SSD8-1
.docYour score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
6.
The load offered to a network is the aggregate data rate at which the hosts connected to it attempt to send data. When the offered load increases by 20%, the amount of data successfully transported
may decrease by more than 30%
may decrease by less than 30%
may increase by less than 30%
(a) I, II, and III
(b) II and III only
(c) III only
(d) I and II only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
7.
TCP provides reliability in the presence of packet losses by
(a) congestion control
(b) acknowledgment timeouts
(c) end-to-end flow control
(d) multiple routes for each packet
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
When an expected acknowledgment has not arrived within a time period, a packet is retransmitted, on the assumption that the data packet was lost. See section 2.1.3 of the course notes.
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8.
A surveillance camera is connected to a computer that sends video frames to a remote site where multiple such cameras are monitored. The video stream uses the TCP transport protocol. When the network experiences congestion
the receiver should adjust the frame playback rate
the sender should adjust the frame capture rate
TCP automatically adjusts the video frame transmission rate
(a) I, II, and III
(b) II only
(c) I and II only
(d) III only
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 2.1.5 of the course notes.
--------------------------------------------------------------------------------
9.
The Pittsburgh Supercomputing Center and the San Diego Supercomputing Center are linked to the Internet via very high-speed lines (in 1999, about 622 Mbps). Separated by about 4,000 Km and several routers, the network installers measured the round trip time between these two sites to be about 50 milliseconds. You want to exchange a large data set between two very fast computers at these sites. The physical network capacity and/or speed of the computers limit the maximum TCP throughput to be about 50 million bytes per second under ideal circumstances. The operating system of the sending computer has allocated 500 Kbytes to the TCP protocol that manages the exchange. The systems administrator then increases this allocation to 2.5 Mbytes. Which of the following are certain to ensue?
Throughput increases
Sender's transmission window grows
Receiver's transmission window shrinks
(a) I and II only
(b) I, II, and III
(c) II only
(d) none
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
The window size may be constrained by congestion, not merely by the capacity of the two hosts involved. The sending host might already be consuming much less than the initially allocated 500 Kbytes. See section 2.1.4 of the course notes.
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10.
The Transmission Control Protocol (TCP) differs from the User Data Protocol (UDP) in that
TCP is connection-oriented
TCP needs to manage buffer space
TCP addresses are a pair (IP address, port number)
(a) III only
(b) I, II, and III
(c) I only
(d) I and II only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
1.
You are charged with setting up the technology required to transmit a video-conference over an IP-based internetwork. You will have to implement a sending and a receiving application. Where will you handle network congestion?
(a) In the sending application only
(b) In neither the sending nor receiving application, because late-arriving video frames are of no use
(c) In neither the sending nor receiving application, because TCP takes care of it
(d) In both the sending and receiving applications
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.5 of the course notes.
--------------------------------------------------------------------------------
2.
In today's Internet, a TCP address is
(a) a 32-bit integer and a process number
(b) a 32-bit integer and a "port" number
(c) a 32-bit integer and an application name
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
3.
A TCP implementation that uses a sliding window for flow control has a coding error that causes it to calculate a window size greater than the ideal. What are some of the likely effects of this error?
Unnecessarily idle network links
Unnecessary packet losses
Greater memory usage in routers
(a) II only
(b) I, II, and III
(c) II and III only
(d) I only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
4.
Computer A has just received a TCP segment with a header that has the values 1500 and 1501 in the ACK and sequence number fields, respectively, from computer B. From this, we know that computer B is waiting for sequence number
(a) 1501
(b) 1500
(c) 1499
(d) 1502
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
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5.
Which of the following functions can the transport layer provide to applications?
End-to-end flow control
Packet forwarding
Congestion control
(a) II and III only
(b) I, II, and III
(c) I only
(d) I and III only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
6.
Most postal systems allow customers to request a receipt notification, by which the Postal Service promises to notify the sender when the letter has been delivered to the recipient. This makes the postal system
a reliable network services provider
a reliable transport services provider
a datagram network service provider
(a) II only
(b) III only
(c) I and III only
(d) I only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
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7.
