Physical Models

{:.def} A physical model is a representation of the underlying hardware elements of a distributed system that abstracts away from specific details of the computer and networking technologies involved.

Baseline model: an extensible set of computer nodes interconnected by a network for the required passing of messages.

Three generations of distributed systems:

  1. Early distributed systems:
    • 10-100 nodes on a LAN
    • openness not a primary concern
  2. Internet-scale distributed systems
    • began to emerge in the 90s
    • physical model is an extensible set of nodes interconnected by a network of networks
    • led to increasing emphasis on open standards/middleware
  3. Contemporary distributed systems
    • today’s physical models include mobile nodes such as laptops and smartphones
    • ubiquitous computing has led to architectures where computers are embedded in the surrounding environment
    • cloud computing has led to a move from autonomous nodes to a pool of provider nodes for a given service

This evolution has resulted in a significant increase in heterogeneity of devices and variation in networking technologies.