15.3.3 Transport Layer Quiz Answers. Networking Basics Module 15 quiz exam answers
1. Which protocol operates at the application layer of the TCP/IP model?
- IP
- TCP
- HTTP
- ICMP
Explanation:
The protocols are associated with the following TCP/IP layers:
- HTTP > application layer
- TCP > transport layer
- IP and ICMP > internet layer.
2. What is a characteristic of UDP?
- It establishes sessions with a three-way handshake.
- It uses sequence numbers to reassemble segments.
- It adds 20 bytes of overhead to application layer data.
- It provides unreliable delivery of segments.
Explanation: UDP is a connectionless protocol that provides unreliable delivery of segments.
3. Which type of applications are best suited to use UDP as the transport layer protocol?
- applications that require flow control
- applications that require data to be reassembled in a specific order
- applications that require minimal transmission delay
- applications that require stateful sessions
Explanation: UDP is a light-weight connectionless protocol that is well-suited for applications that are susceptible to delay or that do not need the features provided by TCP (guaranteed delivery, flow control, or sequencing).
4. A student is sending files from a phone to a computer across a network. Which layer of the TCP/IP model is responsible for reassembling these messages as they are received on the computer?
- application
- transport
- internet
- network access
Explanation: The transport layer of the TCP/IP model is responsible for the following:
- Providing reliability mechanisms to ensure all of the message is received
- Reassembling a message as it is received
- Identifying which network applications are sending and receiving data
5. At which layer of the TCP/IP model does TCP operate?
- transport
- application
- internetwork
- network access
Explanation: TCP is the Transmission Control Protocol and it operates at the transport layer of the TCP/IP model. TCP ensures that IP packets are delivered reliably.
6. What protocol header information is used at the transport layer to identify a target application?
- port number
- IP address
- sequence number
- MAC address
Explanation: The TCP/IP transport layer uses port numbers to identify target applications. Each network application (server or client) has a port number assigned to the application.
7. What type of port number is assigned by IANA to commonly used services and applications?
- well-known port
- registered port
- dynamic port
- private port
Explanation: Well-known ports (0 to 1023) are reserved for common applications and services. Registered ports (1024 to 49151) are assigned to user processes and applications. Dynamic, private, or ephemeral ports (49152 to 65535) are assigned to client applications when initiating a connection.
8. What is the purpose of using a source port number in a TCP communication?
- to notify the remote device that the conversation is over
- to assemble the segments that arrived out of order
- to keep track of multiple conversations between devices
- to inquire for a nonreceived segment
Explanation: The source port number in a segment header is used to keep track of multiple conversations between devices. It is also used to keep an open entry for the response from the server. The incorrect options are more related to flow control and guaranteed delivery.
9. What is an advantage of UDP over TCP?
- UDP communication requires less overhead.
- UDP communication is more reliable.
- UDP reorders segments that are received out of order.
- UDP acknowledges received data.
Explanation: TCP is a more reliable protocol and uses sequence numbers to realign packets that arrive out of order at the destination. Both UDP and TCP use port numbers to identify applications. UDP has less overhead than TCP because the UDP header has fewer bytes and UDP does not confirm the receipt of packets.
10. When is UDP preferred to TCP?
- when a client sends a segment to a server
- when all the data must be fully received before any part of it is considered useful
- when an application can tolerate some loss of data during transmission
- when segments must arrive in a very specific sequence to be processed successfully
Explanation: UDP can be used when an application can tolerate some data loss. UDP is the preferred protocol for applications that provide voice or video that cannot tolerate delay.
11. Which statement correctly describes data transmission at the transport layer?
- Retransmission of lost packets is provided by both TCP and UDP.
- Segmentation is provided by the window size field when the TCP protocol is used.
- A single datagram can include both a TCP and a UDP header.
- Both UDP and TCP use port numbers.
- Segmentation is provided by sequence numbers when UDP is used.
Explanation: Segmentation is handled at Layer 4 by TCP sequence numbers. UDP does not have sequence numbers in the header, but instead, lets the application handle reordering if it is necessary. Only TCP provides reliable deliver and retransmits data. Each segment has either a TCP header or a UDP header; it cannot contain both.