A transport protocol entity determines that the underlying network is able to deliver 100 of its packets every second. Each of these packets contains 1,500 bytes (including transport headers). In addition, the time elapsed between the transmission of a packet and the reception of its acknowledgement is 3 seconds on the average. An efficient and smooth flow would require that the sliding window size be no less than approximately
(a) 600 packets
(b) 34 packets
(c) 100 packets
(d) 300 packets
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
8.
A 4-port Internet router has been designed with enough buffer space and CPU power to service its four links at their maximum capacity. Which of the following is(are) sufficient to keep the router from becoming congested?
Neighboring routers are similarly designed.
All ports have comparable throughput and latency.
Links to other routers have neither interference nor any losses.
(a) II and III only
(b) none
(c) I and II only
(d) I, II, and III
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
9.
TCP packets may be lost
when the sender runs out of buffer space
when a router runs out of buffer space
when the subnet, running IP, is congested
(a) II and III only
(b) I, II, and III
(c) III only
(d) II only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
10.
The Pittsburgh Supercomputing Center and the San Diego Supercomputing Center are linked to the Internet via very high-speed lines (in 1999, about 622 Mbps). Separated by about 4,000 Km, and several routers, the network installers measured the round trip time between these two sites to be about 50 milliseconds. You want to exchange a large data set between two very fast computers at these sites. The physical network capacity and/or speed of the computers limit the maximum TCP throughput to be about 50 million bytes per second under ideal circumstances. Assuming the channel is free of interference and that very few packets, if any, are dropped, how much memory would you allocate for a TCP connection at the sender in order to maximize throughput without spending money unnecessarily?
(a) a few kilobytes, enough to hold one packet and one acknowledgment
(b) a few megabytes
(c) as much as possible
(d) none
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
1.
A surveillance camera is connected to a computer that sends video frames to a remote site where multiple such cameras are monitored. The video stream uses the TCP transport protocol. When the network experiences congestion
the receiver should adjust the frame playback rate
the sender should adjust the frame capture rate
TCP automatically adjusts the video frame transmission rate
(a) I, II, and III
(b) I and II only
(c) III only
(d) II only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.5 of the course notes.
--------------------------------------------------------------------------------
2.
Which of the following apply to the transport protocol (e.g., TCP) but not to the network-layer protocol (e.g., IP)?
It need not be connection-oriented.
It cannot guarantee, by itself, that data is received completely and without errors.
It is only executed at the sender and receiver, not within the network infrastructure of routers and switches.
(a) II and III only
(b) I and II only
(c) II only
(d) III only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1 of the course notes.
--------------------------------------------------------------------------------
3.
The load offered to a network is the aggregate data rate at which the hosts connected to it attempt to send data. When the offered load increases by 20%, the amount of data successfully transported
may decrease by more than 30%
may decrease by less than 30%
may increase by less than 30%
(a) I, II, and III
(b) III only
(c) I and II only
(d) II and III only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
4.
Most postal systems provide a "COD" service, by which the recipient pays for goods when she picks them up at the post office. For the sender and seller, this incurs a delay in payment between the time the goods are sent and the time the post office returns the customer's payment. In a sense, during this period, the seller is loaning money to the buyer. To limit its credit liability, the seller typically limits the number of COD packages that are outstanding to a particular customer. This means that after ordering N items, the customer may be unable to order any more until at least one of the N items has arrived and been paid for. What would you call N now that you are a networking expert?
(a) Maximum Transfer Unit (MTU)
(b) Retransmit timeout
(c) Sliding window size
(d) Store-and-forward buffer
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
5.
You have just written an implementation of a transport protocol. You have aggressively pursued performance. For example, all acknowledgments are piggybacked on top of regular data packets, in order to minimize their overhead. When your company releases your product, however, you get the following complaint:
(a) Many packets are retransmitted many times even though the network is idle.
