18
5.2.5 Content Origin Function (COF) . 18
5.3 Overall Architecture and Reference Points . 19
5.4 Relationship between IPTV Subsystem and CDN . 19
5.5 Interconnection between two TISPAN CDNs within the same service provider domain . 20
6 Reference points . 21
6.1 CDNCF - CCF (Ys) . 21
6.2 CCF - CDF (Yp) . 21
6.3 CCF - UE (Xc') . 21
6.4 CDF - UE (Xc'') . 22
6.5 CDF - UE (Xd') . 22
6.6 CDNCF - CDNCF (Yq) . 22
6.7 CDF-CDF (Cf) . 22
6.8 CDNCF - IPTV Subsystem (Cu) . 22
6.8.1 CDNCF - IMS-based IPTV Subsystem . 22
6.8.2 CDNCF - NGN Integrated IPTV Subsystem . 22
6.9 CDNCF - IPTV Subsystem (Qc) . 22
6.10 CCF - IPTV Subsystem (Ct). 23
6.10.1 CCF - IMS-based IPTV Subsystem . 23
6.10.2 CCF - NGN Integrated IPTV Subsystem . 23
6.11 CDNCF - ALF (Qq) . 23
6.12 ALF - ALF (Qq') . 23
6.13 ALF - CCF (Yy) . 23
6.14 ALF - COF (Yv) . 23
6.15 COF - CDF (Cf') . 23
6.16 COF - COF (Cf'') . 23
7 Procedures . 24
7.1 Request Routing Within CDN . 24
7.1.1 CDN Request routing resolves to a CDF - Content Available . 24
7.1.2 CDN Request routing resolves to a CDF - Dynamic Acquisition . 25
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4 ETSI TS 182 019 V3.1.1 (2011-06)
7.1.2.1 CDN Request Routing resolves to the CDF - Early Dynamic Acquisition . 25
7.1.2.2 CDN Request Routing resolves to CDF - Late Dynamic Acquisition triggered by CCF . 27
7.1.2.3 CDN Request Routing Resolves to CDF - Late Dynamic Acquisition triggered by CDF . 28
7.1.3 CDN Request Routing resolves to a redirect to a new CDNCF . 29
7.1.4 CDN Request Routing resolves to a proxy of the original request to a new CDNCF . 30
7.1.5 CDN Request Routing for Unicast Content Download . 31
7.2 Request Initiation: Service Approach - CDNCF sends IPTV request to CCF . 32
7.2.1 Service Approach: Common Procedures . 32
7.2.1.1 Unicast Streaming Session Initiation - Service Approach. 32
7.2.1.2 Service Approach: CDNCF Query to ALF . 33
7.2.2 Service Approach: Additional Procedures for IMS-based IPTV Subsystem . 33
7.2.2.1 Unicast Streaming Session Initiation (No session delivery established) . 33
7.2.2.2 UE initiated Unicast Streaming Session Modification for IMS based IPTV . 35
7.2.2.3 CDN initiated Unicast Streaming Session Modification for IMS based IPTV . 37
7.2.2.4 SCF initiated Unicast Streaming Session Modification for IMS based IPTV . 38
7.2.2.5 Restricted (Forced-Playout Policies) . 38
7.2.3 Service Approach: Additional Procedures for NGN Integrated IPTV Subsystem . 39
7.2.3.1 UE initiated Unicast Streaming Session Initiation - Coupled mode . 39
7.3 Request Initiation: Query Approach - CDNCF sends CCF address to IPTV . 40
7.3.1 Query Approach: Common Procedures . 40
7.3.1.1 Query Approach: CDNCF (ALF) Query . 40
7.3.1.2 Unicast Streaming Initiation - Query Approach . 41
7.3.1.3 Restricted (Forced-Playout) Policies . 41
7.4 Media Control Procedures . 42
7.4.1 Unicast Streaming Delivery - Trick Play commands - proxy via CCF . 42
7.4.2 Unicast Streaming Delivery - Trick Play commands - direct to CDF . 44
7.5 Upload/Upstream Generic Procedures . 45
7.6 Generic Download Procedures . 46
7.6.1 Unicast Download/Downstream Common Procedures . 46
7.6.1.1 Unicast Download Delivery - Redirect to CDF Mode . 46
7.6.1.2 Unicast Download Delivery - CCF Proxy Redirect Mode . 46
7.6.1.3 Unicast Download Delivery in CCF triangular Proxy Mode . 47
7.6.1.4 Unicast Download Delivery in Redirect Mode . 48
7.6.2 Unicast Download/Downstream Session Initiation for IMS based IPTV . 49
7.6.3 Unicast Download/Downstream initiation for NGN Integrated IPTV . 51
