Transport Layer

Position of Transport Layer

• Responsible for the delivery of a message from one process to another

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

The internetr model has three protocols at the transport layer.

UDP – is the simplest protocolsTCP – is complex than UDPSCTP –

is designed for multimedia applications

Client-Server Paradigm

Address is required for delivery of dataData link layer needs MAC addressesNetwork layer needs IP addressesTransport layer requires port number

Addressing

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

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

Multiplexing and demultiplexing

Connectionless vs. Connection-oriented• Connection-oriented: connection established, data transferred,

connection released

– TCP and SCTP

• Connectionless: UDP

Reliable vs. Unreliable

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

Position of UDP, TCP, and SCTP

UDP

Well-known Ports for UDP

UDP Operation

• Connectionless services

• Flow and error control

• Encapsulation and decapsulation

• Queuing

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