Reinventing Professionals: Where is the legal industry headed in 2017?

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"On the other hand, we denounce with righteous indignation and dislike men who are so beguiled and demoralized by the charms of pleasure of the moment, so blinded by desire, that they cannot foresee the pain and trouble that are bound to ensue; and equal blame belongs to those who fail in their duty through weakness of will, which is the same as saying through shrinking from toil and pain. These cases are perfectly simple and easy to distinguish. In a free hour, when our power of choice is untrammelled and when nothing prevents our being able to do what we like best, every pleasure is to be welcomed and every pain avoided. But in certain circumstances and owing to the claims of duty or the obligations of business it will frequently occur that pleasures have to be repudiated and annoyances accepted. The wise man therefore always holds in these matters to this principle of selection: he rejects pleasures to secure other greater pleasures, or else he endures pains to avoid worse pains."

Wireless Media

Wireless media carry data in the form of electromagnetic signals using radio or microwave frequencies.

Wireless media provides the best mobility options, and the number of wireless-enabled devices continues to increase. As network bandwidth options increase, wireless is quickly gaining in popularity in enterprise networks. Wireless does have some important point to consider before planning:-

• Coverage area: Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings and structures, and the local terrain, will limit the effective coverage.


• Interference: Wireless is at risk to intrusion and can be disrupted by such common devices as household cordless phones, some types of fluorescent lights, microwave ovens, and other wireless communications.


• Security: Wireless communication coverage requires no access to a physical strand of media. thus, devices and users, not authorized for access to the network, can gain access to the transmission. Network security is the main component of wireless network administration.


• Shared medium: WLANs work in half-duplex, which means just one device can send or receive at a time. The wireless medium is shared amongst all wireless users. The more users need to access the WLAN simultaneously, results in less bandwidth for each user.

Types of Wireless Media

The IEEE and telecommunications industry standards for wireless data communications cover both the data link and physical layers. cellular and satellite communications can also provide data network connectivity. But, we are not discussing these wireless technologies here in this chapter. In each of these standards, physical layer specifications are applied to areas that include:

• Transmission Frequency


• Transmission power of transmission


• Data to radio signal encoding


• Signal reception and decoding requirements


• Antenna design and construction

Wi-Fi is a trademark of the Wi-Fi Alliance. Wi-Fi is used with certified products that belong to WLAN devices that are based on the IEEE 802.11 standards. Different standards is following:-

WI-FI standard IEEE 802.11

WLAN technology commonly referred to as Wi-Fi. WLAN uses a protocol known as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). The wireless NIC must first listen before transmitting to determine if the radio channel is clear. If another wireless device is transmitting, then the NIC must wait until the channel is clear. CSMA/CA is will be discussed later.

Bluetooth standard IEEE 802.15

Wireless Personal Area Network (WPAN) standard, commonly known as "Bluetooth", uses a device pairing process to communicate over distances from 1 to 100 meters.

WI-MAX Standard IEEE 802.16

Usually known as Worldwide Interoperability for Microwave Access (WiMAX), uses a point-to-multipoint topology to provide wireless broadband access.

Wireless LAN (WLAN)

General wireless data implementation wireless LAN requires the following network devices:

• Wireless Access Point (AP): In a wireless local area network (WLAN), an access point (AP) is a station that transmits and receives data. An access point connects users to other users within the network and also can serve as the point of interconnection between the WLAN and a fixed wire network. Each access point can serve multiple users within a defined network area; as people move beyond the range of one access point, they are automatically handed over to the next one. A small WLAN may only require a single access point; the number required increases as a function of the number of network users and the physical size of the network.


• Wireless NIC adapters: Provide wireless communication capability to each network host.

As the technology has developed, a number of WLAN Ethernet-based standards have emerged. Care needs to be taken in purchasing wireless devices to ensure compatibility and interoperability.

The benefits of wireless data communications technologies are clear, particularly the savings on costly premises wiring and the convenience of host mobility

KWM LLP files notice of intention to appoint administrators

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Fiber versus Copper

Fiber versus copper - choose the perfect solution for your cabling infrastructure is not an easy task. but; once you be aware of the different properties of copper and fiber your solution may seem clearer.There are many advantages of fiber-optic cable compared to copper cables. Following table highlights some of these differences.

Implementation Issues	UTP Cabling	Fiber-optic-cabling
Bandwidth Supported	Fiber-optic can significantly increase your bandwidth potential and the Bandwidth is upto 10 Mbps to 10 Gbps	Copper wire infrastructure and TDM technology are limited in nature. Because it was originally designed for transmitting voice calls only, the demand for bandwidth wasn't high. So it support 10 Mbps to 100 Gbps.
Distance	The signal travel on copper wire networks degrades as the signal is carried from the central office. So the distance covered by copper wire is very Short which is from 1 meter to 100 meters.	Fiber was originally used for long haul networks. The signal travel on fiber optic cable do not degrades as the signal degrade in copper wire. Distance covered by fiber optic is very long from 1-100,000 meters.
Security	Intercepting copper cable can be performed by just connecting taps to a line to pick up the electronic signals. So it is very easy to compromise your security and dificult to trace compromise cable.	Putting a tap on a fiber-optic cable to intercept data transmissions is very difficult. It's also easy to quickly identify compromised cables, which visibly emit light from transmissions.
Immunity to EMI and RFI	Copper wire is a conductor so there is very low immunity to EMI and RFI for copper wire.	Fiber Optic Cable is non conducting meterial and electrical signal do not interfere on it So the immunity to EMI and RFI is very High (Completely immune)
Immunity to electrical hazards	Low	High (Completely immune)
Size of Cable	The speed via copper cable is directly associated with the weight of cable used. For achieving a higher speeds, more cable must be used, which requires more space in a system room.	Fiber cable's speed is not associated to its size, and it's far lighter weight than copper. This renders it easier to use, and less demanding of limited space in small rooms.
Media and connector costs	Lowest	Highest
Installation skills required	Lowest	Highest
Safety precautions	Lowest	Highest
Power over Ethernet (PoE)	Yes	No
Flexibility	High	Low
Reliability	Less reliable	More reliable

Optical Fiber Cable Testing

Installation and splicing of fiber optic cables required special training and equipment. the wrong termination of fiber-optic media will result in diminished signaling distances or complete transmission failure.

