In data communications networks, packet segmentation is the process of dividing a data
packet into smaller units for transmission over the network. Packet segmentation happens at layer four of the
OSI model
The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...
; the
transport layer
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end ...
.
Segmentation may be required when:
* The data packet is larger than the
maximum transmission unit
In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size th ...
supported by the network
* The network is unreliable and it is desirable to divide the information into smaller segments to maximize the probability that each one of them can be delivered correctly to the destination
Protocols that perform packet segmentation at the source usually include a mechanism at the destination to reverse the process and reassemble the original packet from individual segments. This process may include
automatic repeat-request (ARQ) mechanisms to detect missing segments and to request the source to re-transmit specific segments.
In a communication system based on a layered
OSI model
The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...
, packet segmentation may be responsible for splitting one
MPDU into multiple
physical layer
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip.
Th ...
service data units so that reliable transmission (and potential re-transmission via ARQ) of each one can be performed individually.
The
ITU-T
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Commu ...
G.hn standard, which provides a way to create a high-speed (up to 1 gigabit/s)
local area network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
using existing home wiring (
power lines, phone lines and
coaxial cables), is an example of a protocol that employs packet segmentation to increase reliability over noisy media.
See also
* ''
Fujitsu Ltd. v. Netgear Inc.
''Fujitsu Ltd. v. Netgear Inc.'', 620 F.3d 1321 (Fed. Cir. 2010), was a patent infringement case centered on three patents claimed to be required for full compliance of the IEEE 802.11 (WiFi) standard and the WiFi Alliance Wireless Multimedi ...
''
*
Packet aggregation
*
Segmentation and reassembly
Segmentation and reassembly (SAR) is the process used to fragment and reassemble variable length packets into fixed length cells so as to allow them to be transported across Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM) ...
References
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Packets (information technology)