Networking Exam Questions and Answers

Posted on Feb 21, 2025 in Contemporary Music Composition

Midterm 1

1. Which of the following is an application layer service?

D) Remote log-in, File transfer and access, mail service.

2. You want to implement a mechanism that automates the IP configuration, including IP address, subnet mask, default gateway, and DNS information. Which protocol will you use?

C) DHCP.

3. Internet Control Message Protocol (ICMP):

A) Reports error conditions to the original source; the source must relate errors to individual application.

4. What technique is used for fragmentation?

One of the pieces that results when an IP gateway divides an IP datagram into smaller pieces for transmission across a network that cannot handle the original datagram size.

5. Correct use of packet switching?

The subdivision of information into individually addressed packets in conjunction with alternative routing arrangements enabled the transmission path to be altered in the event of congestion or individual link failure.

6. Which one of the following is not a function of the network layer?

a) routing
b) inter-networking
c) congestion control
d) none of the above

7. The 4-byte IP address consists of:

a) network address
b) host address
c) both (a) and (b)
d) none of the above

8. ICMP is primarily used for:

a) error and diagnostic functions
b) addressing
c) forwarding
d) none of the mentioned

9. Transport layer aggregates data from different applications into a single stream before passing it to:

a) network layer
b) data link layer
c) application layer
d) physical layer

10. User Datagram Protocol is called connectionless because:

a) all UDP packets are treated independently by the transport layer
b) it sends data as a stream of related packets

11. Which one of the following is NOT a function of the transport layer?

p>a) routing

12. Transport layer encapsulates data from:

c) application layer

Free Response

1. What is the difference between MAN and WAN?

A Metropolitan Area Network (MAN) is a large computer network that usually spans a city or a large campus. Its coverage area is of the order of 10km. A WAN is a network that covers an area larger than a single city or campus, such as across cities or countries. Its coverage area is of the order of 100km or 1000km.

2. What are common threats to network security? Mention at least three types.

  • Intrusion Problems/Access Attacks: This occurs when an unauthorized user attempts to access protected, sensitive, or confidential information.
  • Eavesdropping: This refers to unauthorized listening or intercepting of someone else’s private communication, data, or information.
  • Denial of Service (DoS) Attacks: DoS attacks prevent legitimate users of a system from accessing or using the resources, information, or capabilities of the system. It may be of the following types:
    • Denial of access to information: Such attacks cause deletion or modification of important information to a non-readable format.
    • Denial of access to applications: Such attacks make the applications unusable or unavailable for legitimate users of the system.
    • Denial of access to communications: Such attacks include cutting communication wires, jamming radio communications, or flooding a system with junk mail.

3. What is data encapsulation?

Data encapsulation is the mechanism of adding different layers of header information for processing purposes, along with source and destination addresses and parity checks, before data is transmitted across the network.

4. What are the four components of delay in networking?

  1. Processing Delay (dproc): Nodal processing, checking bit errors, and determining the output link.
  2. Queuing Delay
  3. Transmission Delay
  4. Propagation Delay

5. What is data encapsulation?

When data moves from the upper layer to the lower level of the TCP/IP stack (application/transport/network/link/physical), data + header.

6. What is the difference between an iterative and a recursive DNS query? What advantage does a recursive query have over an iterative query?

Iterative Query: The contacted server replies with the name of the server to contact. “I don’t know this name, but ask this server.”

Recursive Query: Puts the burden of name resolution on the contacted name server. This creates a heavy load at the upper levels of the hierarchy. The advantage is that the server holds most of the burden, rather than the client.

7. Why is Network Address Translation (NAT) used? What is a disadvantage of the NAT mechanism?

NAT is used for small networks to hide an outbound router IP into a new local subnet. It is used because of the limited number of IPv4 addresses. A disadvantage is being unable to directly connect to a computer’s IP since all computers on a network have the same outward-facing IP.

8. In TCP estimated RTT calculation, under what circumstances would choosing an Alpha value close to 1 be beneficial? Under what circumstances would choosing an alpha value close to 0 be beneficial?

Choosing an alpha close to 1 would let you better track estimated RTTs in sporadic network conditions and adjust the estimated RTT quickly for new samples. An alpha close to 0 would stick to a near-static RTT estimate. This would be useful in a situation where performance is usually the same, and you want to avoid outliers.

9. What is silly window syndrome in TCP flow control?

A response to poorly timed delays in flow control where too much time is spent acknowledging old information and responding to timeouts.

