David Ross Cheriton (born March 29, 1951) is a Canadian computer scientist, businessman, philanthropist, and venture capitalist. He is a computer science professor at Stanford University , where he founded and leads the Distributed Systems Group.
84-458: He is a distributed computing and computer networking expert, with insight into identifying big market opportunities and building the architectures needed to address such opportunities. He has founded and invested in technology companies, including Google , where he was among the first angel investors ; VMware , where he was an early investor; and Arista , where he was cofounder and chief scientist. He has funded at least 20 companies. Cheriton
168-443: A solution for each instance. Instances are questions that we can ask, and solutions are desired answers to these questions. Theoretical computer science seeks to understand which computational problems can be solved by using a computer ( computability theory ) and how efficiently ( computational complexity theory ). Traditionally, it is said that a problem can be solved by using a computer if we can design an algorithm that produces
252-571: A $ 12 million endowment in 2016 to Stanford University to support Computer Science faculty, graduate fellowships, and undergraduate scholarships. Born in Vancouver , British Columbia , Canada, Cheriton attended public schools in the Highlands neighborhood of Edmonton , Alberta , Canada. He briefly attended the University of Alberta where he had applied for both mathematics and music. He
336-493: A Mux/Demux unit at both ends of the fiber link, a CWDM MUX/DEMUX with corresponding wavelengths, and SFP with corresponding wavelengths. is it also possible to DWDM in serie to increase number of channels. Most uses Wavelengths: 1270 nm, 1290 nm, 1310 nm, 1330 nm, 1350 nm, 1370 nm, 1390 nm, 1410 nm, 1430 nm, 1450 nm, 1470 nm, 1490 nm, 1510 nm, 1530 nm, 1550 nm, 1570 nm, 1590 nm and 1610 nm CWDM
420-474: A common goal for their work. The terms " concurrent computing ", " parallel computing ", and "distributed computing" have much overlap, and no clear distinction exists between them. The same system may be characterized both as "parallel" and "distributed"; the processors in a typical distributed system run concurrently in parallel. Parallel computing may be seen as a particularly tightly coupled form of distributed computing, and distributed computing may be seen as
504-520: A correct solution for any given instance. Such an algorithm can be implemented as a computer program that runs on a general-purpose computer: the program reads a problem instance from input , performs some computation, and produces the solution as output . Formalisms such as random-access machines or universal Turing machines can be used as abstract models of a sequential general-purpose computer executing such an algorithm. The field of concurrent and distributed computing studies similar questions in
588-443: A deadlock. This problem is PSPACE-complete , i.e., it is decidable, but not likely that there is an efficient (centralised, parallel or distributed) algorithm that solves the problem in the case of large networks. Gigabit Ethernet In computer networking , Gigabit Ethernet ( GbE or 1 GigE ) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second . The most popular variant, 1000BASE-T ,
672-504: A decision problem can be solved in polylogarithmic time by using a polynomial number of processors, then the problem is said to be in the class NC . The class NC can be defined equally well by using the PRAM formalism or Boolean circuits—PRAM machines can simulate Boolean circuits efficiently and vice versa. In the analysis of distributed algorithms, more attention is usually paid on communication operations than computational steps. Perhaps
756-414: A departure from both 10BASE-T and 100BASE-TX , 1000BASE-T uses four lanes over all four cable pairs for simultaneous transmission in both directions through the use of echo cancellation with adaptive equalization called hybrid circuits (this is like telephone hybrid ) and five-level pulse-amplitude modulation (PAM-5). The symbol rate is identical to that of 100BASE-TX (125 megabaud (MBd)) and
840-492: A frugal lifestyle, avoiding costly cars or large houses. He was once included in a list of "cheapskate billionaires". On November 18, 2005, the University of Waterloo announced that Cheriton had donated $ 25 million to support graduate studies and research in its School of Computer Science. In recognition of his contribution, the school was renamed the David R. Cheriton School of Computer Science . In 2009, he donated $ 2 million to
924-401: A loosely coupled form of parallel computing. Nevertheless, it is possible to roughly classify concurrent systems as "parallel" or "distributed" using the following criteria: The figure on the right illustrates the difference between distributed and parallel systems. Figure (a) is a schematic view of a typical distributed system; the system is represented as a network topology in which each node
