Transport Layer in OSI Model Last Updated : 31 Jan, 2025 Comments Improve Suggest changes Like Article Like Report The transport layer, or layer 4 of the OSI model, controls network traffic between hosts and end systems to guarantee full data flows. It is positioned between the network and session layers in the OSI paradigm. The data packets must be taken and sent to the appropriate machine by the network layer. After that, the transport layer receives the packets, sorts them, and looks for faults. Subsequently, it directs them to the session layer of the appropriate computer program. Now, the properly structured packets are used by the session layer to hold the data for the application.Transport Layer in OSI ModelFunctions of Transport LayerThe Transport Layer is responsible for end-to-end communication of data packets. It provides a number of important functions that are responsible for reliable, efficient, and organized data transfer between host systems in a networked environment.The primary functions of the Transport Layer are:To read in detail about services offered by transport layer, refer to Transport Layer ServicesWorking of Transport LayerCommunication between end systems is dependable and effective thanks to the Transport Layer. Apart from regulating flow and accommodating numerous applications concurrently, it guarantees data delivery in a manner that guarantees accuracy and minimises mistakes. It accomplishes this by utilising a collection of methods and protocols that provide data transport.The primary function of the transport layer is to give application processes operating on several hosts direct access to communication services.Logical communication between application processes operating on separate hosts is facilitated by the transport layer. Application processes use the logical communication offered by the transport layer to deliver messages to one other even when they are running on different hosts and are not physically connected.The network routers do not implement the transport layer protocols; only the end systems do.For instance, the network layer receives services from TCP and UDP, two transport layer protocols, which offer distinct functionalities.Protocols at the transport layer offer multiplexing and demultiplexing capabilities. In addition, it offers other services including bandwidth assurances, latency guarantees, and dependable data transport.Every application at the application layer is capable of sending a message via either TCP or UDP. Either of these two protocols can be used by the application to interact. The internet protocol on the internet layer will then be communicated with by both TCP and UDP. The transport layer is readable and writeable by the applications.Transport Layer ProtocolsTransport Layer Protocol uses different protocol for the better communication between two ends uses of protocol may differ from specifications. Below mention are some protocols used in Transport Layer1. Transmission Control Protocol(TCP)TCP is connection-oriented Protocol.TCP is reliable protocol.As TCP is connection-oriented protocol, so first the connection is established between two ends and then data is transferred and then the connection is terminated after all data being sent.2. User Datagram Protocol (UDP)UDP is not reliable protocolThe protocol UDP is connectionless.When speed and size are more important than security and dependability, this kind of protocol is employed.The data from the higher layer is supplemented with transport-level addresses, checksum error control, and length information by UDP, an end-to-end transport level protocol.A user datagram is the packet that the UDP protocol generates.3. Stream Control Transmission Protocol (SCTP)Many Internet applications use SCTP to perform transport layer duties, similar to User Datagram Protocol (UDP) and Transmission Control Protocol (TCP). On top of a connectionless packet network like IP, SCTP is a dependable transport protocol that facilitates data transfer over the network in scenarios involving one or more IP addresses.Difference Between TCP and UDP at Transport LayerTCPUDPTCP is a connection-oriented protocolUDP is the connection-less protocolTCP is reliable.UDP is not reliable.TCP supports error-checking mechanisms. UDP has only the basic error-checking mechanism using checksums.An acknowledgment segment is present.No acknowledgment segment.TCP is slower than UDPUDP is faster, simpler, and more efficient than TCP.Retransmission of lost packets is possible in TCP, but not in UDP.There is no retransmission of lost packets in the User Datagram Protocol (UDP)TCP has a (20-60) bytes variable length header.The header length is fixed of 8 bytes.For practice, solve quiz on Transport Layer. 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