Transport Layer Flashcards
Transport layer
Allows traffic to be directed to specific network applications
Application layer
Allows these applications to communicate in a way they understand
Multiplexing
Means nodes on a network have the ability to direct traffic toward many different services.
Send data to IP address
Demultiplexing
Takes traffic that is all aimed at the same node and deliver it to the proper receiving service.
Sends from IP addresses
Port
A 16-bit number that’s used to direct traffic to specific services running on a networked computer
TCP segment
Made up of TCP header and a data section
(Like a ethernet frame and a IP datagram, just on a TCP level)
Source port
A highly numbered port chosen from a special section of ports known as ephemeral ports
Sequence number
A 32 bit number that’s used to keep track of where in a sequence of TCP segments this one is expected to be.
Acknowledgement number
The number of the next expected segment
Data offset field
A 4-bit number that communicates how long the TCP header for this segment
The 6 control flags
- URG- urgent
- ACK- acknowledged
- PSH- push
- RST- reset
- SYN- synchronize
- FIN- finish
Urgent pointer field
Used in conjunction with the TCP control flags to point out particular segments that might be more important than others
Options
Sometimes used for more complicated flow control protocols. Rarely used.
Padding
Sequence of zeros to make sure the data payload begins at the expected location
Buffer
A computing technique where a certain amount of data is held somewhere before sent somewhere else.
Handshake
A way for 2 devices to ensure they are speaking the same protocol and will be able to understand each other.
3 way handshake
SYN > SYN/ACK > ACK
4 way handshake
FIN > ACK > FIN > ACK