10. Find the error, if any, in the following IPv4 addresses:

a) 22.34.7.8.20
b) 75.45.279.14
c) 101000100.23.24.66

Answers:

A) 5 fields instead of 4
B) 279 goes over the maximum of 255 for an 8-bit value
C) 9 bits of binary, not 8

11. What is the difference between an iterative and a recursive DNS query?

An iterative query will ask every DNS where to go, back and forth, until it directly connects with the DNS it wants after forwarding. A recursive query passes the request upstream until a connection is found and then passed downstream to the request. A recursive query reduces the stress on your closest DNS by spreading the work to bigger, more robust DNS locations.

New Midterm

1) Which of the following is NOT a function of the application layer?

a) routing
b) flow-control
c) error-control
d) All of the above

2) Transport layer decapsulates data from___

a) network layer
b) data link layer
c) application layer
d) physical layer

3) User datagram protocol is called connectionless because:

a) all UDP packets are treated independently by the transport layer
b) it sends data as a stream of related packets
c) both (a) and (b)
d) none of the mentioned

4) The time required to examine the packet’s header and determine where to direct the packet is part of:

a) Transmission delay
b) Queuing delay
c) Nodal Processing delay
d) None of the above

5) If a packet size is 2500 bits and the rate at which a router can pump out packets is 5 Mega bits per second, then the transmission delay in milliseconds is:

a) 10 milliseconds
b) 500 microseconds
c) 1 second
d) None of the above

6) What is NOT true about a persistent HTTP connection?

a) multiple objects can be sent over a single TCP connection between client and server
b) downloading multiple objects must require multiple TCP connections
c) Takes lesser time than a non-persistent connection
d) all of the above

7) Which of the following 5 components must be part of a reliable data transfer protocol?

a) Checksum, Timer, Congestion control, Acknowledgement and Pipelining
b) Checksum, Timer, Sequence number, Acknowledgement and Pipelining
c) Checksum, Sequence number, Congestion control, Flow control and Acknowledgement
d) Timer, Sequence number, Congestion control, Flow control and Acknowledgement

8) In TCP, the size of the transmission window is the ___ of rwnd and cwnd.

a) Maximum
b) Sum
c) Minimum
d) Subtraction difference

9) TCP assigns a sequence number to each segment that is being sent. The sequence number for each segment is the number of the ____ byte carried in that segment.

a) First
b) Second
c) Middle
d) Last

10) In modern implementations of TCP, a retransmission occurs if the retransmission timer expires or ___ duplicate ACK segments have arrived.

a) One
b) Two
c) Three
d) Four

Free Response

1) What are the four components of delay in networking? Why does packet loss happen?

Nodal Processing, Queuing, Transmission, and Propagation delay. A router queue (aka buffer) has finite capacity. Packets arriving at a full queue will be dropped, resulting in packet loss. Packet loss can also happen due to link failure or node failure.

2) What are the differences between iterative and recursive DNS queries?

Iterative: Puts the burden of name resolution on the local DNS server. No or low load at upper levels of the hierarchy. No caching of DNS information in upper levels of the hierarchy.
Recursive: Puts the burden of name resolution on the contacted name server. Heavy load at upper levels of the hierarchy. Advantage of caching of DNS information in upper levels of the hierarchy.

3) Why do HTTP, SMTP, and FTP require TCP as the underlying transport layer process, while DNS uses UDP as the underlying transport layer process?

HTTP, SMTP, and FTP require a reliable packet transfer service. They are NOT “so-called best effort services.” TCP provides that reliability through transmission/ACK and retransmissions. DNS is a best-effort service protocol. As a result, DNS is satisfied with UDP. DNS requests have explicit responses in the application layer itself. So, no other acknowledgement is necessary at the transport layer.

4) Why is web-cache needed?

It reduces traffic on an institution’s access link, reduces response time for client requests, reduces load at the server (particularly for static content), and enables content providers to effectively deliver content.

5) What are the differences between TCP Congestion control and TCP flow control?

Congestion control is a method of ensuring that every TCP transmitter is accessing the network in a “fair” way without congesting or overwhelming the network links. Flow control is a method of ensuring that every TCP transmitter is transmitting in a “fair” way without congesting or overwhelming the TCP receiver’s buffer.