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#17327981044161008-456: A maximum segment length of 550 m. For link distances greater than 300 m, the use of a special launch conditioning patch cord may be required. This launches the laser at a precise offset from the center of the fiber which causes it to spread across the diameter of the fiber core, reducing the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in multi-mode fiber. 1000BASE-LX10
1092-431: A much wider sense, even referring to autonomous processes that run on the same physical computer and interact with each other by message passing. While there is no single definition of a distributed system, the following defining properties are commonly used as: A distributed system may have a common goal, such as solving a large computational problem; the user then perceives the collection of autonomous processors as
1176-590: A non-trivial scrambling procedure based on a linear-feedback shift register ; this is similar to what is done in 100BASE-T2 , but uses different parameters. The three-bit symbols are then mapped to voltage levels which vary continuously during transmission. An example mapping is as follows: Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard, meaning that straight-through cables will often work between two GbE-capable network node interfaces (both MDI) and between two switch or hub interfaces (both MDI-X). This feature eliminates
1260-439: A pair of single-mode fibers due to higher quality optics than LX10 and use of DWDM, running on 1528-1565 nm wavelength lasers. The most used channels are CH17-61 on Wavelength 1528.77-1563-86 nm. To use DWDM it is necessary to use a Mux/Demux unit on both ends of the fiber link, a DWDM MUX/DEMUX with corresponding wavelengths, and SFP with corresponding wavelengths. is it also possible to use CWDM in series to increase
1344-559: A pinout different from 1000BASE-T). The short segment length is due to a very high signal transmission rate. Although it is still used for specific applications where cabling is done by IT professionals, for instance, the IBM BladeCenter uses 1000BASE-CX for the Ethernet connections between the blade servers and the switch modules, 1000BASE-T has succeeded it for general copper wiring use. 802.3ap-2007 CL70 standardized 1000BASE-KX
1428-424: A problem is divided into many tasks, each of which is solved by one or more computers, which communicate with each other via message passing. The word distributed in terms such as "distributed system", "distributed programming", and " distributed algorithm " originally referred to computer networks where individual computers were physically distributed within some geographical area. The terms are nowadays used in
1512-654: A schematic architecture allowing for live environment relay. This enables distributed computing functions both within and beyond the parameters of a networked database. Reasons for using distributed systems and distributed computing may include: Examples of distributed systems and applications of distributed computing include the following: According to Reactive Manifesto, reactive distributed systems are responsive, resilient, elastic and message-driven. Subsequently, Reactive systems are more flexible, loosely-coupled and scalable. To make your systems reactive, you are advised to implement Reactive Principles. Reactive Principles are
1596-405: A sequential general-purpose computer? The discussion below focuses on the case of multiple computers, although many of the issues are the same for concurrent processes running on a single computer. Three viewpoints are commonly used: In the case of distributed algorithms, computational problems are typically related to graphs. Often the graph that describes the structure of the computer network
1680-457: A set of principles and patterns which help to make your cloud native application as well as edge native applications more reactive. Many tasks that we would like to automate by using a computer are of question–answer type: we would like to ask a question and the computer should produce an answer. In theoretical computer science , such tasks are called computational problems . Formally, a computational problem consists of instances together with
1764-452: A single twisted pair for automotive and industrial applications. It includes cable specifications for 15 meters (type A) or 40 meters (type B) reach. The transmission is done using PAM-3 at 750 MBd . The Telecommunications Industry Association (TIA) created and promoted a standard similar to 1000BASE-T that was simpler to implement, calling it 1000BASE-TX (TIA/EIA-854). The simplified design would have, in theory, reduced