Three common types of fiber-optic termination and splicing errors are:

• Misalignment: The fiber-optic media are not exactly aligned to one another when joined.


• End gap: The media does not completely touch at the splice or connection.


• End finish: The media ends are not well polished, or dirt is present at the termination.

Testing is used to evaluate the above mention error and performance of fiber optic components; cable plants and systems. As the components like fiber, connectors, splices; LED or laser sources, detectors and receivers are being developed; testing confirms their performance specifications and helps understand how they will work together.

A quick and easy field test can be performed by shining a bright flashlight into one end of the fiber while observing the other end. If the light is visible; the fiber is capable of passing light. Although this does not ensure performance; it is a quick and inexpensive way to find a broken fiber. For quick and easy testing you need the right tools and test equipment for the job. Following is the list of fiber optic testing tool.

• Optical inspection microscope, 100-200X video scope recommended


• Source and power meter, optical loss test set (OLTS) or test kit with proper equipment adapters for the cable plant you are testing.


• optical fiber splicing machine.


• Reference test cables that match the cables to be tested and mating adapters, including hybrids if needed


• Cleaning materials - dry cleaning kits or lint free cleaning wipes and pure alcohol


• Fiber Tracer or Visual Fault Locator


• OTDR with a launch and/or receive cables for outside plant jobs and troubleshooting.

Fiber optic Connectors

Fiber-Optic Connectors

Fiber optic connectors terminate both ends of an optical fiber. A variety of optical connectors is available. The differences between the types of connectors are size and methods of coupling. There is four type of fiber optic connector in use:-

ST Connectors

The ST connector was one of the first connector types broadly implement in fiber optic networking applications. Originally developed by AT&T, it stands for Straight Tip connector. ST connections use a 2.5mm ferrule with a round plastic or metal body. The connector stays in place with a "twist-on/twist-off" bayonet-style mechanism. Although extremely popular for many years, the ST connector is slowly being supplanted by smaller, denser connections in many installations.

 

 

SC Connector

SC connectors also use around 2.5mm ferrule to hold a single fiber. They use a push-on/pull-off mating mechanism which is usually easy to use than the twist-style ST connector when in tight spaces. The connector body of an SC connector is square shaped, and two SC connectors are usually held together with a plastic clip (this is referred to as a duplex connection). The SC connector was developed in Japan by NTT (the Japanese telecommunications company) and is believed to be an abbreviation for Subscriber Connector or possibly Standard Connector.

 

 

LC connector

One popular Small Form Factor (SFF) connector is the LC type. This interface was developed by Lucent Technologies (hence, Lucent Connector). It uses a retaining tab mechanism; similar to a phone or RJ45 connector, and the connector body resembles the square type shape of SC connector. LC connectors are normally held together in a duplex configuration with a plastic clip. The ferrule of an LC connector is 1.25mm.

 

 

Full Duplex patch cords

As we know that light can move in one direction over optical fiber. For full duplex comm. two fibers are required. So, fiber-optic patch cables bundle together two optical fiber cables and terminate them with a pair of standard single fiber connectors. Some fiber connectors accept both the transmitting and receiving fibers in a single connector known as a duplex connector; as shown in below figure  Duplex Multimode LC Connector.

 

Fiber patch cords are required for interconnecting communications devices. Figure ---- show a variety of common patch cords. The use of color distinguishes between single-mode and multimode patch cords. A yellow jacket is for single-mode fiber cables and orange (or aqua) for multimode fiber cables.

Note:-Fiber cables should be protected with a small plastic cap when not in use.

Fiber Optic Cable

Properties of Fiber-Optic Cabling

Fiber optic cable can transmit data over long distances with higher bandwidths than any other networking media. Optic fiber cable can transmit signals with less attenuation and is totally protected to EMI and RFI. OFC is generally used to connect network devices.

Fiber optic cable is a flexible, but very thin; a transparent strand of very pure glass, not much bigger than a human hair. Bits are encoded on the fiber as light impulses. The fiber-optic cable acts as a waveguide; or “light pipe,” to transmit light between the two ends with the minimal loss of signal.

As an analogy, consider an empty paper towel roll with the inside coated like a mirror. It is a thousand meters in length, and a small laser pointer is used to send Morse code signals at the speed of light. Essentially that is how a fiber-optic cable operates; except that it is smaller in diameter and uses sophisticated light technologies.

Fiber-optic cabling is now being used in four types:

• Enterprise Networks: Used for backbone cabling and interconnecting infrastructure devices.


• Fiber-to-the-Home: Used to provide always-on broadband services to homes and small businesses.


• Long-Haul Networks: This type is used by service providers to connect countries and cities.


• Submarine Networks: Used to provide reliable high-speed; high-capacity solutions capable of surviving in harsh undersea environments up to transoceanic distances.

Fiber Optic Cable structure

The optical fiber is composed of two kinds of glass (core and cladding) and a protective outer shield (jacket) as shown in figure 3-8. 

Core

The core is actually the light transmission element at the center of the optical fiber. This core is typically silica or glass. Light pulses travel through the fiber core.

Cladding

Made from little different chemicals than those used to make the core. It tends to perform like a mirror by reflecting light back into the core of the fiber. This keeps the light in the core as it travels down the fiber.

Buffer

Used to help shield the core and cladding from damage.

Strengthening Member

 Surrounds the buffer, prevents the fiber cable from being stretched out when it is being pulled. The material used is often the same material used to manufacture bulletproof vests.