(b) Packet headers have doubled in size, thereby halving the expected performance gains.
(c) ARP responses take a lot longer than before.
(d) Many more packets than before fail to reach the receiving host.
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
6.
In designing a network protocol stack, the end-to-end argument would suggest that
(a) a feature should be implemented in as low a layer as possible
(b) all network devices should support all protocols
(c) each endpoint in a connection is a peer in the protocol
(d) a feature should be implemented in as high a layer as possible
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 2.1 of the course notes.
(c) While true, this is not the end-to-point argument
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7.
Computer A has just received a TCP segment with a header that has the values 1500 and 1501 in the ACK and sequence number fields, respectively, from computer B. From this, we know that computer B is waiting for sequence number
(a) 1502
(b) 1499
(c) 1501
(d) 1500
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
8.
Two programs execute in different computers and communicate through a TCP connection. Which of the following is certain when an IP packet supporting this connection successfully reaches the network interface of the receiving host?
Its payload data will be delivered to the receiving process.
An acknowledgment will be issued from the receiving to the sending computer.
The sending host will move its sliding window forward.
(a) II and III only
(b) II only
(c) I, II, and III
(d) none
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 2.1.1 of the course notes.
(c) The acknowledgment may fail to reach the sending computer, in which case the data will not be delivered.
--------------------------------------------------------------------------------
9.
In today's Internet, a TCP address is
(a) a 32-bit integer and a "port" number
(b) a 32-bit integer and an application name
(c) a 32-bit integer and a process number
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
10.
TCP packets may be lost
when the sender runs out of buffer space
when a router runs out of buffer space
when the subnet, running IP, is congested
(a) II and III only
(b) II only
(c) I, II, and III
(d) III only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
1.
You are charged with setting up the technology required to transmit a video-conference over an IP-based internetwork. You will have to implement a sending and a receiving application. Where will you handle network congestion?
(a) In neither the sending nor receiving application, because late-arriving video frames are of no use
(b) In both the sending and receiving applications
(c) In the sending application only
(d) In neither the sending nor receiving application, because TCP takes care of it
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.5 of the course notes.
--------------------------------------------------------------------------------
2.
An open-loop approach to network congestion may
drop packets
deny connection requests
dynamically adapt to network conditions
(a) I and III only
(b) I and II only
(c) III only
(d) none
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
3.
A transport protocol entity determines that the underlying network is able to deliver 100 of its packets every second. Each of these packets contains 1,500 bytes (including transport headers). In addition, the time elapsed between the transmission of a packet and the reception of its acknowledgement is 3 seconds on the average. An efficient and smooth flow would require that the sliding window size be no less than approximately
(a) 300 packets
(b) 100 packets
(c) 600 packets
(d) 34 packets
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
4.
In a network that is mostly used for HTTP (Web) traffic, which of the following is a reasonable approach to minimizing the amount of wasted bandwidth?
(a) Populate routers with more memory than they will ever need.
(b) Have data sources send data as soon as it is available.
(c) Have data sources increase their sending rate until congestion is detected.
(d) Divide the available bandwidth equally among all connections.
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
5.
TCP packets may be lost
when the sender runs out of buffer space
when a router runs out of buffer space
when the subnet, running IP, is congested
(a) II only
(b) I, II, and III
(c) III only
(d) II and III only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
6.
An open-loop congestion prevention strategy that successfully prevents congestion in all circumstances
(a) piggybacks several acknowledgments into data traffic
(b) wastes available bandwidth
(c) changes packet timeouts depending on network conditions
(d) discards packets that arrive before packets with lower sequence numbers
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
7.
Which of the following apply to the transport protocol (e.g., TCP) but not to the network-layer protocol (e.g., IP)?
It need not be connection-oriented.
It cannot guarantee, by itself, that data is received completely and without errors.
It is only executed at the sender and receiver, not within the network infrastructure of routers and switches.
