Module-14
PORT-NUMBERS
Port Numbers
RELIABILITY AND FLOW CONTROL
Reliability and Flow Control
Which control bit flags are used during the three-way handshake?
SYN and ACK The three-way handshake consists of a three message exchanges with the following control bit flags: SYN, SYN ACK, and ACK.
What field is used by the destination host to reassemble segments into the original order?
Sequence Number The sequence number field is used by the destination host to reassemble segments into the original order.
What is a socket?
the combination of a source IP address and port number or a destination IP address and port number Topic 14.4.0 - A socket is a combination of the source IP address and source port or the destination IP address and the destination port number.
Assume a host with IP address 10.1.1.10 wants to request web services from a server at 10.1.1.254. Which of the following would display the correct socket pair?
10.1.1.10:1099, 10.1.1.254:80 The socket pair for a host with IP address 10.1.1.10 requesting web services from a server at 10.1.1.254 would be 10.1.1.10:1099, 10.1.1.254:80.
Which number or set of numbers represents a socket?
192.1681.1:80 Topic 14.4.0 - A socket is defined by the combination of an IP address and a port number, and uniquely identifies a particular communication.
Which two flags in the TCP header are used in a TCP three-way handshake to establish connectivity between two network devices? (Choose two.)
ACK SYN Topic 14.5.0 - TCP uses the SYN and ACK flags in order to establish connectivity between two network devices.
Which two operations are provided by TCP but not by UDP? (Choose two.)
Acknowledging received data retransmitting any unacknowledged data Topic 14.1.0 - Numbering and tracking data segments, acknowledging received data, and retransmitting any unacknowledged data are reliability operations to ensure that all of the data arrives at the destination. UDP does not provide reliability. Both TCP and UDP identify the applications and track individual conversations. UDP does not number data segments and reconstructs data in the order that it is received.
Which action is performed by a client when establishing communication with a server via the use of UDP at the transport layer?
Client randomly selects a source port number Topic 14.7.0 - 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.
Which two services or protocols use the preferred UDP protocol for fast transmission and low overhead? (Choose two)
DNS VolP Topic 14.3.0 - Both DNS and VoIP use UDP to provide low overhead services within a network implementation.
Which two fields are the same in a TCP and UDP header? (Choose two.)
Destination port number Source port number Both TCP and UDP headers include a source and destination port number fields.
How does a networked server manage requests from multiple clients for different services?
Each request has combination of source and destination port numbers, coming from unique IP addresses Topic 14.4.0 - Each service provided by a server, such as email or file transfers, uses a specific port number. The source port number of a service request identifies the client that is requesting services. The destination port number identifies the specific service. Servers do not use address information to provide services. Routers and switches use addressing information to move traffic through the network.
Which two applications would use the TCP transport layer protocol? (Choose two.)
FTP HTTP FTP and HTTP require the use of the TCP transport layer protocol.
Which TCP header statement is true?
It consists of 10 fields in a 20-byte header. The TCP header consists of 10 fields in a 20-byte header.
Which UDP header statement is true?
It consists of 4 fields in an 8-byte header. The UDP header consists of four fields in an 8-byte header.
Why is UDP desirable for protocols that make a simple request and reply transactions?
Low Overhead UDP is desirable for protocols that make simple request and reply transactions because of its low overhead.
Which of the following would be valid source and destination ports for a host connecting to an email server?
Source 49152, Destination 25 The destination port is the well-known port for Simple Mail Transport Protocol, which is 25. This is the port that the mail server will be listening on. The source port is dynamically selected by the requesting client and can be 49152.
What happens if part of an FTP message is not delivered to the destination?
The part of the FTP message that was lost is re-sent. Topic 14.6.0 - Because FTP uses TCP as its transport layer protocol, sequence and acknowledgment numbers will identify the missing segments, which will be re-sent to complete the message.
What happens when a sending host senses there is congestion?