Quiz 1

1) Which one of the following is NOT part of the network protocol stack?

a) session layer
b) application layer
c) synchronization layer
d) link layer

2) Bluetooth is an example of a:

a) local area network
b) personal area network
c) virtual private network
d) none of the above

3) Which of the following is NOT a correct statement?

a) Router forwards packets
b) Router has multiple IP addresses
c) Routers build the backbone of the Internet
d) Routers examine packets up to the transport layer. Ans: (d)

4) The time required to examine the packet’s header and determine where to direct the packet is part of:

a) Transmission delay
b) Queuing delay
c) Nodal Processing delay
d) All of the above Ans: (c)

5) In the transfer of a file between a server and a client over four hops (links), if the transmission rates along the path are 40Mbps, 30Mbps, 20Mbps, and 10Mbps, the throughput of the connection between the server and client is:

a) 10Mbps
b) 20Mbps
c) 30Mbps
d) 40Mbps Ans: (a)

6) If a packet size is 1500 bits and the rate at which a router can pump out packets is 10 Mega bits per second, then the transmission delay is:

a) 10 milliseconds
b) 150 milliseconds
c) 150 microseconds
d) None of the above Ans: (c)

7) 1 GBps is equivalent to:

a) 8Gbps
b) 80 Gbps
c) 54 MBps
d) None of the above. Ans: (a)

8) In the layer hierarchy, as the data packet moves from the upper to the lower layers, headers are:

a) Added
b) Removed
c) Rearranged
d) Modified Ans: (a)

9) A set of rules that governs data communication is known as:

a) Protocols
b) Standards
c) RFCs
d) None of the above Ans: (a)

10) Multicasting communication is:

a) When a packet is sent from a single source to a single destination
b) When a packet is sent from a single source to multiple destinations
c) When a packet is sent from multiple sources to a single destination
d) None of the above Ans: (b)

Quiz 2

1) Network security is about:

a) preventing unauthorized reading of information
b) preventing unauthorized writing of information
c) making sure data is available in a timely manner when needed
d) all of the above Ans: (d)

2) Application layer protocol defines:

a) types of messages exchanged
b) message format, syntax, and semantics
c) rules for when and how processes send and respond to messages
d) all of the above Ans: (d)

3) The transport layer protocol serving HTTP for web browsing is:

a) RTP
b) TCP
c) UDP
d) all of the above Ans: (b)

4) What is NOT true about a persistent HTTP connection?

a) multiple objects can be sent over a single TCP connection between client and server
b) downloading multiple objects must require multiple TCP connections
c) Takes lesser time than a non-persistent connection
d) all of the above Ans: (b)

5) Which one of the following protocols delivers/stores mail to the receiver’s server?

a) post office protocol
b) internet mail access protocol
c) simple mail transfer protocol
d) file transfer protocol Ans: (c)

6) The domain name system is maintained by:

a) distributed database system
b) a single server
c) a single computer
d) all of the above Ans: (a)

7) DNS database contains:

a) name server records
b) hostname-to-address records
c) hostname aliases
d) all of the above Ans: (d)

8) FTP server listens for connection on port number:

a) 20
b) 21
c) 22
d) 25 Ans: (b)

9) What does the phrase “non-authoritative answer” in the nslookup output mean?

a) The information in the nslookup output is probably false
b) The information in the output was obtained from a server cache
c) The nslookup program is not finding any information at all
d) The nslookup program cannot find a name server to query Ans: (b)

10) By default, what type of query does nslookup do for a domain?

a) MX
b) A
c) CNAME
d) NX Ans: (b)

Quiz 3

1) Which of the following 5 components must be part of a reliable data transfer protocol?

a) Checksum, Timer, Congestion control, Acknowledgement and Pipelining
b) Checksum, Timer, Sequence number, Acknowledgement and Pipelining
c) Checksum, Sequence number, Congestion control, Flow control and Acknowledgement
d) Timer, Sequence number, Congestion control, Flow control and Acknowledgement

2) Assume a client is establishing communication with a server through a 3-way TCP handshake protocol. In this connection establishment phase, when the server is responding, which of the six flags (U, A, P, R, S, F) will be set by the server?

a. U and A
b. S
c. A and S
d. A and P

3) For the following event at the receiver, what would be the TCP receiver’s action?
Event: arrival of an out-of-order segment with a higher-than-expected sequence number. Gap detected.
TCP receiver action:

a) Delayed ACK. Wait up to 500ms for the next segment. If no next segment, send ACK.
b) Send cumulative ACK, ACKing both in-order segments, indicating the sequence number of the next expected byte.
c) Send duplicate ACK, indicating the sequence number of the next expected byte.
d) Do not take any action.