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#17327981044161848-539: A successful public offering in 2007. In 2001 Cheriton and Bechtolsheim founded another start-up company, Palo Alto based Kealia. Kealia designed a high-capacity streaming video server; Galaxy, a range of servers based on AMD's Opteron microprocessor; and Thumper, an enterprise-grade network attached storage system. Kealia was bought by Sun Microsystems in 2004, with Thumper becoming the Sun Fire X4500 . In 2004, Cheriton cofounded (again with Bechtolsheim) and
1932-695: A token ring network in which the token has been lost. Coordinator election algorithms are designed to be economical in terms of total bytes transmitted, and time. The algorithm suggested by Gallager, Humblet, and Spira for general undirected graphs has had a strong impact on the design of distributed algorithms in general, and won the Dijkstra Prize for an influential paper in distributed computing. Many other algorithms were suggested for different kinds of network graphs , such as undirected rings, unidirectional rings, complete graphs, grids, directed Euler graphs, and others. A general method that decouples
2016-434: A unit. Alternatively, each computer may have its own user with individual needs, and the purpose of the distributed system is to coordinate the use of shared resources or provide communication services to the users. Other typical properties of distributed systems include the following: Here are common architectural patterns used for distributed computing: Distributed systems are groups of networked computers which share
2100-477: Is the problem instance. This is illustrated in the following example. Consider the computational problem of finding a coloring of a given graph G . Different fields might take the following approaches: While the field of parallel algorithms has a different focus than the field of distributed algorithms, there is much interaction between the two fields. For example, the Cole–Vishkin algorithm for graph coloring
2184-416: Is a computer and each line connecting the nodes is a communication link. Figure (b) shows the same distributed system in more detail: each computer has its own local memory, and information can be exchanged only by passing messages from one node to another by using the available communication links. Figure (c) shows a parallel system in which each processor has a direct access to a shared memory. The situation
2268-449: Is a field of computer science that studies distributed systems , defined as computer systems whose inter-communicating components are located on different networked computers . The components of a distributed system communicate and coordinate their actions by passing messages to one another in order to achieve a common goal. Three significant challenges of distributed systems are: maintaining concurrency of components, overcoming
2352-418: Is a non-standard but industry accepted term to refer to Gigabit Ethernet transmission. It is very similar to 1000BASE-SX but achieves longer distances up to 2 km over a pair of multi-mode fibers due to higher quality optics than a SX, running on 1310 nm wavelength lasers. It is easily confused with 1000BASE-SX or 1000BASE-LX because the use of -LX, -LX10 and -SX is ambiguous between vendors. The range
2436-402: Is a non-standard but industry accepted term to refer to Gigabit Ethernet transmission. It is very similar to 1000BASE-LX10 but achieves longer distances up to 40 km over a pair of single-mode fibers due to higher quality optics than a LX10, running on 1310 nm wavelength lasers. It is sometimes referred to as LH (Long Haul), and is easily confused with 1000BASE-LX10 or 1000BASE-ZX because
2520-410: Is a non-standard but multi-vendor term to refer to Gigabit Ethernet transmission using 1,550 nm wavelength to achieve distances of at least 70 km (43 mi) over single-mode fiber. Some vendors specify distances up to 120 km (75 mi) over single-mode fiber, sometimes called 1000BASE-EZX. Ranges beyond 80 km are highly dependent upon the path loss of the fiber in use, specifically
2604-485: Is achieved with use of Fabry Perot laser transmitter. 1000BASE-LX is an optical fiber Gigabit Ethernet standard specified in IEEE 802.3 Clause 38 which uses a long wavelength laser (1,270–1,355 nm), and a maximum RMS spectral width of 4 nm. 1000BASE-LX is specified to work over a distance of up to 5 km over 10 μm single-mode fiber. 1000BASE-LX can also run over all common types of multi-mode fiber with
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2688-403: Is also focused on understanding the asynchronous nature of distributed systems: Note that in distributed systems, latency should be measured through "99th percentile" because "median" and "average" can be misleading. Coordinator election (or leader election ) is the process of designating a single process as the organizer of some task distributed among several computers (nodes). Before
