Computer Networks And Internet Protocol - Week 4 Assignment 4 | NPTEL | JAN 2023

Computer Networks And Internet Protocol - Week 4 | Assignment 4 : Answer with Explanation

Computer networks and internet protocols are essential components of today's technology-driven world. They allow devices to connect and communicate with one another, enabling the sharing of information and resources. Multiple choice questions (MCQs) on this topic test a student's understanding of the various concepts and protocols involved in computer networks and internet communication. These include topics such as Transport Layer Primitives – Connection Establishment and Closure

Which is the most popular port number for establishing httpd (Apache HTTP server) connection?

a. 21
b. 46
c. 80
d. 15

Answer

c. 80
The default port number for establishing HTTP (Hypertext Transfer Protocol) connections with Apache HTTP Server is port 80. This is the most common port number used for web traffic and is the default port for HTTP connections. However, HTTPS (HTTP Secure) connections, which use SSL/TLS encryption to provide secure communication, typically use port 443 by default.

In the AIMD algorithm, the sending rate w(t) at the next time interval (t+1) is increased by an additive factor (a>0) when congestion is detected.

a. True
b. False

Answer

b. False
Additive Increase Multiplicative Decrease (AIMD) – Chiu and Jain (1989)
The Additive Increase Multiplicative Decrease (AIMD) algorithm is a congestion control mechanism used in computer networks to control the sending rate of data packets. In AIMD, the sending rate is increased linearly when there is no congestion and decreased multiplicatively when congestion is detected.

In particular, when congestion is detected, the sending rate is reduced by multiplying the current sending rate by a factor of (b<1). This reduction in the sending rate is intended to alleviate the congestion and prevent further packet drops.

On the other hand, when there is no congestion, the sending rate is increased by an additive factor (a>0) at each time interval. This increase in the sending rate is intended to make efficient use of the available network capacity.

Therefore, the sending rate w(t) at the next time interval (t+1) is calculated as:
w(t+1) = w(t) + a, if no congestion is detected
w(t+1) = w(t) * b, if congestion is detected

where w(t) is the sending rate at time t, a is the additive factor, and b is the multiplicative factor.
The AIMD algorithm has been widely used in various network protocols such as TCP to achieve congestion control and prevent network congestion.

Let the maximum TCP payload be given 1450 Bytes; then, what is the maximum network layer payload in Bytes?

a. 1450 Bytes
b. 1470 Bytes
c. 1430 Bytes
d. 1480 Bytes

Answer

b. 1470 Bytes

TCP Service Model supports broadcasting.

a. True
False

Answer

b.false
- All TCP connections are full-duplex and point-to-point.
- TCP does not support multicasting or broadcasting.

Which of the following statement(s) is/are true for the Transport Layer?
(i) The transport layer protocol should be Stateful. (ii) Uses FTP protocols for ensuring flow control.

a. Only i
b. Only ii
c. Both (i) and (ii)
Non of the above

Answer

a. Only i
- Flow Control and Reliability - Use ARQ protocols for ensuring flow control and reliability

TCP header size is of

a. 20 bits
b. 185 bits
c. 150 bytes
d. 160 bits

Answer

d. 160 bits
The TCP header size is variable and can range from 20 to 60 bytes (160 to 480 bits).
The minimum TCP header size is 20 bytes (160 bits) which includes the mandatory fields such as the source and destination port numbers, sequence number, acknowledgement number, and control flags.
The header size can increase up to 60 bytes (480 bits) if optional fields such as window size, urgent pointer, and options are included.

The use of a cryptographic function to generate sequence numbers for TCP connection is helpful to avoid

a. TCP Congestion Overflow
b. DoS attack
c. TCP SYN flood attack
d. None of these

Answer

c. TCP SYN flood attack

For effective congestion avoidance, the sending rate of the network should be a minimum of (network rate, receiver rate)

a. True
b. False

Answer

a. True

What is/are the parameters responsible for restricting TCP segment size?

a. IP address
b. IP payload
c. Maximum Transmission Unit (MTU) of the link
d. Acknowledgment number field size

Answer

b. IP payload,c. Maximum Transmission Unit (MTU) of the link

Consider a network with the link bandwidth = 1Mbps, Delay = 1ms, and segment size is 1KB (1024 bytes). Which of the following relationship between BDP and segment size?

a. BDP = 8 x (segment size)
b. BDP/4 = segment size
c. BDP/8 = segment size
d. BDP x 8 = segment size

Answer

d. BDP x 8 = segment size
The segment size is eight times larger than the BDP
Bandwidth Delay Product (BDP) = Link Bandwidth x Link Delay – an important metric for flow control

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Computer Networks And Internet Protocol, Week 4 : Assignment 4,noc23_cs48

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