Sharing one link without overload

Computing · Networks & Security · ages 18-20

Name ______________________ Date ____________

A sender repeats the additive-increase, multiplicative-decrease rule. What pattern does its sending rate show over time?
- A small rise, a sharp fall, and another rise
- A flat line that never changes its height
- A single jump that stays at the top
In a loss-based congestion-control model, what does a packet loss tell the sender?
- That the path may be congested
- That the receiver has deleted the message
- That the sender should increase its rate
While packets arrive without a congestion signal, the sender raises its rate.
Circle one: True False
One sender never backs off while the rest follow the rule. What happens?
- The queue stays empty because no sender needs to slow
- Polite senders gain capacity when one sender ignores backoff
- The shared queue fills, so other senders see worse service and delay
Losses arrive during probing. What action matches the model?
- Raise the rate at once and keep it high
- Keep sending at the same rate until queues clear
- Cut the rate, then increase it in small steps
Why call loss a signal rather than only a fault?
- It tells the sender to inspect the screen
- It carries information about possible congestion
- It proves that the network cable is broken
A lone sender that ignores backoff harms only itself on a shared link.
Circle one: True False
All senders double their rates after each loss instead of cutting. What happens?
- Queues become smaller because senders add pressure
- Queues grow and service worsens for all senders
- Each sender receives a guaranteed larger share

Answer key

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

Sharing one link without overload W1-mt_y5hPUrdKyq-s1

A small rise, a sharp fall, and another rise · Small increases followed by larger cuts make a repeating sawtooth pattern.
That the path may be congested · The model uses loss as a possible congestion signal, so the sender backs off.
True · The sender probes upward while traffic gets through.
The shared queue fills, so other senders see worse service and delay · A sender that keeps pushing can occupy more queue space, leaving other senders with worse service.
Cut the rate, then increase it in small steps · The model cuts quickly after a congestion signal and then probes upward slowly.
It carries information about possible congestion · In this model, loss changes the sender's estimate of path load and triggers backoff.
False · Its extra queue use leaves less room for other senders and can raise delay and loss for them.
Queues grow and service worsens for all senders · If every sender adds pressure after a loss, the shared queue fills further. The link has not gained capacity, so queues grow and service worsens for all senders.