Abstraction, Federation, and Scalability

I've often mused about the properties of structures that make them scalable. Regularity is often an element, as in geodesic domes. Abstraction is another contributor. An example of this is the layered, hierarchical, and federated structure of the Internet. Sequences of bits (physical transmission) are organized into frames (link structure) that are organized into packets with header and payload structure. TCP organizes sequences of packets into “connections” that deliver abstract sequences of payload bytes (“octets”) and are organized into higher level abstractions. At each “level” of abstraction, the details become less visible, and emergent structure becomes apparent. Groups of computers (for example, routers) form Autonomous Systems (networks) that share a common property (an “internal gateway protocol” such as IS-IS and an “external gateway protocol” such as BGP4). Encapsulation hides the lowerlayer structure in the payload of a “higher”-layer structure.