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by Dinesh Thakur

Data Communication or Network Communication: It is the process of transporting data or information from one device to another.The channel or physical connection (path) through which the information is carried from sender(Source or origin) to the receiver(destination) is established using either cable (Physical media) or wireless media. The physical cable like twisted pair wire, coaxial cable, fiber-optic cable or wireless media like laser, radio waves, and microwaves.



 
by Dinesh Thakur

Many of today’s devices rely heavily on access to your office network and the Internet. In this tutorial, we’ll show you how to connect devices to the company network.

 
by Dinesh Thakur

Setting up and securing a wireless router in your office is something anyone can do. Here, we’ll take you step-by-step through the physical installation and setup of a wireless router.

 
by Dinesh Thakur

Internet access has become a standard feature on most of our mobile devices. But there’s more than one way to connect to the Web with those devices these days. In this article, we’ll help you determine what you need in order to get started with each of these technologies and explain a bit about why you would want to choose one over the other or perhaps go with both.

 
by Dinesh Thakur

WiMAX (Worldwide Interoperability for Microwave Access) is the result of an initiative launched in 2001 by the WiMAX Alliance. Its aim was to promote the IEEE 802.16 standard by proposing to verify compliance and equipment interoperability. As we shall see, many options have been proposed to achieve communication.

 
by Dinesh Thakur

The quality of service is essential to ensure the transfer of real time data such as voice or video. Such services require isochronous transfers, that is to say data transfers that enable to vary the time between the different frames of the same transmission. In the case of a video application, for example, over this period, the greater the quality deteriorates, whether audible or visual. To minimize this delay, priority mechanisms were introduced by an extension to the 802.11 standard, called 802.11e.

 
by Dinesh Thakur

With pre-IEEE 802.11n products, the maximum speed reached in late 2007 is 108 Mbit / s, that is to say double the IEEE 802.11a and 802.11g standards. This flow rate is achieved by increasing the density of transmitted bits. Technological advances are such in the field of radio transmission it is now possible to improve greatly this flow. 802.11n networks offer a potential gross rate of 540 Mbit / s. In fact, the actual flow rate is much lower and is of the order of 100 Mbit/s in the best case.

 
by Dinesh Thakur

The IEEE 802.15 group was set up in March 1999 to reflect on wireless networks with a range of ten meters, or WPAN (Wireless Personal Area Network), with the aim of making connections between different portable one user or multiple users. This type of network can connect a laptop, cell phone, PDA or any other device of this type. Three service groups were defined, A, B and C.



 
by Dinesh Thakur

Ethernet networks at 10 Mbit/s were the first to be introduced in the market. They still represent a significant proportion, although standards to 100 Mbit/s tend to supplant them. This section reviews the various products of the Ethernet shared working at a speed of 10 Mbit/s.

 
by Dinesh Thakur

Another solution to obtain a broadband distribution network is to use the wiring of cable operators, when it exists. This wiring has long been made of CATV (cable TV), whose bandwidth exceeds 800MHz easily. Today, this infrastructure is slightly modified by the introduction of systems HFC (Hybrid Fiber/Coax), combining a fiber portion between the head end and the beginning of the service by the CATV. This topology is illustrated in Figure.

 
by Dinesh Thakur

When the frames transmitted on the PON are Ethernet, EPON talking. The features of this network are identical to those of the other PON: distribution throughout the network, where only the station specified in the Ethernet frame can retrieve the information conveyed. The standardization of EPON technology is performed by the IEEE 802.3ah group. This group has several objectives, including that of introducing Ethernet in the local loop under the name of EFM (Ethernet in the First Mile). The objective was to replace the ATM technology, very expensive to implement on a multipoint technology, the Ethernet technology.



 
by Dinesh Thakur

On the Passive Optical Network (PON), it is possible to transit ATM cells according to the technique developed by the working group FSAN (Full Service Access Network). This solution was then standardized in G.983 recommendation ITU-T. Both ends of the optical shaft are called OLT (Optical Line Termination) and ONU (optical network unit). For reasons of energy loss, it is not possible to exceed fifty branches on the trunk. The figure illustrates the architecture of a passive optical network.