7.7 Termination Procedures . 51
7.7.1 Generic Termination Procedures . 51
7.7.1.1 UE-Initiated Termination . 51
7.7.1.2 IPTV Subsystem-Initiated Termination . 51
7.7.2 Additional Termination Procedures - Query Approach . 52
7.7.2.1 CCF initiated Termination - Query Approach . 52
7.7.2.2 CDF initiated Termination - Query Approach . 53
7.7.3 Additional Termination Procedures - Service Approach - IMS-based Subsystem . 53
7.7.3.1 CCF Initiated Session Termination - IMS-based Service Approach . 53
7.7.3.2 CDF initiated Session Termination - IMS-Based Service Approach . 54
7.7.3.3 UE initiated Session Termination (IMS-based Service Approach - CCF Proxy Mode) . 55
7.7.3.4 SCF initiated Session Termination - IMS-Based Service Approach . 55
7.8 Content Management Procedures within CDN . 56
7.8.1 Content Ingestion Procedures . 56
7.8.1.1 Procedures for pre-positioning . 56
7.8.1.2 Procedures for dynamic acquisition . 57
7.8.2 Content Deployment Procedures . 57
7.8.2.1 Receiver driven pre-positioned content deployment . 57
7.8.2.2 Sender driven pre-positioned content deployment . 58
7.9 Content Replication within the CDN. 60
7.9.1 Duplication of Content Copy within Cluster . 60
7.9.2 Duplication between two Clusters under the same CDNCF . 61
7.9.3 Duplication between two Clusters under different CDNCFs . 62
7.9.4 Media Relay based Unicast Streaming Delivery for IMS based IPTV . 63
7.9.4.1 Content Deployment & Delivery Flow by media relay between two Clusters . 63
7.9.4.2 Content Delivery Flow by media relay via Centre Cache . 64
7.10 Procedures of Content Removal . 66
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5 ETSI TS 182 019 V3.1.1 (2011-06)
7.10.1 Procedures for Content Removal CCF initiated. 66
7.10.2 Procedures for Content Removal CDNCF initiated . 68
7.10.3 Procedures for Mandatory Content Removal COF initiated . 68
7.10.4 Procedures for COF Content Removal . 69
7.10.5 Procedures for Content Removal on CDF (Optional procedure) . 70
Annex A (informative): CDN steps description . 72
Annex B (normative): CDN Mapping to IPTV Subsystems . 74
B.1 CDN Mapping to IMS-based IPTV Subsystem (TS 182 027) . 74
B.2 CDN Mapping to NGN Integrated IPTV Subsystem (TS 182 028) . 74
Annex C (informative): Architectural Topologies . 76
C.1 Single-Instance CDN Architecture . 76
C.2 Flat CDN Architectural Topology . . 76
C.3 Hierarchical CDN Architectural Topology . 77
Annex D (informative): Interconnection scenarios . 78
D.1 Interconnection between TISPAN CDNs in different service provider domains with agreement on
content preparation . 78
D.1.1 Interconnection between TISPAN CDNs in different service provider domains without using content
originating function . 78
D.1.2 Interconnection between TISPAN CDNs in different service provider domains using content originating
function . 79
D.1.3 Interconnection between TISPAN CDNs in different service provider domains using ALF . 79
D.2 Interconnection between TISPAN CDNs in different service provider domains without agreement
on content preparation . 80
D.2.1 Interconnection between TISPAN CDNs in different service provider domains using Cf' . 80
D.2.2 Interconnection between TISPAN CDNs in different service provider domains using Cf'' . 81
History . 82

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6 ETSI TS 182 019 V3.1.1 (2011-06)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Telecommunications and Internet
converged Services and Protocols for Advanced Networking (TISPAN).
