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Network Scheduler
A network scheduler, also called packet scheduler, queueing discipline (qdisc) or queueing algorithm, is an arbiter on a node in a packet switching communication network. It manages the sequence of network packets in the transmit and receive queues of the protocol stack and network interface controller. There are several network schedulers available for the different operating systems, that implement many of the existing network scheduling algorithms. The network scheduler logic decides which network packet to forward next. The network scheduler is associated with a queuing system, storing the network packets temporarily until they are transmitted. Systems may have a single or multiple queues in which case each may hold the packets of one flow, classification, or priority. In some cases it may not be possible to schedule all transmissions within the constraints of the system. In these cases the network scheduler is responsible for deciding which traffic to forward and what ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Queue
Data ( , ) are a collection of discrete or continuous value (semiotics), values that convey information, describing the quantity, qualitative property, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpretation (logic), interpreted formally. A datum is an individual value in a collection of data. Data are usually organized into structures such as table (information), tables that provide additional context and meaning, and may themselves be used as data in larger structures. Data may be Data (computer science), used as variable (research), variables in a computational process. Data may represent abstract ideas or concrete measurements. Data are commonly used in scientific research, economics, and virtually every other form of human organizational activity. Examples of data sets include price indices (such as the consumer price index), unemployment rates, literacy rates, and census data. In this context, data repr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quality Of Service
Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as packet loss, bit rate, throughput, transmission delay, availability, jitter, etc. In the field of computer networking and other packet-switched telecommunication networks, quality of service refers to traffic prioritization and resource reservation control mechanisms rather than the achieved service quality. Quality of service is the ability to provide different priorities to different applications, users, or data Traffic flow (computer networking), flows, or to guarantee a certain level of performance to a data flow. Quality of service is particularly important for the transport of traffic with special requirements. In particula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Early Detection
Random early detection (RED), also known as random early discard or random early drop, is a queuing discipline for a network scheduler suited for congestion avoidance. In the conventional tail drop algorithm, a router or other network component buffers as many packets as it can, and simply drops the ones it cannot buffer. If buffers are constantly full, the network is congested. Tail drop distributes buffer space unfairly among traffic flows. Tail drop can also lead to TCP global synchronization as all TCP connections "hold back" simultaneously, and then step forward simultaneously. Networks become under-utilized and flooded—alternately, in waves. RED addresses these issues by pre-emptively dropping packets before the buffer becomes completely full. It uses predictive models to decide which packets to drop. It was invented in the early 1990s by Sally Floyd and Van Jacobson. Operation RED monitors the average queue size and drops (or marks when used in conjunction with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Netem
tc (traffic control) is the user-space system administration utility program used to configure the Linux kernel packet scheduler. Tc is usually packaged as part of the iproute2 package. Syntax tc filter add dev pppoe-dsl parent 1: prio 1 protocol ip handle 202 fw flowid 1:202 See also * cgroups cgroups (abbreviated from control groups) is a Linux kernel feature that limits, accounts for, and isolates the resource usage (CPU, memory, disk I/O, etc.) of a collection of processes. Engineers at Google started the work on this feature ... References External links Traffic Control HOWTODated but still very relevant HOWTO from the Linux Documentation Project. More up-to-date HOWTO for advanced networking topics, including traffic control Linux TC Notesbrief note of various parts of linux traffic control. English is sometimes broken, but the information is still good. tc: Linux HTTP Outgoing Traffic ShapingExample use of tc for shaping tcp/80 traffic. Advanced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kernel
Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learning * Kernelization, a technique for designing efficient algorithms ** Kernel, a routine that is executed in a vectorized loop, for example in general-purpose computing on graphics processing units *KERNAL, the Commodore operating system Mathematics Objects * Kernel (algebra), a general concept that includes: ** Kernel (linear algebra) or null space, a set of vectors mapped to the zero vector ** Kernel (category theory), a generalization of the kernel of a homomorphism ** Kernel (set theory), an equivalence relation: partition by image under a function ** Difference kernel, a binary equalizer: the kernel of the difference of two functions Functions * Kernel (geometry), the set of points within a polygon from which the whole polygon boundary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FQ-CoDel
