The Protocols: IPv4, IPv6, and IPSec

Thinking about how the evolution of networking has driven the fundamental features of Policy Routing brings up the subject of the other foundations of networking: the protocols. As with many of the facets of modern life, you seldom stop to consider the fundamental building blocks. And yet these fundamentals funnel your actions in many ways.

Consider the way in which an actual information exchange takes place under IPv4. "Ah-hah," you shout, "Are you using TCP or UDP?" "Neither," I will reply, but thanks for asking. The point not so subtly made is that the mere definition of the protocol in question defines the mechanism of communications. As you well know, TCP shakes hands whereas UDP could care less.

But ...

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