laboursonline – MCQs, Mock Tests | Gate GATE STUDY MATERIAL /NETWORKING SET 2

The minimum frame size required for a CSMA/CD based computer network running at 1 Gbps on a 200m cable with a link speed of 2 × 10^8m/s is

1. 120 bytes
2. 60 bytes
3. 240 bytes
4. 90 bytes

✅ Correct Answer: 1

The minimum frame size required for a CSMA/CD based computer network running at 1 Gbps on a 200m cable with a link speed of 2 × 10^8m/s is

1. 125 bytes
2. 250 bytes
3. 500 bytes
4. None of these

✅ Correct Answer: 2

Consider a source computer(S) transmitting a file of size 106 bits to a destination computer(D)over a network of two routers (R1 and R2) and three links(L1, L2, and L3). L1connects S to R1; L2 connects R1 to R2; and L3 connects R2 to D.Let each link be of length 100 km. Assume signals travel over each link at a speed of 108 meters per second.Assume that the link bandwidth on each link is 1Mbps. Let the file be broken down into 1000 packets each of size 1000 bits. Find the total sum of transmission and propagation delays in transmitting the file from S to D?

1. 1005 ms
2. 1010 ms
3. 3000 ms
4. 3003 ms

✅ Correct Answer: 1

One of the header fields in an IP datagram is the Time to Live(TTL)field.Which of the following statements best explains the need for this field?

1. It can be used to prioritize packets
2. It can be used to reduce delays
3. It can be used to optimize throughput
4. It can be used to prevent packet looping

✅ Correct Answer: 4

For which one of the following reasons does Internet Protocol (IP) use the time-to- live (TTL) field in the IP datagram header

1. Ensure packets reach destination within that time
2. Discard packets that reach later than that time
3. Prevent packets from looping indefinitely
4. Limit the time for which a packet gets queued in intermediate routers

✅ Correct Answer: 3

Consider the following three statements about link state and distance vector routing protocols, for a large network with 500 network nodes and 4000 links. [S1] The computational overhead in link state protocols is higher than in distance vector protocols. [S2] A distance vector protocol (with split horizon) avoids persistent routing loops, but not a link state protocol. [S3] After a topology change, a link state protocol will converge faster than a distance vector protocol. Which one of the following is correct about S1, S2, and S3 ?

1. S1, S2, and S3 are all true
2. S1, S2, and S3 are all false
3. S1 and S2 are true, but S3 is false
4. S1 and S3 are true, but S2 is false

✅ Correct Answer: 4

Which one of the following is TRUE about interior Gateway routing protocols - Routing Information Protocol (RIP) and Open Shortest Path First (OSPF)?

1. RIP uses distance vector routing and OSPF uses link state routing
2. OSPF uses distance vector routing and RIP uses link state routing
3. Both RIP and OSPF use link state routing
4. Both RIP and OSPF use distance vector routing

✅ Correct Answer: 1

An IP machine Q has a path to another IP machine H via three IP routers R1, R2, and R3. Q—R1—R2—R3—H H acts as an HTTP server, and Q connects to H via HTTP and downloads a file. Session layer encryption is used, with DES as the shared key encryption protocol. Consider the following four pieces of information: [I1] The URL of the file downloaded by Q [I2] The TCP port numbers at Q and H [I3] The IP addresses of Q and H [I4] The link layer addresses of Q and H Which of I1, I2, I3, and I4 can an intruder learn through sniffing at R2 alone?

1. Only I1 and I2
2. Only I1
3. Only I2 and I3
4. Only I3 and I4

✅ Correct Answer: 3

Host A (on TCP/IP v4 network A) sends an IP datagram D to host B (also on TCP/IP v4 network B). Assume that no error occurred during the transmission of D. When D reaches B, which of the following IP header field(s) may be different from that of the original datagram D? (i) TTL (ii) Checksum (iii) Fragment Offset

1. (i) only
2. (i) and (ii) only
3. (ii) and (iii) only
4. (i), (ii) and (iii)

✅ Correct Answer: 4

Classless Inter-domain Routing (CIDR) receives a packet with address 131.23.151.76. The router’s routing table has the following entries: Prefix Output Interface Identifier 131.16.0.0/12 3 131.28.0.0/14 5 131.19.0.0/16 2 131.22.0.0/15 1 The identifier of the output interface on which this packet will be forwarded is ______.