Jacket

Typically a PVC jacket that protects the fiber against abrasion; moisture, and other contaminants. This outer jacket composition can vary depending on the cable usage.

Types of Fiber Media

Light pulses in lieu of the transmitted data as bits on the media are generated by either:

• Lasers


• Light emitting diodes (LEDs)

Electronic semiconductor devices called photodiodes detect the light pulses and convert them to voltages. The laser light transmitted over fiber-optic cabling can damage the human eye. Care must be taken to avoid looking into the end of an active optical fiber.

Fiber-optic cables are mostly classified into two types:

• Single-mode fiber (SMF): its core is very small and this type of fiber uses very expensive laser technology to send a single ray of light; as shown in Figure 3-9 Popular in long-distance situations spanning hundreds of kilometers; such as those required in long haul telephony and cable TV applications. Following is single mode cable characteristics.
  
  
  
  
  • Small core
  
  
  • Less dispersion
  
  
  • Use laser as the light source
  
  
  • Suited for long distance application
  
  
  • Commonly used with campus backbone for a distance of several thousand meters.
  
  
  
  

• Multimode fiber (MMF): Its core is very large and this type of cable uses LED emitters to send light pulses. Specifically, light from a LED enters the multimode fiber at different angles; as shown in Figure 3-10. Popular in LANs because they can be powered by low-cost LEDs. It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters. Following is single mode cable characteristics.


• Larger core than single mode cable


• Uses LEDs as the light source


• Allows greater dispersion and therefore, loss of signal


• Suited for long distance application; but shorter than single mode


• Commonly used with LANs or distances of a couple hundred meters within a campus network.

Unshielded Twisted Pair (UTP) Cabling

Properties

Unshielded twisted-pair (UTP) cabling consists of four pairs of color-coded copper wires that have been twisted together and then enclosed in a flexible plastic sheath. Its small size can be helpful during installation. UTP cable does not use shielding to counter EMI and RFI effects. Cable designers discovered that they can limit the negative effect of crosstalk by following ways:-

• Cancellation: When two wires in an electrical circuit are placed close jointly, their magnetic fields are the exact opposite of each other. so, the two magnetic fields cancel each other and also cancel out any outside EMI and RFI signals.

• Varying the number of twists per wire pair: To improve the cancellation effect of paired circuit wires, designers vary the number of twists of each wire pair in a cable. UTP cable must follow precise specifications governing how many twists or braids are permitted per meter of cable. Notice in the figure 3-3 that the orange/orange white pair is twisted more than the green/green-white pair. Each colored pair is twisted a different number of times.

Standards of UTP Cabling

UTP cabling conforms to the standards recognized by the TIA/EIA. Specifically, TIA/EIA-568 stipulates the commercial cabling standards for LAN installations and is the standard most commonly used in LAN cabling. Some of the elements defined are below:-
• Cable types
• Cable lengths
• Connectors
• Cable termination
• Methods of testing cable

Electrical and Electronics Engineers (IEEE) define the electrical characteristics of copper cabling. IEEE placed cables into categories based on their ability to carry higher bandwidth rates. For example, Category 5 (Cat5) cable is used commonly in 100BASE-TX Fast Ethernet installations. Other categories include Enhanced Category 5 (Cat5e) cable, Category 6 (Cat6), and Category 6a.
Cables in higher categories are supported higher data rates. As new gigabit speed Ethernet technologies are being developed and adopted, Cat5e is now the minimally acceptable cable type.

CAT-3 UTP

• Used for voice communication
• Most often used for phone lines

CAT-5 and CAT-5e UTP

• Used for data transmission
• Cat5 supports 100 Mb/s and can support 1000 Mb/s, but it is not recommended
• Cat5e supports 1000 Mb/s

CAT-6 UTP

• Used for data transmission
• An added separator is between each pair of wires allowing it to function at higher speeds
• Supports 1000 Mb/s - 10 Gb/s, though 10 Gb/s is not recommended
• UTP Connectors

UTP cable is generally terminated with an RJ-45 connector. This connector is used for a range of physical layer specifications, one of which is Ethernet. The TIA/EIA-568 standard describes the wire color codes to pin assignments for Ethernet cables.
RJ-45 is a male connector, crimped at the end of the cable. The socket is the female component of a network device, wall, cubicle partition outlet, or patch panel.
Figure 3-5 displays an example of RJ-45 Plug and figure 3-6 display the example of RJ-45 Sockets.

Types of UTP cable by use

Different situations may require UTP cables to be wired according to different wiring conventions. This means that the individual wires in the cable have to be connected in different orders to different sets of pins in the RJ-45 connectors. Following are the main cable types that are obtained by using specific wiring conventions:

• Ethernet Straight-through: The most common type of networking cable. It is generally used to connect a host to a switch and a switch to a router.
• Ethernet Crossover: A cable used to connect similar devices. For example to connect a switch to a switch, a host to a host, or a router to a router.
• Rollover: A Cisco proprietary cable used to connect a workstation to a router or switch console port.
The figure 3-7 shows the UTP cable type, related standards, and typical application of these cables. It also identifies the individual wire pairs for the TIA-568A and TIA-568B standards.

Using a crossover or straight-through cable incorrectly between devices may not damage the devices, but connectivity and communication between the devices will not take place. This is a common error in the lab and checking that the device connections are correct should be the first troubleshooting action if connectivity is not achieved.

Cable Type	Standard
Ethernet Straight-through	Both ends T568A or Both end T568B
Crossover	One end T568A, another end T568B
Rollover	Rollover Cisco proprietary

 

Copper Media Safety

All types of copper media are vulnerable to fire and electrical hazards. Fire hazards exist since cable insulation and sheaths may be flammable, or produce toxic fumes when heated or burned. Building authorities or organizations may specify related safety standards for cabling and hardware installations.

