Word Meaning
What does ACK mean?
A) "Got it, it's good"
B) "Got it, but broken"
C) "Nothing came back"
D) "Send it again"
A - ACK is the "got it, it's good" reply.
You open a letter and the ink has run. Half the words are missing.
A) ACK
B) NAK
C) TIMEOUT
D) Ignore it
B - The letter arrived but is unreadable, so it's broken.
You ordered pizza. You waited 45 minutes. The doorbell never rang.
A) ACK
B) NAK
C) TIMEOUT
D) Complain!
C - No doorbell = nothing came back in time.
A box arrives perfect, but it's the same box #2 you already opened earlier. What do you send?
A) Never reply
B) ACK again
C) NAK
D) TIMEOUT
B - The sender may not have heard your first ACK, so confirm again.
Why does the sender need a timer at all?
A) To look busy
B) Because silence could mean the box was lost OR the reply was lost
C) To slow things down
D) To count the boxes
B - Silence is ambiguous — it could be a lost box or a lost reply, so a timer forces action.
What does NAK mean?
A) "Nothing came back"
B) "Got it, but it's broken"
C) "Got it, it's good"
D) "Send it again"
B - NAK means it arrived but is broken.
A parcel arrives in perfect condition, and the objects inside are exactly what you ordered.
A) NAK
B) TIMEOUT
C) ACK
D) Ignore it
C - Perfect parcel = "got it, it's good."
You ship a glass lamp. The customer sends back a photo of it shattered.
A) ACK
B) NAK
C) TIMEOUT
D) Complain!
B - Customer says broken = a NAK came back.
Box #7 shows up before box #6. Under our class rule, what do you send?
A) ACK
B) NAK
C) TIMEOUT
D) Ignore it
B - Out of order = NAK.
If ACKs were never lost, would the sender still need to resend sometimes?
A) Yes — the box itself can still be lost
B) No, never
C) Only for big boxes
D) Only if the sender wants to
A - Even with perfect ACKs, the box itself can still be lost, so resending is still needed.
What is a timeout?
A) When the box arrives twice
B) When the sender waits and gets no reply
C) When the box arrives broken
D) When the receiver says "got it"
B - Timeout = the sender waited and got nothing back.
You order a book. It arrives with pages torn out.
A) ACK
B) TIMEOUT
C) Complain!
D) NAK
D - Pages torn out = arrived but damaged.
You call a friend. It rings and rings. Nobody picks up.
A) ACK
B) NAK
C) TIMEOUT
D) Ignore it
C - Nobody picks up = silence, so timeout.
You sent box #3. The ACK for box #3 finally arrives — but you already resent it twice. What do you do now?
A) Resend a third time
B) Stop resending, it arrived
C) Send a NAK
D) Wait for another timeout
B - The ACK proves it arrived, so you're done.
An ACK arrives for a box you sent long ago, after you already resent it. If the sender kept resending forever, what's the problem?
A) Nothing at all
B) The same box gets sent over and over, wasting time
C) The timer breaks
D) The receiver gets faster
B - Endless resending wastes time and effort on a box that already arrived.
What does "retransmit" mean?
A) Send it again
B) Throw it away
C) Wait forever
D) Open the box
A - Retransmit = send it again.
Someone hands you a note that's clean, clear, and says exactly what you expected.
A) NAK
B) ACK
C) TIMEOUT
D) Ignore it
B - Clean and correct = ACK.
You get a "it's broken" card for box #4. What do you do?
A) Send box #4 again
B) Send box #5
C) Stop sending
D) Send a NAK back
A - A NAK means that box was broken, so resend it.
The sender is waiting for an ACK. The ACK was sent, but it got lost on the way back. What does the sender end up doing?
A) Knows the ACK was lost
B) Gets a timeout and resends
C) Sends a NAK
D) Nothing at all
C - You can't accept it right now, so say it's not good.
Why can the receiver end up with two copies of the same box even when the sender did nothing wrong?
A) Boxes copy themselves
B) The ACK got lost, so the sender resent it
C) The timer made a copy
D) The receiver copied it for fun
B - A lost ACK makes the sender resend, so the receiver sees two copies.
What is a "frame"?
A) The timer
B) The reply card
C) One numbered chunk of data sent as a unit
D) The person receiving
C - A frame is one numbered chunk of data.
You get a voice message, but it's all static. You can't make out a single word.
A) ACK
B) Complain!
C) NAK
D) TIMEOUT
C - Static means you got it but couldn't read it.
You send a letter asking for a reply. Weeks pass. Your mailbox stays empty.
A) ACK
B) NAK
C) TIMEOUT
D) Ignore it
C - Empty mailbox = no reply, so timeout.
You're the receiver. Box #9 arrives perfectly, but your hands are full and you can't take it. What do you send?
A) ACK
B) Ask for help
C) NAK
D) TIMEOUT
B - The sender never learns the ACK was lost, so it times out and resends.
Two senders wait for ACKs. One uses a very short timer, one uses a long timer. Which one is more likely to waste effort resending something that actually arrived?
A) The long timer
B) The short timer
C) Both the same
D) Neither
B - A short timer fires too early and resends things that were actually fine.