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  Software-Defined Networking (SDN) is a network architecture approach that enables the network to be intelligently and centrally controlled, or ‘programmed,’ using software applications. This helps operators manage the entire network consistently and holistically, regardless of the underlying network technology. Enterprises, carriers, and service providers are being surrounded by a number of competing forces. The monumental growth in multimedia content, the explosion of cloud computing, the impact of increasing mobile usage, and continuing business pressures to reduce costs while revenues remain flat are all converging to wreak havoc on traditional business models. To keep pace, many of these players are turning to  SDN  technology to revolutionize network design and operations. SDN enables the programming of network behavior in a centrally controlled manner through software applications using open APIs. By opening up traditionally closed network platforms and implementing a co

  A wide area network (also known as WAN), is a large network of information that is not tied to a single location. WANs can facilitate communication, the sharing of information, and much more between devices from around the world through a WAN provider. WANs can be vital for international businesses, but they are also essential for everyday use, as the internet is considered the largest WAN in the world. Keep reading for more information on WANs, their use, how they differ from other networks and their overall purpose for businesses and people, alike. As described above, wide area networks are a form of telecommunication networks that can connect devices from multiple locations and across the globe. WANs are the largest and most expansive forms of computer networks available to date. These networks are often established by service providers that then lease their WAN to businesses, schools, governments, or the public. These customers can use the network to relay and store data or

Potential transformer is a voltage step-down transformer that reduces the voltage of a high voltage circuit to a lower level for the purpose of measurement. These are connected across or parallel to the line which is to be monitored. The basic principle of operation and construction of this transformer is similar to the standard power transformer. In common, the potential transformers are abbreviated as PT. The primary winding consists of a large number of turns which is connected across the high voltage side or the line in which measurements have to be taken or to be protected. The secondary winding has a lesser number of turns that are connected to the voltmeters, or potential coils of wattmeter and energy meters, relays, and other control devices. These can be single-phase or three-phase potential transformers . Irrespective of the primary  voltage rating, these are designed to have the secondary output voltage of 110 V. Since the voltmeters and potential coils of other meter

  Virtual Local Area Network or Virtual LANs (VLANs) are a logical group of computers that appear to be on the same LAN irrespective of the configuration of the underlying physical network. Network administrators partition the networks to match the functional requirements of the VLANs so that each VLAN comprises a subset of ports on a single or multiple switches or bridges. This allows computers and devices in a VLAN to communicate in the simulated environment as if it is a separate LAN. VLAN  is a custom network that is created from one or more local area networks. It enables a group of devices available in multiple networks to be combined into one logical network. The result becomes a virtual LAN is administered like a physical LAN. The full form of VLAN is defined as Virtual Local Area Network. The below topology depicts a network having all hosts inside the same virtual LAN. Without VLANs, a broadcast sent from a host can easily reach all network devices. Each and every device

  A LAN, abbreviated from Local Area Network  is a network that covers a small geographical area such as homes, offices, and groups of buildings. Whereas a WAN, abbreviated from  Wide Area Network  is a network that covers larger geographical areas that can span the globe. An example of a widely used WAN is the Internet, which is a collection of tens of thousands of networks that connects tens of billions of devices. Local Area Networks predominantly use Ethernet technology, which is a group of networking technologies that dictate how data is transmitted over the physical media, with the most common media being CAT# cabling. Local Area Networks can use both Layer 1 and Layer 2 devices; Layer 1 devices include HUB’s and repeaters and the Layer 2 devices that can be used are switches and bridge devices. While LAN’s use Layer 1 and Layer 2 devices, WAN ’s operate using Layer 3 devices such as multi-layer switches and routers. LAN’s are typically cheaper than WAN’s to both implement an

  The Junction Field Effect Transistor , or JFET, is a voltage controlled three-terminal unipolar semiconductor device available in N-channel and P-channel configurations In the  Bipolar Junction In transistor  tutorials, we saw that the output Collector the current of the transistor is proportional to input current flowing into The base terminal of the device, thereby making the bipolar transistor a “CURRENT” operated device (Beta model) as a smaller current can be used to switch a larger load current. The  Field Effect Transistor , or simply  FET  however, uses the voltage that is applied to their input terminal, called the  Gate  to control the current flowing through them resulting in the output current being proportional to the input voltage. As their operation relies on an electric field (hence the name field effect) generated by the input  Gate  voltage, this then makes the  Field Effect Transistor  a “VOLTAGE” operated device. The  junction Field Effect Transistor  is a thr

