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Medium-dependent Interface
A medium dependent interface (MDI) describes the interface (both physical and electrical/optical) in a computer network from a physical layer implementation to the physical medium used to carry the transmission. Ethernet over twisted pair also defines a medium dependent interface crossover (MDI-X) interface. Auto MDI-X ports on newer network interfaces detect if the connection would require a crossover, and automatically chooses the MDI or MDI-X configuration to properly match the other end of the link. Ethernet The popular Ethernet family defines common medium-dependent interfaces. For 10BASE5, connection to the coaxial cable was made with either a vampire tap or a pair of N connectors. For 10BASE2, the connection to the coaxial cable was typically made with a single BNC connector to which a T-piece was attached. For twisted-pair cabling 8P8C, modular connectors are used (often incorrectly called "RJ45" in this context). For fiber, a variety of connectors are used dependin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4 Port Netgear Ethernet Hub
4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures. In mathematics Four is the smallest composite number, its proper divisors being and . Four is the sum and product of two with itself: 2 + 2 = 4 = 2 x 2, the only number b such that a + a = b = a x a, which also makes four the smallest squared prime number p^. In Knuth's up-arrow notation, , and so forth, for any number of up arrows. By consequence, four is the only square one more than a prime number, specifically three. The sum of the first four prime numbers two + three + five + seven is the only sum of four consecutive prime numbers that yields an odd prime number, seventeen, which is the fourth super-prime. Four lies between the first proper pair of twin primes, three and five, which are the first two Fermat primes, like seventeen, which is the third. On the other ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Hub
In network science, a hub is a node with a number of links that greatly exceeds the average. Emergence of hubs is a consequence of a scale-free property of networks. While hubs cannot be observed in a random network, they are expected to emerge in scale-free networks. The uprise of hubs in scale-free networks is associated with power-law distribution. Hubs have a significant impact on the network topology. Hubs can be found in many real networks, such as the brain or the Internet. A hub is a component of a network with a high-degree node. Hubs have a significantly larger number of links in comparison with other nodes in the network. The number of links ( degrees) for a hub in a scale-free network is much higher than for the biggest node in a random network, keeping the size ''N'' of the network and average degree constant. The existence of hubs is the biggest difference between random networks and scale-free networks. In random networks, the degree ''k'' is comparable for every no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Architecture
Network architecture is the design of a computer network. It is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as communication protocols used. In telecommunication, the specification of a network architecture may also include a detailed description of products and services delivered via a communications network, as well as detailed rate and billing structures under which services are compensated. The network architecture of the Internet is predominantly expressed by its use of the Internet protocol suite, rather than a specific model for interconnecting networks or nodes in the network, or the usage of specific types of hardware links. OSI model The Open Systems Interconnection model (OSI model) defines and codifies the concept of layered network architecture. Abstraction layers are used to subdivide a communications system further into smaller ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Media-independent Interface
The media-independent interface (MII) was originally defined as a standard interface to connect a Fast Ethernet (i.e., ) media access control (MAC) block to a PHY#Ethernet physical transceiver, PHY chip. The MII is standardized by IEEE 802.3u and connects different types of PHYs to MACs. Being ''media independent'' means that different types of PHY devices for connecting to different media (i.e. Ethernet over twisted pair, twisted pair, fiber optic, etc.) can be used without redesigning or replacing the MAC hardware. Thus any MAC may be used with any PHY, independent of the network signal transmission media. The MII can be used to connect a MAC to an external PHY using a pluggable connector, or directly to a PHY chip on the same Printed circuit board, PCB. On a PC the Communications and networking riser, CNR connector Type B carries MII signals. Network data on the interface is Ethernet frame, framed using the IEEE Ethernet standard. As such it consists of a preamble, start frame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversed Polarity (differential Signals)
Differential signalling is a method for electrically transmitting information using two complementary signals. The technique sends the same electrical signal as a differential pair of signals, each in its own conductor. The pair of conductors can be wires in a twisted-pair or ribbon cable or traces on a printed circuit board. Electrically, the two conductors carry voltage signals which are equal in magnitude, but of opposite polarity. The receiving circuit responds to the difference between the two signals, which results in a signal with a magnitude twice as large. The symmetrical signals of differential signalling may be referred to as ''balanced'', but this term is more appropriately applied to balanced circuits and balanced lines which reject common-mode interference when fed into a differential receiver. Differential signalling does not make a line balanced, nor does noise rejection in balanced circuits require differential signalling. Differential signalling is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autonegotiation
