1.
Avaya
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The company also provides business communication solutions for customers. In 1995, Lucent Technologies was spun off from AT&T. Lucent spun off units of its own in an attempt to restructure its struggling, unprofitable operations. Avaya was spun off in 2000, Management chose the name Avaya to set the company apart, Management thought Avaya sounded open and fluid—reflecting a company that’s open-minded and that provides seamless, effortless interconnections among people and businesses. The company was delisted from the New York Stock Exchange after the acquisition was completed, the integrated communication offering Avaya Aura was launched. In December 2009, Avaya acquired Nortel Enterprise assets for $900 million, on October 4,2011, Avaya reported that it was acquiring Sipera Systems for its session border controller functionality and UC security applications. On October 19,2011, it was reported that Avaya would buy Aurix, on April 30,2012, the shareholders approved the acquisition of Radvision by Avaya for about $230 million. The deal closed in June 2012, as of November 2016, Avaya was weighing chapter 11 bankruptcy filing while trying to sell off its call center business. On January 19,2017, Avaya filed for protection under Chapter 11. However, it stated that its operations would remain unaffected. In its petition, Avaya listed $5.5 billion in assets, since 2001, the company has sold and acquired several companies to support its current product set, including VPNet Technologies, Inc. Quintus, RouteScience, Tenovis, Spectel, NimCat Networks, Traverse Networks, Ubiquity Software Corporation, Agile Software NZ Limited, Konftel, Sipera, Aurix, Radvision and Esnatech. Through Nortels bankruptcy proceedings, certain assets related to their Enterprise Voice, Avaya placed a $900 million bid and was formally announced as the winner of these assets on September 14,2009. Avayas headquarters are located at 4655 Great America Parkway, Santa Clara, the company had offices located in over 145 countries worldwide in 2011. The company also sponsors a users group, Avaya sponsors training programs for IT professional certifications and training for use of Avayas products. In 1985, Performance Engineering Corporation was formed to offer services to government customers. On June 6,2005, Nortel Networks Inc. completed the acquisition of PEC Solutions, on January 18,2006, Nortel PEC Solutions was renamed Nortel Government Solutions. On December 21,2009, Avaya acquired Nortels government business as part of Nortels asset sale, the contract includes the 2002 FIFA World Cup in South Korea & Japan and 2006 FIFA World Cup in Germany
2.
ERS 3500 and ERS 2500 series
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Ethernet Routing Switch 3500 Series and Ethernet Routing Switch 2500 Series or in data computer networking terms are stackable routing switches designed and manufactured by Avaya. The Switches can be stacked up to eight units high through a stacking configuration and these Switches are all covered by Avayas Lifetime warranty. In 2008 Layer 3 routing support, secure web access with https, in January 2008 another detailed evaluation of this systems was performed by Tolly Enterprises, LLC. comparing the 2500 systems to Catalyst 2960-24T and HP ProCurve 2626 and 2650 systems. Later in November 2010 IGMP multicast and IPv6 management was added in version 4.3, as of February 2012 the software version 4.4 is the latest software released for the product which was currently published in August 2011. The ERS3500 Series consists or four gigabit Ethernet models the 3510GT, 3510GT-PWR+, 3524GT, and 3524GT-PWR+ along with 2 fast Ethernet models 35265T, and 3526T-PWR+. The switch can be installed initially as standalone and then field-upgraded via a license to support resilient Stackable Chassis configuration of up to eight Switches, the stack-enabled version of the ERS2500 Switches will not require a license kit or license file. The ERS 2550T supports 48 ports of 10/100 plus two Gigabit uplink ports that are a configuration of 1000BASE-T/SFP. The ERS 2550T-PWR supports PoE capabilities on half of the user ports, the ERS 2526T and ERS 2526T-PWR models offer 24 ports of 10/100 plus two Gigabit uplink ports that are a combo configuration of 1000BASE-T/SFP. The ERS 2526T-PWR model offers PoE support on half of the user ports, the system also has the ability to stack any combination of these Switches in a system. The ERS2500 Series of Switches can be stacked with Flexible Advanced Stacking Technology to allows eight switches to operate as single logical system with a 32 Gbit/s virtual backplane, the bi-directional paths allow the traffic to automatically redirect around any switch in the stack that is not operating properly. This stacking technology allows stackable switches to operate with the same performance, Avaya Releases Ethernet Routing Switch 3500. New Ethernet Switches from Avaya Simplify Operations for Small and Midsize Enterprises, Avaya targets small businesses with new network gear. Avaya Unveils Network Switches for Small Enterprises, research Triangle Park, NC, Nortel Press. Pp. 19–20,63,219, 221–223,296, 385–387, 399–400,467, ERS 5000/4500/2500 Advanced Configuration and Maintenance. Archived from the original on 1 March 2012, data Stackables Nortel Ethernet Routing Switch 2500 y 4500. Archived from the original on 28 February 2012, Avaya Official Ethernet Routing Switch Documentation List -Retrieved 22 July 2011 ERS2500 Fact Sheet ERS3500 Fact Sheet Stackable Chassis Architecture
3.
Computer network
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A computer network or data network is a telecommunications network which allows nodes to share resources. In computer networks, networked computing devices exchange data with other using a data link. The connections between nodes are established using either cable media or wireless media, the best-known computer network is the Internet. Network computer devices that originate, route and terminate the data are called network nodes, nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices can be said to be networked together when one device is able to exchange information with the other device, Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the networks size, topology and organizational intent. In most cases, application-specific communications protocols are layered over other more general communications protocols and this formidable collection of information technology requires skilled network management to keep it all running reliably. The chronology of significant computer-network developments includes, In the late 1950s, in 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. Licklider developed a group he called the Intergalactic Computer Network. In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of computer systems. The same year, at Massachusetts Institute of Technology, a group supported by General Electric and Bell Labs used a computer to route. Throughout the 1960s, Leonard Kleinrock, Paul Baran, and Donald Davies independently developed network systems that used packets to transfer information between computers over a network, in 1965, Thomas Marill and Lawrence G. Roberts created the first wide area network. This was an precursor to the ARPANET, of which Roberts became program manager. Also in 1965, Western Electric introduced the first widely used telephone switch that implemented true computer control, in 1972, commercial services using X.25 were deployed, and later used as an underlying infrastructure for expanding TCP/IP networks. In July 1976, Robert Metcalfe and David Boggs published their paper Ethernet, Distributed Packet Switching for Local Computer Networks, in 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s, by 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 100 Gbit/s were added, the ability of Ethernet to scale easily is a contributing factor to its continued use. Providing access to information on shared storage devices is an important feature of many networks, a network allows sharing of files, data, and other types of information giving authorized users the ability to access information stored on other computers on the network
4.
Packet switching
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Packet switching increases network efficiency and robustness, and enables technological convergence of many applications operating on the same network. Packets are composed of a header and payload, Information in the header is used by networking hardware to direct the packet to its destination where the payload is extracted and used by application software. This concept contrasted and contradicted then-established principles of pre-allocation of network bandwidth, the new concept found little resonance among network implementers until the independent work of British computer scientist Donald Davies at the National Physical Laboratory in the late 1960s. Packet mode communication may be implemented with or without intermediate forwarding nodes, in case of a shared physical medium, the packets may be delivered according to a multiple access scheme. In the late 1950s, the US Air Force established a wide area network for the Semi-Automatic Ground Environment radar defense system and they sought a system that might survive a nuclear attack to enable a response, thus diminishing the attractiveness of the first strike advantage by enemies. Report P-2626 described a general architecture for a large-scale, distributed, Barans work was known to Robert Taylor and J. C. R. Licklider at the Information Processing Technology Office, who advocated wide area networks, starting in 1965, Donald Davies at the National Physical Laboratory, UK, independently developed the same message routing methodology as developed by Baran. He called it packet switching, a more accessible name than Barans and he gave a talk on the proposal in 1966, after which a person from the Ministry of Defence told him about Barans work. A member of Davies team met Lawrence Roberts at the 1967 ACM Symposium on Operating System Principles, Davies had chosen some of the same parameters for his original network design as did Baran, such as a packet size of 1024 bits. In 1966, Davies proposed that a network should be built at the laboratory to serve the needs of NPL, the NPL Data Communications Network entered service in 1970. In 1974, Vint Cerf and Bob Kahn published the specifications for Transmission Control Protocol, Packet switching may be classified into connectionless packet switching, also known as datagram switching, and connection-oriented packet switching, also known as virtual circuit switching. Examples of connectionless protocols are Ethernet, Internet Protocol, and the User Datagram Protocol, connection-oriented protocols include X.25, Frame Relay, Multiprotocol Label Switching, and the Transmission Control Protocol. In connectionless mode each packet includes complete addressing information, the packets are routed individually, sometimes resulting in different paths and out-of-order delivery. Each packet is labeled with an address, source address. It may also be labeled with the number of the packet. At the destination, the original message/data is reassembled in the correct order, connection-oriented transmission requires a setup phase in each involved node before any packet is transferred to establish the parameters of communication. The packets include a connection identifier rather than address information and are negotiated between endpoints so that they are delivered in order and with error checking, the signaling protocols used allow the application to specify its requirements and discover link parameters. Acceptable values for service parameters may be negotiated, routing a packet requires the node to look up the connection id in a table
5.
