Transport layer
layer in the OSI and TCP/IP models providing host-to-host communication services for applications
In computer networking, the transport layer is an abstraction layer in a network protocol stack that provides communication services between applications. Depending on the protocol, these services may include connection-oriented communication, reliable and ordered delivery, flow control, congestion control, and the multiplexing of communication between applications.
The transport layer is defined in both the Internet protocol suite and the OSI model, although the functions assigned to it differ between the two architectures. In the OSI model, the transport layer is Layer 4 (L4). The layers of the Internet protocol suite are not formally numbered.
The principal transport protocols of the Internet protocol suite are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP). TCP provides a connection-oriented, reliable byte stream service, while UDP provides a connectionless datagram service with fewer protocol mechanisms. Other transport protocols include the Stream Control Transmission Protocol (SCTP) and the Datagram Congestion Control Protocol (DCCP). Newer transport protocols, such as QUIC, may be implemented over UDP.
Services
Transport layer services are conveyed to an application via a programming interface to the transport layer protocols. The services may include the following features:
Connection-oriented communication: It is normally easier for an application to interpret a connection as a data stream rather than having to deal with the underlying connection-less models, such as the datagram model of the User Datagram Protocol (UDP) and of the Internet Protocol (IP).
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 20, 2026. The linked authority identifier is Q209372. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Transport layer” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.