Electrical hazards are a potential problem because copper wires can conduct electricity in unwanted ways. This could focus personnel and equipment to a range of electrical hazards. For example; a defective network device could conduct currents to the chassis of other network devices. as well; network cabling could present unwanted voltage levels when used to connect devices that have power sources with different ground potentials. Such situations are possible when copper cabling is used to connect networks in different buildings or on separate floors that use disparate power facilities. Finally; copper cabling may conduct voltages caused by lightning strikes to network devices.

The result of unwanted voltages and currents can include harm to network devices and linked computers, or hurt to personnel. It is essential that copper cabling is installed correctly, and according to the relevant specifications and building codes; in order to avoid potentially dangerous and damaging situations.

The figure displays proper cabling practices that help to prevent potential fire and electrical hazards.

During Installation of Copper Cable Use following safety precautions to avoid any incident.  

• Wear safety glasses:


• Use common sense with ladders.


• Wear protective clothing.


• Don't be careless when lifting.


• Don't use power tools unless you know how to use them.


• Be worry of electrical cable.


• Know local code: building code may prohibit drilling holes in firewalls or ceilings.


• Take care what you touch.


• Use the right tools.


• Depending on your project use the right materials.


• Mark junction box locations carefully


• When pulling the cable through drop-in ceilings, you must be sure to prevent the cable from scraping along sharp edges.


• Every rushed install will most likely have something wrong with it, So take your time on installation.

 

Characteristics of Copper Media

The network uses Copper media because of its advantages however it has also some disadvantages. In this session, we will discuss all the characteristics of copper cabling.

Advantages

• It is inexpensive
• Low resistance to electrical signals
• easy to install
• power over Ethernet (POE)
• More flexible

Disadvantages

• Electromagnetic interference (EMI)
• Radio Freq Interference (RFI)
• Crosstalk
• Break Easily
• It can support maximum up to 100 meter

Data is transmitted on copper cables as electrical pulses. A detector in the network interface of a target device should receive a signal that can be successfully decoded to match the signal sent. on the other hand the longer the signal travels the more it deteriorates. This is referred to as signal attenuation. For this reason, all copper media must follow strict distance limitations as specified by the guiding standards. Above mention the advantages and disadvantages are the main characteristics of copper media. Some are general which is no further discussion required. Some are required more attention.

Electromagnetic interference (EMI) or radio frequency interference (RFI)

 EMI and RFI signals can deform and corrupt the data signals being passed by copper media. Potential sources of EMI and RFI include radio waves and electromagnetic devices; such as fluorescent lights or electric motors etc.

Crosstalk 

Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in the closest wire. In telephone circuits; crosstalk can result in hearing part of another voice conversation from a nearby circuit. Specifically, when an electrical current flows through a wire, it creates a small circular magnetic field around the wire, which can be picked up by a nearby wire.

To counter the harmful effects of EMI and RFI; some types of copper cables are wrapped in metallic shielding and require proper grounding connections.
To counter the negative effects of crosstalk; some types of copper cables have opposing circuit wire pairs twisted together; which effectively cancels the crosstalk.
The weakness of copper cables to electronic noise can also be limited by:

•  Selecting the best type of cable most suited to a given networking environment and situation.


• Designing a cable infrastructure to avoid known and potential sources of interference in the building structure.


• Define terms related to callings, such as shielding, crosstalk, attenuation, and plenum.


• Using cabling techniques that include the proper handling and termination of the cables.


• Identify the primary types of network cabling


• Distinguish between baseband and broadband transmissions and identify appropriate uses for each

The top legal stories of 2016: Do you have others?

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Copper Media

The most used media for data communications is cabling (copper media); that uses copper wires to transmit data and control bits between network devices. Cabling used for data communications generally consists of a series of individual copper wires; that form circuits dedicated to specific signaling purposes. 

There are three main types of copper media used in networking:

• Unshielded Twisted-Pair (UTP)


• Shielded Twisted-Pair (STP)


• Coaxial

The above cables are used to interconnect computers on a LAN and other devices such as switches; routers, and wireless access points. Each type of connection and the associated devices has cabling requirements specified by physical layer standards.physical layer standards specify the use of different connectors for different. Physical layer standards also specify the mechanical dimensions of the connectors and the acceptable electrical properties of each type.

Unshielded Twisted-Pair Cable (UTP)

Unshielded twisted-pair (UTP) cabling is the most common networking media for voice; and data communications. UTP cable consists of four pairs of color-coded wires that have been twisted 

together and then encased in a flexible plastic sheath that protects from minor physical damage. The twisting of wires helps to minimize electromagnetic and radio-frequency interference induced from one wire to the other.

 

UTP cabling, terminated with RJ-45 connectors; is used for interconnecting network hosts with intermediate networking devices, such as switches and routers.

In the figure, you can see that the color codes identify the individual pairs and wires and help in cable termination.

Shielded Twisted-Pair Cable(STP)

Shielded twisted-pair (STP) provides better noise protection than UTP cabling. However; compared to UTP cable, STP cable is more expensive and difficult to install. Like UTP cable, STP uses an RJ-45 connector.

The extra covering in shielded twisted pair wiring protects the transmission line from electromagnetic interference leaking into or out of the cable. STP cabling often is used in Ethernet networks, especially fast data rate Ethernets.

Shielded twisted-pair (STP)  cables combine the techniques of shielding to counter EMI and RFI, and wire twisting to counter crosstalk. To put on the full advantage of the shielding; STP cables are terminated with special shielded STP data connectors. If the cable is improperly grounded; the shield may act as an antenna and pick up unwanted signals.

Coaxial Cable

Coaxial cable is called "coaxial" because of the fact that there are two conductors that share the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and; with repeaters, can carry information for a great distance.

As shown in the figure, coaxial cable consists of:

• A copper conductor used to transmit the electronic signals.


