Week 9 Reflection: Which Layer Failed First?

Choose one Week 9 failure: stale DNS, HTTP 503, hostname mismatch, or bad client time.

In 6–9 sentences, explain:

• which lower layers still worked;
• the first layer whose evidence failed;
• the strongest claim supported by that failure;
• one plausible but unsupported story you should reject;
• the corrective change; and
• why the final end-to-end retest is stronger than testing only the repaired layer.