Chapters Of Networking

CHAPTER-1 Networking Basics

Introduction The purpose of the networking guidelines are as follows:   



to assist students in understanding the benefits of networking to help students place in context their current stage of networking development in their school. to assist students in planning the next stage of network development in their school. to provide standard networking ‘models’ and best practice to students that will assist students in their network planning.

1. Basic of Networking A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other. Fig 1 gives an example of a network in a school comprising of a local area network or LAN connecting computers with each other, the internet, and various servers. Broadly speaking, there are two types of network configuration, peer-to-peer networks and client/server networks.

Peer-to-peer networks are more commonly implemented where less then ten computers are involved and where strict security is not necessary. All computers have the same status, hence the term 'peer', and they communicate with each other on an equal footing. Files, such as word processing or spreadsheet documents, can be shared across the network and all the computers on the network can share devices, such as printers or scanners, which are connected to any one computer.

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Fig 1.1: Peer to Peer Networking

Client/server networks are more suitable for larger networks. A central computer, or 'server', acts as the storage location for files and applications shared on the network. Usually the server is a higher than average

Fig 1.2: Client - Server Networking

Table 1 provides a summary comparison between Peer-to-Peer and Client/Server Networks.

Peer-to-Peer Networks vs Client/Server Networks Peer-to-Peer Networks

Client/Server Networks

Easy to set up

More difficult to set up

Less expensive to install

More expensive to install A variety of operating systems can be supported on the client computers,

Can be implemented on a wide but the server needs to run an range of operating systems operating system that supports networking

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More time consuming to

Less time consuming to maintain

maintain the software being used

the software being used (as most of

CHAPTER-2 The OSI model

The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers. The original version of the model defined seven layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that comprise the contents of that path. Two instances at the same layer are visualized as connected by a horizontal connection in that layer. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO), maintained by the identification ISO/IEC 7498-1.

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Layer 1: Physical Layer The physical layer defines the electrical and physical specifications of the data connection. It defines the relationship between a device and a physical transmission medium (for example, an electrical cable, an optical fiber cable, or a radio frequency link). This includes the layout of pins, voltages, line impedance, cable specifications, signal timing and similar characteristics for connected devices and frequency (5 GHz or 2.4 GHz etc.) for wireless devices. It is responsible for transmission and reception of unstructured raw data in a physical medium. It may define transmission mode as simplex, half duplex, and full duplex. It defines the network topology as bus, mesh, or ring being some of the most common. The physical layer of Parallel SCSI operates in this layer, as do the physical layers of Ethernet and other local-area networks, such as token ring, FDDI, ITU-T G.hn, and IEEE 802.11(Wi-Fi), as well as personal area networks such as Bluetooth and IEEE 802.15.4. The physical layer is the layer of low-level networking equipment, such as some hubs, cabling, and repeaters. The physical layer is never concerned with protocols or other such higher-layer items. Examples of hardware in this layer are network adapters, repeaters, network hubs, modems, and fiber media converters. Layer 2: Data Link Layer The data link layer provides node-to-node data transfer—a link between two directly connected nodes. It detects and possibly corrects errors that may occur in the physical layer. It defines the protocol to establish and terminate a connection between two physically connected devices. It also defines the protocol for flow control between them. IEEE 802 divides the data link layer into two sublayers  

Media access control (MAC) layer – responsible for controlling how devices in a network gain access to a medium and permission to transmit data. Logical link control (LLC) layer – responsible for identifying network layer protocols and then encapsulating them and controls error checking and frame synchronization.

The MAC and LLC layers of IEEE 802 networks such as 802.3 Ethernet, 802.11 Wi-Fi, and 802.15.4 ZigBee operate at the data link layer. The Point-to-Point Protocol (PPP) is a data link layer protocol that can operate over several different physical layers, such as synchronous and asynchronous serial lines. The ITU-T G.hn standard, which provides high-speed local area networking over existing wires (power lines, phone lines and coaxial cables), includes a complete data link layer that provides both error correction and flow control by means of a selective-repeat sliding-window protocol. Layer 3: Network Layer The network layer provides the functional and procedural means of transferring variable length data sequences (called datagrams) from one node to another connected to the same "network". A network is a medium to which many nodes can be connected, on which every node has an address and which permits nodes connected to it to transfer messages to other nodes connected to it by merely providing the content of a message and the address of the destination node and letting the network find the way to deliver the message to the destination node,