• A layer of flexible plastic insulation surrounding a copper conductor.


• The insulating material is surrounded in a woven copper braid or metallic foil; that acts as the second wire in the circuit and as a shield for the inner conductor. This second layer, or shield; also reduces the amount of outside electromagnetic interference.


• The entire cable is covered with a cable jacket to prevent minor physical damage.

There are different types of connectors used with coax cable.

Although UTP cable has essentially replaced the coaxial cable in modern Ethernet installations, the coaxial cable design is used in:

• There are many types of coax cable that we can use in different ways following is the table of different types of coax cable

Cable Type	Impedance	Uses
RG-6	75 Ohms	Video, TV
RG-8	50 Ohms	Radio, computer
RG-11	75 Ohms	Long runs
RG-58	50 Ohms	Radio, Computer
RG-59	75 Ohms	Video, TV

 

Types of Physical Media

A network required a physical medium to connect its nodes. The physical media is where the data actually flows. You have most likely heard about OSI reference model, which defines network hardware and services in terms of the functions they perform. The OSI reference model we already discussed in detail in Chapter 1, ("Network and their building blocks.") Transmission media work at Layer 1(physical layer) of the OSI model:The physical layer represents bits as voltages, radio frequencies; or light pulses so various standards organizations have contributed to the definition of the physical; electrical, and mechanical properties of the media available for different data communications. These characteristics guarantee; that cables and connectors will function as expected with different data link layer implementations. There are three main categories of media types that will be discussed in detail later:

Copper cable

Types of cable include unshielded twisted-pair (UTP), shielded twisted-pair (STP), and coaxial cable. Copper-based cables are inexpensive and easy to work with compared to fiber-optic cables, but as you'll learn when we get into the particulars, the main disadvantage of copper cable is that it offers a limited range that cannot handle the advanced applications.

Fiber optics

Fiber offers huge data bandwidth, protection to many types of noise and interference, and enhanced security. 

So, fiber provides clear communications and a comparatively noise-free environment. The disadvantage of fiber is that it is costly to purchase and it requires specialized equipment and techniques for installation.

Wireless

Wireless media include radio frequencies, microwave, satellite, and infrared. Deployment of wireless media is faster and less costly than the deployment of cable, mostly where there is no existing infrastructure. There are a few disadvantages associated with wireless. It supports much lower data rates than do wired media. Wireless is also greatly affected by external environments, such as the impact of weather, as a result reliability can be difficult to guarantee.

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"But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure?"

"At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat."

Data Bandwidth

In computer networks, bandwidth is the amount of data that can be carried from one point to another in a given time period; (generally a second). Network bandwidth is usually expressed in bits per second (bps); kilobits per second (kb/s), megabits per second (Mb/s), or gigabits per second (Gb/s). It sometimes thought of as the speed that bits travel, however, this is not accurate.

For example, in both 100Mb/s and 1000Mb/s Ethernet, the bits are sent at the speed of electricity. The difference is the number of bits that are transmitted per second.

• A combination of factors determines the practical bandwidth of a network.


• The properties of the physical media.


• 
  

  The technologies chosen for signaling and detecting network signals.

  
  


• 
  

  Physical media properties, current technologies, and the laws of physics play a role in determining the available bandwidth.

  
  

The table shows the commonly used units of measure for data bandwidth

Unit	Abbrivation	Decimal Value	Binary value	Decimal Size
Bit	b	0 or 1	0 or 1	1/8 of a byte
Byte	B	8 bits	8 bits	1 byte
Kilobyte	KB	1,0001 bytes	10241 bytes	1,000 bytes
Megabyte	MB	1,0002	10242	1,000,000 bytes
Gigabyte	GB	1,0003	10243	1,000,000,000 bytes
Terabyte	TB	1,0004	10244	1000,000,000,000 bytes
Petabyte	PB	1,0005	10245	1000,000,000,000,000 bytes

Throughput

The measurement of a bits transfer across the media over a given period is called throughput. It is a measure of how many units of information a system can process in a given amount of time. Due to some factors, it generally does not match the specified bandwidth in physical layerimplementations. Many factors manipulate it, including following:

• 
  

  The type of traffic

  
  


• 
  

  The amount of traffic

  
  


• 
  

  The latency created by the number of network devices between source and destination

  
  


• 
  

  Error rate

  
  

Latency is the amount of time, to include delays; for data to travel from one given point to another.

The networks with multiple segments, throughput can’t be faster than the slowest link in the path from source to destination. Even if all or most of the segments have high bandwidth; it will only take one segment in the path with low throughput to create a tailback to the throughput of the entire network.

The average transfer speed over a medium is often described as throughput. This measurement includes all the protocol overhead information; such as packet headers and other data that is included in the transfer process. It also includes packets that are retransmitted because of network conflicts or errors.

There is another measurement to evaluate the transfer of usable data that is known as goodput. Goodput is the measure of usable data transferred over a given period of time. Goodput is throughput minus traffic overhead for establishing sessions, acknowledgments, and encapsulation. It only measures the original data.

Physical Layer Functions

The physical layer standards deal with three basic functions which are described below:

Physical Components

The physical layer takes frames from the data link layer then converts these frames into electrical, electromagnetic; optical signals through different line coding techniques.Transmits these signals through wired/wireless telecommunication links (cables/antennas) to next hop.

Components of this layer are the electronic hardware devices; media, and other connectors such as NIC, cable, and connector that transmit and carry the signals. Hardware components such as NICs, interfaces and connectors, cable materials, and cable designs are all specified in standards associated with the physical layer.

Encoding

Encoding is a technique of converting a stream of data bits into a predefined "code”. Codes are groupings of bits used to provide a predictable pattern that can be recognized by both the sender and the receiver. In the case of networking, encoding is a pattern of voltage or current used to represent bits; the 0s and 1s.