1. 1
2. 2
3. 3
4. 5

✅ Correct Answer: 1

Classless Inter-domain Routing (CIDR) receives a packet with address 131.23.151.76. The router’s routing table has the following entries: Prefix Output Interface Identifier 131.16.0.0/12 3 131.28.0.0/14 5 131.19.0.0/16 2 131.22.0.0/15 1 The identifier of the output interface on which this packet will be forwarded is ______.

1. 1
2. 2
3. 3
4. 5

✅ Correct Answer: 1

Every host in an IPv4 network has a 1-second resolution real-time clock with battery backup. Each host needs to generate up to 1000 unique identifiers per second. Assume that each host has a globally unique IPv4 address. Design a 50-bit globally unique ID for this purpose. After what period (in seconds) will the identifiers generated by a host wrap around?

1. 128
2. 64
3. 256
4. 512

✅ Correct Answer: 3

An IP router with a Maximum Transmission Unit (MTU) of 1500 bytes has received an IP packet of size 4404 bytes with an IP header of length 20 bytes. The values of the relevant fields in the header of the third IP fragment generated by the router for this packet are

1. MF bit: 0, Datagram Length: 1444; Offset: 370
2. MF bit: 1, Datagram Length: 1424; Offset: 185
3. MF bit: 1, Datagram Length: 1500; Offset: 37
4. MF bit: 0, Datagram Length: 1424; Offset: 2960

✅ Correct Answer: 1

Two computers C1 and C2 are configured as follows. C1 has IP address 203.197.2.53 and netmask 255.255.128.0. C2 has IP address 203.197.75.201 and netmask 255.255.192.0. which one of the following statements is true?

1. C1 and C2 both assume they are on the same network
2. C2 assumes C1 is on same network, but C1 assumes C2 is on a different network
3. C1 assumes C2 is on same network, but C2 assumes C1 is on a different network
4. C1 and C2 both assume they are on different networks

✅ Correct Answer: 3

Station A needs to send a message consisting of 9 packets to Station B using a sliding window (window size 3) and go-back-n error control strategy. All packets are ready and immediately available for transmission. If every 5th packet that A transmits gets lost (but no acks from B ever get lost), then what is the number of packets that A will transmit for sending the message to B?

1. 12
2. 14
3. 16
4. 18

✅ Correct Answer: 3

The address resolution protocol (ARP) is used for

1. Finding the IP address from the DNS
2. Finding the IP address of the default gateway
3. Finding the IP address that corresponds to a MAC address
4. Finding the MAC address that corresponds to an IP address

✅ Correct Answer: 4

In a packet switching network, packets are routed from source to destination along a single path having two intermediate nodes. If the message size is 24 bytes and each packet contains a header of 3 bytes, then the optimum packet size is:

1. 4
2. 6
3. 7
4. 9

✅ Correct Answer: 4

The routing table of a router is shown below: Destination Sub net mask Interface 128.75.43.0 255.255.255.0 Eth0 128.75.43.0 255.255.255.128 Eth1 192.12.17.5 255.255.255.255 Eth3 default Eth2 On which interfaces will the router forward packets addressed to destinations 128.75.43.16 and 192.12.17.10 respectively?

1. Eth1 and Eth2
2. Eth0 and Eth2
3. Eth0 and Eth3
4. Eth1 and Eth3

✅ Correct Answer: 1

Which of the following assertions is FALSE about the Internet Protocol (IP) ?

1. It is possible for a computer to have multiple IP addresses
2. IP packets from the same source to the same destination can take different routes in the network
3. IP ensures that a packet is discarded if it is unable to reach its destination within a given number of hops
4. The packet source cannot set the route of an outgoing packets; the route is determined only by the routing tables in the routers on the way

✅ Correct Answer: 4

Routers forward a packet using forwarding table entries. The network address of incoming packet may match multiple entries. How routers resolve this?

1. Forward it the the router whose entry matches with the longest prefix of incoming packet
2. Forward the packet to all routers whose network addresses match
3. Discard the packet
4. Forward it the the router whose entry matches with the longest suffix of incoming packet

✅ Correct Answer: 1

Which one of the following fields of an IP header is NOT modified by a typical IP router?

1. Checksum
2. Source address
3. Time to Live (TTL)
4. Length

✅ Correct Answer: 2

In the network 200.10.11.144/27, the fourth octet (in decimal) of the last IP address of the network which can be assigned to a host is ________.

1. 158
2. 255
3. 222
4. 223

✅ Correct Answer: 1

If a Company require 60 hosts then What is the best possible subnet mask?