2772-419: Is available in their local D-neighbourhood . Many distributed algorithms are known with the running time much smaller than D rounds, and understanding which problems can be solved by such algorithms is one of the central research questions of the field. Typically an algorithm which solves a problem in polylogarithmic time in the network size is considered efficient in this model. Another commonly used measure
2856-408: Is cheaper to use than DWDM, about 1/5-1/3 of the cost. CWDM is about 5-10 times more expensive the if you have the fiber available, then traditional -LX/-LZ transceivers. 1000BASE-DWDM is a non-standard but industry accepted term to refer to Gigabit Ethernet transmission. It is very similar to 1000BASE-LX10 but achieves longer distances up 40–120 km, and up to 64 to 160 parallel channels over
2940-498: Is defined by the IEEE 802.3ab standard. It came into use in 1999, and has replaced Fast Ethernet in wired local networks due to its considerable speed improvement over Fast Ethernet, as well as its use of cables and equipment that are widely available, economical, and similar to previous standards. The first standard for faster 10 Gigabit Ethernet was approved in 2002. Ethernet was the result of research conducted at Xerox PARC in
3024-581: Is further complicated by the traditional uses of the terms parallel and distributed algorithm that do not quite match the above definitions of parallel and distributed systems (see below for more detailed discussion). Nevertheless, as a rule of thumb, high-performance parallel computation in a shared-memory multiprocessor uses parallel algorithms while the coordination of a large-scale distributed system uses distributed algorithms. The use of concurrent processes which communicate through message-passing has its roots in operating system architectures studied in
3108-478: Is necessary to interconnect processes running on those CPUs with some sort of communication system . Whether these CPUs share resources or not determines a first distinction between three types of architecture: Distributed programming typically falls into one of several basic architectures: client–server , three-tier , n -tier , or peer-to-peer ; or categories: loose coupling , or tight coupling . Another basic aspect of distributed computing architecture
3192-551: Is part of the IEEE 802.3ap standard for Ethernet Operation over Electrical Backplanes. This standard defines one to four lanes of backplane links, one RX and one TX differential pair per lane, at link bandwidth ranging from 100 Mbit to 10 Gbit per second (from 100BASE-KX to 10GBASE-KX4). The 1000BASE-KX variant uses 1.25 GBd electrical (not optical) signalling speed. 1000BASE-X is used in industry to refer to Gigabit Ethernet transmission over fiber, where options include 1000BASE-SX, 1000BASE-LX, 1000BASE-LX10, 1000BASE-BX10 or
3276-399: Is recommended to be a maximum length of 100 meters (330 feet), and must use Category 5 cable or better (including Cat 5e and Cat 6 ). Autonegotiation is a requirement for using 1000BASE-T according to Section 28D.5 Extensions required for Clause40 (1000BASE-T) . At least the clock source has to be negotiated, as one endpoint must be master and the other endpoint must be slave. In
3360-492: Is the method of communicating and coordinating work among concurrent processes. Through various message passing protocols, processes may communicate directly with one another, typically in a main/sub relationship. Alternatively, a "database-centric" architecture can enable distributed computing to be done without any form of direct inter-process communication , by utilizing a shared database . Database-centric architecture in particular provides relational processing analytics in
3444-410: Is the number of synchronous communication rounds required to complete the task. This complexity measure is closely related to the diameter of the network. Let D be the diameter of the network. On the one hand, any computable problem can be solved trivially in a synchronous distributed system in approximately 2 D communication rounds: simply gather all information in one location ( D rounds), solve
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3528-511: Is the total number of bits transmitted in the network (cf. communication complexity ). The features of this concept are typically captured with the CONGEST(B) model, which is similarly defined as the LOCAL model, but where single messages can only contain B bits. Traditional computational problems take the perspective that the user asks a question, a computer (or a distributed system) processes
3612-581: Is working with Stanford students on transactional memory , making memory systems that are resilient to failures. In-memory processing leads to dramatically faster computers – in some cases speeding up applications by a factor of 100,000. It changes the complete nature of how a business can run. We’re trying to lower the cost and to fit these systems in existing memory structures and reduce the number of components to make them more reliable and more secure. Cheriton cofounded Granite Systems with Andy Bechtolsheim . The company developed gigabit Ethernet products. It
