As a matter of fact, when I started writing this post I titled it “Layer 4 of the OSI Model – understanding the application layer,” and then I had to go back and correct myself.

At its core, CSOI introduces a software-defined networking (SDN)-based layer between the transport and network layers of the OSI stack. CSOI calls this the “3.5 layer” out of the seven layers of the ...

It’s important to understand that the TCP Reference Model doesn’t really concern itself with the OSI Model. With TCP traffic, the connections are established at the transport layer.

1. In the OSI model, data flows down the transmit layers, over the physical link, and then up through the receive layers.