CCNA 1 v6.0 Chapter 9 Quiz Answers 2019

CCNA 1 v6.0 Chapter 9 Quiz Answers Cisco Last Update 2019

1. Network congestion has resulted in the source learning of the loss of TCP segments that were sent to the destination. What is one way that the TCP protocol addresses this?

The source decreases the amount of data that it transmits before it receives an acknowledgement from the destination.*
The source decreases the window size to decrease the rate of transmission from the destination.
The destination decreases the window size.
The destination sends fewer acknowledgement messages in order to conserve bandwidth.

If the source determines that the TCP segments are either not being acknowledged or are not acknowledged in a timely manner, then it can reduce the number of bytes it sends before receiving an acknowledgment. This does not involve changing the window in the segment header. The source does not decrease the window that is sent in the segment header. The window in the segment header is adjusted by the destination host when it is receiving data faster than it can process it, not when network congestion is encountered.

2. 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.

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.

3. Which action is performed by a client when establishing communication with a server via the use of UDP at the transport layer?

The client sets the window size for the session.
The client sends an ISN to the server to start the 3-way handshake.
The client randomly selects a source port number.*
The client sends a synchronization segment to begin the session.

Because a session does not have to be established for UDP, the client selects a random source port to begin a connection. The random port number selected is inserted into the source port field of the UDP header.

4. Which number or set of numbers represents a socket?


A socket is defined by the combination of an IP address and a port number, and uniquely identifies a particular communication.

5. Which two services or protocols use the preferred UDP protocol for fast transmission and low overhead? (Choose two)


Both DNS and VoIP use UDP to provide low overhead services within a network implementation.​

6. Which transport layer feature is used to guarantee session establishment?

UDP ACK flag
TCP 3-way handshake*
UDP sequence number
TCP port number

TCP uses the 3-way handshake. UDP does not use this feature. The 3-way handshake ensures there is connectivity between the source and destination devices before transmission occurs.

7. 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

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.

8. Refer to the exhibit.

What does the value of the window size specify?

the amount of data that can be sent at one time
the total number of bits received during this TCP session
the amount of data that can be sent before an acknowledgment is required*
a random number that is used in establishing a connection with the 3-way handshake

The window size specifies the amount of data that can be sent before an acknowledgment is received from the receiver. This value specifies the highest number of bytes, not the required number of bytes.

9. What is the purpose of the TCP sliding window?

to inform a source to retransmit data from a specific point forward
to request that a source decrease the rate at which it transmits data*
to end communication when data transmission is complete
to ensure that segments arrive in order at the destination

The TCP sliding window allows a destination device to inform a source to slow down the rate of transmission. To do this, the destination device reduces the value contained in the window field of the segment. It is acknowledgment numbers that are used to specify retransmission from a specific point forward. It is sequence numbers that are used to ensure segments arrive in order. Finally, it is a FIN control bit that is used to end a communication session.

10. What OSI layer is responsible for establishing a temporary communication session between two applications and ensuring that transmitted data can be reassembled in proper sequence?

data link

The transport layer of the OSI model has several responsibilities. One of the primary responsibilities is to segment data into blocks that can be reassembled in proper sequence at the destination device.

11. Which three fields are used in a UDP segment header? (Choose three.)

Window Size
Source Port*
Acknowledgment Number
Sequence Number

A UDP header consists of only the Source Port, Destination Port, Length, and Checksum fields. Sequence Number, Acknowledgment Number, and Window Size are TCP header fields.

12. A client application needs to terminate a TCP communication session with a server. Place the termination process steps in the order that they will occur. (Not all options are used.)

step 1  —-> client sends FIN
step 2 —-> server sends ACK
step 3 —-> server sends FIN
step 4 —-> client sends ACK

In order to terminate a TCP session, the client sends to the server a segment with the FIN flag set. The server acknowledges the client by sending a segment with the ACK flag set. The server sends a FIN to the client to terminate the server to client session. The client acknowledges the termination by sending a segment with the ACK flag set.

13. What are three responsibilities of the transport layer? (Choose three.)

meeting the reliability requirements of applications, if any*
multiplexing multiple communication streams from many users or applications on the same network*
identifying the applications and services on the client and server that should handle transmitted data*
directing packets towards the destination network
formatting data into a compatible form for receipt by the destination devices
conducting error detection of the contents in frames

The transport layer has several responsibilities. Some of the primary responsibilities include the following:
Tracking the individual communication streams between applications on the source and destination hosts
Segmenting data at the source and reassembling the data at the destination
Identifying the proper application for each communication stream through the use of port numbers
Multiplexing the communications of multiple users or applications over a single network
Managing the reliability requirements of applications

14. What type of applications are best suited for using UDP?

applications that are sensitive to delay*
applications that need reliable delivery
applications that require retransmission of lost segments
applications that are sensitive to packet loss

UDP is not a connection-oriented protocol and does not provide retransmission, sequencing, or flow control mechanisms. It provides basic transport layer functions with a much lower overhead than TCP. Lower overhead makes UDP suitable for applications which are sensitive to delay.

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