3696-558: The University of British Columbia , which will go to fund the Carl Wieman Science Education Initiative (CWSEI). He more recently donated $ 7.5M to fund a new chair in computing, and a new course on computational thinking. Cheriton has also funded two graduate student fellowships and one undergrad fellowship at Stanford, and donated several millions of dollars to Stanford to fund research. He campaigned against Asynchronous Transfer Mode (ATM) that
3780-584: The lack of a global clock , and managing the independent failure of components. When a component of one system fails, the entire system does not fail. Examples of distributed systems vary from SOA-based systems to microservices to massively multiplayer online games to peer-to-peer applications . Distributed systems cost significantly more than monolithic architectures, primarily due to increased needs for additional hardware, servers, gateways, firewalls, new subnets, proxies, and so on. Also, distributed systems are prone to fallacies of distributed computing . On
3864-399: The "coordinator" state. For that, they need some method in order to break the symmetry among them. For example, if each node has unique and comparable identities, then the nodes can compare their identities, and decide that the node with the highest identity is the coordinator. The definition of this problem is often attributed to LeLann, who formalized it as a method to create a new token in
3948-518: The 1960s. The first widespread distributed systems were local-area networks such as Ethernet , which was invented in the 1970s. ARPANET , one of the predecessors of the Internet , was introduced in the late 1960s, and ARPANET e-mail was invented in the early 1970s. E-mail became the most successful application of ARPANET, and it is probably the earliest example of a large-scale distributed application . In addition to ARPANET (and its successor,
4032-608: The University of British Columbia, before moving to Stanford. Cheriton was involved in creating three microkernel operating systems (OSes). He was one of the early principal developers of Thoth , a real-time operating system , and then the Verex kernel . He then founded and led the Distributed Systems Group at Stanford University , which developed a microkernel OS named V . He has published profusely in
4116-545: The areas of distributed computing and computer networking . He won the prestigious SIGCOMM award in 2003, in recognition for his lifetime contribution to the field of telecommunications networks . Cheriton was the mentor and advisor of students such as: Sergey Brin and Larry Page (founders of Google), Kenneth Duda (founder of Arista Networks), Hugh Holbrook (VP Software Engineering at Arista Networks), Sandeep Singhal (was GM at Microsoft, now at Google), and Kieran Harty (CTO and founder of Tintri). As of 2016, Cheriton
4200-512: The attenuation figure in dB per km, the number and quality of connectors/patch panels and splices located between transceivers. 1000BASE-CWDM is a non-standard but industry accepted term to refer to Gigabit Ethernet transmission. It is very similar to 1000BASE-LX10 but achieves longer distances up 40–120 km, and up to 18 parallel channels over a pair of single-mode fibers due to higher quality optics than LX10 and use of CWDM, running on 1270-1610 nm wavelength lasers. Use of CWDM requires
4284-419: The case of either multiple computers, or a computer that executes a network of interacting processes: which computational problems can be solved in such a network and how efficiently? However, it is not at all obvious what is meant by "solving a problem" in the case of a concurrent or distributed system: for example, what is the task of the algorithm designer, and what is the concurrent or distributed equivalent of
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#17327981044164368-619: The center of the network to the outside) uses the 1490 nm wavelength, and the one transmitting upstream uses the 1310 nm wavelength. This is accomplished using a passive splitter prism inside each transceiver. Other, non-standard higher-powered single-strand optics commonly known as "BiDi" (bi-directional) utilize wavelength pairs in the 1490/1550 nm range, and are capable of reaching distances of 20, 40 and 80 km, or greater depending on module cost, fiber path loss, splices, connectors and patch panels. Very long reach BiDi optics may use 1510/1590 nm wavelength pairs. 1000BASE-ZX