Signaling

The physical layer must generate the electrical, optical, or wireless signals that represent the "1" and "0" on the media. The method of representing the bits is called the signaling method. The physical layer standards must define what type of signal represents a "1" and what type of signal represents a "0". This can be as simple as a change in the level of an electrical signal or optical pulse. For example, a long pulse might represent a 1 whereas a short pulse represents a 0. Modulation techniques are a common method to send data. Modulation is the process by which the characteristic of one wave modifies another wave.

The Physical Layer

The Physical layer is the lowest layer of OSI Model. It provides the resources to transport the bits; that make up a data link layer frame across the network media. This layer accepts a complete frame from the data link layer and encodes it as a series of signals that are transmitted onto the local media.(see figure 3.1) The encoded bits that comprise a frame are received by either an end device or an intermediate device.

This layer also deals with the physical connection to the network and with transmission and reception of signals. This layer defines electrical and physical details represented as 0 or a 1.It's also decided when the data can be transmitted or not and how the data would be synchronized.

The process that data travel from a source node to a destination node is following:

• The user data is segmented by the transport layer; placed into packets by the network layer, and further encapsulated into frames by the data link layer.Data link layer sent these frames to the physical layer.

• The physical layer encodes the frames and creates the electrical, optical; or radio wave signals that represent the bits(0 and 1) in each frame.

• These signals are then sent to the media, one at a time.

• The destination node physical layer retrieves these individual signals from the media; restores them to their bit representations, and passes the bits up to the data link layer as a complete frame(see figure 3.1).

• Line configuration: - This layer connects devices with the medium;  Point to Point configuration and Multipoint configuration.

• Topologies: - Devices must be connected using the following topologies;  Mesh, Star, Ring and Bus

• Transmission Modes: -  Physical Layer also defines the direction of transmission between devices ( Simplex, Half Duplex, Full Duplex).

Media

Many different types of media can be used for the physical layer. For example, telephone twisted pair, coax cable, shielded copper cable; and fiber optics are the main types used for LANs. Different transmission techniques generally categorized as baseband, or broadband transmission may be applied to each of these media types.

There are three basic types media. The physical layer produces the representation and groupings of bits for each type of media as:

• Copper cable: The signals are patterns of electrical pulses.


• Fiber-optic cable: The signals are patterns of light.


• Wireless: The signals are patterns of microwave transmissions.

To enable physical layer interoperability, all aspects of these functions are governed by standards organizations.

Standards

Upper layer Protocol: - Protocols and operation of the upper OSI layers are totally performed in software. This software is designed by software engineers and computer scientists. IETF (Internet Engineering Task Force ) is an organization which defined the services and protocol for TCP/IP suit.

The physical layer consists of electronic circuitry, media, and connectors. Therefore, it is suitable that the standards governing this hardware are defined by the relevant electrical and communications engineering organizations.

There are many different international and national organizations, regulatory government organizations, and private companies involved in establishing and maintaining physical layer standards. For example, the physical layer hardware, media, encoding, and signaling standards are defined and governed by the following:-

• International Organization for Standardization (ISO)


• International Telecommunication Union (ITU)


• American National Standards Institute (ANSI)


• Institute of Electrical and Electronics Engineers (IEEE)


• Telecommunications Industry Association/Electronic Industries Association (TIA/EIA)


• National telecommunications regulatory authorities including the Federal Communication Commission (FCC) in the USA and the European Telecommunications Standards Institute (ETSI)


• Canadian Standards Association (CSA)


• European Committee for Electrotechnical Standardization(CENELEC)

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Network Interface Card (NIC)

Network Interface Card (NIC) is also referred to as an Ethernet card. It also called network adapter. It is a circuit board that is installed in a computer so that it can be connected to a network.  A network interface card provides the computer with a dedicated, full-time connection to a network. Personal computers and workstations on a local area network typically contain a network interface card specifically designed for the LAN transmission technology. Most new computers have a network interface built-in directly into the motherboard

Network Interface Card enables a computer to connect to a network; such as a home network, or the Internet using an Ethernet cable with an RJ-45 connector and wires

Types of Network Interface

There is a different form of the network card. But the two main ones are wired and wireless. Wireless NICs Uses wireless technologies to connect the network, so they have one or more antennas. Wired NICs just use an RJ45 port since they have an Ethernet cable attached to the end. This makes them much flatter than wireless network cards.

Speed of Network Interface Card

All network interface cards have a different speed rating, such as 10 Mbps, 11 Mbps, 54 Mbps or 100 Mbps, and 1000 Mbps. The speed describes the general performance of the interface card.  It's important that the speed of the NIC does not necessarily determine the speed of the internet connection. This is due to reasons like available bandwidth and the speed you're paying for.For example, if your DSL speed is 16Mbps and your NIC Speed is 100 Mbps, So network interface card will not increase the speed of your internet.  but, if your DSL speed is 16 Mbps and your NIC is 10 Mbps, So your internet speed will also slow down to 10 Mbps.

Network Interface Card Driver

All hardware devices installed in computers need device drivers in order to work with the software on the computer. If installed network card isn't working, it's mean that driver is missing, corrupted or outdated. The updating of driver software required in internet connection in order to download the driver. But problem is that your network card is not working and you cannot access the internet. So you can download a driver on a computer that is connected to the internet from the card manufacturers site and then transfer using a USB drive or CD.

Device communication on a remote network

Here we will discuss the role of the network layer and data link layer when devices communicating on a remote network. Here is the example of PC1 which is communicating with a web server on a different network.

Role of the Network Layer Addresses

When the sender of the packet is on a different network from the receiver, the source and destination IP addresses will represent hosts on different networks. This will be indicated by the network portion of the IP address of the destination host.

Source IP address

The IP address of the sending device, the client computer PC1: 192.168.5.100.

Destination IP address

The IP address of the receiving device, the server, Web Server: 172.17.5.254.
Important is that the network of both sending and receiving end is different.