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7 ETSI TS 182 019 V3.1.1 (2011-06)
1 Scope
The present document describes the Content Delivery Network (CDN) functional architecture, the interconnection with
IMS-based and NGN Integrated IPTV solutions and user-related procedures in relationship with the unicast stored
(e.g. content download) and streaming (e.g. CoD) services as defined in TS 181 016 [1].
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 181 016: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Service Layer Requirements to integrate NGN services and
IPTV".
[2] ETSI TS 182 027: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IPTV Architecture; IPTV functions supported by the IMS
subsystem".
[3] ETSI TS 182 028: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN integrated IPTV subsystem Architecture".
[4] ETSI TS 187 003: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Security; Security Architecture".
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TS 102 990: "Media Content Distribution (MCD); CDN Interconnection, use cases and
requirements".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
content acquisition: act of acquiring content from a content source
content delivery: act of delivering deployed content to a user
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8 ETSI TS 182 019 V3.1.1 (2011-06)
Content Delivery Network (CDN): set of functions managing content acquired from content sources, through delivery
to the user
content deployment: act of replicating and/or moving ingested content to one or more network entities, based on
content deployment policies
content distribution: act of moving content within or between networks
content ingestion: act of preparing and introducing acquired content (and associated data) for the first time to an initial
server location
content publishing: act of making the content available for access
pull: within the CDN, a content delivery method in which the requesting entity initiates the media flow by requesting
content from the providing entity
push: within the CDN, a content delivery method in which the providing entity initiates the media flow to the
requesting destination entity
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ALF Asset Location Function
CCF Cluster Controller Function
CDF Content Delivery Function
CDN Content Delivery Network
CDNCF Content Delivery Network Control Function
COF Content Origin Function
IMS IP Multimedia Subsystem
IPTV Internet Protocol TeleVision
NGN Next Generation Network
SCF Service Control Function
SSF Service Selection Function
UE User Equipment
4 General description of CDN
A Content Delivery Network (CDN) is a collaborative collection of components, where content is replicated over
several mirrored servers in order to perform transparent and effective delivery of content to end users.
The major stages of CDN are:
• Content acquisition: Acquiring content from a content source, including:
- Pre-Positioning: content acquisition triggered prior to actual corresponding content request by users.
- Dynamic Acquisition: content acquisition triggered at the time it is requested by users.
• Content Ingestion: Preparing and introducing acquired content (and associated data) for the first time to an
initial server location.
• Content Deployment: Replicating and/or moving ingested content to one or more network entities, based on
content deployment policies.
The CDN model for distributing content is based on replicated servers located at the edge of the network (to which end
users are connected) for delivering content to end users in a reliable and timely manner. The content can be replicated in
advance or on-demand.
The CDN goals are:
• Scalability: the ability to expand, in order to handle new amount of data and requests.
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9 ETSI TS 182 019 V3.1.1 (2011-06)
• Performance: response time, or latency, that end users perceive.
• Reliability: makes the service always available.
• Security: prevent unauthorized access and modification of the content.
The CDN functional architecture defined in the present document is independent of the service system. The CDN is
transparent to media formats, content protection (whether the content is encrypted or not, or which content protection
solution is implemented) and the service types. While the CDN is specified herein in the context of IPTV, it may be
utilized where appropriate for other services.
NOTE: CDN Interconnection between different service provider domains is addressed in annex D and
TS 102 990 [i.1].
4.1 Functional roles and CDN Relationships
The present document describes the TISPAN CDN architecture, the interconnection of CDNs in the user-facing service
delivery network, including the interfacing with IPTV subsystems defined in TS 182 027 [2] and TS 182 028 [3], and
CDN content ingestion.