Bridging (networking)
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A network bridge is a computer networking device that creates a single aggregate network from multiple communication networks or network segments. This function is called network bridging, bridging is distinct from routing, which allows multiple different networks to communicate independently while remaining separate. In the OSI model, bridging is performed in the first two layers, below the network layer, if one or more segments of the bridged network are wireless, the device is known as a wireless bridge and the function as wireless bridging. There are four types of network bridging technologies, simple bridging, multiport bridging, learning or transparent bridging, a simple bridge connects two network segments, typically by operating transparently and deciding on a frame-by-frame basis whether or not to forward from one network to the other. A store and forward technique is used so, during forwarding. Contrary to repeaters that extend the maximum span of a segment. Additionally, bridges reduce collisions by partitioning the collision domain, a multiport bridge connects multiple networks and operates transparently to decide on a frame-by-frame basis whether and where to forward traffic. Like the simple bridge, a multiport bridge typically uses store, the multiport bridge function serves as the basis for network switches. A transparent bridge uses a database to send frames across network segments. The forwarding database starts empty - entries in the database are built as the bridge receives frames. If an address entry is not found in the forwarding database, by means of these flooded frames, the destination network will respond and a forwarding database entry will be created. In the context of a bridge, one can think of the forwarding database as a filtering database. A bridge reads a frames destination address and decides to forward or filter. If the bridge determines that the node is on another segment on the network. If the destination address belongs to the segment as the source address. As nodes transmit data through the bridge, the bridge establishes a filtering database of known MAC addresses, the bridge uses its filtering database to determine whether a frame should be forwarded or filtered. Transparent bridging can also operate over devices with more than two ports, as an example, consider a bridge connected to three hosts, A, B, and C. A is connected to bridge port 1, B is connected to bridge port 2, C is connected to bridge port 3, a sends a frame addressed to B to the bridge
6.
MAC address
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A media access control address of a computer is a unique identifier assigned to network interfaces for communications at the data link layer of a network segment. MAC addresses are used as an address for most IEEE802 network technologies, including Ethernet. Logically, MAC addresses are used in the access control protocol sublayer of the OSI reference model. MAC addresses are most often assigned by the manufacturer of a network interface controller and are stored in its hardware, if assigned by the manufacturer, a MAC address usually encodes the manufacturers registered identification number and may be referred to as the burned-in address. It may also be known as an Ethernet hardware address, hardware address or physical address and this can be contrasted to a programmed address, where the host device issues commands to the NIC to use an arbitrary address. A network node may have multiple NICs and each NIC must have a unique MAC address, sophisticated network equipment such as a multilayer switch or router may require one or more permanently assigned MAC addresses. MAC addresses are formed according to the rules of one of three numbering name spaces managed by the Institute of Electrical and Electronics Engineers, MAC-48, EUI-48, the IEEE claims trademarks on the names EUI-48 and EUI-64, in which EUI is an abbreviation for Extended Unique Identifier. The original IEEE802 MAC address comes from the original Xerox Ethernet addressing scheme and this 48-bit address space contains potentially 248 or 281,474,976,710,656 possible MAC addresses. The distinction between EUI-48 and MAC-48 identifiers is purely nominal, MAC-48 is used for hardware, EUI-48 is used to identify other devices. Instead, the proprietary term EUI-48 should be used for this purpose, in addition, the EUI-64 numbering system encompasses both MAC-48 and EUI-48 identifiers by a simple translation mechanism. To convert a MAC-48 into an EUI-64, copy the OUI, to convert an EUI-48 into an EUI-64, the same process is used, but the sequence inserted is FF-FE. In both cases, the process can be reversed when necessary. Organizations issuing EUI-64s are cautioned against issuing identifiers that could be confused with these forms, the IEEE has a target lifetime of 100 years for applications using MAC-48 space, but encourages adoption of EUI-64s instead. IPv6 — one of the most prominent standards that uses a Modified EUI-64 — treats MAC-48 as EUI-48 instead and this results in extending MAC addresses to Modified EUI-64 using only FF-FE and with the U/L bit inverted. An Individual Address Block was a 24-bit OUI managed by the IEEE Registration Authority, followed by 12 IEEE-provided bits, an IAB is ideal for organizations requiring fewer than 4097 unique 48-bit numbers. IABs have been replaced with 12-bit MA-S address blocks, addresses can either be universally administered addresses or locally administered addresses. A universally administered address is assigned to a device by its manufacturer. The first three octets identify the organization issued the identifier and are known as the Organizationally Unique Identifier
7.
OSI model
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Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers, the original version of the model defined seven layers. A layer serves the layer above it and is served by the layer below it, two instances at the same layer are visualized as connected by a horizontal connection in that layer. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization and these two international standards bodies each developed a document that defined similar networking models. In 1983, these two documents were merged to form a standard called The Basic Reference Model for Open Systems Interconnection, the standard is usually referred to as the Open Systems Interconnection Reference Model, the OSI Reference Model, or simply the OSI model. It was published in 1984 by both the ISO, as standard ISO7498, and the renamed CCITT as standard X.200. OSI had two components, an abstract model of networking, called the Basic Reference Model or seven-layer model. The concept of a model was provided by the work of Charles Bachman at Honeywell Information Services. Various aspects of OSI design evolved from experiences with the ARPANET, NPLNET, EIN, CYCLADES network, the new design was documented in ISO7498 and its various addenda. In this model, a system was divided into layers. Within each layer, one or more entities implement its functionality, each entity interacted directly only with the layer immediately beneath it, and provided facilities for use by the layer above it. Protocols enable an entity in one host to interact with an entity at the same layer in another host. Service definitions abstractly described the functionality provided to an -layer by an layer, the OSI standards documents are available from the ITU-T as the X. 200-series of recommendations. Some of the specifications were also available as part of the ITU-T X series. The equivalent ISO and ISO/IEC standards for the OSI model were available from ISO, the recommendation X.200 describes seven layers, labeled 1 to 7. Layer 1 is the lowest layer in this model, at each level N, two entities at the communicating devices exchange protocol data units by means of a layer N protocol. Each PDU contains a payload, called the service data unit, data processing by two communicating OSI-compatible devices is done as such, The data to be transmitted is composed at the topmost layer of the transmitting device into a protocol data unit. The PDU is passed to layer N-1, where it is known as the service data unit, at layer N-1 the SDU is concatenated with a header, a footer, or both, producing a layer N-1 PDU
8.
