As a content provider evaluating your delivery strategy, it can be advantageous to use multiple content delivery network (CDN) providers and dynamically route clients to the most appropriate CDN. Still, a multi-CDN architecture has significant challenges in implementation.

Observability is complex when each CDN vendor has a proprietary interface for configuring logging and telemetry, offering different fields, formats, and methods of transport. Differences in supported feature sets lead to complexity in configuration, resulting in lengthy projects to onboard each vendor. Traffic delegation becomes a complicated problem when multiple CDNs with overlapping footprints can all serve the same customer, and you are forced to make a selection before routing.

Open Caching is a non-proprietary specification published by the Streaming Video Technology Alliance [1] based on the Content Delivery Network Interconnection (CDNI) standards of the IETF [2]. It provides interfaces for observability including logging and telemetry, well-defined methods for delegation of traffic, triggers to support content management operations, and enables interoperation between content providers and CDNs using a common configuration language. These pillars form an open platform which enable a multi-CDN strategy, including the use of deep edge networks, but may still require additional aggregation to avoid undue implementation burden as discussed with potential solutions in our recent paper from SCTE TechExpo 2024:  “The Multi-CDN Dilemma: Aggregated Edge Networks at Scale” [3].

Vecima’s MediaScale Open CDN implements the Open Caching specifications at global scale, presenting a unified footprint of the underlying deep edge delivery networks. Content providers can reduce cost and management burden while increasing Quality of Experience (QoE), putting their focus on providing a winning customer experience instead of worrying about delivery, and service providers can ease congestion in their own networks while finding a new source of revenue.

Observability is key to providing your customers a high-quality service, and logging is a core component of that visibility. The newly published Open Caching Logging Specification [4] defines a common interface for configuring, transforming, and delivering CDN access logs with support for a variety of common protocols and formats.

The specification covers several essential use cases for CDN access logs: billing, operational monitoring, and deep-dive troubleshooting. To support this, there is an extensive set of well-defined log record fields organized into three record types. Additionally, it is possible to configure inclusion of arbitrary HTTP header fields into the log records to gain visibility of values not defined in the specification. Entirely custom fields are not yet supported but will be available in a future revision of the specification.

Before delivery, it is often necessary to transform and enrich log data via a processing pipeline, and the specification provides for a set of field-level transformation operations, including regular expression search/replace, truncation, URL operations to alter paths and strip query parameters, IP masking, as well as encoding, hashing, and encryption. With encryption, sensitive PII can be protected, and the encryption keys can be securely delivered to the appropriate party via mechanisms in the configuration interface for delivery of protected secrets. These fields must then be collated into the selected format of JSON, CSV, whitespace, or protobuf.

Figure 1: Logging Transformation and Delivery [3, Sec. 4.1]

Log records may be packaged into several file formats, referred to in the specification as containers. These include JSON, newline delimited, and protobuf, as well as archives (tarballs) that can contain multiple log files. In the case of streaming delivery via Kafka, there is no containing file, and the records are delivered directly within Kafka messages. Options exist to define how the files are produced, based on maximum size and time period, and to name files with a variety of template parameters allowing identification of the logging source or other metadata.

After packaging, the files must be delivered. The specification allows for both pushing logs from the downstream CDN to the upstream consumer or allowing the consumer to fetch the logs from an endpoint provided by the CDN, using SFTP, S3 buckets, Kafka, or HTTP.

Operations teams can utilize these logs to inform their traffic delegation strategy, gain insight into CDN performance, and troubleshoot delivery issues. By taking advantage of the Open Caching Logging Specification, they can configure all their downstream CDNs in a uniform way and receive logs in a common format, simplifying their own ingest pipeline. Combined with the full spectrum of Open Caching interfaces, a true multi-CDN delivery strategy starts to look realistic.

To implement your delivery strategy, consider Vecima’s MediaScale Open CDN solution. Open CDN brings your content all the way to the deepest parts of the network, positioning caches near your subscribers for substantially improved QoE. Reduce your integration burden with an Open Caching-compliant interface that provides easy configuration, observability, and routing while minimizing delivery cost.

For more information about MediaScale Open CDN, vecima.com/content-distribution/open-cache.

References

[1] “Streaming Video Technology Alliance.” SVTA. https://www.svta.org/ (accessed Oct. 3, 2024).
[2] “Content Delivery Networks Interconnection (cdni).” IETF Datatracker. https://datatracker.ietf.org/wg/cdni/documents/ (accessed Oct. 3, 2024).
[3] B. Rosenblum and N. Dunkin, “The Multi-CDN Dilemma: Aggregated Edge Networks at Scale,” presented at SCTE TechExpo 2024, Atlanta, GA, USA, September 24-26 2024.
[4] “SVTA2050: Open Caching Logging Specification.” SVTA. https://www.svta.org/product/svta2050/ (accessed Oct. 3, 2024).