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Selective Repeat ARQ
Selective Repeat ARQ or Selective Reject ARQ is a specific instance of the automatic repeat request (ARQ) protocol used to manage sequence numbers and retransmissions in reliable communications. Summary Selective Repeat is part of the automatic repeat request (ARQ). With selective repeat, the sender sends a number of frames specified by a window size even without the need to wait for individual ACK from the receiver as in Go-Back-N ARQ. The receiver may selectively reject a single frame, which may be retransmitted alone; this contrasts with other forms of ARQ, which must send every frame from that point again. The receiver accepts out-of-order frames and buffers them. The sender individually retransmits frames that have timed out. Concept It may be used as a protocol for the delivery and acknowledgement of message units, or it may be used as a protocol for the delivery of subdivided message sub-units. When used as the protocol for the delivery of messages, the sending process ... [...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 message) and timeouts (specified periods of time allowed to elapse before an acknowledgment is to be received) If the sender does not receive an acknowledgment before the timeout, it re-transmits the message until it receives an acknowledgment or exceeds a predefined number of retransmissions. ARQ is used to achieve reliable data transmission over an unreliable communication channel. ARQ is appropriate if the communication channel has varying or unknown capacity. 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 tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Line Communication
Power-line communication (PLC) is the carrying of data on a conductor (the ''power-line carrier'') 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 envi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Error Detection And Correction
In information theory and coding theory with applications in computer science and telecommunications, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, and thus errors may be introduced during transmission from the source to a receiver. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data in many cases. Definitions ''Error detection'' is the detection of errors caused by noise or other impairments during transmission from the transmitter to the receiver. ''Error correction'' is the detection of errors and reconstruction of the original, error-free data. History In classical antiquity, copyists of the Hebrew Bible were paid for their work according to the number of stichs (lines of verse). As the prose books of the Bible were hardly ever w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logical Link Control
In the IEEE 802 reference model of computer networking, the logical link control (LLC) data communication protocol layer is the upper sublayer of the data link layer (layer 2) of the seven-layer OSI model. The LLC sublayer acts as an interface between the medium access control (MAC) sublayer and the network layer. The LLC sublayer provides multiplexing mechanisms that make it possible for several network protocols (e.g. IP, IPX and DECnet) to coexist within a multipoint network and to be transported over the same network medium. It can also provide flow control and automatic repeat request (ARQ) error management mechanisms. Operation The LLC sublayer is primarily concerned with multiplexing protocols transmitted over the MAC layer (when transmitting) and demultiplexing them (when receiving). It can also provide node-to-node flow control and error management. The flow control and error management capabilities of the LLC sublayer are used by protocols such as the NetBIO ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 by wireless communication. The devices may be connected in a variety of network topologies. In order to communicate over the network, computers use agreed-on rules, called communication protocols, over whatever medium is used. The computer network can include personal computers, Server (computing), servers, networking hardware, or other specialized or general-purpose Host (network), hosts. They are identified by network addresses and may have hostnames. Hostnames serve as memorable labels for the nodes and are rarely changed after initial assignment. Network addresses serve for locating and identifying the nodes by communication protocols such as the Internet Protocol. Computer networks may be classified by many criteria, including the tr ... [...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 message) and timeouts (specified periods of time allowed to elapse before an acknowledgment is to be received) If the sender does not receive an acknowledgment before the timeout, it re-transmits the message until it receives an acknowledgment or exceeds a predefined number of retransmissions. ARQ is used to achieve reliable data transmission over an unreliable communication channel. ARQ is appropriate if the communication channel has varying or unknown capacity. 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 tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pipeline (software)
In software engineering, a pipeline consists of a chain of processing elements ( processes, threads, coroutines, functions, ''etc.''), arranged so that the output of each element is the input of the next. The concept is analogous to a physical pipeline. Usually some amount of buffering is provided between consecutive elements. The information that flows in these pipelines is often a stream of records, bytes, or bits, and the elements of a pipeline may be called filters. This is also called the pipe(s) and filters design pattern which is monolithic. Its advantages are simplicity and low cost while its disadvantages are lack of elasticity, fault tolerance and scalability. Connecting elements into a pipeline is analogous to function composition. Narrowly speaking, a pipeline is linear and one-directional, though sometimes the term is applied to more general flows. For example, a primarily one-directional pipeline may have some communication in the other direction, known as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reliable Data Transfer
Reliable Data Transfer is a topic in computer networking concerning the transfer of data across unreliable channels. Unreliability is one of the drawbacks of packet switched networks such as the modern internet, as packet loss can occur for a variety of reasons, and delivery of packets is not guaranteed to happen in the order that the packets were sent. Therefore, in order to create long-term data streams over the internet, techniques have been developed to provide reliability, which are generally implemented in the transport layer of the internet protocol suite. In instructional materials, the topic is often presented in the form of theoretical example protocols which are themselves referred to as "RDT", in order to introduce students to the problems and solutions encountered in Transport layer protocols such as the Transmission Control Protocol. These sources often describe a pseudo-API and include Finite-state machine diagrams to illustrate how such a protocol might be imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
STANAG 5066
STANAG 5066 (Profile for High Frequency (HF) Radio Data Communication) is a NATO Standardization Agreement specification to enable applications to communicate efficiently over HF radio. STANAG 5066 provides peer protocols that operate above an HF modem and below the application level. STANAG 5066 includes the mandatory SIS ( Subnet Interface Sublayer, sometimes called ''Subnet Interface Service'') protocol that enables an application to connect to an HF modem through a STANAG 5066 server over TCP/IP. This enables a clean separation between application and modem. The standard also defines two more layers, CAS which is intended to establish connections to other HF nodes and control the status of these connections, and DTS, which controls all the data manipulation for transmission (slicing, directioning, timing...) and the reconstruction in reception. There are two basic modes of transmission defined by this standard. ARQ and NON-ARQ. # ARQ uses package confirmation (through ACK res ... [...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. The Institute of Electrical and Electronics Engineers (IEEE) maintains all official Ethernet standards in the IEEE 802 family. 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 the IEEE as of 2011.IEEE 802.3-2012 ''10. Medium attachment unit and baseband medium specifications, type 10BASE2'' 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 tel ... [...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, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of data and sharing network devices, such as printers. The LAN contrasts the wide area network (WAN), which not only covers a larger geographic distance, but also generally involves Leased line, leased telecommunication circuits or Internet links. An even greater contrast is the Internet, which is a system of globally connected business and personal computers. Ethernet and Wi-Fi are the two most common technologies used for local area networks; historical network technologies include ARCNET, Token Ring, and LocalTalk. Cabling Most wired network infrastructures utilize Category 5 cable, Category 5 or Category 6 cable, Category 6 twisted pair cabling with RJ45 (telecommunications), RJ45 compatible terminations. This medium provides physical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reliable Communications
In computer networking, a reliable protocol is a communication protocol that notifies the sender whether or not the delivery of data to intended recipients was successful. Reliability is a synonym for assurance, which is the term used by the ITU and ATM Forum, and leads to fault-tolerant messaging. Reliable protocols typically incur more overhead than unreliable protocols, and as a result, function more slowly and with less scalability. This often is not an issue for unicast protocols, but it may become a problem for reliable multicast protocols. Transmission Control Protocol (TCP), the main protocol used on the Internet, is a reliable unicast protocol; it provides the abstraction of a reliable byte stream to applications. UDP is an unreliable protocol and is often used in computer games, streaming media or in other situations where speed is an issue and some data loss may be tolerated because of the transitory nature of the data. Often, a reliable unicast protocol is also con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
