In
computer networking
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ma ...
, out-of-order delivery is the delivery of
data packets
In telecommunications and computer networking, a network packet is a formatted unit of Data (computing), data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the ''Payload ...
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 packet) and timeouts ...
), 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.Kur ...
*
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 computer ...
*
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 ...
*
Head-of-line blocking
Head-of-line blocking (HOL blocking) in computer networking is a performance-limiting phenomenon that occurs when a line of packets is held up in a queue by a first packet. Examples include input buffered network switches, out-of-order delivery and ...
External links
* RFC 4737, ''Packet Reordering Metrics'', A. Morton, L. Ciavattone, G. Ramachandran, S. Shalunov, J. Perser, November 2006
* RFC 5236, ''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
{{network-stub
Packets (information technology)