Q. Function of TCP/IP Transport Layer ?

TCP/IP Transport Layer

- Defines two standard transport protocols UDP and TCP

- TCP equipment a dependable data-stream protocol

• Connection oriented

- UDP implements an undependable data-stream

• Connectionless

- TCP offers reliable data transmission

- UDP is helpful in many applications

• e.g. Where data requirements to be broadcasted or multicasted

- Primary difference is that UDP doesn't necessarily provide reliable data transmission

- Several programs will use a separate TCP connection as well as a UDP connection

- TCP is accountable for data recovery

• By providing a series number with each packet that it sends
• TCP needs acknowledgement (ACK) to ensure correct data is received

- Packet is able to be retransmitted if error detected

- Use of acknowledgement (ACK)

- Flow control with Window

• by means of specifying an acceptable range of sequence numbers

- UDP and TCP introduce the concept of ports

- Common ports as well as the services that run on them:

 FTP 21 and 20

 telnet 23

 SMTP 25

 http 80

 POP3 110

- By specifying ports as well as including port numbers with TCP/UDP data multiplexing is achieved

- Multiplexing permits multiple network connections to take place simultaneously

- The port numbers together with the source and destination addresses for the data determine a socket