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Bandwidth-delay Product
In data communications, the bandwidth-delay product is the product of a data link's capacity (in bits per second) and its round-trip delay time (in seconds). The result, an amount of data measured in bits (or bytes), is equivalent to the maximum amount of data on the network circuit at any given time, i.e., data that has been transmitted but not yet acknowledged. The bandwidth-delay product was originally proposed as a rule of thumb for sizing router buffers in conjunction with congestion avoidance algorithm Random Early Detection (RED). A network with a large bandwidth-delay product is commonly known as a long fat network (shortened to LFN). As defined in , a network is considered an LFN if its bandwidth-delay product is significantly larger than 105 bits (12,500 bytes). Ultra-high speed local area networks (LANs) may fall into this category, where protocol tuning is critical for achieving peak throughput, on account of their extremely high bandwidth, even though their delay i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Communications
Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibers, wireless communication using radio spectrum, storage media and computer buses. The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal. Analog transmission is a method of conveying voice, data, image, signal or video information using a continuous signal which varies in amplitude, phase, or some other property in proportion to that of a variable. The messages are either represented by a sequence of pulses by means of a line code (''baseband transmission''), or by a limited set of continuously varying waveforms (''passband transmission''), using a digital modulation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DSLAM
A digital subscriber line access multiplexer (DSLAM, often pronounced ''DEE-slam'') is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques. Its cable internet (DOCSIS) counterpart is the Cable modem termination system. Path taken by data to DSLAM # Customer premises: DSL modem terminating the ADSL, SHDSL or VDSL circuit and providing a LAN or interface to a single computer or LAN segment. # Local loop: the telephone company wires from a customer to the telephone exchange or to a serving area interface, often called the " last mile" (LM). # Telephone exchange: #* Main distribution frame (MDF): a wiring rack that connects outside subscriber lines with internal lines. It is used to connect public or private lines coming into the building to internal networks. At the telco, the MDF is generally in proximity to the cable vau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kibibyte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures. To disambiguate arbitrarily sized bytes from the common 8-bit definition, network protocol documents such as The Internet Protocol () refer to an 8-bit byte as an octet. Those bits in an octet are usually counted with numbering from 0 to 7 or 7 to 0 depending on the bit endianness. The first bit is number 0, making the eighth bit number 7. The size of the byte has historically been hardware-dependent and no definitive standards existed that mandated the size. Sizes from 1 to 48 bits have been used. The six-bit character code was an often-used implementation in early encoding systems, and computers using six-bit and nine-bit bytes were common in the 1960s. These systems often had memory words ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agile-SD
Transmission Control Protocol (TCP) uses a network congestion-avoidance algorithm that includes various aspects of an additive increase/multiplicative decrease (AIMD) scheme, along with other schemes including slow start and congestion window (CWND), to achieve congestion avoidance. The TCP congestion-avoidance algorithm is the primary basis for congestion control in the Internet. Per the end-to-end principle, congestion control is largely a function of internet hosts, not the network itself. There are several variations and versions of the algorithm implemented in protocol stacks of operating systems of computers that connect to the Internet. To avoid congestive collapse, TCP uses multi-faceted congestion-control strategy. For each connection, TCP maintains a CWND, limiting the total number of unacknowledged packets that may be in transit end-to-end. This is somewhat analogous to TCP's sliding window used for flow control. Additive increase/multiplicative decrease The addi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compound TCP
Compound TCP (CTCP) is a Microsoft algorithm that was introduced as part of the Windows Vista and Window Server 2008 TCP stack. It is designed to aggressively adjust the sender's congestion window to optimise TCP for connections with large bandwidth-delay products while trying not to harm fairness (as can occur with HSTCP). It is also available for Linux, as well as for Windows XP and Windows Server 2003 via a hotfix. Principles of operation Like FAST TCP and TCP Vegas, Compound TCP uses estimates of queuing delay as a measure of congestion; if the queuing delay is small, it assumes that no links on its path are congested, and rapidly increases its rate. However, unlike FAST and Vegas, it does not seek to maintain a constant number of packets queued. Compound TCP maintains two congestion windows: a regular AIMD window and a delay-based window. The size of the actual sliding window used is the sum of these two windows. The AIMD window is increased the same way that TCP Ren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H-TCP
H-TCP is another implementation of TCP with an optimized congestion control algorithm for high speed networks with high latency (LFN: Long Fat Networks). It was created by researchers at the Hamilton Institute in Ireland. H-TCP is an optional module in Linux since kernel version 2.6, and has been implemented for FreeBSD 7. Principles of operation H-TCP is a loss-based algorithm, using additive-increase/multiplicative-decrease (AIMD) to control TCP's congestion window. It is one of many TCP congestion avoidance algorithms which seeks to increase the aggressiveness of TCP on high bandwidth-delay product (BDP) paths, while maintaining "TCP friendliness" for small BDP paths. H-TCP increases its aggressiveness (in particular, the rate of additive increase) as the time since the previous loss increases. This avoids the problem encountered by HSTCP and BIC TCP of making flows more aggressive if their windows are already large. Thus, new flows can be expected to converge to fai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CUBIC TCP
