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Which OSI layer is associated with the following: The acknowledgement of transmissions, sequencing, and flow control across a network?

A. Layer 2
B. Layer 3
C. Layer 4
D. Layer 5
E. Layer 6
F. Layer 7

Answer: C


The Transport layer (Layer 4) defines several functions, including the choice of protocols. The most important Layer 4 functions are error recovery and flow control. The transport layer may provide for retransmission, i.e., error recovery, and may use flow control to prevent unnecessary congestion by attempting to send data at a rate that the network can accommodate, or it might not, depending on the choice of protocols. Multiplexing of incoming data for different flows to applications on the same host is also performed. Reordering of the incoming data stream when packets arrive out of order is included.

Examples include: TCP, UDP, and SPX.