Ethernet
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Ethernet /ˈiːθərnɛt/ is a family of computer networking technologies commonly used in local area networks, metropolitan area networks and wide area networks. It was commercially introduced in 1980 and first standardized in 1983 as IEEE802.3, over time, Ethernet has largely replaced competing wired LAN technologies such as token ring, FDDI and ARCNET. The original 10BASE5 Ethernet uses coaxial cable as a medium, while the newer Ethernet variants use twisted pair. Over the course of its history, Ethernet data transfer rates have increased from the original 2.94 megabits per second to the latest 100 gigabits per second. The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet, systems communicating over Ethernet divide a stream of data into shorter pieces called frames. As per the OSI model, Ethernet provides services up to, since its commercial release, Ethernet has retained a good degree of backward compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols, the primary alternative for some uses of contemporary LANs is Wi-Fi, a wireless protocol standardized as IEEE802.11. Ethernet was developed at Xerox PARC between 1973 and 1974 and it was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his PhD dissertation. In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker, in 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper. Metcalfe left Xerox in June 1979 to form 3Com and he convinced Digital Equipment Corporation, Intel, and Xerox to work together to promote Ethernet as a standard. The so-called DIX standard, for Digital/Intel/Xerox, specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and it was published on September 30,1980 as The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications, version 2 was published in November,1982 and defines what has become known as Ethernet II. Formal standardization efforts proceeded at the time and resulted in the publication of IEEE802.3 on June 23,1983. Ethernet initially competed with two largely proprietary systems, Token Ring and Token Bus, in the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 NIC in March 1981, an Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. Parallel port based Ethernet adapters were produced for a time, with drivers for DOS, by the early 1990s, Ethernet became so prevalent that it was a must-have feature for modern computers, and Ethernet ports began to appear on some PCs and most workstations. This process was sped up with the introduction of 10BASE-T and its relatively small modular connector. Since then, Ethernet technology has evolved to meet new bandwidth, in addition to computers, Ethernet is now used to interconnect appliances and other personal devices
9.
Kalpana (company)
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Kalpana, a computer-networking equipment manufacturer located in Silicon Valley, operated during the 1980s and 1990s. Its co-founders, Vinod Bhardwaj, an entrepreneur of Indian origin, charles Giancarlo was Kalpanas vice president of products and corporate development, became its General Manager, and went on to roles at Cisco Systems and Silver Lake Partners. In 1989 and 1990, Kalpana introduced the first multiport Ethernet switch, the invention of Ethernet switching made Ethernet networks faster, cheaper, and easier to manage. Multi-port network switches became common, gradually replacing Ethernet hubs for almost all applications, Kalpana also invented EtherChannel, which provides higher inter-switch bandwidth by running several links in parallel. This innovation, more generally called link aggregation, was widely adopted throughout the industry. Cisco Systems acquired Kalpana in 1994
10.
Fibre Channel
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Fibre Channel, or FC, is a high-speed network technology primarily used to connect computer data storage to servers. Fibre Channel is mainly used in storage area networks in commercial data centers, Fibre Channel networks form a switched fabric because they operate in unison as one big switch. Fibre Channel typically runs on optical fiber cables within and between data centers, most block storage runs over Fibre Channel Fabrics and supports many upper level protocols. Fibre Channel Protocol is a protocol that predominantly transports SCSI commands over Fibre Channel networks. Mainframe computers run the FICON command set over Fibre Channel because of its high reliability, Fibre Channel can be used for flash memory being transported over the NVMe interface protocol. To promote the fiber optic aspects of the technology and to make a unique name, Fibre Channel started in 1988, with ANSI standard approval in 1994, to merge the benefits of multiple physical layer implementations including SCSI, HIPPI and ESCON. Fibre Channel was designed as an interface to overcome limitations of the SCSI. FC was developed with leading edge multi-mode fiber technologies that overcame the limitations of the ESCON protocol. Initially, the standard also ratified lower speed Fibre Channel versions with 132.8125 Mbit/s,265.625 Mbit/s, Fibre Channel saw adoption at 1 Gigabit/s Fibre Channel and its success grew with each successive speed. Fibre Channel has doubled in speed every few years since 1996, Fibre channel has seen active development since its inception, with numerous speed improvements on a variety of underlying transport media. There are three major Fibre Channel topologies, describing how a number of ports are connected together, a port in Fibre Channel terminology is any entity that actively communicates over the network, not necessarily a hardware port. This port is usually implemented in a such as disk storage. Two devices are connected directly to each other and this is the simplest topology, with limited connectivity. In this design, all devices are in a loop or ring, adding or removing a device from the loop causes all activity on the loop to be interrupted. The failure of one device causes a break in the ring, Fibre Channel hubs exist to connect multiple devices together and may bypass failed ports. A loop may also be made by cabling each port to the next in a ring, a minimal loop containing only two ports, while appearing to be similar to point-to-point, differs considerably in terms of the protocol. Only one pair of ports can communicate concurrently on a loop, Arbitrated Loop has been rarely used after 2010. In this design, all devices are connected to Fibre Channel switches, advantages of this topology over point-to-point or Arbitrated Loop include, The Fabric can scale to tens of thousands of ports
11.
Asynchronous Transfer Mode
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ATM was developed to meet the needs of the Broadband Integrated Services Digital Network, as defined in the late 1980s, and designed to unify telecommunication and computer networks. It was designed for a network that must handle both traditional high-throughput data traffic, and real-time, low-latency content such as voice and video. The reference model for ATM approximately maps to the three lowest layers of the ISO-OSI reference model, network layer, data link layer, and physical layer. ATM is a protocol used over the SONET/SDH backbone of the public switched telephone network and Integrated Services Digital Network. This differs from approaches such as the Internet Protocol or Ethernet that use variable sized packets, ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins. ATM eventually became dominated by Internet Protocol only technology, in the ISO-OSI reference model data link layer, the basic transfer units are generically called frames. In ATM these frames are of a length and specifically called cells. Under normal queuing conditions the cells might experience maximum queuing delays, to avoid this issue, all ATM packets, or cells, are the same small size. In addition, the cell structure means that ATM can be readily switched by hardware without the inherent delays introduced by software switched and routed frames. Thus, the designers of ATM utilized small data cells to reduce jitter in the multiplexing of data streams.544 to 45 Mbit/s in the USA, at this rate, a typical full-length 1500 byte data packet would take 77.42 µs to transmit. In a lower-speed link, such as a 1.544 Mbit/s T1 line, a queuing delay induced by several such data packets might exceed the figure of 7.8 ms several times over, in addition to any packet generation delay in the shorter speech packet. This was clearly unacceptable for speech traffic, which needs to have low jitter in the stream being fed into the codec if it is to produce good-quality sound. This allows smoothing out the jitter, but the delay introduced by passage through the buffer would require echo cancellers even in local networks, also, it would have increased the delay across the channel, and conversation is difficult over high-delay channels. Build a system that can provide low jitter to traffic that needs it. Operate on a 1,1 user basis, the design of ATM aimed for a low-jitter network interface. However, cells were introduced into the design to provide short queuing delays while continuing to support datagram traffic, ATM broke up all packets, data, and voice streams into 48-byte chunks, adding a 5-byte routing header to each one so that they could be reassembled later. The choice of 48 bytes was political rather than technical, most of the European parties eventually came around to the arguments made by the Americans, but France and a few others held out for a shorter cell length. With 32 bytes, France would have been able to implement an ATM-based voice network with calls from one end of France to the other requiring no echo cancellation,48 bytes was chosen as a compromise between the two sides
12.
InfiniBand
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InfiniBand is a computer-networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers, InfiniBand is also utilized as either a direct, or switched interconnect between servers and storage systems, as well as an interconnect between storage systems. As of 2014 it was the most commonly used interconnect in supercomputers, Mellanox IB cards are available for Solaris, RHEL, SLES, Windows, HP-UX, VMware ESX, AIX. It is designed to be scalable and uses a switched fabric network topology, as an interconnect, IB competes with Ethernet, Fibre Channel, and proprietary technologies such as Intel Omni-Path. The technology is promoted by the InfiniBand Trade Association, links can be aggregated, most systems use a 4X aggregate. 12X links are used for cluster and supercomputer interconnects and for inter-switch connections. InfiniBand also provides RDMA capabilities for low CPU overhead, InfiniBand uses a switched fabric topology, as opposed to early shared medium Ethernet. All transmissions begin or end at a channel adapter, each processor contains a host channel adapter and each peripheral has a target channel adapter. These adapters can also exchange information for security or quality of service, InfiniBand transmits data in packets of up to 4 KB that are taken together to form a message. A message can be, a memory access read from or, write to. A channel send or receive a transaction-based operation a multicast transmission, an atomic operation In addition to a board form factor connection, it supports both active and passive copper and optical fiber cable. The Infiniband Association also specified the CXP copper connector system for speeds up to 120 Gbit/s over copper, the standard only lists a set of verbs like ibv_open_device or ibv_post_send, which are abstract representations of functions or methods that must exist. The syntax of these functions is left to the vendors, the de facto standard software stack is that developed by OpenFabrics Alliance. It is released under two licenses GPL2 or BSD license for GNU/Linux and FreeBSD, and as WinOF under a choice of BSD license for Windows and it has been adopted by most of the InfiniBand vendors, for GNU/Linux, FreeBSD, and Windows. InfiniBand originated in 1999 from the merger of two competing designs, Future I/O and Next Generation I/O and this led to the formation of the InfiniBand Trade Association, which included Compaq, Dell, Hewlett-Packard, IBM, Intel, Microsoft, and Sun. At the time it was some of the more powerful computers were approaching the interconnect bottleneck of the PCI bus. Version 1.0 of the InfiniBand Architecture Specification was released in 2000, initially the IBTA vision for IB was simultaneously a replacement for PCI in I/O, Ethernet in the machine room, cluster interconnect and Fibre Channel. IBTA also envisaged decomposing server hardware on an IB fabric, following the burst of the dot-com bubble there was hesitation in the industry to invest in such a far-reaching technology jump
13.
