export_week 6

Question 1

The Internet Protocol (IP) header may be 21 bytes long.

Answer 1

False

Question 2

The process of determining a path through the internet is called

Answer 2

routing

Question 3

The process of moving a datagram from a router’s input port to output port is called

Answer 3

forwarding

Question 4

When a host in a network needs to obtain a valid IP address for itself, it broadcasts a “discover” message that can be handled by a server, which will “offer” an IP address within the correct domain.

Answer 4

Dynamic Host Configuration Protocol (DHCP)

Question 5

IP datagrams fragments can not be fragmented again.

Answer 5

False

Question 6

The path MTU is the largest MTU on a path from sender to receiver

Answer 6

False

Question 7

A group of hosts sharing a common address prefix, behind a router, is called a/an

Answer 7

subnet

Question 8

Re-assembly of fragmented IP datagrams is handled by…

Answer 8

the destination host

Question 9

In a subnet, the reserved addresses are the and the (with a highest subnet IP address).

Answer 9

• subnet address

* broadcast address

Question 10

if an IP datagram is fragmented into 1000-byte fragments, and later encounters a link with an 800-byte MTU, it is dropped.

Answer 10

False

Question 11

In a fragmented IP datagram, the “offset” IP header field value is exactly equal to the number of bytes of fragmented data preceding this fragment.

Answer 11

False

Question 12

It is the responsibility of a routing algorithm to determine the cost of an output link.

Answer 12

False

Question 13

The transport-layer header is encapsulated in the first fragmented IP datagram.

Answer 13

True

Question 14

It is the responsibility of a routing algorithm to forward packets to the appropriate output link.

Answer 14

False

Question 15

When a destination host’s IP fragment timer expires, it drops all accumulated fragments corresponding to that timer.

Answer 15

True

Question 16

In network graph terminology, [a] represent routers.

Answer 16

Nodes

Question 17

ICMP can carry messages from… (Check all that apply)

Answer 17

Router to Sender Host

Router to Router

Source Host to Destination Host

Destination Host to Source Host

Question 18

Given an internet represented as a weighted undirected graph, the shortest path between node X and node Y is the path that…

Answer 18

has the smallest sum of edge weights.

Question 19

The largest amount of data, in bytes, which can be accomodated by a particilar network, link, or physical-layer is called the [a].

Answer 19

Maximum Transmission Unit (MTU)

Question 20

Flow control is intended primarily to _____________

Answer 20

a. keep a TCP sender from overwhelming a receiver’s buffer

Question 21

A _________ -type retransmission protocol will retransmit all un-ACK’d segments upon a countdown timer interrupt.

Answer 21

a. Go-back-N

Question 22

Which of the following are fields in the TCP header? (Select all that apply)

Answer 22

Source Port  
 Destination Port  
 Header Length/Data Offset  
 Window Size  
 Checksum  
 Sequence Number

Question 23

Which of the following are fields in the UDP header? (Select all that apply)

Answer 23

Checksum
Length
Destination Port
Source Port

Question 24

The TCP sequence numbers are used to implement ___________.

Answer 24

a. in-order delivery

Question 25

UDP uses an additive-increase multiplicative-decrease (AIMD) system to manage flows.

Answer 25

False

Question 26

In ____________ congestion control, congestion is detected based on delayed and/or dropped packets.

Answer 26

host-inferred

Question 27

What are some possible consequences of network-core congestion? (Check all that apply)

Answer 27

Out-of-order packet arrival  
 Increased network congestion  
 Dropped Packets  
 Network collapse  
 Delayed packets

Question 28

UDP has a congestion control mechanism.

Answer 28

False

Question 29

In _______ congestion control, flags may be set during transit which indicate the presence and/or level of congestion in certain portions of the network.

Answer 29

network-assisted

Question 30

What are some causes of network congestion? (Check all that apply)

Answer 30

Parallel TCP Connections.  
 High utilization.  
 Reliable Data Transfer schemes.  
 Dropped TCP Packets.  
 Typical Internet Usage.

Question 31

TCP implements network fairness indirectly.

Answer 31

True

Question 32

In ________ congestion control, flags may be set during transit which indicate the presence and/or level of congestion in certain portions of the network.

Answer 32

network-assisted

Question 33

UDP implements network fairness.

Answer 33

False

Question 34

For the following binary IP address, give the dotted-decimal representation:

10011000 11101110 10011101 11000011

Answer 34

152.238.157.195

Question 35

A network with a connection-oriented network layer is called a ___________.

Answer 35

virtual circuit network

Question 36

What can cause queueing at a router’s input ports? (Check all that apply)

Answer 36

a. Head of Line blocking.
c. Output port contention.
d. Slow outbound link transmission rate.

Question 37

The process of determining a path through the internet is called ________.

Answer 37

routing

Question 38

In a subnet, there are ___ reserved IP addresses.

Answer 38

2

Question 39

A group of hosts sharing a common address prefix, behind a router, is called a/an ______.

Answer 39

subnet

Question 40

The Internet Protocol (IP) implements flow control.

Answer 40

False

Question 41

The Internet Protocol (IP) header may be 28 bytes long.

Answer 41

True

Question 42

Routing would be more complicated if we used hardware addresses as network addresses.

Answer 42

True

Question 43

What can cause packet queueing at a router’s output port? (Check all that apply)

Answer 43

Slow outbound link transmission rate.

Multiple data flows requiring the same outbound link.

Question 44

What are some possible consequences of network-core congestion? (Check all that apply)

Answer 44

Dropped Packets  
 Network collapse  
 Out-of-order packet arrival  
 Increased network congestion  
 Delayed packets

Question 45

Put the steps in the most correct order for closing a TCP Connection.

Answer 45

1. Client sends segment with FIN bit set
2. Server sends ACK of received segment
3. Server sends segment with FIN bit set
4. Client sends ACK of received segment

Question 46

Arrival of out-of-order segment with higher-than-expected sequence number.

Answer 46

Immediately send duplicate ACK, indicating sequence number of next expected byte.

Question 47

Pipelining is intended primarily to

Answer 47

Increase network utilization

Question 48

Retransmitting a missing segment before the segment’s countdown timer expires is called…

Answer 48

fast retransmission

Question 49

What is the minimum UDP header size?

Answer 49

8 bytes

Question 50

What is the minimum TCP header size?

Answer 50

20 bytes

Question 51

Arrival of in-order segment with expected sequence number. All data up to expected sequence number already acknowledged.

Answer 51

Delayed ACK. Wait up to 500ms for arrival of another in-order segment. If next in-order segment does not arrive in this interval, send an ACK.

Question 52

Select the proper equation for TCP’s calculation of the Timeout Interval.

Answer 52

TimeoutInterval = EstimatedRTTn + 4 * DevRTTn

Question 53

Max TCP

Answer 53

60 bytes