1. 255.255.255.0
2. 255.255.255.192
3. 255.255.225.224
4. 225.225.255.240

✅ Correct Answer: 2

In class C , if subnet mask is 255.255.255.224, then calculates number of subnet?

1. 6
2. 8
3. 4
4. None of the Above

✅ Correct Answer: 1

A subnet has been assigned a subnet mask of 255.255.255.192. What is the maximum number of hosts that can belong to this subnet?

1. 14
2. 30
3. 62
4. 126

✅ Correct Answer: 3

A host is connected to a Department network which is part of a University network. The University network, in turn, is part of the Internet. The largest network in which the Ethernet address of the host is unique is:

1. the subnet to which the host belongs
2. the Department network
3. the University network
4. the Internet

✅ Correct Answer: 4

In TCP, a unique sequence number is assigned to each

1. byte
2. word
3. segment
4. message

✅ Correct Answer: 1

Which of the following objects can be used in expressions and scriplets in JSP (Java Server Pages) without explicitly declaring them?

1. session and request only
2. request and response only
3. response and session only
4. session, request and response

✅ Correct Answer: 4

In the TCP/IP protocol suite, which one of the following is NOT part of the IP header?

1. Fragment Offset
2. Source IP address
3. Destination IP address
4. Destination port number

✅ Correct Answer: 4

Suppose that the maximum transmit window size for a TCP connection is 12000 bytes. Each packet consists of 2000 bytes. At some point of time, the connection is in slow-start phase with a current transmit window of 4000 bytes. Subsequently, the transmitter receives two acknowledgements. Assume that no packets are lost and there are no time-outs. What is the maximum possible value of the current transmit window?

1. 4000 bytes
2. 8000 bytes
3. 10000 bytes
4. 12000 bytes

✅ Correct Answer: 2

Traceroute reports a possible route that is taken by packets moving from some host A to some other host B. Which of the following options represents the technique used by traceroute to identify these hosts

1. By progressively querying routers about the next router on the path to B using ICMP packets, starting with the first router
2. By requiring each router to append the address to the ICMP packet as it is forwarded to B. The list of all routers en-route to B is returned by B in an ICMP reply packet
3. By ensuring that an ICMP reply packet is returned to A by each router en-route to B, in the ascending order of their hop distance from A
4. By locally computing the shortest path from A to B

✅ Correct Answer: 1

Count to infinity is a problem associated with

1. link state routing protocol
2. distance vector routing protocol
3. DNS while resolving host name
4. TCP for congestion control

✅ Correct Answer: 2

In a communication network, a packet of length L bits takes link L1 with a probability of p1or link L2 with a probability of p2. Link L1 and L2 have bit error probability of b1 and b2 respectively. The probability that the packet will be received without error via either L1 or L2 is

1. (1 - b1)Lp1 + (1 - b2)Lp2
2. [1 - (b1 + b2)L]p1p2
3. (1 - b1)L (1 - b2)Lp1p2
4. 1 - (b1Lp1 + b2Lp2)

✅ Correct Answer: 1

A company has a class C network address of 204.204.204.0. It wishes to have three subnets, one with 100 hosts and two with 50 hosts each. Which one of the following options represents a feasible set of subnet address/subnet mask pairs?

1. 204.204.204.128/255.255.255.192 204.204.204.0/255.255.255.128 204.204.204.64/255.255.255.128
2. 204.204.204.0/255.255.255.192 204.204.204.192/255.255.255.128 204.204.204.64/255.255.255.128
3. 204.204.204.128/255.255.255.128 204.204.204.192/255.255.255.192 204.204.204.224/255.255.255.192
4. 204.204.204.128/255.255.255.128 204.204.204.64/255.255.255.192 204.204.204.0/255.255.255.192

✅ Correct Answer: 4

Assume that "host1.mydomain.dom" has an IP address of 145.128.16.8. Which of the following options would be most appropriate as a subsequence of steps in performing the reverse lookup of 145.128.16.8? In the following options "NS" is an abbreviation of "nameserver".

1. Query a NS for the root domain and then NS for the "dom" domains
2. Directly query a NS for "dom" and then a NS for "mydomain.dom" domains
3. Query a NS for in-addr.arpa and then a NS for 128.145.in-addr.arpa domains
4. Directly query a NS for 145.in-addr.arpa and then a NS for 128.145.in-addr.arpa domains

✅ Correct Answer: 3

An IP datagram of size 1000 bytes arrives at a router. The router has to forward this packet on a link whose MTU (maximum transmission unit) is 100 bytes. Assume that the size of the IP header is 20 bytes. The number of fragments that the IP datagram will be divided into for transmission is :

1. 0
2. 50
3. 12
4. 13

✅ Correct Answer: 4

Which of the following statements is TRUE ?