For the purpose of the present document, concepts of domains, and roles are defined in this clause and are illustrated in
figure 4.1.1. The terminology in this clause is based on TS 181 016 [1], clause 4.1.
Content
Service and
ingestion
content delivery
Service Domains Content
Consumer
Domain
Domain
IPTV
Service
Provider
CDN
Content
Consumer
Service
Provider
Provider
: Direction of content flow
Figure 4.1.1: Roles and domain relationships for CDN
The CDN Service Provider is the entity that ingests, deploys and delivers content.
NOTE 1: The CDN Service Provider may have multiple interconnected CDNs.
The IPTV Service Provider is the entity that offers IPTV services to the Consumers making use of the Delivering
CDN for content delivery.
NOTE 2: The present document assumes that the roles of CDN Service Provider and IPTV Service Provider take
place within TISPAN-specified service domain(s). The case where these two roles are in different
domains is described in TS 182 027 [2], clause 6.9.
The Consumer is the entity where the content is consumed. The content is delivered through the CDN domain.
The Content Provider is the entity that owns or is licensed to sell content or content assets. The content is delivered to
a user through the CDN. The Content Provider is authoritative with respect to control of consumer access to the content
(i.e. whether a given delivery request from a consumer is to be honoured by the CDN or not).
4.2 High Level functional overview
The following picture shows the main components of a CDN.
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10 ETSI TS 182 019 V3.1.1 (2011-06)
Content Acquisition
Content Preparation Content Ingestion Billing
Content Deployment
CDN
Accounting
Request Routing
Replica server 1 Replica server M
Content Delivery
Figure 4.2.1: Architectural components of a CDN
The Content Deployment component is in charge of generating copies of content inside the CDN and controls the
procedure of content deployment. When content is ingested from a content source (i.e. content provider, or UE for UGC
service) the Content Deployment component should record the metadata and location(s) of the content. More than one
copy of the content may be deployed to different replica servers during the procedure for content ingestion or
afterwards, when the content is frequently accessed. Replica Server components have content storage resources and are
responsible for storing the content, e.g. in order to support time-shifted TV, CoD or other IPTV services.
The Content Deployment component coordinates the delivery and storage resources of replica servers and establishes
the optimal deployment policy for deploying content from content source to replica servers. It also controls the
deployment of content among different replica servers.
The Content Deployment component uses and maintains the deployment information about how the content is deployed
among different replica servers. The Content Deployment component may use the information obtained from the
Request Routing component or the load status of replica servers to optimize the deployment policy.
The Request Routing component is responsible for directing client requests for content to appropriate replica servers
and for interacting with the Content Deployment component to keep an up-to-date view of the content stored in the
CDN.
The Content Delivery component works with Replica Server components and is responsible for streaming (e.g. via RTP
over UDP) or downloading content to the UE. It also provides other functions, such as file downloading and uploading
to and from the UE.
The Content Delivery component also handles control functions on the media during content delivery, including media
control commands such as fast-forward, rewind, etc.
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11 ETSI TS 182 019 V3.1.1 (2011-06)
The Accounting component, which maintains logs of client accesses and records the usage of the CDN. This
information is used for traffic reporting and usage-based billing by the Service or Content Provider itself or by any other
entities (e.g. a third-party billing organization).
The Content Preparation component may include:
• Transcoding.
• Other functions such as watermarking, ad-insertion into streams, format conversion, resolution conversion, etc.
• Encryption.
• Dividing a complete content file into smaller files with pieces of the content.
The abstract components described above may be mapped to one or more logical functional entities.
NOTE: A description of the Steps needed for CDN functionality is provided in annex A.
4.3 Requirements
4.3.1 CDN Functional Requirements
4.3.1.1 The CDN solution shall support both IMS-based and NGN Integrated IPTV subsystems.
4.3.1.2 The CDN solution shall support content delivery for one or more multimedia systems.
4.3.1.3 The CDN solution should support content delivery for more than one kind of multimedia service systems.
4.3.1.4 The CDN solution shall support centralized and P2P content deployment.
4.3.1.5 The CDN solution shall support automatic and manual publishing of the content.
4.3.1.6 The CDN solution shall support automatic deployment of content from central content server to the edge
content servers.
