TCP and UDP in Transport Layer

Layer 3 or the Network layer employs IP, or Internet Protocol, which is a connectionless protocol that processes each packet independently, resulting in a lack of transmission dependability. When data is transmitted from one host to another, each packet, even though it belongs to the same session, may travel a distinct path. This implies that the packets could or might not arrive in the correct order. As a result, IP’s dependability is reliant on higher-layer protocols.

Transmission Control Protocol (TCP)

TCP is a protocol that allows data to be sent from one computer to another. TCP is a layer 4 protocol that offers packet acknowledgment and is also reliable since it resends missed packets. It is superior to UDP. However, because of these qualities, it has a disadvantage.

User Datagram Protocol (UDP)

User Datagram Protocol is also one layer 4 protocol, but unlike Transmission Control Protocol, it doesn’t acknowledge sent packets. Thus, it is unreliable and relies on higher-layer protocols to function. However, as compared to TCP, it is simpler, more scalable, and has a lower overhead. It’s used to stream video and audio.


Following are the major factors that differentiate TCP and UDP −

Session Multiplexing

A single host can interact with many servers using a single IP address. When utilizing TCP, the server and receiver must first create a connection, which must then be terminated after the transfer is complete. TCP also ensures that the transmission is reliable while it is going place.

UDP, on the other hand, does not recognize that the packets have been received. As a result, it is unreliable.


Fastethernet’s Maximum Transmission Unit, or MTU, is 1500 bytes, while TCP’s theoretical limit is 65495 bytes. As UDP does not enable this, data segmentation must rely on higher-layer protocols.

Flow Control

If the transmitter delivers data faster than the receiver can process it, the receiver will drop it and seek a replay, wasting time and resources. TCP offers end-to-end flow control through the use of a sliding window. The sliding window transmits an acknowledgment from the receiver’s end, indicating the amount of data that may be received at any given moment.

UDP does not support flow control and must rely on higher-layer protocols to do so.


TCP is connection orientated, which means it establishes a connection for the transmission and then closes that connection once the transfer is complete. UDP, on the other hand, is connectionless, just like IP (Internet Protocol).

TCP provides an acknowledgment when it gets a packet, which ensures its reliability. If a packet gets lost, it asks for retransmission. For this, UDP relies on higher-layer protocols.