# Recent questions and answers in Computer Networks 30 votes
6 answers
1
Suppose that the stop-and-wait protocol is used on a link with a bit rate of $64$ $\text{kilobits}$ per second and $20$ $\text{milliseconds}$ propagation delay. Assume that the transmission time for the acknowledgment and the processing time at nodes are negligible. Then the minimum frame size in bytes to achieve a link utilization of at least $50$ $\text{%}$ is_________________.
24 votes
7 answers
2
Following $7$ ... (assuming that at most $1$ bit could be corrupted). If the message contains an error find the bit which is erroneous and gives correct message.
1 vote
1 answer
3
Given an IP address 156.233.42.56 with a subnet mask of 7 bits. How many hosts and Subnets are Possible ? 126 hosts and 510 subnet 128 host and 512 subnet 510 hosts and 126 subnet 512 hosts and 128 Subnet
1 vote
3 answers
4
For a Class C network. If IP address of a computer is 200.99.39.112 and subnet mask is 255.255.255.224,the decimal value of last octet of last host of sixth subnet is ?
4 votes
3 answers
5
For a class C network if IP address of a computer is 200.99.39.112 and subnet mask is 255.255.255.224 the decimal value of last octet of last host of sixth subnet is __________ According to me, the answer should be 101 11110 = 190. Because first subnet will have 000, so sixth subnet should have 101. But the answer given is: 110 11110
19 votes
5 answers
6
An organization has a class $B$ network and wishes to form subnets for $64$ departments. The subnet mask would be: $255.255.0.0$ $255.255.64.0$ $255.255.128.0$ $255.255.252.0$
2 votes
2 answers
7
Interface $A - 255.255.255.128$ Interface $B -255.255.255.192$ Interface $C -255.255.255.224$ 1) which one of the following IP addresses belong to interface $B$ ? $200.200.200.130$ & $200.200.200.157$ $200.200.200.200$ & $200.200.200.205$ $200.200.200.30$ ... 2) Based on the subnet masks above , what could be the maximum number of possible subnets in the network $200.200.200$ ? $2$ $4$ $8$ $3$
2 votes
2 answers
8
Consider the following IP address with corresponding subnet mask: IP add: 172.60.50.2 Subnet mask: 255.255.224.0 What is the range of assignable IP addresses on the subnet on which the host belongs: a) 172.60.30.0 - 172.60.63.255 b)172.60.32.1 - 172.60.63.254 c)172.60.32.1 -172.60.64.255 d)172.60.32.0 - 172.60.127.254
1 vote
4 answers
9
A class B network address 130.50.0.0 is submitted as follows. The last 10 bits of the host id are allotted for host number and the remaining 6 bits are reserved for subnet number. How many subnets and number of hosts in each subnet are possible with above scheme ? 62,1022 30,510 14,254 None of these ... ? 130.50.4.1 and 130.50.16.1 130.50.1.1 and 130.50.4.1 130.50.0.0 and 130.50.3.0 None of these
3 votes
2 answers
10
Which of the following is a class $B$ host address ? $230.0.0.0$ $130.4.5.6$ $230.7.6.5$ $30.4.5.6$
1 vote
3 answers
11
i have a self doubt that till now i solve the TCP question where the sender has $1\hspace{0.1cm}mss$ at starting so during time out generally reduced the senders window size to $1 \hspace{0.1cm}mss$ ... be the sender size i.e we will put it down to $1 \hspace{0.1cm}mss$ or to $2\hspace{0.1cm}mss$ .........
3 votes
2 answers
12
In one of the quizes, they asked the following question : "A server typically listens for TCP connections on a particular port (e.g. 80 for HTTP or 22 for SSH). Which fields can the server use to distinguish packets for a particular client connection?" Please ... IP address from the packet received from the client... (After all, this destination IP address corresponds to the Server itself !).
2 votes
5 answers
13
Consider the three-way handshake mechanism followed during $\text{TCP}$ 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 $\text{TCP}$ connection request message to $Q$ with a ... $\text{SEQ}$ number $=Y$, $\text{ACK}$ bit $=1$, $\text{ACK}$ number $=X$, $\text{FIN}$ bit $=0$
2 votes
3 answers
14
Is ALOHA a part of gate syllabus ?
5 votes
2 answers
15
Assume that a $12$-bit Hamming codeword consisting of $8$-bit data and $4$ check bits is $d_8d_7d_6d_5c_8d_4d_4d_3d_2c_4d_1c_2c_1$ ... is $0$ $x$ is $0$ and $y$ is $1$ $x$ is $1$ and $y$ is $0$ $x$ is $1$ and $y$ is $1$
1 vote
2 answers
16
The network $198.78.41.0$ is a : Class A Network Class B Network Class C Network Class D Network
0 votes
2 answers
17
If the channel is band limited to $6\;kHz$ and signal to noise ratio is $16,$ what would be the capacity of channel? $16.15$ kbps $23.24$ kbps $40.12$ kbps $24.74$ kbps
6 votes
5 answers
18
A IP packet has arrived in which the fragmentation offset value is 100,the value of HLEN is 5 and the value of total length field is 200. What is the number of the last byte? 194 394 979 1179
1 vote
2 answers
19
Consider station “A” send data to station “B”. Data frame contain MAC address, IP address and port address. Which of the following address may change on intermediate router A Destination IP address B Destination MAC C Source MAC D Source IP address
1 vote
1 answer
20
In TCP we use single retransmission timer (associated with oldest unacknowledged segment) or multiple timers(one for each unacknowledged segment)?
2 votes
1 answer
21
I have doubt 1: Segment sequence number is equal to the first sequence number of byte in TCP . Is it right ?
