🔠 Distributed Systems Terminology

• Network layers
  • Application layer: email via SMTP, web via HTTP, file transfer via FTP, etc.
  • Transport layer: TCP, UDP, etc.
  • Rest don’t matter for this course
• Heterogeneity: can a single system handle a variety of types of machines and devices
• Robustness: is the system resilient to failures
• Availability: are servers always up and running for clients
• Transparency: can system hides internal workings well
  • Opposite of english definition lol
• Concurrency: can server SIMULTANEOUSLY handle multiple clients
• Efficiency: does server serve clients fast enough
• Scalability: can server scale to handle MORE clients without slowing down service

🌐 HTTP

• Application layer protocol allowing server-client communication via requests & responses

• HTTP uses TCP to establish connection between server-client, closed at the end

  

• Highlighted part = fetching which can be done 2 ways

  • Persistent: multiple object fetched over same TCP connection
    • Ex: webpage text, webpage image 1, webpage image 2, etc.
  • Non-persistent: only one object fetched over one TCP connection
    • Needs multiple connections for multiple objects on the same webpage

• HTTP is stateless: information about previous connections not maintained