Layers that carry your message

Computing · Computer Systems · ages 17-18

Name ______________________ Date ____________

Where does HTTP belong?
- Internet
- Link
- Application
Which layers may one layer talk to directly?
- Every layer at once
- Only above and below
- Only the top app
What is the transport job that TCP does?
- Finding paths across nets
- Keeping delivery reliable
- Moving raw bits
A message travels down the sender stack. What happens at each layer?
- Each adds its wrapping
- Each deletes the message
- Each calls the user
What is the internet job that IP does?
- Serving web pages
- Finding paths
- Drawing app windows
The message climbs the receiver stack. What happens at each layer?
- Each strips and checks
- Each adds another wrapping
- Each rewrites the app
A packet vanishes and a student patches the app. Where is the real fix?
- In the app windows
- In the delivery layer resending it
- In deleting TCP
Cables swap to WiFi and pages still work. Why?
- Link changes leave upper layers untouched
- WiFi holds no protocols
- Apps rewrote themselves

Answer key

For grown-ups. Fold this page away before handing over the rest.

Application · HTTP serves the web, an app level job.
Only above and below · Narrow neighbours keep each promise simple.
Keeping delivery reliable · Transport keeps flows smooth above addressing.
Each adds its wrapping · Headers stack like envelopes inside envelopes.
Finding paths · Ask the job: paths mean internet layer.
Each strips and checks · Matching layers peel their own envelopes.
In the delivery layer resending it · Only the responsible layer should notice and resend.
Link changes leave upper layers untouched · Link changes leave upper layers untouched.