I use NRF24L01 chips from time to time. It’s a low-cost radio with small power consumption. That is why these chips are really useful for communications between IoT devices. NRF24L01 exposes an interface for low-level communications between two chips. Sometimes it’s enough, but the other tasks require higher-level network protocols like TCP. Recently I’ve found an inspiring post that explains how to set up a TCP/IP stack over NRF24L01. The author had developed nrfnet — an application that creates virtual interface on Raspberry PI and uses NRF24L01 as a backend for data transmission. The speed of such connection is not too high, but it allows to use software like SSH or web server.
The nrfnet project looks like a proof of concept that connects two Raspberry PI nodes. I’ve found a more mature project about NRF24L01 Networking — TMRh20. It comprises a plenty of libraries that allow to create a network of Internet enabled RF24/Arduino sensors by providing an API similar to the Arduino Ethernet library. If you are interested in this subject, you should definitely take a look at TMRh20s Project Blog.