The sending host reduces the number of bytes it sends before receiving an acknowledgment from the destination host. When a sending host senses congestion, it reduces the number of bytes it sends before receiving an acknowledgment from the destination host.
END-OF-CHAPTER-14-QUIZ
Transport Layer
Module - 14
Transportation of Data
UDP COMMUNICATION
UDP Communication
Which UDP datagram reassembly statement is true?
UDP reassembles data in order that was received UDP reassembles the data in the order that it was received.
Which transport layer protocol would be used for VoIP applications?
User Datagram Protocol (UDP) UDP would be used by time sensitive VoIP applications.
What field is used to provide flow control?
Windows size The Window Size field is used to provide flow control.
What type of applications are best suited for using UDP?
applications that are sensitive to delay Topic 14.3.0 - 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.
Which three are transport layer responsibilities? (Choose three.)
conversation Multiplexing segmenting Data and reassembling segments tracking Individual Conversations The transport layer is responsible for conversation multiplexing, segmenting data and reassembling segments, and tracking individual conversations.
How many exchanges are needed to end both sessions between two hosts?
four exchanges There are four exchanges to end both sessions between two hosts. (1) Host A sends a FIN. (2) Host B sends an ACK. (3) Host B sends a FIN. (4) Host A sends an ACK.
Which Windows command would display the protocols in use, the local address and port numbers, the foreign address and port numbers, and the connection state?
netstat The netstat Windows command would display protocols in use, the local address and port numbers, the foreign address and port numbers, and the connection state.
What is the purpose of using a source port number in a TCP communication?
to keep track of multiple conversations between devices Topic 14.4.0 - 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.
Which layer is responsible for establishing a temporary communication session between the source and destination host applications?
transport layer The transport layer is responsible for establishing a temporary communication session between the source and destination host applications.
What is the complete range of TCP and UDP well-known ports?
0 to 1023 Topic 14.4.0 - There are three ranges of TCP and UDP ports. The well-know range of port numbers is from 0 - 1023.
What TCP mechanism is used to enhance performance by allowing a device to continuously send a steady stream of segments as long as the device is also receiving necessary acknowledgements?
Sliding window Topic 14.6.0 - TCP uses windows to attempt to manage the rate of transmission to the maximum flow that the network and destination device can support while minimizing loss and retransmissions. When overwhelmed with data, the destination can send a request to reduce the of the window. The process of the destination sending acknowledgments as it processes bytes received and the continual adjustment of the source send window is known as sliding windows.
Which of the following would be valid source and destination ports for a host connecting to a DNS server?
Source: 49152, Destination: 53 The correct valid source and destination ports for a host requesting DNS service is Source: 49152, Destination: 53.
Which transport layer protocol ensures reliable same-order delivery?
TCP The TCP transport layer protocol ensures reliable same-order delivery.
Which transport layer feature is used to establish a connection-oriented session?
TCP 3-way handshake Topic 14.5.0 - 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.
TCP COMMUNICATION PROCESS
TCP Communication Process
TCP
TCP Overview
Which two applications would use the UDP transport layer protocol? (Choose two.)
TFTP VoIP TFTP and VoIP require the use of the UDP transport layer protocol.
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. Topic 14.6.0 - 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.
Which of the following is a stateless best-effort delivery transport layer protocol?
UDP UDP is a stateless best-effort delivery transport layer protocol.
UDP
UDP Overview
Which transport layer protocol statement is true?
UDP is a best-effort delivery protocol UDP is a best-effort delivery protocol while TCP is a reliable transport protocol.
What is a responsibility of transport layer protocols?
tracking individual conversations Topic 14.1.0 - There are three main responsibilities for transport layer protocols TCP and UDP: Tracking individual conversations Segmenting data and reassembling segments Identifying the applications
Which port group includes port numbers for FTP, HTTP, and TFTP applications?
well-known ports FTP, HTTP, and TFTP applications port numbers are defined in the well-known port numbers group.