Hi. Currently, UE4 built-in networking is client-server. It would be cool for UE4 to support peer to peer networking in blueprints. The advantage of Peer to Peer networking is that that a server is not required.
For a better performance, things could be instanced. For example, let's think of an online Hack n' Slash. You are in a map, and other player is in another map. That player streams to you minimal information, that he is in that map. When you get in the same map with him, you get more information, such as its coordonates. When you get more closer, you get even more information, like his equipment, level etc. In this way, the data streaming is minimal.
P2P system is currently used in various console games.
I have found a webpage in which people discuss various aspects on P2P networking:
Could P2P be implemented in Unreal Engine 4 ?