(a) I and II only
(b) II and III only
(c) II only
(d) III only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1 of the course notes.
--------------------------------------------------------------------------------
8.
What is the service that TCP provides but UDP does not?
(a) Addressing
(b) API provided to application layer
(c) Error detection using checksum
(d) Congestion control
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
9.
Most postal systems allow customers to request a receipt notification, by which the Postal Service promises to notify the sender when the letter has been delivered to the recipient. This makes the postal system
a reliable network services provider
a reliable transport services provider
a datagram network service provider
(a) II only
(b) I only
(c) I and III only
(d) III only
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
10.
The load offered to a network is the aggregate data rate at which the hosts connected to it attempt to send data. When the offered load increases by 20%, the amount of data successfully transported
may decrease by more than 30%
may decrease by less than 30%
may increase by less than 30%
(a) I and II only
(b) III only
(c) II and III only
(d) I, II, and III
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
1.
You have just written an implementation of a transport protocol. You have aggressively pursued performance. For example, all acknowledgments are piggybacked on top of regular data packets, in order to minimize their overhead. When your company releases your product, however, you get the following complaint:
(a) Many packets are retransmitted many times even though the network is idle.
(b) Packet headers have doubled in size, thereby halving the expected performance gains.
(c) Many more packets than before fail to reach the receiving host.
(d) ARP responses take a lot longer than before.
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
2.
The router designers of a well-known network equipment manufacturer are having an internal debate. Some of them want to add reliability to the network-layer protocol, because they have devised a way to do this without making the routers any more costly. Their manager likes this, because it will give the marketing department a powerful weapon in promoting the company's products. The manager has hired you to enumerate the technical benefits of the proposal. Which of the following does your list include?
Early detection and recovery of data loss and corruption
Better service to multi-media traffic
Elimination of TCP from routers
(a) I only
(b) II only
(c) I, II, and III
(d) III only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
3.
Two programs execute in different computers and communicate through a TCP connection. Which of the following is certain when an IP packet supporting this connection successfully reaches the network interface of the receiving host?
Its payload data will be delivered to the receiving process.
An acknowledgment will be issued from the receiving to the sending computer.
The sending host will move its sliding window forward.
(a) I, II, and III
(b) II and III only
(c) none
(d) II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
4.
The Transmission Control Protocol (TCP) differs from the User Data Protocol (UDP) in that
TCP is connection-oriented
TCP needs to manage buffer space
TCP addresses are a pair (IP address, port number)
(a) III only
(b) I only
(c) I and II only
(d) I, II, and III
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
5.
A TCP implementation that uses a sliding window for flow control has a coding error that causes it to calculate a window size smaller than the ideal. What are some of the likely effects of this error?
Unnecessarily idle network links
Unnecessary packet losses
Greater memory usage in routers
(a) II only
(b) II and III only
(c) I, II, and III
(d) I only
Correct answer is (d)
Your score on this question is: 0.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
6.
A new telephone company has approached your Internet provider's backbone operator with a new, flexible billing scheme. The phone company will periodically increase the capacity of the links needed by the backbone, at a price. The periodic increase will occur when the links are saturated beyond some threshold. This would be implemented by checking the network status every 10 minutes, and adjusting capacity if needed. The manager at your ISP is very happy about this, because it will entail which of the following?
No congestion ever again
Crystal-clear audio transmissions over the network
Ability to guarantee throughput for high-priority data
(a) III only
(b) I and III only
(c) none
(d) I only
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
Audio is affected by error rate and latency long before congestion becomes a problem. The throughput boost doesn't change the error rate or the latency and will probably increase the latter. Congestion is not exclusively a problem of link throughput: router or host buffer capacity and CPU power are relevant. Since congestion can still occur, a different mechanism will be needed to guarantee a certain quality of service. See section 2.1.4 of the course notes.
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7.
A TCP implementation that uses a sliding window for flow control has a coding error that causes it to calculate a window size greater than the ideal. What are some of the likely effects of this error?
