Networking: Transport and Application Layers

Question 1

ACK flag

Answer 1

One of the TCP control flags. ACK is short for acknowledge. A value of one in this field means that the acknowledgment number field should be examined

Question 2

Acknowledgement number

Answer 2

The number of the next expected segment in a TCP sequence

Question 3

Application layer

Answer 3

The layer that allows network applications to communicate in a way they understand each other

Question 4

Application layer payload

Answer 4

The entire contents of whatever data applications want to send to each other

Question 5

CLOSE

Answer 5

A connection state that indicates that the connection has been fully terminated, and that no further communication is possible

Question 6

CLOSE_WAIT

Answer 6

A connection state that indicates that the connection has been closed at the TCP layer, but that the application that opened the socket hasn’t released its hold on the socket yet

Question 7

Connection-oriented protocol

Answer 7

A data-transmission protocol that establishes a connection at the transport layer, and uses this to ensure that all data has been properly transmitted

Question 8

Connectionless protocol

Answer 8

A data-transmission protocol that allows data to be exchanged without an established connection at the transport layer. The most common of these is known as UDP, or User Datagram Protocol

Question 9

Data offset field

Answer 9

The number of the next expected segment in a TCP packet/datagram

Question 10

Demultiplexing

Answer 10

Taking traffic that’s all aimed at the same node and delivering it to the proper receiving service

Question 11

Destination port

Answer 11

The port of the service the TCP packet is intended for

Question 12

ESTABLISHED

Answer 12

Status indicating that the TCP connection is in working order, and both sides are free to send each other data

Question 13

FIN

Answer 13

One of the TCP control flags. FIN is short for finish. When this flag is set to one, it means the transmitting computer doesn’t have any more data to send and the connection can be closed

Question 14

FIN_WAIT

Answer 14

A TCP socket state indicating that a FIN has been sent, but the corresponding ACK from the other end hasn’t been received yet

Question 15

Firewall

Answer 15

It is a device that blocks or allows traffic based on established rules

Question 16

FTP

Answer 16

An older method used for transferring files from one computer to another, but you still see it in use today

Question 17

Handshake

Answer 17

A way for two devices to ensure that they’re speaking the same protocol and will be able to understand each other

Question 18

Instantiation

Answer 18

The actual implementation of something defined elsewhere

Question 19

Listen

Answer 19

It means that a TCP socket is ready and listening for incoming connections

Question 20

Multiplexing

Answer 20

It means that nodes on the network have the ability to direct traffic toward many different receiving services

Question 21

Options field

Answer 21

It is sometimes used for more complicated flow control protocols

Question 22

Port

Answer 22

It is a 16-bit number that’s used to direct traffic to specific services running on a networked computer

Question 23

Presentation layer

Answer 23

It is responsible for making sure that the unencapsulated application layer data is actually able to be understood by the application in question

Question 24

PSH flag

Answer 24

One of the TCP control flags. PSH is short for push. This flag means that the transmitting device wants the receiving device to push currently- buffered data to the application on the receiving end as soon as possible

Question 25

RST flag

Answer 25

One of the TCP control flags. RST is short for reset. This flag means that one of the sides in a TCP connection hasn’t been able to properly recover from a series of missing or malformed segments

Question 26

Sequence number

Answer 26

A 32-bit number that’s used to keep track of where in a sequence of TCP segments this one is expected to be

Question 27

Server or Service

Answer 27

A program running on a computer waiting to be asked for data

Question 28

Session layer

Answer 28

The network layer responsible for facilitating the communication between actual applications and the transport layer

Question 29

Socket

Answer 29

The instantiation of an endpoint in a potential TCP connection

Question 30

Source port

Answer 30

A high numbered port chosen from a special section of ports known as ephemeral ports

Question 31

SYN flag

Answer 31

One of the TCP flags. SYN stands for synchronize. This flag is used when first establishing a TCP connection and make sure the receiving end knows to examine the sequence number field

Question 32

SYN_RECEIVED

Answer 32

A TCP socket state that means that a socket previously in a listener state, has received a synchronization request and sent a SYN_ACK back

Question 33

SYN_SENT

Answer 33

A TCP socket state that means that a synchronization request has been sent, but the connection hasn’t been established yet

Question 34

TCP checksum

Answer 34

A mechanism that makes sure that no data is lost or corrupted during a transfer

Question 35

TCP segment

Answer 35

A payload section of an IP datagram made up of a TCP header and a data section

Question 36

TCP window

Answer 36

The range of sequence numbers that might be sent before an acknowledgement is required

Question 37

URG flag

Answer 37

One of the TCP control flags. URG is short for urgent. A value of one here indicates that the segment is considered urgent and that the urgent pointer field has more data about this

Question 38

Urgent pointer field

Answer 38

A field used in conjunction with one of the TCP control flags to point out particular segments that might be more important than others