Content Delivery Networks Interconnection

Document Charter Content Delivery Networks Interconnection WG (cdni)
Title Content Delivery Networks Interconnection
Last updated 2013-12-06
State Approved
WG State Active
IESG Responsible AD Alexey Melnikov
Charter Edit AD Spencer Dawkins
Send notices to (None)


A Content Delivery Network (CDN) is an infrastructure of network
elements operating at layer 4 through layer 7, arranged for the
efficient distribution and delivery of digital content. Such content
includes, but is not limited to, web pages and images delivered via
HTTP, and streaming of continuous media delivered via HTTP, RTSP, RTMP,
etc. CDNs typically provide services to multiple Content Service
Providers (CSPs).

CDNs provide numerous benefits: a shared platform for multi-service
content delivery, reduced transmission costs for cacheable content,
improved quality of experience for end users and increased robustness of
delivery. For these reasons they are frequently used for large-scale
content delivery.

As a result of the significant growth in content delivered over IP
networks, existing CDN providers are scaling up their infrastructure and
many Network Service Providers and Enterprise Service Providers are
deploying their own CDNs. Subject to the policy of the CSP, it is
generally desirable that a given item of content can be delivered to an
end user regardless of that end user's location or attachment network.
This creates a need for interconnecting (previously) standalone CDNs so
they can interoperate and collectively behave as a single delivery

The goal of the CDNI Working Group is to allow the interconnection of
separately administered CDNs in support of the end-to-end delivery of
content from CSPs through multiple CDNs and ultimately to end users (via
their respective User Agents). The CDNI WG aims at delivering a
targeted, deployable solution in a short timeframe as
needed by the industry. It is expected that the CDNI interfaces will be
realized using existing IETF protocols for transport and message
exchange, and using existing object notation grammars/languages for the
definition of CDNI objects and semantics. In the event that protocol
extensions or new protocols are deemed necessary by the WG, the WG will

The working group will focus on the following items:

- A "requirements" document. This document lists the requirements for
  the CDNI architecture and the CDNI interfaces. In particular, this
  document will focus on identifying a reasonable set of more urgent and
  important requirements that will be addressed in the initial set of
  CDNI protocols and solutions produced by the working group. This
  document will list the requirements stemming from the threat analysis
  and to be met by each of the CDNI interfaces.

- A "framework" document providing a description of the different
  components of the CDNI architecture and how they interact with one
  another. This document will also include a "threat analysis"
  discussing the security concerns and threats, the trust model and
  privacy issues specific to CDNI.

- A specification of the "CDNI Request Routing Redirection interface".
  This interface will allow an upstream CDN Request Routing system to
  obtain from the downstream CDN the information necessary to perform
  request redirection. It is actually a logical bundling of two separate
  but related interfaces:

   *  Footprint & Capability Advertisement interface: Asynchronous
      operations to exchange routing information (e.g., the network
      footprint and capabilities served by a given CDN) that enables CDN
      selection for subsequent user requests; and

   *  Request Routing Redirection interface: Synchronous operations to
      select a delivery CDN (surrogate) for a given user request.

- A specification of the "CDNI Metadata interface". This interface will
  allow the CDNs to exchange content distribution metadata of inter-CDN
  scope. Content distribution metadata refers to the subset of content
  metadata that is relevant to the distribution of the content and
  therefore is to be processed by CDNs (for example, this may include
  information enabling: content acquisition, geo-blocking, enforcement
  of availability windows or access control).

- A specification of the "CDNI Logging interface". This interface will
  allow CDN logging systems to exchange logging information associated
  with actions that are relevant across CDNs (such as content
  distribution, content delivery and content routing actions) for
  purposes of accounting, analytics, monitoring, etc.

- A specification of the "CDNI Control interface". In particular, this
  interface will allow an upstream CDN to remove or invalidate content
  in a downstream CDN.

- A specification for "CDNI URI Signing". This document will specify a
  mechanism that allows interconnected CDNs to support access control
  by signing content URIs. This may involve extensions to the CDNI
  interfaces (e.g. CDNI Metadata interface, CDNI Logging interface).

The WG will discuss and address the security, management and operational
issues specific to CDNI, inside the above documents and specifications.

The working group will only define solutions for aspects of the CDN
Interconnection problem space that require direct communication or
interoperation between CDNs.

In particular, the WG will not define:

- New session, transport or network protocols.

- New protocols for delivering content from a CDN to an End User/User

- New protocols for ingestion of content or metadata between a CSP and a

- New protocols for acquiring content across CDNs.

- Protocols and algorithms for intra-CDN operations.

- Support for Transparent Caching across CDNs.

- New applications consuming CDNI logs.

- Digital Right Management (DRM) mechanisms.

The CDNI WG will work with other IETF WGs to assess, and where
appropriate, leverage protocols developed by those WGs, in order to
realize the CDNI requirements and CDNI interfaces. For example, the WG
may assess the suitability of the ALTO protocol as a protocol to enable
downstream CDNs to exchange information which may aid an upstream CDN
with making CDNI request routing decisions. The CDNI WG will also
coordinate with relevant groups outside the IETF, if and where