In
computer networking
A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or b ...
, out-of-order delivery is the delivery of
data packets
In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the '' payload''. Control inform ...
in a different order from which they were sent. Out-of-order delivery can be caused by packets following multiple paths through a network, by lower-layer
retransmission procedures (such as
automatic repeat request
Automatic repeat request (ARQ), also known as automatic repeat query, is an error-control method for data transmission that uses acknowledgements (messages sent by the receiver indicating that it has correctly received a message) and timeout ...
), or via parallel processing paths within network equipment that are not designed to ensure that packet ordering is preserved. One of the functions of
TCP is to prevent the out-of-order delivery of data, either by reassembling packets in order or requesting retransmission of out-of-order packets.
See also
*
Packet loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Ku ...
*
Selective ACK
Retransmission, essentially identical with automatic repeat request (ARQ), is the resending of packets which have been either damaged or lost. Retransmission is one of the basic mechanisms used by protocols operating over a packet switched comp ...
*
IP fragmentation
400px, An example of the fragmentation of a protocol data unit in a given layer into smaller fragments
IP fragmentation is an Internet Protocol (IP) process that breaks packets into smaller pieces (fragments), so that the resulting pieces can p ...
*
Head-of-line blocking
Head-of-line blocking (HOL blocking) in computer networking is a performance-limiting phenomenon that occurs when a queue of packets is held up by the first packet in the queue. This occurs, for example, in input-buffered network switches, out-o ...
External links
* , ''Packet Reordering Metrics'', A. Morton, L. Ciavattone, G. Ramachandran, S. Shalunov, J. Perser, November 2006
* , ''Improved Packet Reordering Metrics'', A. Jayasumana, N. Piratla, T. Banka, A. Bare, R. Whitner, June 2008
* https://web.archive.org/web/20171022053352/http://kb.pert.geant.net/PERTKB/PacketReordering
* http://www-iepm.slac.stanford.edu/monitoring/reorder/
* https://www.usenix.org/conference/nsdi12/minion-unordered-delivery-wire-compatible-tcp-and-tls
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Packets (information technology)