4452-516: The cost of the required electronics by only using four unidirectional pairs (two pairs TX and two pairs RX) instead of four bidirectional pairs. However, this solution has been a commercial failure, likely due to the required Category 6 cabling and the rapidly falling cost of 1000BASE-T products. 802.3z-1998 CL39 standardized 1000BASE-CX is an initial standard for Gigabit Ethernet connections with maximum distances of 25 meters using balanced shielded twisted pair and either DE-9 or 8P8C connector (with
4536-479: The early 1970s, and later evolved into a widely implemented physical and link layer protocol. Fast Ethernet increased the speed from 10 to 100 megabits per second (Mbit/s). Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. Initially, Gigabit Ethernet was deployed in high-capacity backbone network links (for instance, on a high-capacity campus network). In 2000 and 2001, Apple's Power Mac G4 and PowerBook G4 respectively were
4620-685: The first mass-produced personal computers to feature the 1000BASE-T connection. It quickly became a built-in feature in many other computers. Half-duplex GbE links connected through repeater hubs were part of the IEEE specification, but the specification is not updated anymore and full-duplex operation with switches is used exclusively. There are five physical layer standards for Gigabit Ethernet using optical fiber (1000BASE-X), twisted pair cable (1000BASE-T), or shielded balanced copper cable (1000BASE-CX). The IEEE 802.3z standard includes 1000BASE-SX for transmission over multi-mode fiber , 1000BASE-LX for transmission over single-mode fiber , and
4704-401: The focus has been on designing a distributed system that solves a given problem. A complementary research problem is studying the properties of a given distributed system. The halting problem is an analogous example from the field of centralised computation: we are given a computer program and the task is to decide whether it halts or runs forever. The halting problem is undecidable in
4788-452: The general case, and naturally understanding the behaviour of a computer network is at least as hard as understanding the behaviour of one computer. However, there are many interesting special cases that are decidable. In particular, it is possible to reason about the behaviour of a network of finite-state machines. One example is telling whether a given network of interacting (asynchronous and non-deterministic) finite-state machines can reach
4872-483: The global Internet), other early worldwide computer networks included Usenet and FidoNet from the 1980s, both of which were used to support distributed discussion systems. The study of distributed computing became its own branch of computer science in the late 1970s and early 1980s. The first conference in the field, Symposium on Principles of Distributed Computing (PODC), dates back to 1982, and its counterpart International Symposium on Distributed Computing (DISC)
4956-415: The highest common denominator (HCD), but the link will never come up. Most GbE physical devices have a specific register to diagnose this behavior. Some drivers offer an "Ethernet@Wirespeed" option where this situation leads to a slower yet functional connection. The data is transmitted over four copper pairs, eight bits at a time. First, eight bits of data are expanded into four three-bit symbols through
5040-489: The infra cost must be considered. A computer program that runs within a distributed system is called a distributed program , and distributed programming is the process of writing such programs. There are many different types of implementations for the message passing mechanism, including pure HTTP, RPC-like connectors and message queues . Distributed computing also refers to the use of distributed systems to solve computational problems. In distributed computing ,
5124-456: The issue of the graph family from the design of the coordinator election algorithm was suggested by Korach, Kutten, and Moran. In order to perform coordination, distributed systems employ the concept of coordinators. The coordinator election problem is to choose a process from among a group of processes on different processors in a distributed system to act as the central coordinator. Several central coordinator election algorithms exist. So far
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#17327981044165208-509: The nearly obsolete 1000BASE-CX for transmission over shielded balanced copper cabling. These standards use 8b/10b encoding , which inflates the line rate by 25%, from 1000 Mbit/s to 1250 Mbit/s, to ensure a DC balanced signal, and allow for clock recovery. The symbols are then sent using NRZ . Optical fiber transceivers are most often implemented as user-swappable modules in SFP form or GBIC on older devices. IEEE 802.3ab, which defines