Ethernet hub
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It has multiple input/output ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. A hub works at the layer of the OSI model. Repeater hubs also participate in collision detection, forwarding a jam signal to all if it detects a collision. In addition to standard 8P8C ports, some hubs may also come with a BNC or Attachment Unit Interface connector to allow connection to legacy 10BASE2 or 10BASE5 network segments, hubs are now largely obsolete, having been replaced by network switches except in very old installations or specialized applications. As of 2011, connecting network segments by repeaters or hubs is deprecated by IEEE802.3, a network hub is an unsophisticated device in comparison with a switch. As a multiport repeater it works by repeating bits received from one of its ports to all other ports. It is aware of physical layer packets, that is it can detect their start, a hub cannot further examine or manage any of the traffic that comes through it, any packet entering any port is rebroadcast on all other ports. A hub/repeater has no memory to store any data in – a packet must be transmitted while it is received or is lost when a collision occurs, due to this, hubs can only run in half duplex mode. Consequently, due to a larger collision domain, packet collisions are frequent in networks connected using hubs than in networks connected using more sophisticated devices. The need for hosts to be able to detect collisions limits the number of hubs, for 10 Mbit/s networks built using repeater hubs, the 5-4-3 rule must be followed, up to five segments are allowed between any two end stations. For 10BASE-T networks, up to five segments and four repeaters are allowed between any two hosts, for 100 Mbit/s networks, the limit is reduced to 3 segments between any two end stations, and even that is only allowed if the hubs are of Class II. Most hubs detect typical problems, such as collisions and jabbering on individual ports. Thus, hub-based twisted-pair Ethernet is generally more robust than coaxial cable-based Ethernet, to pass data through the repeater in a usable fashion from one segment to the next, the framing and data rate must be the same on each segment. This means that a repeater cannot connect an 802.3 segment,100 Mbit/s hubs and repeaters come in two different speed grades, Class I delay the signal for a maximum of 140 bit times and Class II hubs delay the signal for a maximum of 92 bit times. In the early days of Fast Ethernet, Ethernet switches were relatively expensive devices, hubs suffered from the problem that if there were any 10BASE-T devices connected then the whole network needed to run at 10 Mbit/s. Therefore, a compromise between a hub and a switch was developed, known as a dual-speed hub and these devices make use of an internal two-port switch, bridging the 10 Mbit/s and 100 Mbit/s segments. When a network device becomes active on any of the physical ports and this obviated the need for an all-or-nothing migration to Fast Ethernet networks. These devices are considered hubs because the traffic between devices connected at the speed is not switched
14.
Cisco Systems
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Through its numerous acquired subsidiaries, such as OpenDNS, WebEx, and Jasper, Cisco specializes into specific tech markets, such as Internet of Things, domain security, and energy management. Cisco is the largest networking company in the world, the stock was added to the Dow Jones Industrial Average on June 8,2009, and is also included in the S&P500 Index, the Russell 1000 Index, NASDAQ-100 Index and the Russell 1000 Growth Stock Index. By the time the company went public in 1990, when it was listed on the NASDAQ, Cisco was the most valuable company in the world by 2000, with a more than $500 billion market capitalization. Despite founding Cisco in 1984, Bosack, along with Kirk Lougheed, continued to work at Stanford on Ciscos first product and it consisted of exact replicas of Stanfords Blue Box router and a stolen copy of the Universitys multiple-protocol router software. The software was written some years earlier at Stanford medical school by research engineer William Yeager. Bosack and Lougheed adapted it into what became the foundation for Cisco IOS, in 1987, Stanford licensed the router software and two computer boards to Cisco. In addition to Bosack, Lerner and Lougheed, Greg Satz, a programmer, and Richard Troiano, the companys first CEO was Bill Graves, who held the position from 1987 to 1988. In 1988, John Morgridge was appointed CEO, the name Cisco was derived from the city name San Francisco, which is why the companys engineers insisted on using the lower case cisco in its early years. The logo is intended to depict the two towers of the Golden Gate Bridge, on February 16,1990, Cisco Systems went public and was listed on the NASDAQ stock exchange. On August 28,1990, Lerner was fired, upon hearing the news, her husband Bosack resigned in protest. The couple walked away from Cisco with $170 million, 70% of which was committed to their own charity, although Cisco was not the first company to develop and sell dedicated network nodes, it was one of the first to sell commercially successful routers supporting multiple network protocols. Classical, CPU-based architecture of early Cisco devices coupled with flexibility of operating system IOS allowed for keeping up with evolving technology needs by means of frequent software upgrades, some popular models of that time managed to stay in production for almost a decade virtually unchanged—a rarity in high-tech industry. This philosophy dominated the companys product lines throughout the 1990s, in 1995, John Morgridge was succeeded by John Chambers. The phenomenal growth of the Internet in mid-to-late 1990s quickly changed the telecom landspe, as the Internet Protocol became widely adopted, the importance of multi-protocol routing declined. In late March 2000, at the height of the bubble, Cisco became the most valuable company in the world. In July 2014, with a cap of about US$129 billion. One of them, Juniper Networks, shipped their first product in 1999, Cisco answered the challenge with homegrown ASICs and fast processing cards for GSR routers and Catalyst 6500 switches. In 2004, Cisco also started migration to new high-end hardware CRS-1, as part of a massive rebranding campaign in 2006, Cisco Systems adopted the shortened name Cisco and created The Human Network advertising campaign
15.
Broadcasting (networking)
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In telecommunication and information theory, broadcasting is a method of transferring a message to all recipients simultaneously. All-to-all communication is a communication method in which each sender transmits messages to all receivers within a group. This contrasts with the point-to-point method in which each sender communicates with one receiver, in computer networking, broadcasting refers to transmitting a packet that will be received by every device on the network. In practice, the scope of the broadcast is limited to a broadcast domain, Broadcasting a message is in contrast to unicast addressing in which a host sends datagrams to another single host identified by a unique IP address. Broadcasting is the most general method, and is also the most intensive in the sense that a large number of messages are required. Broadcasting may be performed as all scatter in which each sender performs its own scatter in which the messages are distinct for each receiver, the MPI message passing method which is the de facto standard on large computer clusters includes the MPI_Alltoall method. Not all network technologies support broadcast addressing, for example, neither X.25 nor frame relay have broadcast capability, instead it relies on multicast addressing - a conceptually similar one-to-many routing methodology. However, multicasting limits the pool of receivers to those that join a specific multicast receiver group, both Ethernet and IPv4 use an all-ones broadcast address to indicate a broadcast packet. Token Ring uses a value in the IEEE802.2 control field. Broadcasting may be abused to perform a type of DoS-attack known as a Smurf attack, the attacker sends fake ping requests with the source IP-address of the victim computer. The victim computer is flooded by the replies from all computers in the domain, broadcast radiation Point-to-multipoint communication Unicast Encyclopædia Britannica entry broadcast network Network Broadcasting and Multicast
16.
