quartz/content/notes/18-transport-layer.md

title	aliases	tags
18-transport-layer		cosc203 lecture

chapter 3

service provided by transport layer

services

• process to process communication
  • logical communication between application processes
• multi and demulti plexing
  • communication for multiple applications of the same host
• flow control
  • ensure production reate <= consuption rate
• congestion control
  • too many sender, sending too fast

protocols

• TCP transmission control protocol
• UDP user datagram protocol

actions and sender

• is passed an app layer lessage
• determines segment header fields values
• creates segment
• passes segement to IP

actions at reciever

• recieves segment from IP
• checks header values
• extract app layer message
• de multiplexes message up to application via socket

multiplexing and demultiplexing

sender: handle data from multiple sockets, add transport header reciever: user header info to deliver segments to correct socket

how it works

port number

• 16 bit integer (0, 66635)
• segment has a source and a port number
• host uses IP and port to direct segment to appropriate socket

IANA (internet assign number authority) has divded port number into three ranges

• 0-1023 well known
• 1024-49151 registered
• 49152-65535 dynamic

principle of reliable data transfer

• compexity of reliable data transfer protocol depends on character istics of unreliable channel
• sender and reciever do not know the 'state' of each other. they need to communicate via a message - ACKknowledgement

TCP

• point to point communicate
  • one sender, one reciever
• reliable, in-order byte stream
  • no message boundaries
  • each byte has a position in the stream
• full duplex data
  • bi directional data flow in the same connection
  • MSS: maximum segment size
• cumulative ACKs
• connection-oriented
  • handshaking (exchange of control messages) initializes se

UDP