5292-655: The need for crossover cables , making obsolete the uplink vs normal port choices and manual selector switches found on many older hubs and switches and greatly reduces installation errors. In order to extend and maximize the use of existing Cat-5e and Cat-6 cabling, the newer standards 2.5GBASE-T and 5GBASE-T operate at 2.5 and 5.0 Gbit/s, respectively, on existing copper infrastructure designed for use with 1000BASE-T. They are based on 10GBASE-T but use lower signaling frequencies. IEEE 802.3 standardized 1000BASE-T1 in IEEE Std 802.3bp-2016. It defines Gigabit Ethernet over
5376-427: The noise immunity of the five-level signaling is also identical to that of the three-level signaling in 100BASE-TX, since 1000BASE-T uses four-dimensional trellis coded modulation (TCM) to achieve a 6 dB coding gain across the four pairs. Since negotiation takes place on only two pairs, if two GbE interfaces are connected through a cable with only two pairs, the interfaces will successfully choose 'gigabit' as
5460-678: The non-standard -EX and -ZX implementations. Included are copper variants using the same 8b/10b line code. 1000BASE-X is based on the physical-layer standards developed for Fibre Channel . 1000BASE-SX is an optical fiber Gigabit Ethernet standard for operation over multi-mode fiber using a 770 to 860 nanometer , near infrared (NIR) light wavelength . The standard specifies a maximum length of 220 meters for 62.5 μm/160 MHz×km multi-mode fiber , 275 m for 62.5 μm/200 MHz×km, 500 m for 50 μm/400 MHz×km, and 550 m for 50 μm/500 MHz×km multi-mode fiber. Fiber optic cable manufacturers have extended
5544-448: The number of channels. IEEE 802.3bv-2017 defines standardizes Gigabit Ethernet over step-index plastic optical fiber (POF) using -R 64b/65b large block encoding with red light (600–700 nm). 1000BASE-RHA is intended for home and consumer use (just clamping the bare POF), 1000BASE-RHB for industrial, and 1000BASE-RHC for automotive applications. There may be optical interoperability with respective 1000BASE-X Ethernet interfaces on
5628-401: The other hand, a well designed distributed system is more scalable, more durable, more changeable and more fine-tuned than a monolithic application deployed on a single machine. According to Marc Brooker: "a system is scalable in the range where marginal cost of additional workload is nearly constant." Serverless technologies fit this definition but the total cost of ownership, and not just
5712-408: The problem, and inform each node about the solution ( D rounds). On the other hand, if the running time of the algorithm is much smaller than D communication rounds, then the nodes in the network must produce their output without having the possibility to obtain information about distant parts of the network. In other words, the nodes must make globally consistent decisions based on information that
5796-629: The question, then produces an answer and stops. However, there are also problems where the system is required not to stop, including the dining philosophers problem and other similar mutual exclusion problems. In these problems, the distributed system is supposed to continuously coordinate the use of shared resources so that no conflicts or deadlocks occur. There are also fundamental challenges that are unique to distributed computing, for example those related to fault-tolerance . Examples of related problems include consensus problems , Byzantine fault tolerance , and self-stabilisation . Much research
5880-404: The reach of 1000BASE-SX to at least 1km when used with more modern fiber optic grades such as OM3 and OM4. This standard is highly popular for intra-building links in large office buildings, co-location facilities and carrier-neutral Internet exchanges. Optical power specifications of SX interface: Minimum output power = −9.5 dBm . Minimum receive sensitivity = −17 dBm. 1000BASE-LSX
5964-403: The same place as the boundary between parallel and distributed systems (shared memory vs. message passing). In parallel algorithms, yet another resource in addition to time and space is the number of computers. Indeed, often there is a trade-off between the running time and the number of computers: the problem can be solved faster if there are more computers running in parallel (see speedup ). If
6048-423: The simplest model of distributed computing is a synchronous system where all nodes operate in a lockstep fashion. This model is commonly known as the LOCAL model. During each communication round , all nodes in parallel (1) receive the latest messages from their neighbours, (2) perform arbitrary local computation, and (3) send new messages to their neighbors. In such systems, a central complexity measure
6132-432: The task is begun, all network nodes are either unaware which node will serve as the "coordinator" (or leader) of the task, or unable to communicate with the current coordinator. After a coordinator election algorithm has been run, however, each node throughout the network recognizes a particular, unique node as the task coordinator. The network nodes communicate among themselves in order to decide which of them will get into