Local area network
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By contrast, a wide area network, not only covers a larger geographic distance, but also generally involves leased telecommunication circuits or Internet links. An even greater contrast is the Internet, which is a system of globally connected business, Ethernet and Wi-Fi are the two most common transmission technologies in use for local area networks. Historical technologies include ARCNET, Token ring, and AppleTalk, the increasing demand and use of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A1970 report from the Lawrence Radiation Laboratory detailing the growth of their Octopus network gave an indication of the situation. A number of experimental and early commercial LAN technologies were developed in the 1970s, Cambridge Ring was developed at Cambridge University starting in 1974. Ethernet was developed at Xerox PARC in 1973–1975, and filed as U. S, in 1976, after the system was deployed at PARC, Robert Metcalfe and David Boggs published a seminal paper, Ethernet, Distributed Packet-Switching for Local Computer Networks. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977 and it had the first commercial installation in December 1977 at Chase Manhattan Bank in New York. The initial driving force for networking was generally to share storage and printers, there was much enthusiasm for the concept and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, “The year of the LAN”. In practice, the concept was marred by proliferation of incompatible physical layer and network protocol implementations, typically, each vendor would have its own type of network card, cabling, protocol, and network operating system. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT Advanced Server, of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. During the same period, Unix workstations were using TCP/IP networking, early LAN cabling had generally been based on various grades of coaxial cable. This led to the development of 10BASE-T and structured cabling which is still the basis of most commercial LANs today, while fiber-optic cabling is common for links between switches, use of fiber to the desktop is rare. Many LANs use wireless technologies that are built into Smartphones, tablet computers, in a wireless local area network, users may move unrestricted in the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation, guests are often offered Internet access via a hotspot service. Network topology describes the layout of interconnections between devices and network segments, at the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star. At the higher layers, NetBEUI, IPX/SPX, AppleTalk and others were once common, simple LANs generally consist of cabling and one or more switches. A switch can be connected to a router, cable modem, a LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection. LANs can maintain connections with other LANs via leased lines, leased services, depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network or a wide area network
17.
Small office/home office
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Small office/home office refers to the category of business or cottage industry that involves from 1 to 10 workers. Before the 19th century, and the spread of the industrial revolution around the globe, nearly all offices were small offices and/or home offices, most businesses were small, and the paperwork that accompanied them was limited. The industrial revolution aggregated workers in factories, to mass-produce goods, in most circumstances, the white collar counterpart—office work—was aggregated as well in large buildings, usually in cities or densely populated suburban areas. Beginning in the mid-1980s, the advent of the computer and fax machine, plus breakthroughs in telecommunications. Decentralization was also perceived as benefiting employers in terms of lower overheads, many consultants and the members of such professions as lawyers, real estate agents, and surveyors in small and medium-size towns operate from home offices. Several ranges of products, such as the desk and all-in-one printer, are designed specifically for the SOHO market. A number of books and magazines have published and marketed specifically at this type of office. These range from general advice texts to specific guidebooks on such challenges as setting up a small PBX for the office telephones, technology has also created a demand for larger businesses to employ individuals who work from home. Sometimes these people remain as independent businesspersons, and sometimes they become employees of a larger company, the small office home office has undergone a transformation since its advent as the internet has enabled anyone working from a home office to compete globally. Technology has made possible through email, the World-Wide Web, e-commerce, videoconferencing, remote desktop software, webinar systems. Bless This Home Office. With tax credits, An Adam Compilation, johnson, Karen K. ed. Orthos All About Home Offices. The Home Office, Setting Up, Furnishing and Decorating Your Own Work Space
18.
Residential gateway
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In telecommunications networking, a residential gateway allows the connection of a local area network to a wide area network. The WAN can be a computer network, or the Internet. WAN connectivity may be provided through DSL, cable modem, a mobile phone network. The term residential gateway was originally used to distinguish the inexpensive networking devices designated for use in the home from devices used in corporate LAN environments. In recent years, however, the expensive residential gateways have gained many of the capabilities of corporate gateways. Many home LANs now are able to provide most of the functions of small corporate LANs, as a part of the carrier network, the home gateway supports remote control, detection and configuration. A modem by itself provides none of the functions of a router and it merely allows ATM or Ethernet or PPP traffic to be transmitted across telephone lines, cable wires, optical fibers, or wireless radio frequencies. On the receiving end is another modem that re-converts the transmission back into digital data packets. This allows network bridging using telephone, cable, optical, the modem also provides handshake protocols, so that the devices on each end of the connection are able to recognize each other. However, a modem generally provides few other network functions, a USB modem plugs into a single PC and allows a connection of that single PC to a WAN. If properly configured, the PC can also function as the router for a home LAN, an internal modem can be installed on a single PC, also allowing that single PC to connect to a WAN. Again, the PC can be configured to function as a router for a home LAN, a wireless access point can function in a similar fashion to a modem. It can allow a connection from a home LAN to a WAN. However, many modems now incorporate the features mentioned below and thus are appropriately described as residential gateways, may also have an internal modem, most commonly for DSL or Cable ISP. It may also provide functions such as Dynamic DNS. Most routers are self-contained components, using internally stored firmware and they are generally OS-independent, i. e. they can be accessed with any operating system. Wireless routers perform the functions as a router, but also allow connectivity for wireless devices with the LAN. Majority of the vulnerabilities were present in the web administration consoles of the routers, allowing unauthorised control either via default passwords, vendor backdoors, the Residential Gateway Home Gateway Initiative, a group of broadband providers proposing specifications for residential gateways The Residential Home Gateway on About. com
19.
Digital subscriber line
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Digital subscriber line is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line, DSL service can be delivered simultaneously with wired telephone service on the same telephone line. This is possible because DSL uses higher frequency bands for data, on the customer premises, a DSL filter on each non-DSL outlet blocks any high-frequency interference to enable simultaneous use of the voice and DSL services. Bit rates of 1 Gbit/s have been reached in trials, in ADSL, the data throughput in the upstream direction is lower, hence the designation of asymmetric service. In symmetric digital subscriber line services, the downstream and upstream data rates are equal, researchers at Bell Labs have reached speeds of 10 Gbit/s, while delivering 1 Gbit/s symmetrical broadband access services using traditional copper telephone lines. These higher speeds are lab results, however, a 2012 survey found that DSL continues to be the dominant technology for broadband access with 364.1 million subscribers worldwide. For a long time it was thought that it was not possible to operate a conventional phone-line beyond low-speed limits, in the 1950s, ordinary twisted-pair telephone-cable often carried four megahertz television signals between studios, suggesting that such lines would allow transmitting many megabits per second. One such circuit in the UK ran some ten miles between the BBC studios in Newcastle-upon-Tyne and the Pontop Pike transmitting station and it was able to give the studios a low quality cue feed but not one suitable for transmission. However, these cables had other impairments besides Gaussian noise, preventing such rates from becoming practical in the field, the 1980s saw the development of techniques for broadband communications that allowed the limit to be greatly extended. A patent was filed in 1979 for the use of existing telephone wires for both telephones and data terminals that were connected to a computer via a digital data carrier system. Joseph W. Lechleiders contribution to DSL was his insight that an asymmetric arrangement offered more than double the capacity of symmetric DSL. ADSL supports two modes of transport—fast channel and interleaved channel, fast channel is preferred for streaming multimedia, where an occasional dropped bit is acceptable, but lags are less so. Interleaved channel works better for file transfers, where the data must be error-free. Older ADSL standards delivered 8 Mbit/s to the customer over about 2 km of unshielded twisted-pair copper wire, distances greater than 2 km significantly reduce the bandwidth usable on the wires, thus reducing the data rate. But ADSL loop extenders increase these distances by repeating the signal, until the late 1990s, the cost of digital signal processors for DSL was prohibitive. All types of DSL employ highly complex digital signal processing algorithms to overcome the inherent limitations of the twisted pair wires. Due to the advancements of very-large-scale integration technology, the cost of the equipment associated with a DSL deployment lowered significantly, the two main pieces of equipment are a digital subscriber line access multiplexer at one end and a DSL modem at the other end. A DSL connection can be deployed over existing cable, such deployment, even including equipment, is much cheaper than installing a new, high-bandwidth fiber-optic cable over the same route and distance
20.
