The transport layer is responsible for process-to-process delivery of data across network layers. There are three main protocols at the transport layer: UDP, TCP, and SCTP. UDP provides connectionless and unreliable data delivery, while TCP and SCTP provide connection-oriented and reliable delivery. The transport layer requires port numbers along with IP addresses to uniquely identify the sending and receiving processes and allow for multiplexing and demultiplexing of data between different applications and processes.

1. Transport Layer

2. Position of Transport Layer
• Responsible for the delivery of a message from one process to another

3. Types of data deliveries
• The transport layer is responsible for process-to-process
delivery.
• Process (application program ??)

4. The internetr model has three protocols at the
transport layer.
UDP – is the simplest protocols
TCP – is complex than UDP
SCTP –
is designed for multimedia applications

5. Client-Server Paradigm

6. Addressing
Address is required for delivery of data
Data link layer needs MAC addresses
Network layer needs IP addresses
Transport layer requires port number

7. The internet uses specific port numbers for servers, called
well known port numbers.

10. Socket address
• Process-to-process delivery needs two identifiers, IP address
and the port number
• Socket address is the combination of an IP address and a port
number
• A transport-layer protocol needs a pair of socket addresses; the
client and server socket address
• IP header contains IP address and UDP/TCP contain port
number

11. Multiplexing and demultiplexing

13. Connectionless vs. Connection-oriented
• Connection-oriented: connection established, data transferred,
connection released
– TCP and SCTP
• Connectionless: UDP

14. Reliable vs. Unreliable

15. Reliability at the data link layer is between two nodes,
whereas Reliability at the transport layer is between two
ends

16. Position of UDP, TCP, and SCTP

17. UDP

18. Well-known Ports for UDP

22. UDP Operation
• Connectionless services
• Flow and error control
• Encapsulation and decapsulation
• Queuing

25. Use of UDP
• Suitable for a process that requires simple request-response
communication with little concern for flow and error control,
not suitable for FTP which sends a bulk of data.
• Suitable for a process with internal flow and error control
mechanisms such as TFTP( )
• Suitable for multicasting. Multicasting is available in UDP but
not in TCP.
• Used for management processes such as SNMP
• Used for some route updating protocols such as RIP