Course 2 Module 3 Flashcards

ACK flag

One of the TCP control flags indicating that the acknowledgment number field should be examined.

Acknowledgement number

The number of the next expected segment in a TCP sequence.

Application layer

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

Application layer payload

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

CLOSE

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

CLOSE_WAIT

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

Connection-oriented protocol

A data-transmission protocol that establishes a connection at the transport layer, ensuring proper data transmission.

Connectionless protocol

A data-transmission protocol that allows data to be exchanged without an established connection at the transport layer, the most common being UDP.

Data offset field

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

Demultiplexing

Taking traffic aimed at the same node and delivering it to the proper receiving service.

Destination port

The port of the service the TCP packet is intended for.

ESTABLISHED

Status indicating that the TCP connection is operational, allowing both sides to send data.

FIN

One of the TCP control flags indicating that the transmitting computer has no more data to send.

FIN_WAIT

A TCP socket state indicating that a FIN has been sent, but the corresponding ACK has not yet been received.

Firewall

A device that blocks or allows traffic based on established rules.

FTP

An older method used for transferring files from one computer to another.

Handshake

A method for two devices to ensure they are using the same protocol.

Instantiation

The actual implementation of something defined elsewhere.

Listen

Indicates that a TCP socket is ready and listening for incoming connections.

Multiplexing

The ability of nodes on the network to direct traffic toward different receiving services.

Options field

A field sometimes used for complicated flow control protocols.

Port

A 16-bit number used to direct traffic to specific services on a networked computer.

Presentation layer

Responsible for ensuring that unencapsulated application layer data is understandable by the application.

PSH flag

One of the TCP control flags indicating that the receiving device should push buffered data to the application.

RST flag

One of the TCP control flags indicating that one side of a TCP connection hasn't recovered properly from issues.

Sequence number

A 32-bit number used to track the position in a sequence of TCP segments.

Server or Service

A program running on a computer that awaits requests for data.

Session layer

The network layer facilitating communication between applications and the transport layer.

Socket

The instantiation of an endpoint in a potential TCP connection.

Source port

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

SYN flag

One of the TCP flags used when initially establishing a TCP connection.

SYN_RECEIVED

A TCP socket state where a listener has received a synchronization request and sent back a SYN_ACK.

SYN_SENT

A TCP socket state indicating that a synchronization request is sent, but the connection isn't established.

TCP checksum

A mechanism ensuring no data is lost or corrupted during transfer.

TCP segment

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

TCP window

The range of sequence numbers that can be sent before an acknowledgment is required.

URG flag

One of the TCP control flags indicating that the segment is considered urgent.

Urgent pointer field

A field used to indicate that certain segments are more important than others.