# Recent questions and answers in Computer Networks

1 vote
1
Datagram fragmentation and reassembly are handled by IP and are invisible to TCP. Does this mean that TCP does not have to worry about data arriving in the wrong order?
1 vote
2
A process on host 1 has been assigned port p, and a process on host 2 has been assigned port q. Is it possible for there to be two or more TCP connections between these two ports at the same time?
1 vote
3
In Fig. 6-36 we saw that in addition to the 32-bit acknowledgement field, there is an ACK bit in the fourth word. Does this really add anything? Why or why not?
1 vote
4
The maximum payload of a TCP segment is 65,495 bytes. Why was such a strange number chosen?
5
Suppose that you are measuring the time to receive a segment. When an interrupt occurs, you read out the system clock in milliseconds. When the segment is fully processed, you read out the clock again. You measure 0 msec 270,000 times and 1 msec 730,000 times. How long does it take to receive a segment?
6
A computer on a $10$ $Mbps$ network is regulated by a token bucket. The token bucket is filled at a rate of $2$ $Mbps$. It is initially filled to capacity with $16$ $Megabits$. What is the maximum duration for which the computer can transmit at the full $10$ $Mbps$? $1.6$ seconds $2$ seconds $5$ seconds $8$ seconds
7
1 vote
8
Consider the following statements, when a distance vector routing protocol finding minimum cost paths suffers from count to infinity problem: S1 : The count-to-infinity problem may arise in distance vector routing protocol, when network gets disconnected. S2 : The count to infinity problem may arise in ... the following is correct? (A) Only S1 AND S3 (B) Only S2 AND S3 (C) Only S2 (D) All of them
1 vote
9
I have a doubt here. When timeout occurs, the congestion windows size is 18MSS.and Till now total RTT before this timeout were 6. Now, my threshold will be set to 9MSS and congestion window will start from 1 MSS.So, now when I send 1MSS window and receive it's ack and then my window size changes to 2MSS, will this RTT be counted as 7th RTT or the 8th RTT?
10
In TCP, a unique sequence number is assigned to each byte word segment message
11
A $20$ $\text{Kbps}$ satellite link has a propagation delay of $400$ $\text{ms}$. The transmitter employs the "go back $n$ $ARQ$" scheme with $n$ set to $10$. Assuming that each frame is $100$ $\text{byte}$ long, what is the maximum data rate possible? $5$ $\text{Kbps}$ $10$ $\text{Kbps}$​​​​​​​ $15$ $\text{Kbps}$​​​​​​​ $20$ $\text{Kbps}$​​​​​​​
12
Consider a source using TCP-Reno (fast-retransmit and fast-recovery mechanisms) to send data to a destination. It is given the RTT of the link is 800 ms and the sender's window size is 8 segments. The sender sends segments at a regular rate of ... ACK of the retransmitted segment before advancing the window then the total time the sender lost (as compared to lossless transmission) is ________.
13
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 ... is $255.255.255.224$. Given the information above, how many distinct subnets are guaranteed to already exist in the network? $1$ $2$ $3$ $6$
14
The address of a class $B$ host is to be split into subnets with a $6$-$bit$ subnet number. What is the maximum number of subnets and the maximum number of hosts in each subnet? $62$ subnets and $262142$ hosts. $64$ subnets and $262142$ hosts. $62$ subnets and $1022$ hosts. $64$ subnets and $1024$ hosts.
15
An organization has a class $B$ network and wishes to form subnets for $64$ departments. The subnet mask would be: $255.255.0.0$ $255.255.64.0$ $255.255.128.0$ $255.255.252.0$
16
A 1024-bit message is sent that contains 992 data bits and 32 CRC bits. CRC is com- puted using the IEEE 802 standardized, 32-degree CRC polynomial. For each of the following, explain whether the errors during message transmission will be detected by the receiver: (a) There ... bit long burst error. (f) There was a 35-bit long burst error. In the above question can anyone explain for option (c).
1 vote
17
A 1024-bit message is sent that contains 992 data bits and 32 CRC bits. CRC is computed using the IEEE 802 standardized, 32-degree CRC polynomial. For each of the following, explain whether the errors during message transmission will be detected by the receiver: (a) There was a ... were 47 isolated bit errors. (e) There was a 24-bit long burst error. (f) There was a 35-bit long burst error.
18
Let transmission time = 1ms , propagation delay = 1 ms and we have used TDM access control method. What is the efficiency of the network and what is throughput if we are given a bandwidth of 4mbps. If we want to have N number of nodes/stations in this network and each requires 2kbps of bandwidth. Then what is the value of N ?