4.3.1.7 The CDN solution shall provide support for the definition of different virtual deployment channels for different
content providers.
4.3.1.8 The CDN solution shall provide support for the definition of different virtual deployment channels for different
service providers.
4.3.1.9 The CDN solution shall support mechanisms to deploy content to a specific server or set of servers based on
specific policies, e.g.:
• Deploy contents to the servers based on an estimation of the popularity of a specific content.
• Deploy contents to the servers based on geographical location.
• Deploy contents based on different user groups (e.g. hotel industry, school, white-collar community, rural
groups, etc.).
4.3.1.10 The CDN solution shall support content deployment via both Pre-positioning of content and Dynamic
Acquisition of content.
4.3.1.11 The CDN solution should provide different priority levels for contents/services, and contents/services with
high priority should be guaranteed when conflicts occurs between contents/services, e.g. when the bandwidth is not
enough, the CDN should guarantee the QoS of high priority contents/services.
4.3.1.12 The CDN solution shall provide mechanisms to collect and maintain the data related to the content deployment
in order to allocate user's request to the appropriate servers.
4.3.1.13 The CDN solution shall provide mechanisms to collect data related to the content popularity, (e.g. the number
of user's requests, etc.).
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12 ETSI TS 182 019 V3.1.1 (2011-06)
4.3.1.14 The CDN solution shall provide support for integration with an external alerting system.
4.3.1.15 The CDN solution control entities shall have a view of the maximum/actual capacity of the delivery servers
(e.g. number of users served, bandwidth, etc.) within the content delivery network. This information shall be organized
and distributed to the control entities depending on the content delivery network topological organization.
4.3.1.16 The CDN solution control entities shall be able to detect a change in the capacity of the content delivery
servers within an organized group of server (e.g. a cluster or a set of clusters). The content delivery network control
entities shall be able to notify other control entities in the Content Delivery Network of these changes.
4.3.1.17 The CDN solution control entities shall be able to detect a change in the availability of the content within a
group of content delivery servers (e.g. a cluster or a set of clusters). Content delivery network control entities shall be
able to notify other control entities in the Content Delivery Network as well as other entities in the Service Provider
platform of changes in content availability and/or distribution.
NOTE: The CDN solution control entities should make use of the information provided by other Content
Delivery network entities in determining their server or cluster assignment policy. The Service Platform
Provider will process the request for a content item based on the latest updated content availability
information in one or more Content Delivery Networks.
4.3.1.18 The CDN solution Entities shall be able to detect an irregular signalling from the UE (e.g. irregular frequency
of requests for content, unexpected messages etc). The documentation of such irregular signalling is service provider
dependent. The Content Delivery Network control entities shall be able to notify other control entities in the Content
Delivery Network as well as other entities in the Service Provider platform of irregular signalling.
4.3.1.19 The CDN solution shall support efficient content deployment, e.g. content segmentation mechanism (dividing
the content file into smaller pieces).
4.3.1.20 The CDN solution shall support content acquisition from different content providers.
4.3.1.21 The CDN solution content deployment shall support a mechanism taking into account content aging (lifecycle
of the content based on specific policy, e.g. LRU).
4.3.1.22 The CDN solution shall support unicast and can optionally support multicast content delivery mechanism.
4.3.1.23 The CDN solution should support CDN resources sharing between multiple Service Providers.
4.3.1.24 The CDN solution shall be able to retrieve content from another CDN belonging to the same or a different
service provider.
4.3.2 Functional Requirements for interconnecting a CDN with an IPTV
subsystem
The following requirements apply when an IPTV subsystem is interconnected with a CDN:
4.3.2.1 The CDN solution should provide mechanisms to request and acquire content from external systems based on
the user's request.
