When files are transferred between a host and an FTP server, the data is divided into smaller pieces for transmission. As these pieces arrive at the destination host, they must be reassembled to reconstruct the original file. What provides for the reassembly of these pieces into the correct order?

A. The sequence number in the TCP header
B. The Start Frame Delimiter in the 802.3 Preamble
C. The TTL in the IP header
D. The acknowledgement number in the segment header
E. The frame check sequence in the Ethernet frame trailer

Answer: A

Explanation:

The Transport layer can provide reliable networking via acknowledgments, sequencing, and flow control.Acknowledgments Delivered segments are acknowledged to the sender. If they are not acknowledged, the sender will retransmit.Sequencing Data segments are sequenced into their original order when they arrive at the destination.

Flow Control Provides buffer controls that prevent packet flooding to the destination host. Buffers store bursts of data for processing when the transmission is complete.

Layer 4 protocols include the following:
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)
Sequenced Packet Exchange (SPX)A reliable communications protocol created by Novell
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