|  | 2.1 | General Model of Communication
| 2.1.2 | Source, destination, and data packets

As you learned in chapter 1, the most basic level of computer information consists of binary digits, or bits (0s and 1s). Computers that send one or two bits of information, however, would not be very useful, so other groupings - bytes, kilobytes, megabytes, and gigabytes - are necessary. In order for computers to send information through a network, all communications on a network originate at a source, then travel to a destination.

As illustrated in the Figure, the information that travels on a network is referred to as data, packet, or data packet. A data packet is a logically grouped unit of information that moves between computer systems. It includes the source information along with other elements that are necessary in order to make communication possible and reliable with the destination device. The source address in a packet specifies the identity of the computer that sends the packet. The destination address specifies the identity of the computer that finally receives the packet.

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