Transport Layer Flashcards
Main purpose
Data is segmented and sent to destination device
Multiplexing
Multiple apps use network at the same time
Reliable delivery
Lost segments of data are resent so data is received complete
Same order delivery
Ensures segments are reassembled into the proper order
Flow control
Manages data delivery if there is congestion on the host
Uses of TCP
Web browsers, email, file transfers; reliable delivery, connection oriented
Uses of UDP
DNS, VoIP, video streaming, TFTP, snmp, online games, RIP; uses datagrams
Socket
IP address + port number
Ex. 192.168.1.20:80
Well known port numbers
0 to 1023
Netstat command
Lists protocols in use
TCP headers contain…
Sequence numbers, order matters during reassembly
TCP initial session
- Initiates process to create connection with destination, initial sequence value
- Dest sends ack back
- Client sends ack back and session is established
Side note
An individual server cannot have two services assigned to the same port number
TCP session termination
- Send fin
- Destination sends ack
- Destination sends fin
- Host sends ack
RST reset connections
PSH PUSH FUNCTIONS
URG Urgent pointer field significant
Expectational acknowledgement
Multiple segments can be sent before acknowledgement to avoid overhead
Flow control
Adjusting rate of data flow between services in the session
Window size
Number of bytes sent before an acknowledgement is sent; can also be controlled dynamically
More UDP
Reliability provided by the application layer; no guaranteed delivery of datagrams
Registered ports
1034-49151; user processes or applications dynamically selected as client source port
Dynamic or private ports
49152-65535; to client apps when initiating a connection
Port number
Address for various applications and services; servers have static port numbers, clients have dynamic port numbers