 
by Dinesh Thakur

The package level or network layer is located on the third level of the hierarchy architecture reference model as shown in Figure.

 
by Dinesh Thakur

The Ethernet frame is designed to transport packets in enterprise networks by an original method for broadcasting on a local network. This solution gave birth shared Ethernet, in which the broadcast frame is transmitted and where only the station that recognizes the right to copy the information. To this solution dissemination has added Ethernet switching.



 
by Dinesh Thakur

How to encode the digital signal is an important function of coupler communication. This main function is to adapt the signals transmission channel. In the case of local networks, the transmission rate is tens or hundreds of megabits per second. Therefore, the choice of representation Physical data is important. To perform the synchronization bit, that is to say, to ensure that each bit is read at the right time, you need a minimum of transitions are made to extract the clock signal.

 
by Dinesh Thakur

Before transmitting information on a transmission medium, it must be encoded of adequately. Networks must allow very high speeds over distances more or shorter. In this context, three approaches are possible for coding bits from applications:



 
by Dinesh Thakur

ISO (International Standardization Organization) standard has its own architecture as the OSI (Open Systems Interconnection). The architecture ISO is the first to be defined, and so relatively parallel to the Internet. The distinction between the two is that the ISO formally defines the different layers architecture, while the Internet architecture is applied to achieve a practical environment.

 
by Dinesh Thakur

The MAC layer is the "Brain" of WiFi. The first version of 802.11 (the 802.11 legacy published in 1997), defined the MAC layer by incorporating a number of features crucial, such as sharing of speech among users, the terms of network connection, error control or security.

 
by Dinesh Thakur

Short communication

The infrared light is used for many years for the communication directly between nearby devices to each other, such as remote control and your television, for example.

 
by Dinesh Thakur

The extension of the corporate network

Although there are a multitude of applications in WiFi technology, it is clear as its primary target is the corporate network. As we have seen, the WiFi was designed for a wireless version of Ethernet and the latter is found in almost all businesses. In most cases, a company that decides be equipped with a WiFi network already has a wired Ethernet network. It is therefore generally build a wireless extension to an existing wired network.

 
by Dinesh Thakur

The transfer rate, or "data rate" refers to the speed with which data is transferred from its source to its destination, such as from one computer to another over a network, or from the computer to the disk drive. It's measured like we would measure any rate of speed-in units of information per the unit of time, like miles per hour. On a computer you may hear transfer rates expressed in terms like bits per second, megabytes per second, or characters per second.



 
by Dinesh Thakur

Parity is a form of "error checking" where the computer checks to see if all the data it was supposed to get really did come through. You will most likely be confronted with parity when you use a telecommunications package to communicate through your modem. In fact, that's probably why you're reading this. The dialog box where you can set the serial port settings always wants to know the parity. The default setting is probably the safest thing to use if you don't know a reason to change it.



 
by Dinesh Thakur

Half duplex means data can be relayed in only one direction at a time. Two-way transmission is possible, but the transmissions must be alternate. A walkie-talkie is half duplex-when one person is speaking, she cannot also listen A telephone is full duplex-information can go both ways simultaneously; both ends can talk and hear all the time-so does a modem.

 
by Dinesh Thakur

EtherTalk is Apple Computer software that allows the Macintosh to hook into Ethernet networks. To use EtherTalk and Ethernet, the Mac must have the Ethernet interface card installed inside the computer.



 
by Dinesh Thakur

Ethernet(pronounced "eether net") is a local area network, connecting computers together with cables so the computers can share information. Within each main branch of the network, Ethernet can connect up to 1,024 personal computers and workstations. In effect:



 
by Dinesh Thakur

From the early 1900s until now, long distance communication has primarily been in the form of the telephone line. Now telephone lines are being used for more than the transmission of voice; they are also used for the transmission of computer data. There are many reasons why someone might want to transfer data between one PC and another using phone lines.



