Eventually the destination computer will be a local computer on a network served by the last router in the
chain. When the data link software at the destination computer receives the message, the data link software will
strip the data link header from the IP packet, and pass the IP packet to the IP software. The IP software
CHAP. 7] NETWORKING 133
will verify the IP header checksum, reassemble the IP packet, if necessary, strip the IP header off the TCP
packet, and pass the TCP packet to the TCP software.
The TCP software will check the sequence number and verify the TCP checksum. If everything is in order,
the TCP software will remove the TCP header and transfer the line of HTML text to the waiting application
program, in this case a web browser.
THE WORLD WIDE WEB, HTTP, AND HTML
What we now call ???the Internet??? started with a US military project called ARPAnet. ARPA stands for
Advanced Research Projects Agency, which is part of the US Department of Defense. Work on ARPAnet began
in the late 1960s, with the goals of creating a universal and fault-tolerant mechanism for linking computers in
a wide network.
Packet switching, now the primary messaging technique of the Internet, was a new concept at the time, and
the ARPAnet developed its protocols around packet switching.
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