Multiplexing and Demultiplexing in Transport Layer

Multiplexing and Demultiplexing are essential functions of the Transport Layer that enable multiple applications to communicate simultaneously over a single network connection. These processes allow efficient sharing of network resources by managing data flow from multiple sources.

Multiplexing

Multiplexing is the process of collecting data from multiple application processes of the sender, enveloping that data with headers, and sending them as a whole to the intended receiver.

• In Multiplexing at the Transport Layer, data is collected from various application processes. These segments contain the source port number, destination port number, header files, and data.

• These segments are passed to the Network Layer which adds the source and destination IP address to create the datagram.

Demultiplexing

Delivering the received segments at the receiver side to the correct application layer processes is called demultiplexing.

• The destination host receives IP datagrams; each datagram has a source IP address and a destination IP address.

• Each datagram carries one transport layer segment with source and destination port numbers.

• The destination host uses the IP addresses and port numbers to direct the segment to the appropriate socket.

How It Works

The Transport Layer uses port numbers as unique identifiers to distinguish between different applications running on the same host. Common port numbers include:

• HTTP − Port 80

• HTTPS − Port 443

• FTP − Port 21

• SMTP − Port 25

When data arrives at the Transport layer, each segment is independently processed based on its destination port number and sent to the appropriate application on the destination machine.

Key Benefits

Conclusion

Multiplexing and demultiplexing enable multiple applications to share a single network connection efficiently. These processes use port numbers to identify and route data to the correct applications, making modern multitasking network communications possible.