 
by Dinesh Thakur

Broadband ISDN (BISON) The next-generation of ISDN technology, with promised bandwidths from 150 megabits per second upward, sufficient to carry video-phone calls and movies. BISON will be carried over FIBRE-OPTIC cabling rather than wire, and the underlying transport protocol will be ASYNCHRONOUS TRANSFER MODE. Different implementations are planned in the USA, which will employ YNCHRONOUS OPTICAL NETWORK and Europe, which will use SYNCHRONOUS DIGITAL HIERARCHY.



 
by Dinesh Thakur

Bit Error: An error in a single BIT within a BYTE or WORD of data transmitted over a noisy channel: for example if the byte sent was 11111111 then a received value of 11111101 would represent a bit error in the second bit. There are well-known ERROR DETECTION AND CORRECTION algorithms that can correct one or more such bit errors, given some extra, redundant information, and these techniques are widely applied in the mechanisms of HARDDISK and CD-ROM drives, as well as in telecommunication systems.



 
by Dinesh Thakur

Let us examine the transmission technique that is to say how a transmitter can send a signal that the receiver will recognize as a 1 or a 0.

 
by Dinesh Thakur

1 Literally, not synchronized; that is, proceeding at its own pace.

2 In electronics, it describes circuits that do not operate in step with other devices controlled by a shared CLOCK SIGNAL.

 
by Dinesh Thakur

AppleTalk: A proprietary LAN protocol that is built into Apple's MACINTOSH computers. AppleTalk is independent of the underlying network transport, and is currently able to run over serial cable (LocalTalk) or over an ETHERNET network (EtherTalk).  An AppleTalk port is built in to all Macs.



 
by Dinesh Thakur

The purpose of error control is to ensure that the information received by the receiver is exactly the information transmitted by the sender. As the communication channel is highly unreliable, the receiver must be able to deal with the received data, if it contains error. The term error control is defined as the process of identification or correction of error occurred in the transmitted data. There are two types of error control mechanisms. They are:



 
by Dinesh Thakur

Data is transmitted between communication devices in multiples of fixed-length units, typically 8-bits. For example, if the computer is transferring a source program, the data will be made up of a block of 8-bit binary-encoded characters. On the other hand, if the data is in the form of a compiled object code of the program, the data will be made up of a block of 8-bit bytes. At the receiving end, the following parameters are determined to decode and interpret the message correctly.



 
by Dinesh Thakur

This is very simple optical fiber communication system. In this particular scenario, the optical fiber requires one connection to the transmitter side and another connection at the receiver side. In another scenario when it is required to communicate over long distances where more than one length of fiber cable and other supporting equipment are placed in the system.

 
by Dinesh Thakur

Like other communication system, fiber optic communication has also a transmitter at one end of the system, which injects information on to the fiber cables. The transmitter processes and translates coded electronic pulse information coming from copper wire into equivalently coded light pulses. The basic concept behind the optical transmitter is that it converts electrical input signals into modulated light for transmission over an optical fiber. The input signal determines the characteristics of the resulting modulated light, which may be turned on and off or may be linearly varied in intensity between two predetermined levels.



 
by Dinesh Thakur

In case of coaxial cables and twisted cable the maximum signal frequency, and hence the information rate that can be transmitted using a solid conductor is limited. Optical fiber differs from both these transmission media in that it carries the transmitted information in the' form of a fluctuating beam of light in a glass fiber rather than as an electrical signal on a wire. This type of transmission has become strong support for digital network owing to its high capacity and other factors favorable for digital communication.