3 votes
3 answers
22
Consider an instance of TCP's Additive Increase Multiplicative Decrease (AIMD) algorithm where the window size at the start of slow start phase is 2 KB and the threshold at the start of first transmission is 32 KB. Assume that 3 duplicate ACK are received ... 5th transmission and 1 duplicate ACK received during 6th transmission. what is the congestion window size at the end of 10th transmission?
2 votes
3 answers
23
Do all the TCP segments travel through same path once the connection is established ?
2 votes
2 answers
24
An ACK number of $1000$ in TCP always means that $999$ bytes have been successfully received $1000$ bytes have been successfully received $1001$ bytes have been successfully received None of the above
3 votes
1 answer
25
In a TCP connection, the initial sequence number at the client site is 1846. The client opens the connection, sends only one segment carrying 1200 bytes of data, and closes the connection. What is the value of the sequence number in SYN, DATA and FIN segment sent by the client? 1200, 3046, 4246 1846, 1200, 3046 1200, 1846, 3046 1846, 3046, 3046
0 votes
1 answer
26
A large law firm, which has many employees, provides a single email address for each employee. Each employee's email address is <login>@lawfirm.com. However, the firm did not explicitly define the format of the login. Thus, some employees use their first names as their ... com, that can be used for the email addresses of all its employees. How can this be done without rocking the boat too much?
2 votes
1 answer
27
Say the receiver host B, has a buffer size of 4500 bytes and 1500 bytes of received and unprocessed data. If the value of congestion window is 3500 bytes then what will be the size of the window for sender host A?( Marks: -0.33 ) 3500 B 4500 B 4000 ... is 3000B as congestion window is 3500 B and receiver window is 4500-1500 = 3000B Can anyone please explain it in details about congestion window?
3 votes
3 answers
28
A $\text{TCP}$ server application is programmed to listen on port number $P$ on host $S$. A $\text{TCP}$ client is connected to the $\text{TCP}$ server over the network. Consider that while the $\text{TCP}$ connection was active, the server machine $S$ crashed ... it will receive a $\text{RST}$ segment If the client sends a packet after the server reboot, it will receive a $\text{FIN}$ segment
1 vote
1 answer
29
What does this 2nd points means wrt TCP window. We need not send complete window everytime..but we send complete window data once at a time. Right? Is it something related to PUSH flag
1 vote
1 answer
30
When a TCP segment arrives at a host, in order to direct it to the appropriate socket, the operating system's network stack uses which of the following? (a)Transport protocol number (b)Destination IP Address (c)Source port number (d)Destination port number ( ... why a,b and d are needed. Why source port number is needed? Document Ref: https://gateoverflow.in/?qa=blob&qa_blobid=8025344419025703520
2 votes
2 answers
31
Say Client buffer is of 12000 Bytes and MSS is 1200 B and this info is sent to server and now server send the info in (SYN +ACK) segment as Server Buffer = 18000 B and MSS is 600 B Now in data transfer phase does both Client and Server will choose 600 Bytes data segments ... ) = Min (1200, 600) = 600 Bytes? Or does the sever will send 1200 Bytes segments to C and C sends 600 B segments to server?
2 votes
1 answer
32
If TCP RTT is currently 20 ms and following acknowledgement come in after 22,24 and 23 ms respectively. What is new RTT estimate ? 28.527 28.82 20.82 21.22
1 vote
1 answer
33
When during TCP congestion control, timeout occurs in 5th transition, then shall those packets be considered as received or shall be resent? Asking for if question asks for number of transmission to send given number of packets using TCP congestion slow start phase.
5 votes
3 answers
34
Consider two hosts $P$ and $Q$ connected through a router $R$. The maximum transfer unit $\text{(MTU)}$ value of the link between $P$ and $R$ is $1500$ bytes, and between $R$ and $Q$ is $820$ bytes. A $\text{TCP}$ segment of size $1400$ bytes ... is required to resend the whole $\text{TCP}$ segment. $\text{TCP}$ destination port can be determined by analysing $\textit{only}$ the second fragment.
1 vote
1 answer
35
4 votes
2 answers
36
In distance vector routing how the distance vectors are update when two paths have same cost eg. Initial Distance vector of A B C D are A- [0 &infin; 1 2] B- [&infin; 0 3 2] C- [1 3 0 &infin;] D- [2 2 &infin; 0] what will be distance vector of A after 1 iteration. Please mention via node and why u choose that node??
4 votes
3 answers
37
Consider a router is working based on the Distance Vector Routing Algorithm. Consider the five-node network of the following figure. Assume all nodes building distance from that node to $A$ (number of hops) and after initial set up, suddenly either $A$ goes down or the link between $A$ and $B$ is cut. What are the distance ... $(C) B - 4, C - 5, D - 4, E - 5$ $(D)$ None
1 vote
2 answers
38
Consider a network system having 4 routers P,Q,R AND S as shownbelow.initially, the routersise Distance vector routing and use number of hops as distance metric. Initially, link p-q was down and all other routers agree p is unreachable.thr link p-q comes back up. ... will not be "count to infinity" problem as all routers are sending the information at the same instant. How to solve this ques?
0 votes
5 answers
39
Station $A$ uses $32$ byte packets t transmit messages to station $B$ using sliding window protocol. The round trip delay between $A$ and $B$ is $40$ milliseconds and the bottleneck bandwidth on the path between $A$ and $B$ is $64$ kbps. The optimal window size of $A$ is $20$ $10$ $30$ $40$
1 vote
3 answers
40
Suppose there are $n$ stations in a slotted $LAN$. Each station attempts to transmit with a probability $P$ in each time slot. The probability that only one station transmits in a given slot is $nP(1-P)^{n-1}$ $nP$ $P(1-P)^{n-1}$ $n^{P}(1-P)^{n-1}$
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