Much tuning can be done in the lower layers of the OSI model, but there is also much that can be done in the higher levels, such as the application layer. HTTP 1.1 is the standard protocol used today on the Web, but is slowly being replaced with the new HTTP/2 standard.
Google started a couple of years ago with creating a protocol called SPDY that is a multiplexing, binary protocol. Much of the work that was started there was ported into HTTP/2, now being worked on by the IETF.
Today, most web servers already support HTTP/2:
Nginx
Apache
IIS Windows Server 2016
It also has the benefit of using GZIP or deflate on the transmission headers, which allows for less overhead; since the protocol is pure binary transmission data, it is not directly readable and is much easier to send across the wire. This of course requires a browser that supports HTTP/2, but the latest versions of Google Chrome, Internet Explorer, Microsoft Edge, and Firefox support this already.