# Computer Network

 Question 1
Consider the data transfer using TCP over a 1 Gbps link. Assuming that the maximum segment lifetime (MSL) is set to 60 seconds, the minimum number of bits required for the sequence number field of the TCP header, to prevent the sequence number space from wrapping around during the MSL is
 A 31 B 32 C 33 D 34
GATE CSE 2022      Transport Layer Protocol
Question 1 Explanation:
 Question 2
Consider a 100 Mbps link between an earth station (sender) and a satellite (receiver) at an altitude of 2100 km. The signal propagates at a speed of $3 \times 10^8$ m/s. The time taken (in milliseconds, rounded off to two decimal places) for the receiver to completely receive a packet of 1000 bytes transmitted by the sender is
 A 15.06 B 54.25 C 7.08 D 4.25
GATE CSE 2022      Data Link Layer
Question 2 Explanation:
 Question 3
Consider a network with three routers P, Q, R shown in the figure below. All the links have cost of unity.

The routers exchange distance vector routing information and have converged on the routing tables, after which the link Q-R fails. Assume that P and Q send out routing updates at random times, each at the same average rate. The probability of a routing loop formation (rounded off to one decimal place) between P and Q, leading to count-to-infinity problem, is ____
 A 0.25 B 0.33 C 0.5 D 0.75
GATE CSE 2022      Network Layer Protocol
Question 3 Explanation:
 Question 4
Consider routing table of an organization's router shown below:
$\begin{array}{|l|l|l|} Subnet Number & Subnet Mask & Next Hop \\ 12.20.164.0 & 255.255.252.0 & R1 \\ 12.20.170.0 & 255.255.254.0 & R2 \\ 12.20.168.0 & 255.255.254.0 & Interface 0 \\ 12.20.166.0 & 255.255.254.0 & Interface 1 \\ default & ~ & R3 \\ \hline \end{array}$
Which of the following prefixes in CIDR notation can be collectively used to correctly aggregate all of the subnets in the routing table?
MSQ
 A 12.20.164.0/20 B 12.20.164.0/22 C 12.20.164.0/21 D 12.20.168.0/22
GATE CSE 2022      Network Layer Protocol
Question 4 Explanation:
 Question 5
Consider the resolution of the domain name $www.gate.org.in$ by a DNS resolver. Assume that no resource records are cached anywhere across the DNS servers and that iterative query mechanism is used in the resolution. The number of DNS query-response pairs involved in completely resolving the domain name is .
 A 2 B 3 C 4 D 5
GATE CSE 2022      Application Layer Protocols
Question 5 Explanation:
 Question 6
Consider an enterprise network with two Ethernet segments, a web server and a firewall, connected via three routers as shown below.

What is the number of subnets inside the enterprise network?
 A 3 B 12 C 6 D 8
GATE CSE 2022      Network Layer Protocol
Question 6 Explanation:
 Question 7
Consider a network using the pure ALOHA medium access control protocol, where each frame is of length 1,000 bits. The channel transmission rate is 1 Mbps (=$10^6$ bits per second). The aggregate number of transmissions across all the nodes (including new frame transmissions and retransmitted frames due to collisions) is modelled as a Poisson process with a rate of 1,000 frames per second. Throughput is defined as the average number of frames successfully transmitted per second. The throughput of the network (rounded to the nearest integer) is ______________
 A 180 B 160 C 135 D 115
GATE CSE 2021 SET-2      Data Link Layer
Question 7 Explanation:
 Question 8
Consider a computer network using the distance vector routing algorithm in its network layer. The partial topology of the network is shown below.

The objective is to find the shortest-cost path from the router R to routers P and Q. Assume that R does not initially know the shortest routes to P and Q. Assume that R has three neighboring routers denoted as X, Y and Z. During one iteration, R measures its distance to its neighbors X, Y, and Z as 3, 2 and 5, respectively. Router R gets routing vectors from its neighbors that indicate that the distance to router P from routers X, Y and Z are 7, 6 and 5, respectively. The routing vector also indicates that the distance to router Q from routers X, Y and Z are 4, 6 and 8 respectively. Which of the following statement(s) is/are correct with respect to the new routing table o R, after updation during this iteration?
[MSQ]
 A The distance from R to P will be stored as 10 B The distance from R to Q will be stored as 7 C The next hop router for a packet from R to P is Y D The next hop router for a packet from R to Q is Z
GATE CSE 2021 SET-2      Network Layer Protocol
Question 8 Explanation:
 Question 9
Consider the cyclic redundancy check (CRC) based error detecting scheme having the generator polynomial $X^3+X+1$. Suppose the message $m_4m_3m_2m_1m_0=11000$ is to be transmitted. Check bits $c_2c_1c_0$ are appended at the end of the message by the transmitter using the above CRC scheme. The transmitted bit string is denoted by $m_4m_3m_2m_1m_0c_2c_1c_0$. The value of the checkbit sequence $c_2c_1c_0$ is
 A 101 B 110 C 100 D 111
GATE CSE 2021 SET-2      Data Link Layer
Question 9 Explanation:
 Question 10
Consider the three-way handshake mechanism followed during TCP connection establishment between hosts P and Q. Let X and Y be two random 32-bit starting sequence numbers chosen by P and Q respectively. Suppose P sends a TCP connection request message to Q with a TCP segment having SYN bit =1, SEQ number =X, and ACK bit =0. Suppose Q accepts the connection request. Which one of the following choices represents the information present in the TCP segment header that is sent by Q to P?
 A SYN bit =1, SEQ number =X+1, ACK bit =0, ACK number =Y, FIN bit =0 B SYN bit =0, SEQ number =X+1, ACK bit =0, ACK number =Y, FIN bit =1 C SYN bit =1, SEQ number =Y, ACK bit =1, ACK number =X+1, FIN bit =0 D SYN bit =1, SEQ number =Y, ACK bit =1, ACK number =X, FIN bit =0
GATE CSE 2021 SET-2      Transport Layer Protocol
Question 10 Explanation:

There are 10 questions to complete.

### 1 thought on “Computer Network”

1. Question 60 is wrongly tagged here, it belongs to object oriented programming.