Router (computing)
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A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet, a data packet is typically forwarded from one router to another router through the networks that constitute the internetwork until it reaches its destination node. A router is connected to two or more lines from different networks. When a data packet comes in on one of the lines, then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. The most familiar type of routers are home and small office routers that simply pass IP packets between the computers and the Internet. An example of a router would be the cable or DSL router. Though routers are typically dedicated hardware devices, software-based routers also exist, when multiple routers are used in interconnected networks, the routers can exchange information about destination addresses using a dynamic routing protocol. Each router builds up a table listing the preferred routes between any two systems on the interconnected networks. A router may have interfaces for different physical types of connections, such as copper cables, fibre optic. Its firmware can also support different networking communications protocol standards, each network interface is used by this specialized computer software to enable data packets to be forwarded from one protocol transmission system to another. Routers may also be used to two or more logical groups of computer devices known as subnets, each with a different network prefix. The network prefixes recorded in the table do not necessarily map directly to the physical interface connections. It does this using internal pre-configured directives, called static routes, static and dynamic routes are stored in the Routing Information Base. The control-plane logic then strips non-essential directives from the RIB and builds a Forwarding Information Base to be used by the forwarding-plane, Forwarding plane, The router forwards data packets between incoming and outgoing interface connections. It routes them to the network type using information that the packet header contains. It uses data recorded in the routing control plane. Routers may provide connectivity within enterprises, between enterprises and the Internet, or between internet service providers networks, the largest routers interconnect the various ISPs, or may be used in large enterprise networks. Smaller routers usually provide connectivity for typical home and office networks, other networking solutions may be provided by a backbone Wireless Distribution System, which avoids the costs of introducing networking cables into buildings
21.
RapidIO
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The RapidIO architecture is a high-performance packet-switched, interconnect technology. RapidIO supports messaging, read/write and cache coherency semantics, RapidIO fabrics guarantee in-order packet delivery, enabling power- and area- efficient protocol implementation in hardware. Based on industry-standard electrical specifications such as those for Ethernet, RapidIO can be used as a chip-to-chip, board-to-board, RapidIO has its roots in energy-efficient, high-performance computing. The protocol was designed by Mercury Computer Systems and Motorola as a replacement for Mercurys RACEway proprietary bus. This specification did not achieve extensive commercial adoption, the RapidIO Specification Revision 1.2, released in 2002, defined a serial interconnect based on the XAUI physical layer. Devices based on this specification achieved significant commercial success within wireless baseband, imaging, the RapidIO Specification Revision 2.0, released in 2008, added more port widths and increased the maximum lane speed to 6.25 GBd /5 Gbit/s. Revision 2.1 has repeated and expanded the success of the 1.2 specification. RapidIO fabrics were originally designed to support connecting different types of processors from different manufacturers together in a single system and this allows the system to meet many unique HPC applications where efficient localized traffic is needed. Also, using an open modular data center and compute platform, in March 2015 a top-of-rack switch was announced to drive RapidIO into mainstream data center applications. The interconnect or bus is one of the technologies in the design and development of spacecraft avionic systems that dictates its architecture. There are a host of existing architectures that are still in use given their level of maturity and these existing systems are sufficient for a given type of architecture need and requirement. Unfortunately, for next generation missions a more capable avionics architecture is desired, a viable option toward the design and development of these next generation architectures is to leverage existing commercial protocols capable of accommodating high levels of data transfer. In 2012, RapidIO was selected by the Next Generation Spacecraft Interconnect Standard working group to serve as the foundation for standard communication interconnects to be used in spacecraft. The NGSIS is an umbrella standards effort that includes RapidIO Version 3.1 development, the NGSIS requirements committee developed extensive requirements criteria with 47 different elements for the NGSIS interconnect. Independent trade study results by NGSIS member companies demonstrated the superiority of RapidIO over other existing commercial protocols, such as InfiniBand, Fibre Channel, as a result, the group decided that RapidIO offered the best overall interconnect for the needs of next-generation spacecraft. The RapidIO Specification Revision 3.1, released in 2014, was developed through a collaboration between the RapidIO Trade Association and NGSIS, Revision 3.1 has the following enhancements compared to the 3.0 specification, MECS Time Synchronization protocol for smaller embedded systems. MECS Time Synchronization supports redundant time sources and this protocol is lower cost than the Timestamp Synchronization Protocol introduced in revision 3.0 PRBS test facilities and standard register interface. Structurally Asymmetric Link behavioral definition and standard register interface, Structurally Asymmetric Links carry much more data in one direction than the other, for applications such as sensors or processing pipelines
22.
G.hn
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G. hn is a specification for home networking with data rates up to 1 Gbit/s and operation over three types of legacy wires, telephone wiring, coaxial cables and power lines. A single G. hn semiconductor device is able to network over any of the supported home wire types, some benefits of a multi-wire standard are lower equipment development costs and lower deployment costs for service providers. It was developed under the International Telecommunication Unions Telecommunication Standardization sector and promoted by the HomeGrid Forum, ITU-T Recommendation G.9960, which received approval on October 9,2009, specified the physical layers and the architecture of G. hn. The Data Link Layer was approved on June 11,2010, key promoters CEPCA, HomePNA, and UPA, creators of two of these interfaces, united behind the latest version of the standard in February 2009. The ITU-T extended the technology with multiple input, multiple output technology to increase data rates, the work on MIMO for G. hn at ITU-T is under the G.9963 standard. G. hn specifies a single physical layer based on fast Fourier transform orthogonal frequency-division multiplexing modulation, G. hn includes the capability to notch specific frequency bands to avoid interference with amateur radio bands and other licensed radio services. G. hn includes mechanisms to avoid interference with legacy home networking technologies, OFDM systems split the transmitted signal into multiple orthogonal sub-carriers. In G. hn each one of the sub-carriers is modulated using QAM, the maximum QAM constellation supported by G. hn is 4096-QAM. There are two types of TXOPs, Contention-Free Transmission Opportunities, which have a duration and are allocated to a specific pair of transmitter and receiver. CFTXOP are used for implementing TDMA Channel Access for specific applications that require quality of service guarantees, shared Transmission Opportunities, which are shared among multiple devices in the network. STXOP are divided into Time Slots, there are two types of TS, Contention-Free Time Slots, which are used for implementing implicit token passing Channel Access. In G. hn, a series of consecutive CFTS is allocated to a number of devices, the allocation is performed by the domain master and broadcast to all nodes in the network. There are pre-defined rules that specify which device can transmit after another device has finished using the channel, as all devices know who is next, there is no need to explicitly send a token between devices. The process of passing the token is implicit and ensures there are no collisions during Channel access. Contention-Based Time Slots, which are used for implementing CSMA/CARP Channel Access, in general, CSMA systems cannot completely avoid collisions, so CBTS are only useful for applications that do not have strict Quality of Service requirements. Although most elements of G. hn are common for all three media supported by the standard, G. hn includes media-specific optimizations for each media. Some of these parameters include, OFDM Carrier Spacing,195.31 kHz in coaxial,48.82 kHz in phone lines,24.41 kHz in power lines. FEC Rates, G. hns FEC can operate with code rates 1/2, 2/3, 5/6, 16/18 and 20/21
23.
IEEE 802.11
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They are created and maintained by the Institute of Electrical and Electronics Engineers LAN/MAN Standards Committee. The base version of the standard was released in 1997, and has had subsequent amendments, the standard and amendments provide the basis for wireless network products using the Wi-Fi brand. As a result, in the marketplace, each tends to become its own standard. The 802.11 family consists of a series of half-duplex over-the-air modulation techniques that use the basic protocol. 802. 11-1997 was the first wireless networking standard in the family, but 802. 11b was the first widely accepted one, followed by 802. 11a,802. 11g,802. 11n, and 802. 11ac. Other standards in the family are service amendments that are used to extend the current scope of the existing standard, which may also include corrections to a previous specification. 802. 11b and 802. 11g use the 2.4 GHz ISM band, operating in the United States under Part 15 of the U. S. Federal Communications Commission Rules and Regulations. Because of this choice of band,802. 11b and g equipment may occasionally suffer interference from microwave ovens, cordless telephones. Better or worse performance with higher or lower frequencies may be realized,802. 11n can use either the 2.4 GHz or the 5 GHz band,802. 11ac uses only the 5 GHz band. The segment of the frequency spectrum used by 802.11 varies between countries. In the US,802. 11a and 802. 11g devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations. Frequencies used by one through six of 802. 11b and 802. 11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802. 11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption. 802.11 technology has its origins in a 1985 ruling by the U. S. Federal Communications Commission that released the ISM band for unlicensed use, in 1991 NCR Corporation/AT&T invented a precursor to 802.11 in Nieuwegein, the Netherlands. The inventors initially intended to use the technology for cashier systems, the first wireless products were brought to the market under the name WaveLAN with raw data rates of 1 Mbit/s and 2 Mbit/s. Vic Hayes, who held the chair of IEEE802.11 for 10 years, in 1999, the Wi-Fi Alliance was formed as a trade association to hold the Wi-Fi trademark under which most products are sold. The original version of the standard IEEE802.11 was released in 1997 and clarified in 1999 and it specified two net bit rates of 1 or 2 megabits per second, plus forward error correction code. The latter two radio technologies used microwave transmission over the Industrial Scientific Medical frequency band at 2.4 GHz, some earlier WLAN technologies used lower frequencies, such as the U. S.900 MHz ISM band
24.