Role of the Data Link Layer Addresses

When the sender and receiver of the IP packet are on different networks, the Ethernet data link frame cannot be sent directly to the destination host because the host is not directly reachable in the network of the sender. In that case, the Ethernet frame must be sent to another device known as the router or default gateway. In the present example, the default gateway is R1. R1 has an Ethernet data link address that is on the same network as PC1. This allows PC1 to reach the router directly.

Source MAC address

Sending device MAC address which is PC1 - 22-22-22-22-22-22

Destination MAC address

When the receiving device, the destination IP address, is on a different network from the sending device, the sending device uses the Ethernet MAC address of the default gateway or router. In this example, the destination MAC address is the MAC address of R1's Ethernet interface, BB-BB-BB-BB-BB-BB. This is the interface that is attached to the same network as PC1.
The Ethernet frame with the encapsulated IP packet can now be transmitted to R1. R1 forwards the packet to the destination, Web Server. This may mean that R1 forwards the packet to another router or directly to Web Server if the destination is on a network connected to R1.
It is important that the IP address of the default gateway be configured on each host on the local network. All packets to a destination on remote networks are sent to the default gateway.

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Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

"Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur?

Devices communication on the same network

To understand how devices communicate within a network. It is important to understand the roles of both the network layer addresses and the data link layer addresses.

Role of the Network Layer Addresses

The network layer addresses, or IP addresses, indicate the original source and final destination. An IP address contains two parts:

• 
  

  Network portion

  
  

The left-most part of the address that indicates which network the IP address is a member. All devices on the same network will have the same network portion of the address.

• 
  

  Host portion

  
  
  The remaining part of the address that identifies a specific device on the network. The host portion is unique for each device on the network.

Note: The subnet mask is used to identify the network portion of an address from the host portion.

In this example, we have a client computer PC1 FTP server on the same IP network.

• 
  

  Source IP address - The IP address of the sending device, the client computer PC1: 192.168.5.100.

  
  


• 
  

  Destination IP address - The IP address of the receiving device, FTP server: 192.168.5.102

  
  

Notice in the figure that the network portion of both the source IP address and destination IP address are on the same network.

Role of the Data Link Layer Addresses

When the sender and receiver of the IP packet are on the same network, the data link frame is sent directly to the receiving device. On an Ethernet network, the data link addresses are known as Ethernet (Media Access Control) addresses. MAC addresses are physically embedded on the Ethernet NIC.MAC Address also called Physical address.

• Source MAC address- This is the data link address, or the Ethernet MAC address, of the device that sends the data link frame with the encapsulated IP packet. The MAC address of the Ethernet NIC of PC1 is AA-AA-AA-AA-AA-AA, written in hexadecimal notation.


• Destination MAC address- When the receiving device is on the same network as the sending device; this is the data link address of the receiving device. In this example, the destination MAC address is the MAC address of the FTP server: CC-CC-CC-CC-CC-CC, written in hexadecimal notation.

The frame with the encapsulated IP packet can now be transmitted from PC1 directly to the FTP server.

 Figure 2.7 Device on the same network

Network Layer and Data link Layer Addresses

The network and data link layers are responsible for delivering the data from the source device to the destination device. As shown in Figure2-4; protocols at both layers contain a source and destination address, but their addresses have different purposes.

Network Layer Addresses

• 
  

  Network layer address (source and destination)

  
  
  Responsible for delivering the IP packet from the original source to the final destination; whichever on the same network or to a remote network.


• 
  

  Data link layer address (source and destination)

  
  
  Responsible for delivering the data link frame from one network interface card (NIC) to another NIC on the same network.

An IP address is the network layer, or Layer 3; logical address used to deliver the IP packet from the original source to the final destination; as shown in Figure 2-5.

The IP packet contains two IP addresses:

• Source IP address- The IP address of the sending device; the original source of the packet.


• Destination IP address- The IP address of the receiving device; the final destination of the packet.

Data Link Layer Addresses

The data link, or Layer 2, physical address(MAC Address) has a different role. The function of the data link address is to deliver the data link frame from one network interface; to another network interface on the same network. This process is illustrated in Figures 2.6

Before an IP packet to be sent over a wired or wireless network; it must be encapsulated in a data link frame so it can be transmitted over the physical medium.

As the IP packet travels from host to router; router to router, and finally router to host; at each point along the way the IP packet is encapsulated in a new data link frame. Each data link frame contains the source data link address of the NIC card sending the frame, and the destination data link address of the NIC card receiving the frame.

The Layer 2, data link protocol is only used to deliver the packet from NIC-to-NIC on the same network. The router removes the Layer 2 information as it is received on one NIC and adds new data link information before forwarding out the exit NIC on its way towards the final destination.

The IP packet is encapsulated in a data link frame that contains data link information, including a:

• 
  

  Source data link layer addresses

  
  
  The physical address of the device’s NIC that is sending the data link frame.


• 
  

  Destination data link layer addresses

  
  
  The physical address of the NIC that is receiving the data link frame. This address is either the next hop router or of the final destination device.

Data Encapsulation , De-encapsulation and Protocol Data Units (PDU),

What is Encapsulation 

Commonly, encapsulation is used for the inclusion of one thing within another thing so that the included thing is not apparent. In networking, encapsulation is the process which includes one data structure within another data structure as a result that the first data structure is hidden for the time being.

As application layer data is passed down the protocol stack on its way to being transmitted across the network media; various protocol information is added at each level and the original data structure is changed. This is known as the encapsulation process.

What is De-encapsulation

Decapsulation is the removal or the making apparent a thing previously encapsulated during the encapsulation process. This process is reversed at the receiving host and is known as de-encapsulation. It is the process used by a receiving device to remove one or more of the protocol headers. The data is de-encapsulated as it moves up the stack toward the end-user application.

