Rackspace CDN concepts

To use the Rackspace CDN API effectively, you should understand several key concepts.

Content delivery network

A content delivery network (CDN) is a system of multiple computers that contains copies of data stored at various network nodes. A CDN is designed to improve performance of publicly distributed assets. Assets can be anything from website content, to web application components, to media such as videos, ads, and interactive experiences.  CDNs decrease the load time of these assets by caching them on edge nodes, also called edge servers or point of presence (PoPs) servers.  Edge nodes are distributed around the globe, so requests travel to a local location to get assets rather than to and from a data center based far from the end user.

Point of presence

A point of presence (PoP) is the point at which two or more different networks or communication devices build a connection with each other. PoP mainly refers to an access point, location, or facility that connects to and helps other devices establish a connection with the Internet.

Edge node

CDN providers have many points of presence (PoP) servers around the world. These servers are known as edge nodes. These edge nodes cache the content and serve it directly to customers, thus reducing transit time to a customer’s location.

Edge server

An edge server is the same as an edge node.

Domain

A domain represents the domain name through which visitors retrieve content. The underlying site might be served through a CDN. A service can have multiple domains. The CDN provider provides users with a Canonical Name (CName) to specify for their domain name as an alias.

Origin

An origin is an address (IP or domain) from which the CDN provider pulls content. A service can have multiple origins.

Flavor

A flavor is a mapping configuration to a CDN provider that enables you to decide which CDN features that you want your service to use. In the request and response examples for Rackspace CDN, the flavor is referred to with the flavor_id parameter. For this release of Rackspace CDN, the flavor_id value is cdn. The cdn flavor enables your service content to be delivered across the network using the Rackspace CDN partner, Akamai. In the future, Rackspace might offer other flavors.

Service

A service represents an application that has its content cached to the edge nodes.

Status

The status indicates the current state of a service. The time it takes for a service configuration to be distributed to a CDN provider cache can vary.

Purge

Purging removes content from the edge nodes thus invalidating the content so that the content can be refreshed from your origin servers. Currently in Rackspace CDN, purges require the URL of the file to purge; use of wildcards is not in effect.

Caching rule

A caching rule provides you with fine-grained control over the time-to-live (TTL) of an object. When the TTL expires for an object, the edge node pulls the object from the origin again.

Restriction

A restriction enables you to define rules about who can or cannot access content from the cache. An example of a restriction is allowing requests only from certain domains based on HTTP Referrer headers.