UPDATE: As of mid-2018, Varnish now solely administers this product. You can get information on the latest capabilities and pricing here.
You use Varnish because you don't want your server regenerating the same dynamic content from scratch every time it gets accessed. Varnish handles requests before they make it to your backend, increasing offload and performance significantly.
You use Akamai to ensure that no matter where in the world your user is located, it feels like they are one hop away from your server. Akamai flattens the world.
In the past, putting these two technologies together sometimes resulted in duplicative work. For example, if you were setting cache TTL settings, you would set them once in the VCL ruleset, then configure another set of TTL rules for Akamai. This process poses multiple potential problems: cache settings not set correctly, human error, and time consumed in synchronization efforts.
The Akamai Connector for Varnish eases your life as a Varnish administrator or developer. Using the Connector, you can signal the effects of cache rule changes to Akamai automatically. Changes at the origin Varnish Cache server will take effect in real time. This also ensures that you are maximizing offload at multiple application tiers for better performance.
If you purge cacheable content locally, those changes will automatically be echoed back to Akamai. This is workflow you only need to build once, and it ensures that Akamai reflects any status change of a cached object as it changes at origin.
Finally, as you add sites to Akamai over time, it's easy to forget to enable the fundamental operational elements that unlock Akamai's power. These include ensuring persistent connections are timed correctly, the configuration of the SureRoute Test Object, and logging of the IP address that is contacting the Edge server. The Connector will perform tests to ensure all of these items (and more ) are properly configured.
And did I mention that the Connector is FREE if you're an Akamai customer? The Connector marks the beginning of a new way of thinking about how origin infrastructure and CDN's can cooperate more closely with one another. Using the two technologies together ensures you are maximizing offload and providing the absolute best experience for your users, wherever they are.