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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] |
Random Early Detection Algorithm En
In common usage, randomness is the apparent or actual lack of definite pattern or predictability in information. A random sequence of events, symbols or steps often has no order and does not follow an intelligible pattern or combination. Individual random events are, by definition, unpredictable, but if there is a known probability distribution, the frequency of different outcomes over repeated events (or "trials") is predictable.Strictly speaking, the frequency of an outcome will converge almost surely to a predictable value as the number of trials becomes arbitrarily large. Non-convergence or convergence to a different value is possible, but has probability zero. Consistent non-convergence is thus evidence of the lack of a fixed probability distribution, as in many evolutionary processes. For example, when throwing two dice, the outcome of any particular roll is unpredictable, but a sum of 7 will tend to occur twice as often as 4. In this view, randomness is not haphazardne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Van Jacobson
Van Jacobson is an American computer scientist, renowned for his work on TCP/IP network performance and scaling.2001 SIGCOMM Award for Lifetime Achievement to Van Jacobson "for contributions to protocol architecture and congestion control." He is one of the primary contributors to the TCP/IP protocol stack—the technological foundation of today’s Internet. Since 2013, Jacobson is an at the (UCLA) working on |
Active Queue Management
In routers and switches, active queue management (AQM) is the policy of dropping packets inside a buffer associated with a network interface controller (NIC) before that buffer becomes full, often with the goal of reducing network congestion or improving end-to-end latency. This task is performed by the network scheduler, which for this purpose uses various algorithms such as random early detection (RED), Explicit Congestion Notification (ECN), or controlled delay (CoDel). RFC 7567 recommends active queue management as a best practice. Overview An Internet router typically maintains a set of queues, one or more per interface, that hold packets scheduled to go out on that interface. Historically, such queues use a ''drop-tail'' discipline: a packet is put onto the queue if the queue is shorter than its maximum size (measured in packets or in bytes), and dropped otherwise. Active queue disciplines drop or mark packets before the queue is full. Typically, they operate by maintai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue (queue Management Algorithm)
Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The term ''blue'' generally describes colours perceived by humans observing light with a dominant wavelength that's between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colours; azure contains some green, while ultramarine contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called the Tyndall effect explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective. Blue has been an important colour in art and decoration since ancient times. The semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and later, in the Renaissance, to make the pig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differentiated Services Code Point
Differentiated services or DiffServ is a computer networking architecture that specifies a mechanism for classifying and managing network traffic and providing quality of service (QoS) on modern Internet Protocol, IP networks. DiffServ can, for example, be used to provide Network delay, low-latency to critical network traffic such as Voice over IP, voice or streaming media while providing best-effort service to non-critical services such as web traffic or file transfers. DiffServ uses a 6-bit differentiated services code point (DSCP) in the 6-bit differentiated services field (DS field) in the IP header for packet classification purposes. The DS field, together with the ECN field, replaces the outdated Type of service, IPv4 TOS field. Background Modern data networks carry many different types of services, including voice, video, streaming music, web pages and email. Many of the proposed QoS mechanisms that allowed these services to co-exist were both complex and failed to scale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Of Service
The type of service (ToS) field is the second byte of the IPv4 IPv4 header, header. It has had various purposes over the years, and has been defined in different ways by five Request for Comments, RFCs. Prior to the redefinition, the ToS field could specify a datagram's priority and request a route for low-latency, high-throughput, or highly-reliable service. Based on these ToS values, a packet would be placed in a prioritized outgoing queue, or take a route with appropriate latency, throughput, or reliability. In practice, the ToS field never saw widespread use outside of US Department of Defense networks. However, a great deal of experimental, research, and deployment work has focused on how to make use of these eight bits, resulting in the current DS field definition. The modern redefinition of the ToS field (as well as the Traffic Class field, ''Traffic Class'' field in IPv6 packets) splits this byte into a 6-bit Differentiated Services (DS) field and a 2-bit Explicit Congesti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weighted Random Early Detection
A weight function is a mathematical device used when performing a sum, integral, or average to give some elements more "weight" or influence on the result than other elements in the same set. The result of this application of a weight function is a weighted sum or weighted average. Weight functions occur frequently in statistics and analysis, and are closely related to the concept of a measure. Weight functions can be employed in both discrete and continuous settings. They can be used to construct systems of calculus called "weighted calculus" and "meta-calculus".Jane Grossma''Meta-Calculus: Differential and Integral'' , 1981. Discrete weights General definition In the discrete setting, a weight function w \colon A \to \R^+ is a positive function defined on a discrete set A, which is typically finite or countable. The weight function w(a) := 1 corresponds to the ''unweighted'' situation in which all elements have equal weight. One can then apply this weight to various conce ... [...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] |
Probability
Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an event is to occur."Kendall's Advanced Theory of Statistics, Volume 1: Distribution Theory", Alan Stuart and Keith Ord, 6th ed., (2009), .William Feller, ''An Introduction to Probability Theory and Its Applications'', vol. 1, 3rd ed., (1968), Wiley, . This number is often expressed as a percentage (%), ranging from 0% to 100%. A simple example is the tossing of a fair (unbiased) coin. Since the coin is fair, the two outcomes ("heads" and "tails") are both equally probable; the probability of "heads" equals the probability of "tails"; and since no other outcomes are possible, the probability of either "heads" or "tails" is 1/2 (which could also be written as 0.5 or 50%). These concepts have been given an axiomatic mathematical formaliza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Explicit Congestion Notification
Explicit Congestion Notification (ECN) is an extension to the Internet Protocol and to the Transmission Control Protocol and is defined in (2001). ECN allows end-to-end notification of network congestion without dropping packets. ECN is an optional feature that may be used between two ECN-enabled endpoints when the underlying network infrastructure also supports it. Conventionally, TCP/IP networks signal congestion by dropping packets. When ECN is successfully negotiated, an ECN-aware router may set a mark in the IP header instead of dropping a packet in order to signal impending congestion. The receiver of the packet echoes the congestion indication to the sender, which reduces its transmission rate as if it detected a dropped packet. Rather than responding properly or ignoring the bits, some outdated or faulty network equipment has historically dropped or mangled packets that have ECN bits set. , measurements suggested that the fraction of web servers on the public Internet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sally Floyd
Sally Jean Floyd (May 20, 1950 – August 25, 2019) was an American computer scientist known for her work on computer networking. Formerly associated with the International Computer Science Institute in Berkeley, California, she retired in 2009 and died in August 2019. She is best known for her work on Internet congestion control, and was in 2007 one of the top-ten most cited researchers in computer science."Sally Floyd Wins 2007 SIGCOMM Award" ICSI, Sept. 2007 (last visited Oct. 7, 2012). Biography Born in , Floyd received a[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Queue Management
In routers and switches, active queue management (AQM) is the policy of dropping packets inside a buffer associated with a network interface controller (NIC) before that buffer becomes full, often with the goal of reducing network congestion or improving end-to-end latency. This task is performed by the network scheduler, which for this purpose uses various algorithms such as random early detection (RED), Explicit Congestion Notification (ECN), or controlled delay (CoDel). RFC 7567 recommends active queue management as a best practice. Overview An Internet router typically maintains a set of queues, one or more per interface, that hold packets scheduled to go out on that interface. Historically, such queues use a ''drop-tail'' discipline: a packet is put onto the queue if the queue is shorter than its maximum size (measured in packets or in bytes), and dropped otherwise. Active queue disciplines drop or mark packets before the queue is full. Typically, they operate by maintai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