Token ring
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Token ring local area network technology is a communications protocol for local area networks. It uses a special three-byte frame called a token that travels around a ring of workstations or servers. This token passing is an access method providing fair access for all stations. Proteon later evolved a 16 Mbit/s version that ran on unshielded twisted pair cable, IBM launched their own proprietary token ring product on October 15,1985. It ran at 4 Mbit/s, and attachment was possible from IBM PCs, midrange computers and it used a convenient star-wired physical topology, and ran over shielded twisted-pair cabling, and shortly thereafter became the basis for the /IEEE standard 802.5. During this time, IBM argued strongly that token ring LANs were superior to Ethernet, especially under load, but these claims were fiercely debated. In 1988 the faster 16 Mbit/s token ring was standardized by the 802.5 working group, Token ring does not inherently support this feature and requires additional software and hardware to operate on a direct cable connection setup. Token ring eliminates collision by the use of a single-use token, Token ring network interface cards contain all of the intelligence required for speed autodetection, routing and can drive themselves on many Multistation Access Units that operate without power. Ethernet network interface cards can operate on a passive hub to a degree, but not as a large LAN. Token ring employs access priority in which certain nodes can have priority over the token, unswitched Ethernet does not have provisioning for an access priority system as all nodes have equal contest for traffic. Multiple identical MAC addresses are supported on token ring, switched Ethernet cannot support duplicate MAC addresses without reprimand. Token Ring was more complex than Ethernet, requiring a specialized processor, by contrast, Ethernet included both the firmware and the lower licensing cost in the MAC chip. The cost of a token ring interface using the Texas Instruments TMS380C16 MAC, even more significant when comparing overall system costs was the much-higher cost of router ports and network cards for token-ring vs Ethernet. The emergence of Ethernet switches may have been the final straw, similar token passing mechanisms are used by ARCNET, token bus, 100VG-AnyLAN and FDDI, and they have theoretical advantages over the CSMA/CD of early Ethernet. A token ring network can be modeled as a system where a single server provides service to queues in a cyclic order. The data transmission process goes as follows, Empty information frames are continuously circulated on the ring, when a computer has a message to send, it seizes the token. The computer will then be able to send the frame, the frame is then examined by each successive workstation. The workstation that identifies itself to be the destination for the copies it from the frame
25.
Firewall (computing)
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In computing, a firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure network and another outside network, such as the Internet. Firewalls are often categorized as either network firewalls or host-based firewalls, Network firewalls filter traffic between two or more networks, they are either software appliances running on general purpose hardware, or hardware-based firewall computer appliances. Host-based firewalls provide a layer of software on one host that controls network traffic in, Firewall appliances may also offer other functionality to the internal network they protect, such as acting as a DHCP or VPN server for that network. The term firewall originally referred to a wall intended to confine a fire or potential fire within a building, later uses refer to similar structures, such as the metal sheet separating the engine compartment of a vehicle or aircraft from the passenger compartment. Firewall technology emerged in the late 1980s when the Internet was a new technology in terms of its global use. It has hit Berkeley, UC San Diego, Lawrence Livermore, Stanford, the Morris Worm spread itself through multiple vulnerabilities in the machines of the time. Although it was not malicious in intent, the Morris Worm was the first large attack on Internet security. The first type of firewall was the packet filter which looks at network addresses and ports of the packet, the first paper published on firewall technology was in 1988, when engineers from Digital Equipment Corporation developed filter systems known as packet filter firewalls. This fairly basic system was the first generation of what is now a highly involved, packet filters act by inspecting the packets which are transferred between computers on the Internet. If a packet does not match the packet filters set of filtering rules, conversely, if the packet matches one or more of the programmed filters, the packet is allowed to pass. This type of packet filtering pays no attention to whether a packet is part of a stream of traffic. Instead, it filters each packet based only on information contained in the packet itself, when the packet passes through the firewall, it filters the packet on a protocol/port number basis. For example, if a rule in the firewall exists to block telnet access, from 1989–1990 three colleagues from AT&T Bell Laboratories, Dave Presotto, Janardan Sharma, and Kshitij Nigam, developed the second generation of firewalls, calling them circuit-level gateways. Second-generation firewalls perform the work of their predecessors but operate up to layer 4 of the OSI model. This is achieved by retaining packets until enough information is available to make a judgement about its state, though static rules are still used, these rules can now contain connection state as one of their test criteria. Certain denial-of-service attacks bombard the firewall with thousands of fake connection packets in an attempt to overwhelm it by filling its connection state memory, Marcus Ranum, Wei Xu, and Peter Churchyard developed an application firewall known as Firewall Toolkit. In June 1994, Wei Xu extended the FWTK with the enhancement of IP filter
26.
Power over Ethernet
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Power over Ethernet or PoE describes any of several standardized or ad-hoc systems which pass electric power along with data on twisted pair Ethernet cabling. This allows a single cable to provide both data connection and electric power to such as wireless access points, IP cameras. There are several techniques for transmitting power over Ethernet cabling. Two of them have been standardized by IEEE802.3 since 2003 and these standards are known as Alternative A and Alternative B. For 10BASE-T and 100BASE-TX, only two of the four pairs in typical CAT-5 cable are used. Alternative B separates the data and the conductors, making troubleshooting easier. It also makes use of all four twisted pair, copper wires. The positive voltage runs along pins 4 and 5, and the negative along pins 7 and 8, Alternative A transports power on the same wires as data for 10 and 100 Mbit/s. This is similar to the phantom power technique commonly used for powering condenser microphones, Power may be transmitted on the data conductors by applying a common voltage to each pair. Because twisted-pair Ethernet uses differential signalling, this does not interfere with data transmission, the common mode voltage is easily extracted using the center tap of the standard Ethernet pulse transformer. For Gigabit Ethernet and faster, all four pairs are used for data transmission and this signaling allows the presence of a conformant device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available. Up to 25.5 W is available for a device, the IEEE standards for PoE require category 5 cable or better for high power levels but allow using category 3 cable if less power is required. A midspan power supply, also known as a PoE power injector, is an additional PoE power source that can be used in combination with a non-PoE switch, the original IEEE802. 3af-2003 PoE standard provides up to 15.4 W of DC power on each port. Only 12.95 W is assured to be available at the device as some power dissipates in the cable. The updated IEEE802. 3at-2009 PoE standard also known as PoE+ or PoE plus, the 2009 standard prohibits a powered device from using all four pairs for power. Both of these amendments have since incorporated into the IEEE802. 3-2012 publication. Standards body IEEE is currently looking at ways of increasing the amount of power transmitted, the upcoming IEEE802. 3bt aka 4PPoE standard will introduce two new levels of power,55 W and 90-100 W. Each twisted pair can handle a current of up to one ampere, additionally, support for 2. 5GBASE-T, 5GBASE-T and 10GBASE-T is planned
27.
