Flow Control

Question 1

Some packets might be _____ or _______ during transmission

Answer 1

Lost, Corrupted

Question 2

Combination of two mechanisms for reliable transmission

Answer 2

Acknowledgements and timeouts

Question 3

Acknowledgement(ACK)

Answer 3

A small control frame that a protocol sends back to its peer saying that it has received an earlier frame

Question 4

Timeout

Answer 4

The action of awaiting for a reasonable amount of time before retransmitting original frame(in case no ACK is received)

Question 5

Two primary methods of flow control

Answer 5

Stop and Wait
Sliding window

Question 6

Stop and wait ARQ consists of three parts

Answer 6

Stop and Wait
Timeout Timer
Sequence number

Question 7

Main shortcoming of the stop and wait algorithm

Answer 7

It allows the sender to have only one outstanding frame on the link at a time
The sender should wait till it gets an ACK of previous frame before it sends the next frame
As a result, it wastes a substantial amount of network bandwidth

Question 8

In sliding window flow control name three variables that sender maintains.

Answer 8

Sender Window Size[SWS] - Upper bound on the number of unacknowledged frames that the sender hopes to transmit
LAR - sequence number of the last acknowledgment received.
LFS- Sequence number of the last frame sent

Question 9

In sliding window flow control name three variables that receiver maintains.

Answer 9

Receiver Window Size[SWS] - Upper bound on the number of out-of-order frames that the receiver is willing to accept.
LAF - sequence number of the largest acceptable frame
LFR - Sequence number of the last frame received.

Question 10

When an acknowledgment arrives, the sender moves __________ to the right,
thereby allowing the sender to transmit another frame

Answer 10

LAR

Question 11

Sender maintains the following invariant(Inequality)

Answer 11

LFS−LAR ≤ SWS