Unnecessarily idle network links
Unnecessary packet losses
Greater memory usage in routers
(a) II only
(b) I only
(c) II and III only
(d) I, II, and III
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
--------------------------------------------------------------------------------
8.
The load offered to a network is the aggregate data rate at which the hosts connected to it attempt to send data. When the offered load increases by 20%, the amount of data successfully transported
may decrease by more than 30%
may decrease by less than 30%
may increase by less than 30%
(a) II and III only
(b) III only
(c) I and II only
(d) I, II, and III
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
--------------------------------------------------------------------------------
9.
Most postal systems provide a "COD" service, by which the recipient pays for goods when she picks them up at the post office. For the sender and seller, this incurs a delay in payment between the time the goods are sent and the time the post office returns the customer's payment. In a sense, during this period, the seller is loaning money to the buyer. To limit its credit liability, the seller typically limits the number of COD packages that are outstanding to a particular customer. This means that after ordering N items, the customer may be unable to order any more until at least one of the N items has arrived and been paid for. What would you call N now that you are a networking expert?
(a) Store-and-forward buffer
(b) Retransmit timeout
(c) Sliding window size
(d) Maximum Transfer Unit (MTU)
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
10.
TCP provides reliability in the presence of packet losses by
(a) congestion control
(b) acknowledgment timeouts
(c) end-to-end flow control
(d) multiple routes for each packet
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
When an expected acknowledgment has not arrived within a time period, a packet is retransmitted, on the assumption that the data packet was lost. See section 2.1.3 of the course notes.
1.
Computer A has just received a TCP segment with a header that has the values 1500 and 1501 in the ACK and sequence number fields, respectively, from computer B. From this, we know that computer B is waiting for sequence number
(a) 1499
(b) 1501
(c) 1502
(d) 1500
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
2.
Which of the following apply to the transport protocol (e.g., TCP) but not to the network-layer protocol (e.g., IP)?
It need not be connection-oriented.
It cannot guarantee, by itself, that data is received completely and without errors.
It is only executed at the sender and receiver, not within the network infrastructure of routers and switches.
(a) II only
(b) II and III only
(c) III only
(d) I and II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1 of the course notes.
--------------------------------------------------------------------------------
3.
What is the service that TCP provides but UDP does not?
(a) Addressing
(b) Error detection using checksum
(c) API provided to application layer
(d) Congestion control
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
4.
Most postal systems provide a "COD" service, by which the recipient pays for goods when she picks them up at the post office. For the sender and seller, this incurs a delay in payment between the time the goods are sent and the time the post office returns the customer's payment. In a sense, during this period, the seller is loaning money to the buyer. To limit its credit liability, the seller typically limits the number of COD packages that are outstanding to a particular customer. This means that after ordering N items, the customer may be unable to order any more until at least one of the N items has arrived and been paid for. What would you call N now that you are a networking expert?
(a) Maximum Transfer Unit (MTU)
(b) Store-and-forward buffer
(c) Sliding window size
(d) Retransmit timeout
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
5.
The Transmission Control Protocol (TCP) differs from the User Data Protocol (UDP) in that
TCP has lower overhead
TCP is a transport-layer protocol
TCP provides reliable transmission
(a) I and II only
(b) II and III only
(c) III only
(d) II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
6.
Computer A has just received a TCP segment with a header that has the values 1500 and 1501 in the ACK and sequence number fields, respectively, from computer B. The TCP segment has one byte of payload. From this, we know the following about the sequence number sendseqno that computer B will send next:
(a) sendseqno <= 1501
(b) sendseqno <= 1502
(c) sendseqno == 1502
(d) sendseqno == 1501
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
7.
As you access a remote Web site (as you are currently doing), a TCP segment is received from the Web server that advertises a receive window size of 20 Kbytes. From the round trip delay and recent history, your computer's TCP code decides to expand its congestion window to 15 Kbytes, in order to take advantage of an apparent improvement in network conditions. What TCP sending window size will be in effect in your computer at this point?