4) In TCP, the size of the transmission window is the ________ of rwnd and cwnd.

a) Maximum
b) Sum
c) Minimum
d) Subtraction difference

5) In the congestion detection algorithm, if detection is by a time-out, a new _______ phase starts.

a) slow start
b) congestion avoidance
c) congestion detection
d) none of the above

6) If the ACK value is 200, then byte _______ has been received successfully.

a) 200
b) 199
c) 201
d) None of the above

7) TCP is a(n) _______________ transport protocol.

a) protocol delivery
b) reliable
c) best-effort delivery
d) effortless delivery

8) TCP assigns a sequence number to each segment that is being sent. The sequence number for each segment is the number of the __________ byte carried in that segment.

a) first
b) second
c) middle
d) last

9) UDP and TCP are both ____________ layer protocols.

a) Application
b) Session
c) Presentation
d) Transport

10) A source or destination port address in a TCP segment is ________________ bits long.

a) 48
b) 32
c) 24
d) 16

Quiz 4

1) How many bytes of mandatory header are used in an IPv4 datagram?

a) 4 bytes
b) 20 bytes
c) 32 bytes
d) 16 bytes.

2) In a class C IP address, how many bits are used for the network part and how many bits are used for the host part?

a. 12, 20
b. 20, 12
c. 24, 8
d. 28, 4.

3) What are the leading two bits in a class B IP address?

a) 00
b) 01
c) 10
d) 11.

4) Your home network router address is 192.168.2.1. Which class is this IP address in?

a) B
b) C
c) D
d) None of the above.

5) The special IP address 255.255.255.255 is used for _______ purpose.

a) broadcasting
b) multicasting
c) unicasting
d) booting-up.

6) In addition to assigning an IP address, what other information is provided by DHCP?

a) Network mask
b) First hop router information
c) DNS server information
d) All of the above

7) NAT is controversial because:

a) NAT uses a forwarding table
b) NAT obscures the inside of the network from the outside
c) NAT reuses IP addresses
d) Routers should only process up to layer 3, but NAT routers process up to layer 4

8) How many bits are used by IPv6 for the source or destination IP address?

a) 128 bits
b) 256 bits
c) 512 bits
d) 1024 bits

9) Distance vector routing algorithm is an example of a:

a) Proactive Centralized routing algorithm
b) Proactive Decentralized routing algorithm
c) Reactive Centralized routing algorithm
d) Reactive Decentralized routing algorithm

10) Convert the IP address from binary to dotted decimal notation: 01111111.11111111.11111111.11111111

a) 192.168.1.1
b) 255.255.255.255
c) 127.1.1.1
d) 127.255.255.255

Quiz 5

Which route computation algorithm is used by the OSPF routing mechanism?

a) Bellman-Ford
b) Dijkstra
c) DSR
d) None of the above

5) For an IP address 191.54.38.207 with netmask 255.255.0.0 and subnet mask 255.255.255.224, what is the total number of subnets?

a) 256
b) 512
c) 1024
d) 2048

6) For an IP address 191.54.38.207 with netmask 255.255.0.0 and subnet mask 255.255.255.224, what is the number of hosts per subnet?

a) 30
b) 62
c) 126
d) 254

7) DSR algorithm is an example of a:

a. Proactive Centralized routing algorithm
b. Proactive Decentralized routing algorithm
c. Reactive Centralized routing algorithm
d. Reactive Decentralized routing algorithm

8) In the RIP algorithm, if no advertisement is heard from a neighbor after __ seconds, the neighbor/link is declared dead.

a) 30 sec
b) 60 sec
c) 180 sec
d) 360 sec

9) How many bits are used for the AS number field?

a) 1 bit
b) 8 bits
c) 16 bits
d) 64 bits

10) What is the mandatory header length of BGP packets?

a) 32 bytes
b) 19 bytes
c) 7 bytes
d) 1 byte

Quiz 6

1) How many bits are there in a MAC address?

a. 16 bits
b. 32 bits
c. 48 bits
d. 128 bits

2) Ethernet is a __ protocol.

a. Time division multiple access
b. Random access
c. Token ring
d. Frequency division multiple access

3) Which protocol helps us in resolving a MAC address given the host’s IP address?

a. IGMP
b. ICMP
c. DNS
d. ARP

4) Gigabit Ethernet has a data rate of __ Mbps.

a. 10
b. 100
c. 1000
d. 10000

5) Which of the following statements is correct?