 
by Dinesh Thakur

Open Systems Interconnection (OSI) was set up as an international standard for network architecture. The International Organization for Standardization (ISO) took the initiative in setting up OSI. OSI has two meanings. It 'refers to:

 
by Dinesh Thakur

Network Architecture defines the communications products and services, which ensure that the various components can work together. In the early days of data communication systems, the majority of communications were between the DTE and the host computer. Therefore, transmission control procedures were alone enough as communication protocols. However, recent computer systems link with other systems to form a network which result in a situation where different protocols serving different purposes are required. Hence, the network architecture represents a systemization of the various kinds of protocols needed to build a network.



 
by Dinesh Thakur

VLANs have the primary role to enable easier configuration and management of large corporate networks built around many bridges. There are several implementation strategies for these virtual networks.

 
by Dinesh Thakur

A switch, which resembles a hub, is known as switching hub. But there is stark difference between hub and switching hub or a switch. Hub acts as a LAN concentrator, and repeater. It consists of a single box with multiple ports. Each port is connected with a separate computer. A signal transmitted by a computer travels to all ports like a bus topology.



 
by Dinesh Thakur

This advises the routers are used to connect dissimilar LANs and perform all the functions of bridges and routers. It operates at all seven layers of the OSI Reference Model. These are actually predecessors of router nowadays and are technology wise more expensive and highly functional. They in general consist of software which resides in a host computer, such as mid-range or mainframe.



 
by Dinesh Thakur

Routers are used to connect both similar and dissimilar LANs. Router operates on the network layer of OSI model using the physical layer, data link layer and network layer to provide connectivity, addressing and switching. These are highly intelligent devices. In case of TCP/IP network, Internet Protocol (IP) is used as addresses for network; this is the router which interprets the IP address and delivers the packet reliably.

 
by Dinesh Thakur

Like repeaters, bridges are used to connect similar LANs together, for example, Ethernet-to-Ethernet and operate at the bottom two layers of the OSI model, i.e. physical layer and data link layer. As it operates on second layer of the OSI model,' it relays only necessary data to other signals. MAC addresses (physical addresses) are used to determine whether data is necessary or not.

 
by Dinesh Thakur

When an electrical signal travels along a medium it gets attenuated depending upon the medium characteristics. That is why a LAN cannot send signal beyond a certain limit imposed by the different types of LAN technologies. To increase the length of the LAN, repeaters are frequently used. Repeaters in its simplest form relay analog electric signal. It means that they transmit the physical layer signals or data and therefore correspond to the bottom layer of OSI model.

 
by Dinesh Thakur

100VG-AnyLan (VG =Voice Grade) is a joint development of AT&T Microelectronics, Hewlett-Packard, and IBM and is standardized by the newly created IEEE 802.12 committee. 100VG-AnyLAN supports Ethernet, Token Ring, and other LAN standards, incorporating a collision less polling technique. It is not that simple as it appears. A router upgrade is required to connect 100VG Ethernet and 100VG Token Ring.

 
by Dinesh Thakur

With the advancement of time and intensive use of LAN, more workstations and more active users have resulted in more LAN traffic. Increased use of graphics and other bandwidth-intensive applications have increased LAN traffic. Other applications like video conferencing and multimedia have created a demand for fast LANs. Bandwidth of 10 Mbps, 16 Mbps and even 20 Mbps are becoming bottleneck. In response to this, Fast LANs have been developed, offering bandwidth of 100 Mbps and soon to 1 Gbps. Fast LAN options currently include:

 
by Dinesh Thakur

Wireless LANs offer the obvious advantage of avoidance of cabling costs, which can be especially important in a dynamic environment where there is frequent reconfiguration of the workplace. Additionally, wireless LANs provides LAN capabilities in temporary quarters where costly cabling would have to be abandoned. Each workstation is fitted with a low power radio antenna.

 
by Dinesh Thakur

Due its outstanding performance characteristics, fiber-optic cable is also used in LAN s. FDD I (Fiber Distributed Data Interface) is the current LAN standard (IEEE and ANSI) for such a network. FDDI can be extended to the desktop, either directly or through the use of twisted pair in a CDDI application.