CUBIC is a network congestion avoidance algorithm for TCP which can achieve high bandwidth connections over networks more quickly and reliably in the face of high latency than earlier algorithms. It helps optimize long fat networks. In 2006, the first CUBIC implementation was released in Linux kernel 2.6.13. Since kernel version 2.6.19, CUBIC replaces BIC-TCP as the default TCP congestion control algorithm in the Linux kernel. MacOS adopted TCP CUBIC with the OS X Yosemite release in 2014, while the previous release OS X Mavericks still used TCP New Reno. Microsoft adopted it by default in Windows 10.1709 Fall Creators Update (2017), and Windows Server 2016 1709 update. Characteristics CUBIC is a less aggressive and more systematic derivative of BIC TCP, in which the window size is a cubic function of time since the last congestion event, with the inflection point set to the window size prior to the event. Because it is a cubic function, there are two components to wind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BIC TCP
BIC TCP (Binary Increase Congestion control) is one of the congestion control algorithms that can be used for Transmission Control Protocol (TCP). BIC is optimized for high speed networks with high latency: so-called "long fat networks". For these networks, BIC has significant advantage over previous congestion control schemes in correcting for severely underutilized bandwidth. BIC implements a unique congestion window (cwnd) algorithm. This algorithm tries to find the maximum cwnd by searching in three parts: binary search increase, additive increase, and slow start. When a network failure occurs, the BIC uses multiplicative decrease in correcting the cwnd. BIC TCP is implemented and used by default in Linux kernels 2.6.8 and above. The default implementation was again changed to CUBIC TCP in the 2.6.19 version. Algorithm Define the following variables: Smax: the maximum increment Smin: the minimum increment wmax: the maximum window size β: mul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FAST TCP
FAST TCP (also written FastTCP) is a TCP congestion avoidance algorithm especially targeted at long-distance, high latency links, developed at the Netlab, California Institute of Technology and now being commercialized by FastSoft. FastSoft was acquired by Akamai Technologies in 2012. FastTCP is compatible with existing TCP algorithms, requiring modification only to the computer which is sending data. Name The name FAST is a recursive acronym for FAST AQM Scalable TCP, where AQM stands for Active Queue Management, and TCP stands for Transmission Control Protocol. Principles of operation The role of congestion control is to moderate the rate at which data is transmitted, "congestion", according to the capacity of the network and the rate at which other users are transmitting. Like TCP Vegas, FAST TCP uses queueing delay instead of loss probability as a congestion signal. Most current congestion control algorithms detect congestion and slow down when they discover that packe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HSTCP
HighSpeed TCP (HSTCP) is a congestion control algorithm protocol defined in RFC 3649 for Transport Control Protocol (TCP). Standard TCP performs poorly in networks with a large bandwidth-delay product. It is unable to fully utilize available bandwidth. HSTCP makes minor modifications to standard TCP's congestion control mechanism to overcome this limitation. Algorithm When an ACK is received (in congestion avoidance), the window is increased by a(w)/w and when a loss is detected through triple duplicate acknowledgments, the window equals (1-b(w))w, where w is the current window size. When the congestion window is small, HSTCP behaves exactly like standard TCP so a(w) is 1 and b(w) is 0.5. When TCP's congestion window is beyond a certain threshold, a(w) and b(w) become functions of the current window size. In this region, as the congestion window increases, the value of a(w) increases and the value of b(w) decreases. This means that HSTCP's window will grow faster than standard ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bufferbloat
Bufferbloat is a cause of high latency and jitter in packet-switched networks caused by excess buffering of packets. Bufferbloat can also cause packet delay variation (also known as jitter), as well as reduce the overall network throughput. When a router or switch is configured to use excessively large buffers, even very high-speed networks can become practically unusable for many interactive applications like voice over IP (VoIP), audio streaming, online gaming, and even ordinary web browsing. Some communications equipment manufacturers designed unnecessarily large buffers into some of their network products. In such equipment, bufferbloat occurs when a network link becomes congested, causing packets to become queued for long periods in these oversized buffers. In a first-in first-out queuing system, overly large buffers result in longer queues and higher latency, and do not improve network throughput. It can also be induced by specific slow-speed connections hindering ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet2
Internet2 is a not-for-profit United States computer networking consortium led by members from the research and education communities, industry, and government. The Internet2 consortium administrative headquarters are located in Ann Arbor, Michigan, with offices in Washington, D.C. and Emeryville, California. As of November 2013, Internet2 has over 500 members including 251 institutions of higher education, 9 partners and 76 members from industry, over 100 research and education networks or connector organizations, and 67 affiliate members. Internet2 operates the Internet2 Network, an Internet Protocol network using optical fiber that delivers network services for research and education, and provides a secure network testing and research environment. In late 2007, Internet2 began operating its newest dynamic circuit network, the Internet2 DCN, an advanced technology that allows user-based allocation of data circuits over the fiber-optic network. The Internet2 Network, thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
