Traffic Control is a CDN control plane. It is made up of a suite of applications which are used to configure, manage, and direct client traffic to a tiered system of HTTP caching proxy servers (herein referred to as cache servers). In principle, a CDN may be implemented with any HTTP caching proxy. The caching software chosen for Traffic Control is Apache Traffic Server. Although the current release supports only ATS as a cache server implementation, this may change with future releases.
Traffic Control was first developed at Comcast for internal use and released to Open Source in April of 2015. Traffic Control moved into the Apache Incubator in August of 2016.
Traffic Control implements the elements illustrated in green in the diagram below.
- Traffic Ops
Traffic Ops stores the configuration of cache servers and CDN Delivery Services. It also serves the Traffic Ops API which can be used by tools, scripts, and programs to access and manipulate CDN data.
- Traffic Router
Traffic Router is used to route client requests to the closest healthy cache server by analyzing the health, capacity, and state of the cache servers according to the Health Protocol and relative geographic distance between each Cache Group and the client.
- Traffic Monitor
Traffic Monitor does health polling of the cache servers on a very short interval to keep track of which servers should be kept in rotation.
- Traffic Stats
Traffic Stats collects and stores real-time traffic statistics aggregated from each of the cache servers. This data is used by the Traffic Router to assess the available capacity of each cache server which it uses to balance traffic load and prevent overload.
- Traffic Portal
Traffic Portal is a web interface which uses the Traffic Ops API to present CDN data and the controls to manipulate it in a user-friendly interface.
New in version 2.2: As of Traffic Control 2.2, this is the recommended, official UI for the Traffic Control platform. In Traffic Control 3.x, the Traffic Ops UI has been deprecated and disabled by default, and it will be removed with the release of Traffic Control 4.0.
- Traffic Vault
Traffic Vault is used as a secure key/value store for SSL private keys used by other Traffic Control components.