 
by Dinesh Thakur

The maximum allowable length of a segment for the 10Base5 is 500 meters. Up to 100 nodes can be connected to a segment. That is up to 100 transceivers can be connected. Repeaters are used to connect terminals that are separated from one another beyond the distance specified above, or to connect more than a limited number of nodes. Each repeater has two ports so that it receives signals through one of these ports and sends them through the other port after amplification. An example of the 10Base5 LAN, Up to 1024 nodes can be connected to a LAN expanded by using repeaters.

 
by Dinesh Thakur

CDDI is also known as TPDDI (Twisted-pair Distributed Data Interface). CDDI employs Cat 5 UTP as an inexpensive means of connecting workstations and peripherals to FDDI fiber optic backbone LANs. A transmission rates up to 100 Mbps may be achieved in this scheme.

 
by Dinesh Thakur

Hubs receive signals through one port and send them through all other ports. That is, a LAN configures with hubs physically falls under the category of a star type topology. However, logically, it falls under the category of a bus type topology. Commercially available hubs normally have eight or sixteen ports.

 
by Dinesh Thakur

A pair of wires twisted together form a twisted pair. They have more noise immunity than the two-wire open lines. Each wire is insulated and has thickness in the order of 0.016 inches to 0.015 inches.

 
by Dinesh Thakur

The Figure shows the BNC connector and T-connector. The BNC connector and T-connector, these are simple connectors that cannot exchange data. An NIC and T-connector must be directly connected.

 
by Dinesh Thakur

This is also known as 10Base2, uses coaxial of thinner gauge of5 mm in diameter and bus topology as in the case of 10Base5 so that multiple computers can be connected to a single transmission line. Primarily it was used in office environments. The thinner cable is less costly to acquire and deploy, although its performance is less in terms of transmission distance. Because of its cost it is sometimes called as cheapnet. 10Base2 signifies in the same manner as 10Bases5except 2 is signified here as 200 meters maximum segment length (actually 185 meters).



 
by Dinesh Thakur

The transceiver exchanges data signals handled by the NIC and electric signals sent over a transmission line. A I5-pin D-SUB connector is used to connect transceivers and transceiver cables. Multiport transceiver supports more than one NIC.

 
by Dinesh Thakur

This uses traditional thick baseband coaxial cable in bus topology to connect multiple computers as shown. This single transmission line is called a segment. A coaxial cable 10mm in diameter, known as a thick coaxial cable is used as a transmission line. A terminator is connected at each end of the cable. Note that proper data communication cannot be assured even if one of these terminators is missing or not properly connected.



 
by Dinesh Thakur

Media Access Control (MAC) describes the process that is employed to control the basis on which devices can access the shared network. Some level of control is required to ensure the ability of all devices to access the network within a reasonable period of time, thereby resulting in acceptable access and response times.

 
by Dinesh Thakur

Broadband A communications medium that can carry a wide range of signal frequencies, typically from audio up to video frequencies. In telecommunications the significance of a broadband system is that it can carry television and videoconferencing data as well as voice calls. A broadband medium can be made to carry many signals at once by apportioning its total bandwidth into many independent channels, each of which carries only a specific range of frequencies. In contrast, a BASEBAND can carry only a single channel. ATM, ADSL and Cable TV are all broadband media, while standard ISDN barely qualifies.

 
by Dinesh Thakur

It is required that information must be encoded into signals before it can be transported across communication media. In more precise words we may say that the waveform pattern of voltage or current used to represent the 1s and 0s of a digital signal on a transmission link is called digital to digital line encoding. There are different encoding schemes available:



 
by Dinesh Thakur

Infrared light transmissions have existed for many years and their use having been limited to TV remote controls and wireless slide projector remote controls. However, they now are assuming a position of some, if still limited, importance. Infrared systems use the infrared light spectrum to send a focused light beam to a receiver, much, as would a microwave system, although no reflective dish is used. Rather, pair of lenses is used, with a focused lens employed in the transmitting device and a collective lens in the receiving device as shown in Figure. Infrared is an airwave, rather that a conducted transmission system. Although generally used in short-haul transmission, they do offer substantial bandwidth, but with risks of interference.

