PART 2 - FOUR HIDDEN CHIMNEYS CHAPTER 10: BUILDING-BLOCK REALITY Blocks Tend to Stick Around

"Widespread deployment and Internet ossification make the IP service model harder to evolve, and changes must account for existing TCP/IP applications."

RFC 6250 explicitly says Internet ossification makes the IP model harder to evolve and that changes must be made carefully because a huge number of business-critical applications already use TCP/IP.

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