Transport Layer Quiz Questions And Answers

1.

Which port number is used by HTTP?

A.

23
B.

80
C.

53
D.

110

Correct Answer
B. 80

Explanation
HTTP (Hypertext Transfer Protocol) is a protocol used for transmitting and receiving web pages and other resources over the internet. It operates on port number 80, which is the standard port for HTTP communication. Port 23 is used for Telnet, port 53 is used for DNS (Domain Name System), and port 110 is used for POP3 (Post Office Protocol version 3).

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2.

Which port number is used by SMTP?

A.

20
B.

23
C.

25
D.

143

Correct Answer
C. 25

Explanation
SMTP (Simple Mail Transfer Protocol) is a communication protocol used for sending email messages between servers. It operates on port number 25, which is specifically designated for SMTP. This port allows the transfer of email data from the sender's mail server to the recipient's mail server, ensuring the reliable delivery of emails across the internet.

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3.

Which characteristics are part of TCP? (Choose two.)

A.

Reliable
B.

Connectionless
C.

No flow control
D.

Resends anything not received

Correct Answer(s)
A. Reliable
D. Resends anything not received

Explanation
Two characteristics of TCP (Transmission Control Protocol) are:

1. Reliable: TCP is a reliable transport protocol that ensures the reliable and error-free delivery of data. It guarantees that data sent from one end will be received correctly at the other end.

2. Resends anything not received: TCP includes mechanisms for detecting and retransmitting any data that is not received correctly at the destination. This ensures that data is not lost during transmission and is delivered reliably.

TCP is a connection-oriented protocol, meaning it establishes a connection before data transfer and uses flow control to prevent network congestion, making it highly reliable for applications that require error-free and ordered data delivery.

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4.

End system use port numbers to select the proper applications. What is the lowest port number that can be dynamically assigned by the host system?

A.

1
B.

128
C.

256
D.

1024

Correct Answer
A. 1

Explanation
The lowest port number that can be dynamically assigned by the host system is 1. Port numbers are used by end systems to identify specific applications or services running on a network. These port numbers range from 1 to 65535, with the well-known ports reserved for specific services and the dynamic or private ports available for temporary use by applications. Since the question asks for the lowest port number, the correct answer is 1.

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5.

During data transfer, what is the receiving host responsible for? Choose two.

A.

Encapsulation
B.

Bandwidth
C.

Segmentation
D.

Acknowledgment
E.

Reassembly

Correct Answer(s)
D. Acknowledgment
E. Reassembly

Explanation
The receiving host is responsible for two tasks during data transfer: acknowledgment and reassembly. Acknowledgment refers to the process of confirming that data has been received successfully, ensuring reliable communication between the sender and receiver. Reassembly involves reconstructing the received data packets into their original order to restore the complete message or file. Both acknowledgment and reassembly are crucial for ensuring the integrity and completeness of the transferred data.

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6.

Which protocol is used by FTP to transfer files over the Internet?

A.

TCP
B.

SMTP
C.

UDP
D.

SNMP

Correct Answer
A. TCP

Explanation
FTP (File Transfer Protocol) uses TCP (Transmission Control Protocol) to transfer files over the Internet. TCP is a reliable, connection-oriented protocol that ensures the successful delivery of data packets between devices. It establishes a connection between the FTP client and server, allowing for the transfer of files in a secure and efficient manner. TCP provides error checking, flow control, and congestion control mechanisms, making it suitable for file transfer applications like FTP. SMTP (Simple Mail Transfer Protocol) is used for sending emails, UDP (User Datagram Protocol) is a connectionless protocol, and SNMP (Simple Network Management Protocol) is used for network management, so they are not the correct protocols for FTP file transfers.

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7.

Which of the following describes the operation of TCP window size?

A.

Window size increases as all data transfers.
B.

Window size is the TCP process used to prepare data for transmission.
C.

Window size is decreased if packets are lost.
D.

Window size of 15 means that the next byte expected is byte number 15.

Correct Answer
C. Window size is decreased if packets are lost.

Explanation
The TCP window size refers to the amount of data that can be sent by a sender without receiving an acknowledgment from the receiver. If packets are lost during transmission, the window size is decreased to prevent further congestion and ensure reliable delivery. This allows the sender to adjust the amount of data being sent based on the network conditions and the receiver's ability to handle the incoming data.

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1

8.

Which protocol can be used to load or retrieve Cisco IOS images to or from a router?

A.

SNMP
B.

TFTP
C.

UDP
D.

TCP

Correct Answer
B. TFTP

Explanation
TFTP (Trivial File Transfer Protocol) can be used to load or retrieve Cisco IOS images to or from a router. TFTP is a simple file transfer protocol that operates on top of UDP (User Datagram Protocol), making it lightweight and suitable for transferring small files such as router firmware. SNMP (Simple Network Management Protocol) is used for network management and monitoring, while UDP and TCP (Transmission Control Protocol) are transport layer protocols that are not specifically designed for file transfer.

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9.

What is the purpose of TCP/UDP port numbers?

A.

To indicate the beginning of a three-way handshake.
B.

To reassemble the segments into the correct order.
C.

To identify the numbers of the data packets that can be sent without acknowledgment.
D.

To track the different conversations crossing the network at the same time.

Correct Answer
D. To track the different conversations crossing the network at the same time.

Explanation
TCP/UDP port numbers are used to track the different conversations crossing the network at the same time. Each network communication is assigned a unique port number, which helps in distinguishing between different conversations or connections. This allows multiple applications or services to run simultaneously on a device, with each conversation being assigned a different port number. By tracking these port numbers, the network can ensure that the data packets are delivered to the correct application or service and that the responses are sent back to the correct source.

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10.

Which of the following services is used to translate a web address into an IP address?

A.

DNS
B.

WINS
C.

DHCP
D.

Telnet

Correct Answer
A. DNS

Explanation
DNS (Domain Name System) is the correct answer. DNS is a service that translates domain names (web addresses) into IP addresses. When a user enters a domain name in a web browser, DNS resolves that domain name to the corresponding IP address of the server where the website is hosted. This allows users to access websites using user-friendly domain names instead of having to remember and type in the numerical IP addresses.

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