 
by Dinesh Thakur

Satellite radio, quite simply, is a non-terrestrial microwave transmission system utilizing a space relay station. Satellites have proved invaluable in extending the reach of voice, data, and video communications around the globe and into the most remote regions of the world. Exotic applications such as the Global Positioning System (GPS) would have been unthinkable without the benefit of satellites.

 
by Dinesh Thakur

Microwave radio, a form of radio transmission that use. Ultra-high frequencies developed out of experiments with radar (radio detecting and ranging) during the period preceding World War II. There are several frequency ranges assigned to microwave systems, all of which are in the Giga Hertz (GHz) range and the wavelength in the millimeter range. This very short wavelength gives rise to the term microwave. Such high frequency signals are especially susceptible to attenuation and, therefore must be amplified or repeated after a particular distance.

 
by Dinesh Thakur

Radio waves, also called radio waves as they were discovered by German physicist Heinrich Hertz in 1888, are electromagnetic waves, that is to say the combined oscillation of an electric field and a magnetic field. Radio waves, infrared, visible light, ultraviolet, X-rays or gamma rays are all examples of electromagnetic waves.

 
by Dinesh Thakur

Data transmission can be divided into parallel and serial data transmission.

 
by Dinesh Thakur

Now, in wider sense we may understand that a transmitter or sender may be a terminal (computer) responsible for with communication and application software controls the terminal and processes data. There may be more than one terminal connected to the sender.



 
by Dinesh Thakur

This may be considered as the breakthrough for many of current ideas, algorithms and Internet technologies. It started in 1960s funded by Advanced Research Projects Agency (ARPA), an organization of the US Defense Department and, therefore, named as ARPANET.

 
by Dinesh Thakur

Flooding is the static routing algorithm. In this algorithm, every incoming packet is sent on all outgoing lines except the line on which it has arrived.

One major problem of this algorithm is that it generates a large number of duplicate packets on the network.

 
by Dinesh Thakur

• Tunneling is an internetworking strategy that is used when source and destination networks of same type are connected through a network of different type.

• In such a case, the packet from one network reaches the other network via different kind pf network that interconnects them.

 
by Dinesh Thakur

The notion of quality of service, or QoS, concerns certain characteristics of a network connection under the sole of the network service provider liability.

A QoS value applies to the whole of a network connection. It must be identical at both ends of the connection, even if it is supported by several interconnected subnetworks each offering different services.

 
by Dinesh Thakur

• Bluetooth is, with the infrared, one of the major wireless technologies developed to achieve WPAN. Bluetooth is a wireless LAN technology used to connect devices of different functions such as telephones, computers (laptop or desktop), notebooks, cameras, printers and so on.

• Bluetooth project was started by SIG (Special Interest Group) formed by four companies  IBM, Intel, Nokia and Toshiba for interconnecting computing and communicating devices using short-range, lower-power, inexpensive wireless radios.



 
by Dinesh Thakur

We are talking of Wireless LAN (WLAN) that is to say, "Wireless LAN", not to be confused with WAN course. Also referred Radio LAN (WLAN) if the communication medium is the radio (not light infrared for example).The stations of the wireless network can communicate directly with each other, we called Ad Hoc network type, or via relay terminals called APs (Access Points, PA) then it is an infrastructure network. the second type is by far the most common in business.

 
by Dinesh Thakur

Gigabit Ethernet or GbE, is the penultimate evolution of Ethernet standard. Several improvements have been made for it to Fast Ethernet at 100 Mbit/s.

