DARPA supported the evolution of the ARPANET ( the first wide-area packet switching network ), Packet Radio Network, Packet Satellite Network and ultimately, the Internet and research in the artificial intelligence fields of speech recognition and signal processing, including parts of Shakey the robot.

This began with point-to-point communication between mainframe computers and terminals, expanded to point-to-point connections between computers and then early research into packet switching.

The Institute was founded in 1972, when packet switching pioneer Keith Uncapher left RAND Corporation with backing from the Defense Advanced Research Projects Agency.

Specifically, it is the worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol ( IP ).

Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links.

This article is concerned primarily with routing in electronic data networks using packet switching technology.

Once the 3B21D has loaded the software into the 5ESS and the switch is activated, packet switching takes place without further action by the 3B21D.

Instead of using leased lines, WANs can also be built using less costly circuit switching or packet switching methods.

Frame Relay is a standardized wide area network technology that specifies the physical and logical link layers of digital telecommunications channels using a packet switching methodology.

X. 25 remained the primary standard until the wide availability of IP made packet switching almost obsolete.

In a packet switched network, burst switching is a capability in which each network switch extracts routing instructions from an incoming packet header to establish and maintain the appropriate switch connection for the duration of the packet, following which the connection is automatically released.

Circuit switching contrasts with packet switching which divides the data to be transmitted into packets transmitted through the network independently.

In packet switching, instead of being dedicated to one communication session at a time, network links are shared by packets from multiple competing communication sessions, resulting in the loss of the quality of service guarantees that are provided by circuit switching.

In circuit switching, the bit delay is constant during a connection, as opposed to packet switching, where packet queues may cause varying and potentially indefinitely long packet transfer delays.

Some offer access thfough packet switched networks, or packet radio connections.

HTTPS is especially important over unencrypted networks such as WiFi as anyone on the same local network can do packet sniffing and discover sensitive information.

Additionally, many free to use and even paid for WLAN networks do packet injection for serving their own ads on webpages or just for pranks, however this can be exploited maliciously e. g. by injecting malware and spying on users.

ISDN is a circuit-switched telephone network system, which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide.

In 1972, Robert E. Kahn joined the DARPA Information Processing Technology Office, where he worked on both satellite packet networks and ground-based radio packet networks, and recognized the value of being able to communicate across both.

The technology itself was a leap forward, making it possible for nearly any packet station to act as a digipeater, linking distant stations with each other through ad hoc networks.

The most common use of packet is in amateur radio, to construct wireless computer networks.

Since radio circuits inherently possess a broadcast network topology ( i. e., many or all nodes are connected to the network simultaneously ), one of the first technical challenges faced in the implementation of packet radio networks was a means to control access to a shared communications channel.

These experiments were generally considered to be successful, and also marked the first demonstration of Internetworking, as in these experiments data was routed between the ARPANET, PRNET, and SATNET ( a satellite packet radio network ) networks.

Throughout the 1970s and 1980s, DARPA operated a number of terrestrial and satellite packet radio networks connected to the ARPANET at various military and government installations.

There are two principal approaches to QoS in modern packet-switched IP networks, a parameterized system based on an exchange of application requirements with the network, and a prioritized system where each packet identifies a desired service level to the network.

A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it gets to its destination node.

These devices were different from most previous packet networks in two ways.

The Real-time Transport Protocol ( RTP ) defines a standardized packet format for delivering audio and video over IP networks.

In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel.

Wiretaps were expanded to include addressing and routing information to allow surveillance of packet switched networks

The use of Wake-on-LAN technology on enterprise networks can sometimes conflict with network access control solutions such as 802. 1x or MAC-based authentication, which may prevent magic packet delivery if a machine's WoL hardware has not been designed to maintain a live authentication session while in a sleep state.

Extension headers carry options that are used for special treatment of a packet in the network, e. g., for routing, fragmentation, and for security using the IPsec framework.

Since routing is dynamic for every packet and the network maintains no state of the path of prior packets, it is possible that some packets are routed on a longer path to their destination, resulting in improper sequencing at the receiver.

A routing node calculates a checksum for a packet.

If the checksum is bad, the routing node discards the packet.

The forwarding of the packet is done based on the contents of the labels, which allows " protocol-independent packet forwarding " that does not need to look at a protocol-dependent routing table and avoids the expensive IP longest prefix match at each hop.

For end-users the use of MPLS is not visible directly, but can be assumed when doing a traceroute: only nodes that do full ip routing are shown as hops in the path, thus not the MPLS nodes used in between, therefore when you see that a packet hops between two very distant nodes and hardly any other ' hop ' is seen in that providers network ( or AS ) it is very likely that that network uses MPLS.

Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.

* Control plane: A router records a routing table listing what route should be used to forward a data packet, and through which physical interface connection.

Modern high-speed routers are highly specialized computers with extra hardware added to speed both common routing functions, such as packet forwarding, and specialised functions such as IPsec encryption.

When each router receives a packet, it searches its routing table to find the best match between the destination IP address of the packet and one of the network addresses in the routing table.

Besides making decision as which interface a packet is forwarded to, which is handled primarily via the routing table, a router also has to manage congestion, when packets arrive at a rate higher than the router can process.

Yet another function a router performs is called policy-based routing where special rules are constructed to override the rules derived from the routing table when a packet forwarding decision is made.