What is Facebook FNA?

Hello Experts,

What is Facebook FNA?
Does anyone have experience with it?

Hello.

Facebook Network Appliance (as known as FNA) is a content caching program.

It is a way ISPs have to to efficiently deliver static Facebook content from within their existing networks.

By doing it, the ISP can offload significant amount of Facebook content from its backbone network and vastly improve the Facebook user experience.

In practice, it means Switchs and Servers installed in ISP data centers.

What about other Applications?
Is it only useful for Facebook users?
How about Instagram/WhatsApp users (also from Facebook). Are they included in Cache?

Also: other Applications, like Google?
Does every Company has its Cache?