The new interface is called modified GMII (Gigabit Media Independent Interface). It includes a data path 8 bits, instead of 4 in the less powerful version. The transceivers operate with a clock operating at 125 MHz.

 
by Dinesh Thakur

Fast Ethernet is the name of the extension to 100 Mbit/s Ethernet network to 10 Mbit/s. This is the IEEE 802.3u working group that is at the origin. Access technique is the same as in the Ethernet Version 10 Mbit/s, but at a speed multiplied by 10. transported frames are identical. This increase in speed may conflict with the wiring system and the possibility or not there such important transit flows.

 
by Dinesh Thakur

The parity check method is used fro error detection. It is also known as VRC method.

(a) In this method, a redundant bit called parity bit is added to each data.

 
by Dinesh Thakur

• In all practical situations, the transmission of data needs to be bi-directional. This is called as full-duplex transmission.

• We can achieve this full duplex transmission i.e. by having two separate channels-one for forward data transfer and the other for separate transfer i.e. for acknowledgements.

 
by Dinesh Thakur

• In sliding window method, multiple frames are sent by sender at a time before needing an acknowledgment.

• Multiple frames sent by source are acknowledged by receiver using a single ACK frame.

 
by Dinesh Thakur

• In this method of flow control, the sender sends a single frame to receiver & waits for an acknowledgment.

• The next frame is sent by sender only when acknowledgment of previous frame is received.

 
by Dinesh Thakur

Hamming code is technique developed by R.W. Hamming for error correction. This method corrects the error by finding the state at which the error has occurred.

 
by Dinesh Thakur

Cyclic Redundancy Check (CRe) An error detection mechanism in which a special number is appended to a block of data in order to detect any changes introduced during storage (or transmission). The CRe is recalculated on retrieval (or reception) and compared to the value originally transmitted, which can reveal certain types of error. For example, a single corrupted bit in the data results in a one-bit change in the calculated CRC, but multiple corrupt bits may cancel each other out.

 
by Dinesh Thakur

When data is being transmitted from one machine to another, it may be possible that data become corrupted on its, way. Some of the bits may be altered, damaged or lost during transmission. Such a condition is known as error.

 
by Dinesh Thakur

The pair of twisted is the simplest transmission medium. it consists of one or more pairs of electrical son arranged spiral. This type of support is suitable for transmission both analog and digital.

 
by Dinesh Thakur

There are two different approaches for the transmission of digital signals: baseband transmission and broadband transmission.

Baseband transmission

Baseband transmission means sending a digital signal over a channel without changing the digital signal to an analog signal.

 
by Dinesh Thakur

Computers are digital in nature. Computers process, store, and communicate information in binary form, i.e. in the combination of 1s and 0s which has specific meaning in computer language. A binary digit (bit) is an individual 1 or O. Multiple bit streams are used in a computer network.



 
by Dinesh Thakur

Analog is best explained by the transmission of signal such as sound or human speech, over an electrified copper wire. In its native form, human speech is an oscillatory disturbance in the air. Which varies in terms of its volume or power (amplitude) and its pitch or tone (frequency)? Analogous variations in electrical or radio waves are created in order to transmit the analog information signal for video or audio or both over a network from a transmitter (TV station or CATV source) to a receiver (TV set, computer connected with antenna). At the receiving end an approximation (analog) of the original information is presented.



 
by Dinesh Thakur

Definition Data Transmission

When we enter data into the computer via keyboard, each keyed element is encoded by the electronics within the keyboard into an equivalent binary coded pattern, using one of the standard coding schemes that are used for the interchange of information. To represent all characters of the keyboard, a unique pattern of 7 or 8 bits in size is used. The use of 7 bits means that 128 different elements can be represented, while 8 bits can represent 256 elements. A similar procedure is followed at the receiver that decodes every received binary pattern into the corresponding character.



 
by Dinesh Thakur

Data communication refers to the exchange of data between a source and a receiver. Data communication is said to be local if communicating devices are in the same building or a similarly restricted geographical area.