  Using a transistor as a switch is the simplest application of the device. A transistor can be extensively used for switching operations either for opening or closing of a circuit. Meanwhile, the basic concept behind the operation of a transistor as a switch relies on its mode of operation. Generally, the low voltage DC is turned on or off by transistors in this mode. Both PNP and NPN transistors can be utilized as switches. A basic terminal transistor can be handled differently from a signal amplifier by biasing both NPN and PNP bipolar transistors by an “ON / OFF” static switch. One of the main uses of the transistor to transform a DC signal “On” or “OFF” is solid-state switches. Some devices, including LEDs, only require several milliamperes of DC voltages at the logical level and can be directly controlled via the logical gate output. High-power devices such as generators, solenoids, or lamps usually need more power to use transistor switches than the usual logic gate. As o

  Software-defined wide area network (SD-WAN) is a type of computer network that enables the bonding of multiple internet access resources – such as DSL, cable, cellular, or any other IP transport – to provide reliable high throughput data channels. SD-WAN abstracts connectivity options – like multiprotocol label switching (MPLS), mobile, and broadband – to create a virtual enterprise wide-area network (WAN). An SD-WAN has a virtual WAN architecture and software-driven technology. A key element of a Software-defined wide area network is its centralized control, so those network connections, security mechanisms, policies, application flows, and general administration are separated from the associated hardware. For security considerations, data communications between offices are typically transmitted via VPN and funneled through the main office facility. It is critical to have a high-throughput IP tunnel that is reliable for this data connection. If a branch office uses a single

  The Darlington Transistor configuration of two bipolar transistors offer increased current switching for a given base current. The  Darlington Transistor  named after its inventor, Sidney Darlington is a special arrangement of two standard NPN or PNP bipolar junction transistors (BJT) connected together. The Emitter of one transistor is connected to the base of the other to produce a more sensitive transistor with a much larger current gain being useful in applications where current amplification or switching is required. Darlington Transistor  pairs can be made from two individually connected bipolar transistors or one single device commercially made in a single package with the standard: Base, Emitter and Collector connecting leads and are available in a wide variety of case styles and voltage (and current) ratings in both NPN and PNP versions. As we saw in our  Transistor as a Switch  tutorial, as well as being used as an amplifier, the bipolar junction transistor, (BJT) can

  Current Transformers produce output in proportion to the current flowing through the primary winding as a result of a constant potential on the primary. The  Current Transformer  (  C.T.  ), is a type of “instrument transformer” is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary.  Current transformers   reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the actual electrical current flowing in an AC transmission line using a standard ammeter. The principle of operation of a basic current transformer is slightly different from that of an ordinary voltage transformer. Unlike the voltage or power transformer looked at previously, the current transformer consists of only one or very few turns as its primary winding. This primary winding can be of either a single flat turn, a coil of heavy-duty wire wrapped around the core, or just a conductor or bus ba

  We saw previously, that the N-channel, Enhancement-mode MOSFET (e-MOSFET) operates using a positive input voltage and has an extremely high input resistance (almost infinite) making it possible to interface with nearly any logic gate or driver capable of producing a positive output. We also saw that due to this very high input (Gate) resistance we can safely parallel together with many different MOSFET until we achieve the current handling capacity that we required. While connecting together various MOSFETS in parallel may enable us to switch high currents or high voltage loads, doing so becomes expensive and impractical in both components and circuit board space. To overcome this problem  Power Field Effect Transistors  or  Power FET’s  where developed. We now know that there are two main differences between field-effect transistors, depletion-mode only for JFET’s and both enhancement-mode and depletion-mode for MOSFETs. In this tutorial, we will look at using the  Enhancemen

  A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home. A LAN can be small or large, ranging from a home network with one user to an enterprise network with thousands of users and devices in an office or school. Regardless of size, a LAN's single defining characteristic is that it connects devices that are in a single, limited area. In contrast, a  wide area network  (WAN) or metropolitan area network (MAN) covers larger geographic areas. Some WANs and MANs connect many LANs together. A LAN comprises cables, access points, switches, routers, and other components that enable devices to connect to internal servers, web servers, and other LANs via wide area networks. The rise of virtualization has also fueled the development of virtual LANs , which enable network administrators to logically group network nodes and partition their networks without a need for major infrastructure changes. For exa