4.3.2.2 The CDN solution shall support mechanisms to select the content server for a specific user or set of users
based on specific policies, for example:
• Pre-defined content server.
• User location.
• User group.
• Content availability.
• Network traffic.
4.3.2.3 The CDN solution shall support delivery of the content to the user through streaming, download and
progressive download.
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13 ETSI TS 182 019 V3.1.1 (2011-06)
4.3.2.4 The CDN solution shall support deployment and delivery of content protected by protection schemes in line
with TS 187 003 [4].
4.3.2.5 The CDN solution shall support distribution of metadata related to the content.
4.3.2.6 The CDN solution shall provide load balancing mechanisms among the servers, e.g. content servers, control
servers, the criteria for balance the load can be: the network resources, e.g. network bandwidth, server capability and
load, etc.
4.3.2.7 The CDN solution shall support distribution and delivery of user generated content through
upstreaming/upload mode.
4.3.2.8 The CDN solution can optionally support forward error correction (FEC) or other retransmission mechanisms.
4.3.2.9 The CDN solution should be capable of supporting enforcement of access control policies for content
deployment and delivery (e.g. start time when content becomes accessible to user, end time when content stops
being accessible to users, geo-locations for determining from where users can or cannot access content).
4.3.3 CDN Non-Functional Requirements
4.3.3.1 The CDN solution should provide geographical scalability maintaining performances and effectiveness from a
limited local area deployment to a more geographically distributed pattern.
4.3.3.2 The CDN solution shall provide support for high availability (i.e. server mirroring, dynamic traffic forwarding,
etc.).
4.3.3.3 The CDN solution shall provide support for secure management and operations.
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14 ETSI TS 182 019 V3.1.1 (2011-06)
5 Content Delivery Network (CDN) Functional
Architecture
5.1 General Description
The Content Delivery Network (CDN) allows the optimization of the network use through a distribution of the content
delivery servers in the physical network, and the optimization of the storage resources through mechanisms such as
popularity-based distribution of the content on the content servers. Figure 5.1.1 shows the functional architecture of a
CDN.
ALF
COF
CDNCF
-
Cluster
CCF
CDF
Figure 5.1.1: Functional architecture of CDN
The Content Delivery Network interfaces with IPTV Service Platforms, UEs, and content distribution systems.
1) A Content Delivery Network offers two main interfaces to IPTV service platforms:
- A service control related interface:
� This interface is in charge of initiating the delivery the requested content to the UE: This requires
electing the best suited CDN cluster and content delivery server.
- A management related interface:
� This interface is in charge of administration and provisioning tasks.
2) A Content Delivery Network offers two interfaces towards UEs:
- A content control related interface:
- A media delivery interface:
� Delivery information is sent to the UE, after which delivery is initiated and completed by the UE.
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15 ETSI TS 182 019 V3.1.1 (2011-06)
NOTE 1: Both the content control related and media delivery interfaces are reflected in the present document in
order to fully describe the functions of the CDN interfaces with the UE. Further specification of these
interfaces is not in the scope of the present document, as they are specified within the relevant IPTV
Service Platforms, and in coordination with other standards organizations.
3) A Content Delivery Network offers two interfaces towards content distribution systems:
- A service control related interface.
- A media delivery interface.
NOTE 2: Both the service control related and media delivery interfaces are reflected in the present document in
order to fully describe the functions of the CDN within a user-facing network. Specification of these
interfaces outside of the TISPAN CDN is not in the scope of the present document, and will be
coordinated with other standards organizations.
5.2 Functional entities
The Content Delivery Network contains one or more Content Delivery Functions (CDF) grouped geographically or
administratively in clusters. The CDFs in one cluster are controlled by a specific Cluster Controller Function (CCF).
One or more CCFs are controlled by the Content Delivery Network Controller Function (CDNCF).
The CDF and CCF are directly involved in delivering content to the UE. The CDNCF controls content by interacting
with the IPTV subsystem.
The Asset Location Function (ALF) contains knowledge of content available to the CDN.
The Content Origin Function (COF) provides content ingestion to the CDN.
5.2
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