 
by Dinesh Thakur

Open System Interconnection (OSI) model, an ISO standard for worldwide communication Networks that defines a networking framework for implementing protocols in seven layers. Layering the communications process means breaking down the communication process into Smaller and Easier to handle interdependent categories. The convention and rules used in such communications are collectively known as Layer protocolOpen Systems Interconnection (OSI) model is developed by ISO (International organization for standardization) in 1984. ISO is the organization dedicated to defining global communication and standards.



 
by Dinesh Thakur

Transmission media is a pathway that carries the information from sender to receiver. We use different types of cables or waves to transmit data. Data is transmitted normally through electrical or electromagnetic signals.



 
by Dinesh Thakur

Unbound transmission media extend beyond the limiting confines of cabling. They provide an excellent Communication Networks alternative for WANS. The lack of physical restrictions provides larger bandwidth as well as wide area capabilities. Unbound media typically operate at very high frequencies. The three types of unbound transmission media are: Radio wave, Micro wave, Infrared.

 
by Dinesh Thakur

Bound Transmission Media in Communication Networks are the cables that are tangible or have physical existence and are limited by the physical geography. Also known as Conducted systems, wired media generally employ a metallic or glass conductor which serves to conduct, some form of electromagnetic energy.

 
by Dinesh Thakur

The first layer (physical layer) of Communication Networks the OSI Seven layer model is dedicated to the transmission media. Due to the variety of transmission media and network wiring methods, selecting the most appropriate media can be confusing - what is the optimal cost-effective solution.

 
by Dinesh Thakur

Unshielded Twisted Pair (UTP) : UTP is the copper media, inherited from telephony, which is being used for increasingly higher data rates, and is rapidly becoming the de facto standard for horizontal wiring, the connection between, and including, the outlet and the termination in the communication closet.

 
by Dinesh Thakur

Optical fiber consists of thin glass fibers or plastic that can carry information at frequencies in the visible light spectrum and beyond. The typical optical fiber consists of a very narrow strand of glass called the core. Around the core is a concentric layer of glass called the cladding?



 
by Dinesh Thakur

Data link layer is the second layer in OSI reference model and lies above the physical layer. The data link layer performs the following functions.

1. Data link layer receives the data from the network layer & divide it into manageable units called frames.

 
by Dinesh Thakur

Hubs/Repeaters are used to connect together two or more network segments of any media type. In larger design, signal quality begins to deteriorate as segment exceeds their maximum length. A hub provides the signal amplification required to allow a segment to be extended a greater distance.

 
by Dinesh Thakur

The term Transmission Mode defines the direction of the flow of information between two communication devices i.e. it tells the direction of signal flow between the two devices.

There are three ways or modes of data transmission: Simplex, Half duplex (HDX), Full duplex (FDX)



 
by Dinesh Thakur

Congestion is an important issue that can arise in packet switched network. Congestion is a situation in Communication Networks in which too many packets are present in a part of the subnet, performance degrades. Congestion in a network may occur when the load on the network (i.e. the number of packets sent to the network) is greater than the capacity of the network (i.e. the number of packets a network can handle.)

 
by Dinesh Thakur

In Communication Networks External electromagnetic signals can cause incorrect delivery of data. By this, data in the communication Networks can be received incorrectly, data can be lost or unwanted Communication Networks data can be generated. Any of these problems are called transmission errors in communication networks.

 
by Dinesh Thakur

Error detection and correction has great practical importance in maintaining data (information) integrity across noisy Communication Networks channels and lessthan- reliable storage media.



 
by Dinesh Thakur

The Media Access Control (MAC) data communication Networks protocol sub-layer, also known as the Medium Access Control, is a sub-layer of the data link layer specified in the seven-layer OSI model. The medium access layer was made necessary by systems that share a common communications medium. Typically these are local area networks. The MAC layer is the "low" part of the second OSI layer, the layer of the "data link". In fact, the IEEE divided this layer into two layers "above" is the control layer the logical connection (Logical Link Control, LLC) and "down" the control layer The medium access (MAC).



 

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