Week 3 Transport Layer Flashcards
Transport Layer
Allow traffic to be directed to specific network applications
Application Layer
Allows these applications to communicate in a way to understand
Port
16-bit number that’s used to direct traffic to specific services running on a network computer
TCP segment
Made up of a TCP header and a data section
Destination port
The port of the service the traffic is intended for
Source port
A high level port chosen from a special section of ports known as ephemeral ports
Sequence number
32 bit number that used to keep track of where in a sequence of TCP segments this one is expected to be
Acknowledge number
The number of the expected segment
Data offset field
4 bit number that communicates how long the TCP header for the segment is
TCP window
Specifies the range of sequence numbers that might be sent before an acknowledgement is required
Checksum
16 bit, once all segments has been ingested by recipient it is calculated across the entire segment and is compare with checksum header to make sure there is no data lost or corruption
Urgent pointer field
Used in conjunction with one of the TCP control flags to point out particular segments that might be more important than others
Options field
Sometimes used for more complicated flow control protocols
Padding
A sequence of zeros to make sure the data payload begins at the expected location
URG (urgent)
(Control Flag)
A value of one here indicates that the segment is considered urgent and that the urgent pointer field has more data about this
ACK (acknowledged)
(Control flag)
A value of one in this field means that the acknowledgment number field should be examined
PSH (push)
(control flag)
The transmitting device wants the receiving device to push currently buffered data to the application on the receiving end as soon as possible
RST (reset)
( control flag)
One of the sides in a tcp connection hasn’t been able to properly recover from a series of missing or malformed segments
SYN (synchronize)
(Control flag)
It’s used when first establishing a tcp connection and makes sure the receiving end knows to examine the sequence number field
FIN (finish)
(control flag)
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
Handshake
A way for two devices to ensure that they’re speaking the same protocol and will be able to understand each other
Socket
The installation of end point in a potential tcp connection
Instantiating
The actual implementation of something defined elsewhere
LISTEN
(Server side)
A tcp socket is ready and listening for incoming connections
SYN_SENT
(Client side)
A synchronization request has been sent, but the connection hasn’t been established yet
SYN_RECEIVED
(Server side)
A socket previously in a listen state has received a synchronization request and sent a SYN/ACK back
ESTABLISHED
The TCP connection is in working order and both sides are free to send each other data
FIN_WAIT
A FIN been sent, but the corresponding ACK from the other end hasn’t been received yet
CLOSE_WAIT
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
CLOSED
The connection has been fully terminated and that no further communication is possible
Connection oriented protocol
Establishes a connection and uses this to ensure that all data has been properly transmitted
Firewall
A device that blocks traffic that reaches certain criteria
Which TCP flag is used to make listing program respond immediately?
PSH
What is identified as ports 49152 through 65535?
Ephemeral ports
User data protocol (UDP)
A transfer protocol that does not rely on connections. This protocol does not support the concept of acknowledgement. With UDP, you just set a destination port and send data packet.
Multiplexing
Means that nodes on the network have the ability to direct traffic toward many different receiving services
Demultiplexing
Taking traffic that’s all aimed at the same node and delivering it to the proper receiving services
