ARPANET

• ARPANET stands for Advanced Research Projects Agency Network (ARPANET).
• It was the world’s first fully operational packet switching computer network.
• It was built to accommodate research equipment on packet switching technology and to allow resource sharing.
• ARPANET became popular among academicians and research scholars for collaboration through electronic mail and other services.
• It is also called a predecessor of the modern Internet.
• Because many of the protocols used by computer networks today were developed for ARPANET.
• Such as the TCP/IP reference model was used earlier by ARPANET, before being used on the Internet.
• Therefore, it is considered the forerunner of the modern internet.
• Before ARPANET, the networks were the telephone networks that operated on the circuit switching principle.
• But this circuit-switched network was too vulnerable, the loss of even one line or switch would terminate all the conversations.
• To overcome this problem ARPANET was built with the concept of a packet switching network consisting of the subnet and host computers.
• The subnet was a datagram subnet and each subnet consists of mini-computers called Interface Message Processors (IMPs).
• Each node of the network used to have an IMP and a host connected by a short wire
• The host could send messages of up to 8063 bits to its IMP which would break them into packets and forward them independently toward the destination.
• The subnet was the first electronic store-and-forward type packet-switched network.
• So each packet was stored before it was forwarded.
• Therefore, the software for ARPANET was split into two parts namely subnet and host.
• The TCP/IP model and protocol were invented specifically to handle communication over internetwork because more and more networks were getting connected to ARPANET.
• ARPANET is considered a version of WAN.
• In 1983 the management of ARPANET was handed over to the Defense Communications Agency (DCA) which separated the military portion into a separate MILNET.
• By 1990 the ARPANET was shut down and dismantled, however, MILNET continues to operate.

Benefits of ARPANET:

• ARPANET was first built to service even in a Nuclear Attack by the US.
• It allows collaborations through Emails.
• It improves the process of transfer of files and data of defense.

Limitations of ARPANET:

• Increased number of LAN connections resulted in difficulty handling.
• It was unable to cope-up with advancements in technology.

DARPANET

• DARPANET meaning is Defense ARPANET.
• The United States government network merged with the ARPANET to form the DARPA Internet.
• This was during the height of the Cold War.
• The U.S. military was interested in creating computer networks that could continue to function after having portions removed, such as in the case of a nuclear strike.
• This eventually gave rise to the Internet.
• In 1972, the name of the department changed to the Defense Advanced Research Projects Agency (DARPA), and so many assume that the name of the network also changed to DARPANET.