On the ‘net: Networking Models

I’m writing a series on network models over at Packet Pushers; links to the first three are below.

Looking back at my career in network engineering, beyond some basic concepts and naming conventions, I cannot remember using the OSI model once. I have used the concept of layering, but never the OSI model specifically.

First, models are not sacrosanct. A model is just a tool. If the model you are using is not working for you, feel free to modify it. I find simpler yet extensible models far more effective than complex models for channeling my thoughts. In the past I have tried building huge models that “put everything in one place,” but they do not work for me.

How does a host differ from a middlebox? Hosts are designed to run applications that create and consume packets rather than quickly forwarding traffic through the network. The primary difference is that the source and destination are not two different ports on the same device but rather a virtual interface representing an application and a physical interface.