19
In a class $C$ address, $3$ bits are borrowed for subnetting of host id part. Total possible number of subnet masks are _________________.
20
a) lower line efficiency b) higher line efficiency c) no change in line efficiency d) no relation between line efficiency and frame size
1 vote
21
Do we have token ring in Gate 2018 syllabus
1 vote
22
23
Assume 2 computers are connected via a network. The network uses Go-Back 7 sliding window protocol for maintaining flow control. It is observed that every 5th packet that has been sent through the network is lost. What will be the number of extra packets that has to be resent for transmitting 10 such packet through the network? With explanation.
24
Consider the following clauses: Not inherently suitable for client authentication. Not a state sensitive protocol. Must be operated with more than one server. Suitable for structured message organization. May need two ports on the serve side for proper operation. The option that has the maximum number of ... -v POP3-i; SMTP-ii; DNS-iii; IMAP-iv; HTTP-v SMTP-i; HTTP-ii; IMAP-iii; DNS-iv; FTP-v
1 vote
25
why stop and wait protocol has flow control but not error control ?
26
How many bytes of data can be sent in $15$ seconds over a serial link with baud rate of $9600$ in asynchronous mode with odd parity and two stop bits in the frame? $10,000$ bytes $12,000$ bytes $15,000$ bytes $27,000$ bytes
27
Dynamic routing protocol enable routers to Dynamically discover and maintain routes Distribute routing updates to other routers Reach agreement with other routers about the network topology All of the above
1 vote
28
Consider a code with only four valid code words: $0000000000$, $0000011111$, $1111100000$, and $1111111111$. This code has distance $5$. If the code word arrived is $0000000111$ then the original code word must be _______ $0000011111$ $0000000000$ $1111100000$ $1111111111$
29
Using ‘RSA’ public key cryptosystem, if $p=3$, $q=11$ and $d=7$, find the value of $e$ and encrypt the number $’19’$ $20, 19$ $33,11$ $3, 28$ $77, 28$
30
Protocols in which the sender sends one frame and then waits for an acknowledgment before proceeding for next frame are called as ______ Simplex protocols Unrestricted simplex protocols Simplex stop and wait protocols Restricted simplex protocols
31
Which among the following statement(s) is(are) true? A hash function takes a message of arbitrary length and generates a fixed length code A hash function takes a message of fixed length and generates a code of variable length A hash function may give same hash value for distinct messages Choose the correct ... options given below: $(a)$ only $(b)$ and $(c)$ only $(a)$ and $(c)$ only $(b)$ only
32
Post office protocol (POP) is a message access protocol which is used to extract message for client. In this regards, which of the following are true? POP has two modes, Delete mode and keep In Delete mode, mail is deleted from mail box after each retrival In Delete mode, mail is deleted from mail box before each ... $(e)$ only $(a)$, $(b)$, $(c)$ and $(d)$ only $(a)$, $(b)$ and $(e)$ only
1 vote
33
Firewall is a device that filters access to the protected network from the outside network. Firewalls can filter the packets on the basis of Source IP address Destination IP address TCP Source Port UDP Source Port TCP Destination Port Choose the correct answer from the options given below: $(a), (b)$ and $(c)$ only $(b)$ and $(e)$ only $(c)$ and $(d)$ only $(a), (b), (c), (d)$ and $(e)$ only
34
Match $\text{List I}$ with $\text{List II}$ ... $A-III, B-IV, C-II, D-I$ $A-II, B-III, C-IV, D-I$ $A-III, B-I, C-IV, D-II$
35
Given below are two statements: Statement $I$: The laws of nature put two fundamental limits on data rate of a channel. The H.Nyquist limit restricts the number of independent samples per second to twice the band-width in a Noiseless channel Statement $II$: Shannon's major ... $II$ are false Statement $I$ is correct but Statement $II$ is false Statement $I$ is incorrect but Statement $II$ is true
36
Given below are two statements: Statement $I$: In Ceasar Cipher each letter of Plain text is replaced by another letter for encryption Statement $II$: Diffie-Hellman algorithm is used for exchange of secret key In the light of the above statements, choose the correct answer ... $I$ is correct but Statement $II$ is false Statement $I$ is incorrect but Statement $II$ is true
1 vote
37
Given a mask, M=255.255.255.248. How many subnet bits are required for given mask M? (A) 2 (B) 3 (C) 4 (D)5