Which layers do these "system level approaches" operate?

In Kurose' Computer Networking book:

9.5 Network Support for Multimedia

In Sections 9.2 through 9.4, we learned how application-level mechanisms such as client buffering, prefetching, adapting media quality to available bandwidth, adap- tive playout, and loss mitigation techniques can be used by multimedia applications to improve a multimedia application’s performance. We also learned how content distribution networks and P2P overlay networks can be used to provide a system- level approach for delivering multimedia content. These techniques and approaches are all designed to be used in today’s best-effort Internet. Indeed, they are in use today precisely because the Internet provides only a single, best-effort class of service. But as designers of computer networks, we can’t help but ask whether the network (rather than the applications or application-level infrastructure alone) might provide mechanisms to support multimedia content delivery. As we’ll see shortly, the answer is, of course, “yes”! But we’ll also see that a number of these new
network-level mechanisms have yet to be widely deployed. This may be due to their complexity and to the fact that application-level techniques together with best-effort service and properly dimensioned network resources (for example, bandwidth) can indeed provide a “good-enough” (even if not-always-perfect) end-to-end multimedia delivery service.

Is "system level" some layer in the Internet Protocol stack or the OSI model? If yes, which layer?

In which layers in the Internet Protocol stack or the OSI model do the following "system level approaches" respectively operate

• content distribution networks
• P2P overlay networks?

Thanks.