CoDel (''Controlled Delay''; pronounced " coddle") is an active queue management (AQM) algorithm in network routing, developed by Van Jacobson and Kathleen Nichols and published as RFC8289. It is designed to overcome bufferbloat in networking hardware, such as routers, by setting limits on the delay network packets experience as they pass through buffers in this equipment. CoDel aims to improve on the overall performance of the random early detection (RED) algorithm by addressing some of its fundamental misconceptions, as perceived by Jacobson, and by being easier to manage. In 2012, an implementation of CoDel was written by Dave Täht and Eric Dumazet for the Linux kernel and dual licensed under the GNU General Public License and the 3-clause BSD license. Dumazet's improvement on CoDel is called FQ-CoDel, standing for "Fair/Flow Queue CoDel"; it was first adopted as the standard AQM and packet scheduling solution in 2014 in the OpenWrt 14.07 release called "Barrier Breaker" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fair Queuing
Fair queuing is a family of scheduling algorithms used in some process and network schedulers. The algorithm is designed to achieve fairness when a limited resource is shared, for example to prevent flows with large packets or processes that generate small jobs from consuming more throughput or CPU time than other flows or processes. Fair queuing is implemented in some advanced network switches and routers. History The term ''fair queuing'' was coined by John Nagle in 1985 while proposing round-robin scheduling in the gateway between a local area network and the internet to reduce network disruption from badly-behaving hosts. A byte-weighted version was proposed by Alan Demers, Srinivasan Keshav and Scott Shenker in 1989, and was based on the earlier Nagle fair queuing algorithm. The byte-weighted fair queuing algorithm aims to mimic a bit-per-bit multiplexing by computing theoretical departure date for each packet. The concept has been further developed into weighted fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FIFO (computing And Electronics)
Representation of a FIFO queue In computing and in systems theory, first in, first out (the first in is the first out), acronymized as FIFO, is a method for organizing the manipulation of a data structure (often, specifically a data buffer) where the oldest (first) entry, or "head" of the queue, is processed first. Such processing is analogous to servicing people in a queue area on a first-come, first-served (FCFS) basis, i.e. in the same sequence in which they arrive at the queue's tail. FCFS is also the jargon term for the FIFO operating system scheduling algorithm, which gives every process central processing unit (CPU) time in the order in which it is demanded. FIFO's opposite is LIFO, last-in-first-out, where the youngest entry or "top of the stack" is processed first. A priority queue is neither FIFO or LIFO but may adopt similar behaviour temporarily or by default. Queueing theory encompasses these methods for processing data structures, as well as interactions be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CAKE (queue Management Algorithm)
CoDel (''Controlled Delay''; pronounced " coddle") is an active queue management (AQM) algorithm in network routing, developed by Van Jacobson and Kathleen Nichols and published as RFC8289. It is designed to overcome bufferbloat in networking hardware, such as routers, by setting limits on the delay network packets experience as they pass through buffers in this equipment. CoDel aims to improve on the overall performance of the random early detection (RED) algorithm by addressing some of its fundamental misconceptions, as perceived by Jacobson, and by being easier to manage. In 2012, an implementation of CoDel was written by Dave Täht and Eric Dumazet for the Linux kernel and dual licensed under the GNU General Public License and the 3-clause BSD license. Dumazet's improvement on CoDel is called FQ-CoDel, standing for "Fair/Flow Queue CoDel"; it was first adopted as the standard AQM and packet scheduling solution in 2014 in the OpenWrt 14.07 release called "Barrier Breaker". ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Generic Cell Rate Algorithm
The generic cell rate algorithm (GCRA) is a leaky bucket-type scheduling algorithm for the network scheduler that is used in Asynchronous Transfer Mode (ATM) networks. It is used to measure the timing of cells on virtual channels (VCs) and or Virtual Paths (VPs) against bandwidth and jitter limits contained in a traffic contract for the VC or VP to which the cells belong. Cells that do not conform to the limits given by the traffic contract may then be re-timed (delayed) in traffic shaping, or may be dropped (discarded) or reduced in priority (demoted) in traffic policing. Nonconforming cells that are reduced in priority may then be dropped, in preference to higher priority cells, by downstream components in the network that are experiencing congestion. Alternatively they may reach their destination (VC or VP termination) if there is enough capacity for them, despite them being excess cells as far as the contract is concerned: see priority control. The GCRA is given as the refere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Latency
Network delay is a design and performance characteristic of a telecommunications network. It specifies the latency for a bit of data to travel across the network from one communication endpoint to another. It is typically measured in multiples or fractions of a second. Delay may differ slightly, depending on the location of the specific pair of communicating endpoints. Engineers usually report both the maximum and average delay, and they divide the delay into several parts: * Processing delay time it takes a router to process the packet header * Queuing delay time the packet spends in routing queues * Transmission delay time it takes to push the packet's bits onto the link * Propagation delay time for a signal to propagate through the media A certain minimum level of delay is experienced by signals due to the time it takes to transmit a packet serially through a link. This delay is extended by more variable levels of delay due to network congestion. IP network delays can ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
