Optimizing CDN Infrastructure for Live Streaming with Constrained Server Chaining

Content Delivery Networks (CDNs) are increasingly being used to deliver live streaming on today´s Internet. The new application type of live streaming exposes unique characteristics and challenges that require more advanced design of CDN infrastructure. Unlike traditional web-object delivering, which allows CDN content servers to cache contents and thus typically only involves certain CDN servers (e.g. edge content servers) for delivering contents, live streaming requires a real-time full CDN streaming path that spans across the streaming source, the CDN ingest server, the CDN content server, and end-viewers. Though the ingest server is typically fixed for a particular live stream, appropriate content servers need to be selected for delivering the stream to end viewers. Though today´s CDNs typically employ layered infrastructure for delivering live streaming, in this work, we propose a flat-layered design which is referred to as Constrained Server Chaining (CSC) for selecting optimal content servers to deliver live streams. Rather than employing a strictly layered infrastructure, CSC allows CDN streaming servers to dynamically choose upstream servers, thus saves transit cost for CDN providers.