VoIP phone
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Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol, Skinny Client Control Protocol or various other proprietary protocols. VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like a telephone or a cordless phone. Traditional PSTN phones are used as VoIP phones with analog telephone adapters, two combined signal-and-power wired cable interfaces are in common use to communicate between computer networks and physically separate VoIP phones, USB and Power over Ethernet. By contrast, a USB3.0 only supports up to 4. 5W devices, insufficient for cordless, conference, videoconferencing, by contrast USB supports under 3m and with extensions and boosters perhaps 10m maximum. Single connector, PoE relies on the single uniform RJ-45 connector, by contrast there are six USB connectors and each change to the USB standard so far has involved at least one new type of connector. Ethernet protocol, Scalable from its original 1 megabit to modern 100 gigabit applications and it makes effective use of many different cable types and has robust wireless equivalents when power and wired security is not required. Generally the features of VoIP phones follow those of Skype, Google Voice and other PC-based phone services, iPhone, Android and the QNX OS used in 2012-and-later BlackBerry phones are generally capable of VoIP performance even on small battery-charged devices. They also typically support the USB but not Ethernet or Power over Ethernet interfaces, the components of a VoIP telephone consist of the hardware and software components. The software requires standard networking components such as a TCP/IP network stack, client implementation for DHCP, in addition, a VoIP signalling protocol stack, such as for the Session Initiation Protocol, H.323, Skinny Call Control Protocol, and Skype, is needed. For media streams, the Real-time Transport Protocol is used in most VoIP systems. For voice and media encoding, a variety of coders are available, such as for audio, G.711, GSM, iLBC, Speex, G.729, G.722, G.722.2, other audio codecs, and for video H.263, H. 263+, H.264. User interface software controls the operation of the components. A Session Traversal Utilities for NAT client is used on some SIP-based VoIP phones as firewalls on network interface sometimes block SIP/RTP packets, some special mechanism is required in this case to enable routing of SIP packets from one network to other. STUN is used in some of the sip phones to enable the SIP/RTP packets to cross boundaries of two different IP networks, a packet becomes unroutable between two sip elements if one of the networks uses private IP address range and other is in public IP address range. Stun is a mechanism to enable this border traversal, there are alternate mechanisms for traversal of NAT, STUN is just one of them. STUN or any other NAT traversal mechanism is not required when the two SIP phones connecting are routable from each other and no firewall exists in between, a DHCP client may be used to configure the TCP/IP parameters and server details if a network segment uses dynamic IP address configuration. The DHCP client then provides central and automatic management of VoIP phones configuration, the overall hardware may look like a telephone or mobile phone. A VoIP phone has the following hardware components, speaker/ear phone and microphone Key pad/touch pad to enter phone number and text
28.
Wireless access point
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In computer networking, a wireless access point is a networking hardware device that allows a Wi-Fi compliant device to connect to a wired network. The WAP usually connects to a router as a standalone device, a WAP is differentiated from a hotspot, which is the physical location where Wi-Fi access to a WLAN is available. With the creation of the access point, network users are now able to add devices that access the network with few or no cables. A WAP normally connects directly to a wired Ethernet connection and the WAP then provides wireless connections using radio links for other devices to utilize that wired connection. Most WAPs support the connection of multiple devices to one wired connection. Modern WAPs are built to support a standard for sending and receiving data using these radio frequencies and those standards, and the frequencies they use are defined by the IEEE. Most APs use IEEE802.11 standards, typical corporate use involves attaching several WAPs to a wired network and then providing wireless access to the office LAN. The wireless access points are managed by a WLAN Controller which handles automatic adjustments to RF power, channels, authentication, furthermore, controllers can be combined to form a wireless mobility group to allow inter-controller roaming. The controllers can be part of a mobility domain to allow clients access throughout large or regional office locations and this saves the clients time and administrators overhead because it can automatically re-associate or re-authenticate. A hotspot is a public application of WAPs, where wireless clients can connect to the Internet without regard for the particular networks to which they have attached for the moment. A collection of connected hotspots can be referred to as a lily pad network, WAPs are commonly used in home wireless networks. Home networks generally have only one AP to connect all the computers in a home, most are wireless routers, meaning converged devices that include the WAP, a router, and, often, an Ethernet switch. Many also include a broadband modem, a WAP may also act as the networks arbitrator, negotiating when each nearby client device can transmit. However, the vast majority of currently installed IEEE802.11 networks do not implement this, some people confuse wireless access points with wireless ad hoc networks. An ad hoc network uses a connection between two or more devices without using an access point, the devices communicate directly when in range. An ad hoc network is used in such as a quick data exchange or a multiplayer LAN game because setup is easy. Due to its layout, ad hoc connections are similar to Bluetooth ones. But ad hoc connections are not recommended for a permanent installation
29.
Uninterruptible power supply
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The on-battery runtime of most uninterruptible power sources is relatively short but sufficient to start a standby power source or properly shut down the protected equipment. UPS units range in size from units designed to protect a computer without a video monitor to large units powering entire data centers or buildings. The worlds largest UPS, the 46-megawatt Battery Electric Storage System, in Fairbanks, Alaska, powers the entire city, the primary role of any UPS is to provide short-term power when the input power source fails. The three general categories of modern UPS systems are on-line, line-interactive and standby, a line-interactive UPS maintains the inverter in line and redirects the batterys DC current path from the normal charging mode to supplying current when power is lost. In a standby system the load is powered directly by the input power, most UPS below 1 kVA are of the line-interactive or standby variety which are usually less expensive. For large power units, Dynamic Uninterruptible Power Supplies are sometimes used, a synchronous motor/alternator is connected on the mains via a choke. Energy is stored in a flywheel, when the mains power fails, an eddy-current regulation maintains the power on the load as long as the flywheels energy is not exhausted. DUPS are sometimes combined or integrated with a generator that is turned on after a brief delay. A fuel cell UPS has been developed in recent years using hydrogen, the offline/standby UPS offers only the most basic features, providing surge protection and battery backup. The protected equipment is connected directly to incoming utility power. When the incoming voltage falls below or rises above a level the SPS turns on its internal DC-AC inverter circuitry. The UPS then mechanically switches the connected equipment on to its DC-AC inverter output, the switchover time can be as long as 25 milliseconds depending on the amount of time it takes the standby UPS to detect the lost utility voltage. The UPS will be designed to power equipment, such as a personal computer. The line-interactive UPS is similar in operation to a standby UPS and this is a special type of transformer that can add or subtract powered coils of wire, thereby increasing or decreasing the magnetic field and the output voltage of the transformer. This may also be performed by a buck–boost transformer which is distinct from an autotransformer and this type of UPS is able to tolerate continuous undervoltage brownouts and overvoltage surges without consuming the limited reserve battery power. It instead compensates by automatically selecting different power taps on the autotransformer, depending on the design, changing the autotransformer tap can cause a very brief output power disruption, which may cause UPSs equipped with a power-loss alarm to chirp for a moment. This has become popular even in the cheapest UPSs because it takes advantage of components already included, the difference between the two voltages is because charging a battery requires a delta voltage. Furthermore, it is easier to do the switching on the side of the transformer because of the lower currents on that side
30.
Computer port (hardware)
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In computer hardware, a port serves as an interface between the computer and other computers or peripheral devices. In computer terms, a port generally refers to the part of connection. Computer ports have many uses, to connect a monitor, webcam, speakers, on the physical layer, a computer port is a specialized outlet on a piece of equipment to which a plug or cable connects. Electronically, the several conductors where the port and cable contacts connect, Port connectors may be male or female, but female connectors are much more common. Bent pins are easier to replace on a cable than on an attached to a computer. Computer ports in common use cover a variety of shapes such as round, rectangular, square, trapezoidal. There is some standardization to physical properties and function, for instance, most computers have a keyboard port, into which the keyboard is connected. The original IBM PC also had two identical 5 pin DIN connectors, one used for the keyboard, the second for a cassette recorder interface, the two were not interchangeable. Electronically, hardware ports can almost always be divided into two based on the signal transfer, Serial ports send and receive one bit at a time via a single wire pair. Parallel ports send multiple bits at the time over several sets of wires. After ports are connected, they typically require handshaking, where transfer type, transfer rate, hot-swappable ports can be connected while equipment is running. Almost all ports on personal computers are hot-swappable, plug-and-play ports are designed so that the connected devices automatically start handshaking as soon as the hot-swapping is done. USB ports and FireWire ports are plug-and-play, auto-detect or auto-detection ports are usually plug-and-play, but they offer another type of convenience. An auto-detect port may automatically determine what kind of device has been attached, the users response determines the purpose of the port, which is physically a 1/8 tip-ring-sleeve mini jack. Some auto-detect ports can even switch between input and output based on context, as of 2006, manufacturers have nearly standardized colors associated with ports on personal computers, although there are no guarantees. The two extra conductors in the 6-pin connection carry electrical power and this is why a self-powered device such as a camcorder often connects with a cable that is 4-pins on the camera side and 6-pins on the computer side, the two power conductors simply being ignored. This is also why laptop computers usually have only 4-pin FireWire ports, optical fiber, microwave, and other technologies have different kinds of connections, as metal wires are not effective for signal transfers with these technologies. Optical connections are usually a glass or plastic interface, possibly with an oil that lessens refraction between the two interface surfaces
