II. OSI Transport Layer

Question 1

• Tracking the individual communications between applications on the source and destination hosts.
• Segmenting data and managing each piece.
• Reassembling the segments into streams of application data at the receiving host.
• Identifying the different applications using port numbers.
• Performing flow control between end users.
• Enabling error recovery
• Initiating a session

Answer 1

the primary responsibilities of the transport layer:

Question 2

Numbering and sequencing the segments ensure that segments are reassembled into the proper order.

Answer 2

Reassembling Segments

Question 3

an identifier to an application, used in the transport layer header to indicate to which application that piece of data is associated.

Answer 3

Port Number

Question 4

each particular set of pieces flowing between a source application and a destination application

Answer 4

Conversation

Question 5

____ can prevent the loss of segments on the network and avoid the need for retransmission.

Answer 5

Flow Control

Question 6

ensure that all pieces reach their destination by having the source device retransmit any data that is lost.

Answer 6

Error Recovery

Question 7

can provide connection orientation by creating a session between the applications.

Answer 7

Initiating a Session

Question 8

is connectionless, and provide just the basic functions for efficiently delivering the data pieces between the appropriate applications.

useful for applications whose data is sensitive to delays.

Answer 8

UDP (User Datagram Protocol)

Question 9

• connection-oriented
• describe processes that provide additional features, such as ensuring reliable delivery between the applications.

Answer 9

TCP (Transmission Control Protocol)

Question 10

At the transport layer, the three basic operations of reliability are

Answer 10

• Tracking transmitted data
• Acknowledging received data
• Retransmitting any unacknowledged data

Question 11

Additional functions of TCP

Answer 11

same-order delivery, reliable delivery, and flow control

Question 12

Each segment has ___ bytes of overhead

Answer 12

20

Question 13

To support these reliability operations, more ____ is exchanged between the sending and receiving hosts.

Answer 13

control data

Question 14

simple, connectionless protocol

Answer 14

UDP

Question 15

• has the advantage of providing low-overhead data delivery
• sends datagrams (segments of communication) as “best effort”
• each segment has only 8 bytes of overhead.

Answer 15

UDP

Question 16

In UDP, it sends datagrams (segments of communication) as “____”

Answer 16

best effort

Question 17

• the number for a communication associated with the originating application on the local host
  
  • must not conflict with other ports in use at the time
  • acts as a ‘return address’ of sorts for the requesting application

Answer 17

source port number

Question 18

• the number for a communication associated with the destination application on the remote host
  
  • assigned to the service daemon running on the remote host

Answer 18

destination port number

Question 19

• combination of the transport layer port number and the network layer IP address assigned to the host
• uniquely identifies a particular process running on a specific host device

Answer 19

Socket

Question 20

• assigns port numbers
• standards body that is responsible for assigning various addressing standards.

Answer 20

Internet Assigned Numbers Authority (IANA)

Question 21

● An important network utility that can be used to verify which active TCP connections are open and running on a networked host

● Lists the protocol in use, the local address and port number, the destination address and port number, and the state of the connection

Answer 21

netstat Command

Question 22

Use ____ to examine the open connections on a host when performance appears to be compromised.

Answer 22

netstat

Question 23

Dividing data into manageable pieces ensures data is transmitted within the limits of the media
and can be multiplexed onto the media.

Answer 23

Segmentation and Reassembly

Question 24

○ sequence numbers are used for reassembly at the destination in the correct order.
○ data is ensured to be in the exact form the sender intended.

Answer 24

TCP Segmentation and Reassembly

Question 25

○ not concerned with order or maintaining a connection.
○ generates less overhead which means faster data transfer.
○ applications that use UDP must tolerate the fact that data may not arrive in the order that
it was sent.
○ does NOT require reliable delivery of packets.

Answer 25

UDP Segmentation and Reassembly

Question 26

The key distinction between TCP and UDP is _____.

Answer 26

reliability

Question 27

Before a host using TCP sends data to another host, the transport layer initiates a ______ with the destination.

Answer 27

process to create a connection

Question 28

This connection enables ____, between the hosts.

Answer 28

the tracking of a session, or communication stream

Question 29

This process ensures that each host is____ for the communication.

Answer 29

aware of and prepared

Question 30

When two hosts communicate using TCP, a ____ is established before data can be exchanged.

Answer 30

connection

Question 31

After the communication is completed, the ___ and the connection is terminated.

Answer 31

sessions are closed

Question 32

● Establishes that the destination device is present on the network.

● Verifies that the destination device has an active service and is accepting requests on the
destination port number that the initiating client intends to use for the session.

● Informs the destination device that the source client intends to establish a communication session
on that port number.

Answer 32

TCP Three-Way Handshake

Question 33

If an acknowledgement isn’t sent that data was received, the host will ____ the data because it has reached a timeout.

Answer 33

Resend

Question 34

the amount of data a source can transmit before an ACK must be received. It enables the mgt. of lost data and flow control.

Answer 34

Window size

Question 35

also known as ephemeral ports, are
usually assigned dynamically to client applications when initiating a connection.

Answer 35

Dynamic or Private Ports

Question 36

is a standards body that is responsible for assigning various addressing standards.

Answer 36

Internet Assigned Numbers Authority (IANA)