Autonegotiation is a signaling mechanism and procedure used by Ethernet over twisted pair by which two connected devices choose common transmission parameters, such as speed, duplex mode, and flow control. In this process, the connected devices first share their capabilities regarding these parameters and then choose the highest performance transmission mode they both support. Autonegotiation is defined in clause 28 of IEEE 802.3. and was originally an optional component in the Fast Ethernet standard. It is backwards compatible with the normal link pulses (NLP) used by 10BASE-T. The protocol was significantly extended in the Gigabit Ethernet standard, and is mandatory for 1000BASE-T gigabit Ethernet over twisted pair. In the OSI model, autonegotiation resides in the physical layer. Standardization and interoperability In 1995, the Fast Ethernet standard was released. Because this introduced a new speed option for the same wires, it included a means for connected network adapter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1000BASE-T
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, 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. History Ethernet was the result of research conducted at Xerox PARC in 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. * The initial standard for Gigabit Ethernet was produced by the IEEE in June 1998 as IEEE 802.3z, and required optical fiber. 802.3z is commonly referred to as 1000BASE-X, whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components, as well as software and related services to consumers, small and medium-sized businesses ( SMBs), and large enterprises, including customers in the government, health, and education sectors. The company was founded in a one-car garage in Palo Alto by Bill Hewlett and David Packard in 1939, and initially produced a line of electronic test and measurement equipment. The HP Garage at 367 Addison Avenue is now designated an official California Historical Landmark, and is marked with a plaque calling it the "Birthplace of 'Silicon Valley'". The company won its first big contract in 1938 to provide test and measurement instruments for Walt Disney's production of the animated film ''Fantasia'', which allowed Hewlett and Packard to formally esta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Network
A star network is an implementation of a spoke–hub distribution paradigm in computer networks. In a star network, every host is connected to a central hub. In its simplest form, one central hub acts as a conduit to transmit messages. The star network is one of the most common computer network topologies. The hub and hosts, and the transmission lines between them, form a graph with the topology of a star. Data on a star network passes through the hub before continuing to its destination. The hub manages and controls all functions of the network. It also acts as a repeater for the data flow. The star topology reduces the impact of a transmission line failure by independently connecting each host to the hub. Each host may thus communicate with all others by transmitting to, and receiving from, the hub. The failure of a transmission line linking any host to the hub will result in the isolation of that host from all others, but the rest of the network will be unaffected. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethernet Crossover Cable
An Ethernet crossover cable is a crossover cable for Ethernet used to connect computing devices together directly. It is most often used to connect two devices of the same type, e.g. two computers (via their network interface controllers) or two switches to each other. By contrast, ''straight through'' patch cables are used to connect devices of ''different types'', such as a computer to a network switch. Intentionally crossed wiring in the crossover cable connects the transmit signals at one end to the receive signals at the other end. Many network devices today support auto MDI-X (aka "auto crossover") capability, wherein a patch cable can be used in place of a crossover cable, or vice versa, and the receive and transmit signals are reconfigured automatically within the device to yield a working connection. Motivation The 10BASE-T and 100BASE-TX Ethernet standards use one wire pair for transmission in each direction. This requires that the transmit pair of each device ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethernet MDI Crossover
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. 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 shared medium, while the newer Ethernet variants use twisted pair and fiber optic links in conjunction with switches. Over the course of its history, Ethernet data transfer rates have been increased from the original to the latest , with rates up to under development. The Ethernet standards include several wiring and signaling variants of the OSI physical layer. Systems communicating over Ethernet div ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structured Cabling
In telecommunications, structured cabling is building or campus cabling infrastructure that consists of a number of standardized smaller elements (hence structured) called subsystems. Structured cabling components include twisted pair and optical cabling, patch panels and patch cables. Overview Structured cabling is the design and installation of a cabling system that will support multiple hardware uses and be suitable for today's needs and those of the future. With a correctly installed system, current and future requirements can be met, and hardware that is added in the future will be supported Structured cabling design and installation is governed by a set of standards that specify wiring data centers, offices, and apartment buildings for data or voice communications using various kinds of cable, most commonly category 5e (Cat 5e), category 6 (Cat 6), and fiber optic cabling and modular connectors. These standards define how to lay the cabling in various topologies in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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