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packet - technical definition

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In the generic sense, referring to the manner in which data are organized into discrete units for transmission and switching through a data network.The data unit can be known as a block, frame, cell, or packet, depending on the protocol specifics. The packet comprises a header, payload, and sometimes a trailer, again depending on protocol specifics. The packet can be a user packet containing user data, or a signaling and control packet for various network monitoring, alerting and alarming, maintenance, and other administrative purposes. The payload can be a complete message, a fragment or segment of a message, or an aggregation of bits or bytes that form a short portion of a long data stream associated with a voice or video call. See also bit, block, byte, cell, data stream, fragment, frame, header, message, payload, protocol, segment, and trailer.
In a technology-specific sense, a packet is a data unit in an internetwork, such as the Internet or other packet-switched network in which routers interconnect networks and subnetworks to exchange traffic between nodes. In terms of the OSI Reference Model, a packet is defined in Layer 3, the Network Layer. Blocks, cells, and frames are defined in Layer 2, the Data Link Layer, and have local significance, only. See also block, cell, datagram, Data Link Layer, frame, Internet, Network Layer, OSI Reference Model, packet switch, and router.

See packet in Webster''s New World Hacker Dictionary

Data travels along the Internet in packets that are sent individually across the network and then reassembled into the original data at the correct recipient address. Each packet is like a letter in that it has a sender and a receiver. When the packet reaches the correct receiver address, it stops traveling.

Every packet has the following fields: source IP address (such as 10.23.1.156); destination IP address; transport type (such as ICMP=1, TCP=6, UDP=17); source port and destination port (such as DNS=53, FTP=21, HTTP=80); and flags (such as SYN).

See Also: Encapsulation; Internet; Internet Protocol (IP); IP Address; Port and Port Numbers; Synchronize Packet (SYN).

Graham, R. Hacking Lexicon. [Online, 2001.] Robert Graham Website. http://www.linuxsecurity.com/resource_files/documentation/hacking-dict.html.

See packet in Computer

A block of data that is transmitted over the network in a packet-switched system. The terms frame, packet and datagram are often used synonymously. See packet switching.

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