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OSI Model Transport Layer (Layer 4)
The transport layer implements reliable
internetwork data transport services that are transparent to upper layers.
Transport-layer functions typically include flow control, multiplexing, virtual
circuit management, and error checking and recovery.
Flow control manages data transmission between devices so that the transmitting device
does not send more data than the receiving device can process. Multiplexing enables
data from several applications to be transmitted onto a single physical link. Virtual
circuits are established, maintained, and terminated by the transport layer. Error
checking involves creating various mechanisms for detecting transmission errors, while
error recovery involves taking an action, such as requesting that data be
retransmitted, to resolve any errors that occur.
Some transport-layer implementations include Transmission Control Protocol, Name
Binding Protocol, and OSI transport protocols. Transmission Control Protocol (TCP) is
the protocol in the TCP/IP suite that provides reliable transmission of data. Name
Binding Protocol (NBP) is the protocol that associates AppleTalk names with addresses.
OSI transport protocols are a series of transport protocols in the OSI protocol suite.
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