(a) 5 Kbytes
(b) 35 Kbytes
(c) 20 Kbytes
(d) 15 Kbytes
Correct answer is (d)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
--------------------------------------------------------------------------------
8.
Because of a faulty routing table, a network provider is temporarily unable to successfully deliver packets from host B to host A, even though packets from A to B experience no problems. This malfunction lasts 15 minutes. At the time the malfunction occurred, the TCP entity at host A was sending a large file to host B. Which of the following is true of the packets that had not yet been sent to B?
(a) No packets will reach B.
(b) All packets will reach B normally.
(c) Some packets will reach B, but most will not.
(d) All packets will reach B at a degraded rate.
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
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9.
A TCP implementation that uses a sliding window for flow control has a coding error that causes it to calculate a window size greater than the ideal. What are some of the likely effects of this error?
Unnecessarily idle network links
Unnecessary packet losses
Greater memory usage in routers
(a) I only
(b) II and III only
(c) II only
(d) I, II, and III
Correct answer is (c)
Your score on this question is: 0.00
Feedback:
See section 2.1.1 of the course notes.
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10.
TCP packets may be lost
when the sender runs out of buffer space
when a router runs out of buffer space
when the subnet, running IP, is congested
(a) I, II, and III
(b) II only
(c) III only
(d) II and III only
Correct answer is (a)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
1.
TCP packets may be lost
when the sender runs out of buffer space
when a router runs out of buffer space
when the subnet, running IP, is congested
(a) II and III only
(b) I, II, and III
(c) II only
(d) III only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.1 of the course notes.
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2.
The Pittsburgh Supercomputing Center and the San Diego Supercomputing Center are linked to the Internet via very high-speed lines (in 1999, about 622 Mbps). Separated by about 4,000 Km, and several routers, the network installers measured the round trip time between these two sites to be about 50 milliseconds. You want to exchange a large data set between two very fast computers at these sites. The physical network capacity and/or speed of the computers limit the maximum TCP throughput to be about 50 million bytes per second under ideal circumstances. Assuming the channel is free of interference and that very few packets, if any, are dropped, how much memory would you allocate for a TCP connection at the sender in order to maximize throughput without spending money unnecessarily?
(a) none
(b) a few megabytes
(c) as much as possible
(d) a few kilobytes, enough to hold one packet and one acknowledgment
Correct answer is (b)
Your score on this question is: 0.00
Feedback:
See section 2.1.1 of the course notes.
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3.
The load offered to a network is the aggregate data rate at which the hosts connected to it attempt to send data. When the offered load increases by 20%, the amount of data successfully transported
may decrease by more than 30%
may decrease by less than 30%
may increase by less than 30%
(a) II and III only
(b) III only
(c) I, II, and III
(d) I and II only
Correct answer is (c)
Your score on this question is: 10.00
Feedback:
See section 2.1.4 of the course notes.
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4.
The Transmission Control Protocol (TCP) differs from the User Data Protocol (UDP) in that
TCP is connection-oriented
TCP needs to manage buffer space
TCP addresses are a pair (IP address, port number)
(a) I only
(b) I and II only
(c) I, II, and III
(d) III only
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.
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5.
Most postal systems provide a "COD" service, by which the recipient pays for goods when she picks them up at the post office. For the sender and seller, this incurs a delay in payment between the time the goods are sent and the time the post office returns the customer's payment. In a sense, during this period, the seller is loaning money to the buyer. To limit its credit liability, the seller typically limits the number of COD packages that are outstanding to a particular customer. This means that after ordering N items, the customer may be unable to order any more until at least one of the N items has arrived and been paid for. What would you call N now that you are a networking expert?
(a) Maximum Transfer Unit (MTU)
(b) Sliding window size
(c) Retransmit timeout
(d) Store-and-forward buffer
Correct answer is (b)
Your score on this question is: 10.00
Feedback:
See section 2.1.3 of the course notes.