DNS, HTTP & the Web

By the end, you can

• Identify the scheme, host, and path in any URL.
• Explain why a domain name is not the same as an IP address.
• Trace the DNS resolution steps from browser to recursive resolver through root, TLD, and authoritative servers.
• Describe the difference between a recursive DNS query and an iterative one, and explain how TTL-based caching makes DNS fast.
• Describe the TCP three-way handshake and explain what TLS adds on top.
• Read an HTTP request and response and identify their components (start line, headers, body).
• State what each of GET, POST, PUT, and DELETE does and which are idempotent.
• Classify a status code as success, redirect, client error, or server error from its hundreds digit.
• Explain how cookies let a stateless protocol maintain login sessions.
• Explain what HTTPS adds over plain HTTP and why certificates matter.
• Describe what a REST API is and how it reuses HTTP conventions.
• Recite the six-step journey from URL to rendered page in order.