In the formal treatment by Beck, the hourglass model explains why a tightly constrained waist tends to maximize deployment scalability: a simple, general spanning layer lowers coordination costs for both implementers (below) and application developers (above).OverviewIn, the hourglass model—also called the narrow (or thin) waist—is a way of describing. The conceptual root of the hourglass is the idea of a, articulated by to mean the minimal common service that hides differences in lower layers and presents a uniform service to higher la. In the Internet hourglass, the waist historically corresponds to, with many link/network technologies below (e.g.,,, ) and many and above (e.g.,,. The hourglass model and the end-to-end principle are related but distinct. The end-to-end principle argues that many functions (e.g., correctness, security) must be provided by end systems to be complete and is ofte.
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