Protocol Data Unit (PDU),

The form that a piece of data takes at any layer is called a protocol data unit (PDU). During encapsulation; each succeeding layer encapsulates the PDU; that it receives from the layer above in accordance with the protocol being used. At each stage of the process; a PDU; has a different name to reflect its new functions. The PDUs are named according to the protocols of the TCP/IP suite, as shown below. Figure 2.3 Shows the protocol data unit(PDU) at different layers.

Data - The general term for the PDU used at the application layer and upper layers of the OSI Model.

Segment – This is the transport layer PDU.

Packet – This is the Network layer PDU.

Frame – This is Data Link layer PDU.

Bits - A Physical layer PDU is used when physically transmitting data over the medium.

Figure 2-3 PDU- PDUs at different layers

TCP/IP Communication Process

Figures 2-2 show the complete communication process using an example of a web server transmitting data to a client. This process and these protocols will be covered in more detail in later chapters.

1. Web server is sending data using Hypertext Markup Language (HTML) page to be sent to web clients.

2. The application protocol HTTP header is added to the front of the HTML data. The header contains a variety of information just like IP header, Ethernet header, TCP header as well as the HTTP version the server is using and a status code representing it has information for the web client.

3. The HTTP application layer protocol forwards the HTML-formatted web page data to the transport layer (Layer 4 of the OSI Model). The TCP transport layer protocol is used to handle individual conversations; in this example between the web server and web client.

4. Next, the IP information is added to the front of the  TCP information. IP assigns the appropriate source and destination IP addresses. This information is known as an IP packet.

5. The Ethernet protocol adds information to both ends of the IP packet; known as a data link frame. This frame is delivered to the nearest router along the path towards the web client. This router removes the Ethernet information; analyzes the IP packet; determines the best path for the packet; inserts the packet into a new frame; and sends it to the next neighboring router towards the destination. Each router removes and adds new data link information before forwarding the packet.

6. This data is now transported through the internetwork; which consists of media and intermediary devices.

7. At the receiving end, the client receiving the data link frames that contain the data. Each protocol header is processed and then removed in the opposite order it was added. After removing all headers the user received and see the original data.

OSI Model and TCP/IP Model Comparison

Comparison

The protocols that make up the TCP/IP protocol suite can also be described in terms of the OSI reference model. Network access layer and Application layer of TCP/IP model are further divided In the OSI model describe discrete functions that must occur at these layers.

Network Access layer of TCP/IP model does not specify which protocols to use when transmitting over a physical medium. It only describes the handover from the internet layer to physical layer. On the other hand, OSI Layer physical and data link layer discuss the basic process to access the media and the physical means to send data over a network.

OSI Layer 3

The network layer maps directly to the TCP/IP Internet layer. This layer is used to explain protocols that address and route messages from end to end an internetwork.

OSI Layer 4

The transport layer maps directly to the TCP/IP Transport layer. This layer explains general services and functions that provide ordered and reliable delivery of data between source and destination hosts.

The application layer of the TCP/IP model includes a number of protocols that provide specific functionality to a variety of end-user applications. The OSI Model Layers 5, 6, and 7 are used as references for application software developers and vendors to produce products that operate on networks.

Both the TCP/IP and OSI models are commonly used when referring to protocols at various layers. Because the OSI model separates the data link layer from the physical layer, it is commonly used when referring to these lower layers.

OSI is a generic, protocol-independent standard, acting as a communication gateway between the network and end user.TCP/IP model is based on standard protocols around which the Internet has developed. It is a communication protocol, which allows connection of hosts over a network.

OSI is a reference model around which the networks are built. Generally, it is used as a guidance tool.TCP/IP model is, in a way implementation of the OSI model.

OSI has 7 layers and TCP has 4 Layer model. following is the comparison model of both layer.

 

What is a computer

A computer is a device that accepts information and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. It has also the ability to retrieve and store data.

A computer is a machine, It is also called a PC. it looks like a television. It can show pictures like a TV. Can your TV do any homework for you? NO! but a computer can.

You want to do sums on this machine, you can do so, if your mummy wants to keep information about her monthly expenses, she can also do it, using this machine, IF your Daddy wants to do some office work , he can do it sitting at home just by connecting his PC at home to the PC in his office so does it mean that there is some kind of magic involved in machine for doing such job ? no, not at all, ALL these are the abilities that are built into the computer at the time of its manufacturing.

Types of Computer

Most of the people understand that computer is only in the shape of a personal computer such as a desktop or laptop. but, computers come in many shapes and sizes, and they also perform different functions. When you withdraw cash from an ATM, scan groceries at the store, or use a calculator, all are types of computers. Smart Phone, Smart TV, Game Console and many others are the types of computers. Personal computers come in two different styles,  PCs and Mac. Both are fully functional, but they have a different look and feel.

The PCs begin with the original IBM PC that was introduced in 1981. Other companies began creating similar computers, which were called IBM PC Compatible Today, this is the most common type of personal computer, and it typically includes the Microsoft Windows operating system.

The Macintosh was introduced in 1984, and it was the first widely-sold personal computer with a graphical user interface. All Macs are made by one company (Apple), and they almost always use the Mac OS X operating system.

Desktop Computer

Most of the people used desktop computers in the workplace, home, and school. Desktop computers are designed to be placed on a desk. The desktop computer is made up of different parts, that including the casing, monitor, keyboard, and mouse. The desktop computer is available, one is called desktop and the other is called the tower.

Laptop

The second type of computer, most of the people are familiar with the laptop. The Laptops are battery-powered computers that are more portable than desktops, allowing you to use them almost anywhere.

Tablets

The handheld computers that are even more portable than laptops. Instead of a keyboard and mouse, tablets use a touch-sensitive screen for typing and navigation.

Servers

A server is a computer that provides services to another computer on the same network or remote networks. The computer that a server program runs in is also frequently referred to as a server. That machine may be a dedicated server or used for other purposes as well.