1. Both Ethernet frame and IP packet include checksum fields
2. Ethernet frame includes a checksum field and IP packet includes a CRC field
3. Ethernet frame includes a CRC field and IP packet includes a checksum field
4. Both Ethernet frame and IP packet include CRC fields

✅ Correct Answer: 3

Two popular routing algorithms are Distance Vector(DV) and Link State (LS) routing. Which of the following are true? (S1) Count to infinity is a problem only with DV and not LS routing (S2) In LS, the shortest path algorithm is run only at one node (S3) In DV, the shortest path algorithm is run only at one node (S4) DV requires lesser number of network messages than LS

1. S1, S2 and S4 only
2. S1, S3 and S4 only
3. S2 and S3 only
4. S1 and S4 only

✅ Correct Answer: 4

Host X has IP address 192.168.1.97 and is connected through two routers R1 and R2 to another host Y with IP address 192.168.1.80. Router R1 has IP addresses 192.168.1.135 and 192.168.1.110. R2 has IP addresses 192.168.1.67 and 192.168.1.155. The netmask used in the network is 255.255.255.224. Given the information above, how many distinct subnets are guaranteed to already exist in the network?

1. 1
2. 2
3. 3
4. 6

✅ Correct Answer: 3

The transport layer protocols used for real time multimedia, file transfer, DNS and email, respectively are:

1. TCP, UDP, UDP and TCP
2. UDP, TCP, TCP and UDP
3. UDP, TCP, UDP and TCP
4. TCP, UDP, TCP and UDP

✅ Correct Answer: 4

Consider an instance of TCP’s Additive Increase Multiplicative Decrease (AIMD) algorithm where the window size at the start of the slow start phase is 2 MSS and the threshold at the start of the first transmission is 8 MSS. Assume that a timeout occurs during the fifth transmission. Find the congestion window size at the end of the tenth transmission.

1. 8 MSS
2. 14 MSS
3. 7 MSS
4. 12 MSS

✅ Correct Answer: 3

A layer-4 firewall (a device that can look at all protocol headers up to the transport layer) CANNOT

1. block entire HTTP traffic during 9:00PM and 5 :0OAM
2. block all ICMP traffic
3. stop incoming traffic from a specific IP address but allow outgoing traffic to the same IP address
4. block TCP traffic from a specific user on a multi-user system during 9:00PM and 5:00AM

✅ Correct Answer: 4

While opening a TCP connection, the initial sequence number is to be derived using a time-of-day(ToD) clock that keeps running even when the host is down. The low order 32 bits of the counter of the ToD clock is to be used for the initial sequence numbers. The clock counter increments once per millisecond. The maximum packet lifetime is given to be 64s. Which one of the choices given below is closest to the minimum permissible rate at which sequence numbers used for packets of a connection can increase?

1. 0.015/s
2. 0.064/s
3. 0.135/s
4. 0.327/s

✅ Correct Answer: 1

Which of the following system calls results in the sending of SYN packets?

1. socket
2. bind
3. listen
4. connect

✅ Correct Answer: 4

In the slow start phase of the TCP congestion control algorithm, the size of the congestion window

1. does not increase
2. increases linearly
3. increases quadratically
4. increases exponentially

✅ Correct Answer: 4

Which one of the following uses UDP as the transport protocol?

1. HTTP
2. Telnet
3. DNS
4. SMTP

✅ Correct Answer: 3

Let the size of congestion window of a TCP connection be 32 KB when a timeout occurs. The round trip time of the connection is 100 msec and the maximum segment size used is 2 KB. The time taken (in msec) by the TCP connection to get back to 32 KB congestion window is _________.

1. 1100 to 1300
2. 800 to 1000
3. 1400 to 1600
4. 1500 to 1700

✅ Correct Answer: 1

Which one of the following socket API functions converts an unconnected active TCP socket into a passive socket.

1. connect
2. bind
3. listen
4. accept

✅ Correct Answer: 3

Packets of the same session may be routed through different paths in

1. TCP, but not UDP
2. TCP and UDP
3. UDP, but not TCP
4. Neither TCP, nor UDP

✅ Correct Answer: 2

The maximum window size for data transmission using the selective reject protocol with n-bit frame sequence numbers is:

1. 2^n
2. 2^(n-1)
3. 2^n – 1
4. 2^(n-2)

✅ Correct Answer: 2