a. Bridge is used to connect networks using IP layer mechanism
b. Hub has multiple separate collision domains
c. Hub uses buffers
d. Switch eliminates collisions

6) Which protocol helps us in managing multicast groups?

a. IGMP
b. ICMP
c. DNS
d. ARP

7) ARP requests and ARP replies are done using _ and __ communication mechanisms.

a. Unicasting; unicasting
b. Unicasting; broadcasting
c. Broadcasting; unicasting
d. Broadcasting; broadcasting

8) Membership in a VLAN can be based on:

a. Port numbers
b. MAC addresses
c. IP addresses
d. All of the above

9) A spanning tree is a graph in which there is no:

a. Node
b. Edge
c. Cycle
d. Root

Old Quiz 1

1) HTTP client requests by establishing a ___ connection to a particular port on the server.

a) user datagram protocol
b) transmission control protocol
c) broader gateway protocol
d) none of the mentioned.

2) Which of the following is not correct?

a) Web cache doesn’t have its own disk space
b) Web cache can act both like server and client
c) Web cache might reduce the response time
d) Web cache contains copies of recently requested objects.

3) If there are N routers between source to destination, total end to end delay in sending a packet of size L and with R bits/sec transmissions rate is:

a)L/R
b)(N*L)/R
c)((N+1)*L)/R
d)((N+2)*L)/R
Assume zero propagation delay, zero nodal delay and zero queuing delay.

4) I plan to start a company abc. I plan to have only one webserver (abc.com) for my company. The IP address of the Webserver is 198.132.55.1. I have my DNS server (dns.abc.com). The IP address of the DNS server is 212.212.212.1. What resource record (RR) information do I have to register into TLD server? (Hint: two rows of RR)

RR format: (name, value, type, ttl)
(abc.com, dns.abc.com, NS)
(dns.abc.com, 212.212.212.1, A)

Old Quiz 2

1) TCP is ____ protocol.

a) stream-oriented
b) message-oriented
c) block-oriented
d) none of the above

3) A special segment called a probe is sent by a sending TCP when the __ timer goes off.

a)transmission b)persistence c)keepalive d)none of the above. 4)A port address in UDP is __ bits long. a) 8 b)16 c)32 d)any of the above 5)UDP packets are encapsulated in __. a)an ethernet frame b)a TCP segment c)an IP datagramd)none of the above. OQuiz 3 2) In BGP, the ___ message is used by a router to withdraw destinations that have been advertised previously, or to announce a route to a new destination, or both. a) open b)update c) keepalive d) none of the above 3)BGP messagesare encapsulated in ___. a) TCP segments b) UDP user datagrams c) IP datagrams d) NOTA 4) What is prefix hijacking attack in BGP? When false BGP data is created which opens a vector for actions like routing table spamming,viewing, and intercepting traffic, or routing to a malicious destination 5)In the ____ tree approach, each router needs to have one shortest path tree for each group. a) group-shared b)source-based c) a or b) NOTA 6) RPF guarantees that each router receives only __ of the multicast packet. a) one copy b) two copies c) three copies d) none of the above. 7) In ___, the router forwards the received packet through only ones of its interface, while, in ___, the router may forward the received packet through some of its interfaces. a) unicasting, broadcasting b) broacasting, multicasting c) unicasting, multicasting, d) multicasting, broadcasting. 8) What is pruning in multicasting protocols? Messages sent upstream by routers which do not have hosts that belong to a group in a multicasting tree.Quiz 4 1)In ethernet addressing, if the least significant bit of the first byte is 0, the address is __. a)unicast b)multicast c)broadcasting d)NOA. 2)Two stations using ethernet protocol collided for 5 times in a row for a particular frame transmission. What will be the new random backoff range now?

(Hint:stations using ethernet protocol start backoff algorithm after 1st collision). a)[0,1] b)[0,15]c)[0,31]d[0,63] 3)Two stations using Wi-Fi protocol collided for 5 times in a row for a particular frame transmission. What will be the new random backoff range now?(Hint: stations using Wi-Fi protocol start backoff algorithm before 1st collision) a)[0,7] b)[0,63] c)[0,127]d)[0,255] 4)What MAC protocol does Wi-Fi use? a)CSMA/CD b)CSMA/CA c) Token ring d)Round-robin 5)State atleast one major difference between hub, switch, and router. Hub sends datagram to all connected divices. Switch are smart and send datagram to intended destination while avoiding collisions. Routers don’t look at link layer, create a route table from algorithm for best path.