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Hierarchical Fair-service Curve
The hierarchical fair-service curve (HFSC) is a network scheduling algorithm for a network scheduler proposed by Ion Stoica, Hui Zhang (computer scientist), Hui Zhang, and T. S. Eugene from Carnegie Mellon University at SIGCOMM 1997 It is based on a Quality of service, QoS and Class-based queueing, CBQ. An implementation of HFSC is available in all operating systems based on the Linux kernel, such as e.g. OpenWrt, and also in DD-WRT, NetBSD 5.0, FreeBSD 8.0 and OpenBSD 4.6. References External links Hierarchical Packet SchedulersHFSC Scheduling with LinuxHFSC Tutorial
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Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use Conditional (computer programming), conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning). In contrast, a Heuristic (computer science), heuristic is an approach to solving problems without well-defined correct or optimal results.David A. Grossman, Ophir Frieder, ''Information Retrieval: Algorithms and Heuristics'', 2nd edition, 2004, For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation. As an e ...
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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 ...
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Ion Stoica
Ion Stoica (born ) is a Romanian–American computer scientist specializing in distributed systems, cloud computing and computer networking. He is a professor of computer science at the University of California, Berkeley and co-director of AMPLab. He co-founded Conviva and Databricks with other original developers of Apache Spark and Anyscale with other original developers of Ray. As of April 2025, Forbes ranked him and Matei Zaharia as the 3rd- richest people in Romania with a net worth of $2.7 billion. Education Stoica was born in Romania, where he grew up and attended Polytechnic University of Bucharest, receiving a MS in Electrical Engineering and Computer Science in 1989. He moved to the U.S. in 1994 to start a PhD at Old Dominion University with computer-science professor Hussein Abdel-Wahab. Together with Wahab, in 1995 he published the algorithm for earliest eligible virtual deadline first scheduling, which is the current process scheduler in the Linux kernel. In 1996 ...
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Hui Zhang (computer Scientist)
Hui Zhang () is a Chinese-American computer scientist and professor at Carnegie Mellon University, and an entrepreneur who co-founded Conviva. Education Zhang received a B.S. in computer science from Peking University in 1988, an M.S. in computer engineering from Rensselaer Polytechnic Institute in 1989, and a Ph.D. in computer science from the University of California, Berkeley in 1993 under Domenico Ferrari with a thesis titled ''Service Disciplines for Integrated Services Packet-Switching Networks''. Career Zhang, together with Ion Stoica, Aditya Ganjam, and Jibin Zhan, co-founded Conviva, where he is chief scientist and chairman of the board. Zhang's research focus is in Internet QoE, video streaming, network architecture, and real-time big data analytics. Zhang's End System Multicast (ESM) project pioneered the overlay multicast architecture and developed the world's first peer-to-peer live streaming system. The ESM paper published in year 2000 won the ACM SIGMETRICS Te ...
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Carnegie Mellon University
Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania, United States. The institution was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools. In 1912, it became the Carnegie Institute of Technology and began granting four-year degrees. In 1967, it became Carnegie Mellon University through its merger with the Mellon Institute of Industrial Research, founded in 1913 by Andrew Mellon and Richard B. Mellon and formerly a part of the University of Pittsburgh. The university consists of seven colleges, including the College of Engineering, the School of Computer Science, and the Tepper School of Business. The university has its main campus located 5 miles (8 km) from downtown Pittsburgh. It also has over a dozen degree-granting locations in six continents, including campuses in Qatar, Silicon Valley, and Kigali, Rwanda ( Carnegie Mellon University Africa) and partnerships with universities nationally and glob ...
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SIGCOMM
SIGCOMM is the Association for Computing Machinery's Special Interest Group on Data Communications, which specializes in the field of communication and computer networks. It is also the name of an annual 'flagship' conference, organized by SIGCOMM, which is considered to be the leading conference in data communications and networking in the world. Known to have an extremely low acceptance rate (~10%), many of the landmark works in Networking and Communications have been published through it. Of late, a number of workshops related to networking are also co-located with the SIGCOMM conference. These include Workshop on Challenged Networks (CHANTS), Internet Network Management (INM), Large Scale Attack Defense (LSAD) and Mining Network Data (MineNet). SIGCOMM also produces a quarterly magazine, ''Computer Communication Review'', with both peer-reviewed and editorial (non-peer reviewed) content, and a bi-monthly refereed journal '' IEEE/ACM Transactions on Networking'', co-sponsored ...
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NetBSD
NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was fork (software development), forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems. The NetBSD project focuses on code clarity, careful design, and portability across many computer architectures. Its source code is publicly available and Permissive free software licence, permissively licensed. History NetBSD was originally derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, Berkeley, via its Net/2 source code release and the 386BSD project. The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development. The ...
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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 ...
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Class-based Queueing
Class-based programming, or more commonly class-orientation, is a style of object-oriented programming (OOP) in which inheritance occurs via defining ''classes'' of objects, instead of inheritance occurring via the objects alone (compare prototype-based programming). The most popular and developed model of OOP is a class-based model, instead of an object-based model. In this model, objects are entities that combine ''state'' (i.e., data), ''behavior'' (i.e., procedures, or ''methods'') and '' identity'' (unique existence among all other objects). The structure and behavior of an object are defined by a class, which is a definition, or blueprint, of all objects of a specific type. An object must be explicitly created based on a class and an object thus created is considered to be an instance of that class. An object is similar to a structure, with the addition of method pointers, member access control, and an implicit data member which locates instances of the class (i.e., objects ...
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Linux Kernel
The Linux kernel is a Free and open-source software, free and open source Unix-like kernel (operating system), kernel that is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the kernel for the GNU operating system (OS) which was created to be a free software, free replacement for Unix. Since the late 1990s, it has been included in many Linux distributions, operating system distributions, many of which are called Linux. One such Linux kernel operating system is Android (operating system), Android which is used in many mobile and embedded devices. Most of the kernel code is written in C (programming language), C as supported by the GNU compiler collection (GCC) which has extensions beyond standard C. The code also contains assembly language, assembly code for architecture-specific logic such as optimizing memory use and task execution. The kernel has a Modular programming, modular design such that modules can be inte ...
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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 ...
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OpenWrt
OpenWrt (from ''open wireless router'') is an open-source project for embedded operating systems based on Linux kernel, Linux, primarily used on Embedded system, embedded devices to Router (computing), route network traffic. The main components are Linux, util-linux, musl, and BusyBox. All components have been optimized to be small enough to fit into the limited storage and memory available in home routers. OpenWrt is configured using a command-line interface (Almquist shell, ash shell) or a web interface (LuCI). There are about 8000 optional software package (installation), software packages available for installation via the opkg package management system. OpenWrt can run on various types of devices, including Customer-premises equipment, CPE routers, residential gateways, smartphones, pocket computers (e.g., Ben NanoNote). It is also possible to run OpenWrt on personal computers and laptops. History The OpenWrt project was started in 2004 after Linksys had built the firmw ...
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