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Packet Segmentation
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 transport layer. Segmentation may be required when: * The data packet is larger than the maximum transmission unit 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, packet segmentation may be responsible for splitt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Packet
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 information provides data for delivering the payload (e.g., source and destination network addresses, error detection codes, or sequencing information). Typically, control information is found in packet headers and trailers. In packet switching, the bandwidth of the transmission medium is shared between multiple communication sessions, in contrast to circuit switching, in which circuits are preallocated for the duration of one session and data is typically transmitted as a continuous bit stream. Terminology In the seven-layer OSI model of computer networking, ''packet'' strictly refers to a protocol data unit at layer 3, the network layer. A data unit at layer 2, the data link layer, is a ''frame''. In layer 4, the transport layer, the data u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 between a computing system are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. The model partitions the flow of data in a communication system into seven abstraction layers to describe networked communication from the physical implementation of transmitting bits across a communications medium to the highest-level representation of data of a distributed application. Each intermediate layer serves a class of functionality to the layer above it and is served by the layer below it. Classes of functionality are realized in all software development through all and any standardized communication protocols. Each layer in the OSI model has its own well-defined functi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 communication services for applications. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing. The details of implementation and semantics of the transport layer of the Internet protocol suite, which is the foundation of the Internet, and the OSI model of general networking are different. The protocols in use today in this layer for the Internet all originated in the development of TCP/IP. In the OSI model the transport layer is often referred to as Layer 4, or L4, while numbered layers are not used in TCP/IP. The best-known transport protocol of the Internet protocol suite is the Transmission Control Protocol (TCP). It is used for connection-oriented transmissions, whereas the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 that can be transported on the data link layer, e.g. Ethernet frame. Larger MTU is associated with reduced overhead. Smaller MTU values can reduce network delay. In many cases, MTU is dependent on underlying network capabilities and must be adjusted manually or automatically so as to not exceed these capabilities. MTU parameters may appear in association with a communications interface or standard. Some systems may decide MTU at connect time, e.g. using Path MTU Discovery. Applicability MTUs apply to communications protocols and network layers. The MTU is specified in terms of bytes or octets of the largest PDU that the layer can pass onwards. MTU parameters usually appear in association with a communications interface ( NIC, serial port, et ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 (specified periods of time allowed to elapse before an acknowledgment is to be received) to achieve reliable data transmission over an unreliable communication channel. If the sender does not receive an acknowledgment before the timeout, it re-transmits the packet until it receives an acknowledgment or exceeds a predefined number of retransmissions. Variations of ARQ protocols include Stop-and-wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. All three protocols usually use some form of sliding window protocol to help the sender determine which (if any) packets need to be retransmitted. These protocols reside in the data link or transport layers (layers 2 and 4) of the OSI model. Examples The Transmission Control Protocol uses a varia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MPDU
In telecommunications, a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. It is composed of protocol-specific control information and user data. In the layered architectures of communication protocol stacks, each layer implements protocols tailored to the specific type or mode of data exchange. For example, the Transmission Control Protocol (TCP) implements a connection-oriented transfer mode, and the PDU of this protocol is called a ''segment'', while the User Datagram Protocol (UDP) uses datagrams as protocol data units for connectionless communication. A layer lower in the Internet protocol suite, at the Internet layer, the PDU is called a packet, irrespective of its payload type. Packet-switched data networks In the context of packet switching data networks, a protocol data unit (PDU) is best understood in relation to a service data unit (SDU). The features or services of the network are implemented in disti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to broadcast on, the line code to use and similar low-level parameters, are specified by the physical layer. Role The physical layer defines the means of transmitting a stream of raw bits over a physical data link connecting network nodes. The bitstream may be grouped into code words or symbols and converted to a physical signal that is transmitted over a transmission medium. The physical layer consists of the electronic circuit transmission technologies of a network. It is a fundamental layer underlying the higher level functions in a network, and can be imple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Service Data Unit
In Open Systems Interconnection (OSI) terminology, a service data unit (SDU) is a unit of data that has been passed down from an OSI layer or sublayer to a lower layer. This unit of data (SDU) has not yet been encapsulated into a protocol data unit (PDU) by the lower layer. That SDU is then encapsulated into the lower layer's PDU and the process continues until reaching the PHY, physical, or lowest layer of the OSI ''stack''. The SDU can also be thought of as a set of data that is sent by a user of the services of a given layer, and is transmitted semantically unchanged to a peer service user. SDU and PDU It differs from a PDU in that the PDU specifies the data that will be sent to the peer protocol layer at the receiving end, as opposed to being sent to a lower layer. The SDU accepted by any given layer (n) from layer (n+1) above, is a PDU of the layer (n+1) above. In effect the SDU is the ' payload' of a given PDU. The layer (n) may add headers or trailers, or both, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Communication Technology such as X.509 for cybersecurity, Y.3172 and Y.3173 for machine learning, and H.264/MPEG-4 AVC for video compression, between its Member States, Private Sector Members, and Academia Members. The first meeting of the World Telecommunication Standardization Assembly (WTSA), the sector's governing conference, took place on 1 March of that year. ITU-T has a permanent secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland. The current director of the TSB is Chaesub Lee (of South Korea), whose first 4-year term commenced on 1 January 2015, and whose second 4-year term commenced on 1 January 2019. Chaesub Lee succeeded Malcolm Johnson (Director), Malc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 geographic distance, but also generally involves leased telecommunication circuits. Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical network technologies include ARCNET, Token Ring and AppleTalk. History The increasing demand and usage of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation. A number of experimental and early commercial LAN technologies were developed in the 1970s. Cambridge Ring was developed at Cambridge University starting in 1974. Ethe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power-line Communication
Power-line communication (also known as power-line carrier or PLC) carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers. A wide range of power-line communication technologies are needed for different applications, ranging from home automation to Internet access which is often called broadband over power lines (BPL). Most PLC technologies limit themselves to one type of wires (such as premises wiring within a single building), but some can cross between two levels (for example, both the distribution network and premises wiring). Typically transformers prevent propagating the signal, which requires multiple technologies to form very large networks. Various data rates and frequencies are used in different situations. A number of difficult technical problems are common between wireless and power-line communication, notably those of spread spectrum radio signals operating in a crowded environment. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethernet Over Coax
Ethernet over Coax (EoC) is a family of technologies that supports the transmission of Ethernet frames over coaxial cable. History The first Ethernet standard, known as 10BASE5 (ThickNet) in the family of IEEE 802.3, specified baseband operation over 50 ohm coaxial cable, which remained the principal medium into the 1980s, when 10BASE2 (ThinNet) coax replaced it in deployments in the 1980s; both being replaced in the 1990s when thinner, cheaper twisted pair cabling came to dominate the market. The use of coaxial cable for Ethernet has been deprecated by 2011. Research in Ethernet transmission over coaxial cable continued, as both consumers and telecommunications operators strive to use existing 75 ohm coaxial cable installations (from cable television or CATV), to carry broadband data into and through the home, and into multiple dwelling unit (MDU) installations. Most EoC technologies are being developed for in home or on premises networking and are expected to be operated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