6216-416: The use of -LX(10), -LH, -EX, and -ZX is ambiguous between vendors. 1000BASE-ZX is a very similar non-standard longer-reach variant that uses 1550 nm wavelength optics. 1000BASE-BX10 is capable of up to 10 km over a single strand of single-mode fiber , with a different wavelength going in each direction. The terminals on each side of the fiber are not equal, as the one transmitting downstream (from
6300-523: The widely used 1000BASE-T interface type, uses a different encoding scheme in order to keep the symbol rate as low as possible, allowing transmission over twisted pair. IEEE 802.3ap defines Ethernet Operation over Electrical Backplanes at different speeds. Ethernet in the First Mile later added 1000BASE-LX10 and -BX10. 1000BASE-T (also known as IEEE 802.3ab) is a standard for Gigabit Ethernet over twisted-pair wiring. Each 1000BASE-T network segment
6384-454: Was acquired by Cisco Systems in 1996. In August 1998, Stanford students Sergey Brin and Larry Page met Bechtolsheim on Cheriton's front porch. At the meeting, Bechtolsheim wrote the first cheque to fund their company, Google , and Cheriton joined him as an angel investor with a $ 200,000 investment. Cheriton was also an early investor in compute virtualization leader VMware , which was later acquired for $ 625M by EMC in 2004. VMware had
6468-651: Was also an early investor in in-video advertising company Zunavision , and he founded OptumSoft . In 2014, Cheriton cofounded and invested in Apstra , Inc. In 2015, he cofounded and invested in BrainofT, Inc. (Caspar). He currently serves as the Chief Data Center Scientist at Juniper Networks . Although the Google investment alone would be worth over US$ 1 billion, Cheriton has a reputation for
6552-610: Was chief scientist of Arista Networks , where he worked on the foundations of the Extensible Operating System (EOS). Arista had a successful public offering in 2014. Cheriton is an investor in and advisory board member for frontline data warehouse company Aster Data Systems , which was acquired by Teradata in 2011 for $ 263M. Cheriton is also one of the earliest investors in Tintri , a storage virtualization company founded by his student Kieran Harty . Cheriton
6636-480: Was favored by telephone carriers, preferring Ethernet , which he saw as a simpler, proven option. Ethernet gradually superseded alternatives. In 1980, Cheriton married Iris Fraser. They divorced in 1994. According to public record, Cheriton has made donations to Republican causes including the party, candidate PACs, senators, and made a total of over $ 5,000 donations to the presidential candidate Donald Trump . Distributed computing Distributed computing
6720-540: Was first held in Ottawa in 1985 as the International Workshop on Distributed Algorithms on Graphs. Various hardware and software architectures are used for distributed computing. At a lower level, it is necessary to interconnect multiple CPUs with some sort of network, regardless of whether that network is printed onto a circuit board or made up of loosely coupled devices and cables. At a higher level, it
6804-423: Was originally presented as a parallel algorithm, but the same technique can also be used directly as a distributed algorithm. Moreover, a parallel algorithm can be implemented either in a parallel system (using shared memory) or in a distributed system (using message passing). The traditional boundary between parallel and distributed algorithms (choose a suitable network vs. run in any given network) does not lie in
6888-459: Was ranked by Forbes with an estimated net worth of US$ 8.8 billion , as of April 2021. He has made contributions to education, with a $ 25 million donation to support graduate studies and research in the School of Computer Science (subsequently renamed David R. Cheriton School of Computer Science ) at the University of Waterloo , a $ 7.5 million donation to the University of British Columbia , and
6972-424: Was rejected by the music program, and then went on to study mathematics and received his Bachelor of Science (B.S.) degree from the University of British Columbia in 1973. Cheriton received his Master of Science (M.S.) and Doctor of Philosophy (Ph.D.) degrees in computer science from the University of Waterloo in 1974 and 1978, respectively. He spent three years as an assistant professor at his alma mater ,
7056-519: Was standardized six years after the initial gigabit fiber versions as part of the Ethernet in the First Mile task group. It is practically identical to 1000BASE-LX, but achieves longer distances up to 10 km over a pair of single-mode fiber due to higher quality optics. Before it was standardized, 1000BASE-LX10 was essentially already in widespread use by many vendors as a proprietary extension called either 1000BASE-LX/LH or 1000BASE-LH. 1000BASE-EX
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