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possibly routing it through intermediate nodes. If the message is too large to be transmitted from one node to another on the data link layer between those nodes, the network may implement message delivery by splitting the message into several fragments at one node, sending the fragments independently, and reassembling the fragments at another node. It may, but need not, report delivery errors. Message delivery at the network layer is not necessarily guaranteed to be reliable; a network layer protocol may provide reliable message delivery, but it need not do so. A number of layer-management protocols, a function defined in the management annex, ISO 7498/4, belong to the network layer. These include routing protocols, multicast group management, network-layer information and error, and network-layer address assignment. It is the function of the payload that makes these belong to the network layer, not the protocol that carries them. Layer 4: Transport Layer The transport layer provides the functional and procedural means of transferring variable-length data sequences from a source to a destination host via one or more networks, while maintaining the quality of service functions. An example of a transport-layer protocol in the standard Internet stack is Transmission Control Protocol (TCP), usually built on top of the Internet Protocol (IP). The transport layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state- and connection-oriented. This means that the transport layer can keep track of the segments and retransmit those that fail. The transport layer also provides the acknowledgement of the successful data transmission and sends the next data if no errors occurred. The transport layer creates packets out of the message received from the application layer. Packetizing is a process of dividing the long message into smaller messages. OSI defines five classes of connection-mode transport protocols ranging from class 0 (which is also known as TP0 and provides the fewest features) to class 4 (TP4, designed for less reliable networks, similar to the Internet). Class 0 contains no error recovery, and was designed for use on network layers that provide error-free connections. Class 4 is closest to TCP, although TCP contains functions, such as the graceful close, which OSI assigns to the session layer. Also, all OSI TP connection-mode protocol classes provide expedited data and preservation of record boundaries. Detailed characteristics of TP0-4 classes are shown in the following table:[7] Feature name

5

TP0 TP1 TP2 TP3 TP4

Connection-oriented network

Yes

Yes

Yes

Yes

Yes

Connectionless network

No

No

No

No

Yes

Concatenation and separation

No

Yes

Yes

Yes

Yes

Segmentation and reassembly

Yes

Yes

Yes

Yes

Yes

Error recovery

No

Yes

Yes

Yes

Yes

Reinitiate connectiona

No

Yes

No

Yes

No

Multiplexing / demultiplexing over single virtual circuit

No

No

Yes

Yes

Yes

Explicit flow control

No

No

Yes

Yes

Yes

Retransmission on timeout

No

No

No

No

Yes

Reliable transport service

No

Yes

No

Yes

Yes

a

If an excessive number of PDUs are unacknowledged.

An easy way to visualize the transport layer is to compare it with a post office, which deals with the dispatch and classification of mail and parcels sent. Do remember, however, that a post office manages the outer envelope of mail. Higher layers may have the equivalent of double envelopes, such as cryptographic presentation services that can be read by the addressee only. Roughly speaking, tunneling protocols operate at the transport layer, such as carrying non-IP protocols such as IBM's SNA or Novell's IPX over an IP network, or end-to-end encryption with IPsec. While Generic Routing Encapsulation (GRE) might seem to be a network-layer protocol, if the encapsulation of the payload takes place only at endpoint, GRE becomes closer to a transport protocol that uses IP headers but contains complete frames or packets to deliver to an endpoint. L2TP carries PPP frames inside transport packet. Although not developed under the OSI Reference Model and not strictly conforming to the OSI definition of the transport layer, the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite are commonly categorized as layer-4 protocols within OSI. Layer 5: Session Layer The session layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. The OSI model made this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session checkpointing and recovery, which is not usually used in the Internet Protocol Suite. The session layer is commonly implemented explicitly in application environments that use remote procedure calls. Layer 6: Presentation Layer The presentation layer establishes context between application-layer entities, in which the application-layer entities may use different syntax and semantics if the presentation service provides a mapping between them. If a mapping is available, presentation service data units are encapsulated into session protocol data units and passed down the protocol stack.

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This layer provides independence from data representation by translating between application and network formats. The presentation layer transforms data into the form that the application accepts. This layer formats and encrypts data to be sent across a network. It is sometimes called the syntax layer.[8] The original presentation structure used the Basic Encoding Rules of Abstract Syntax Notation One (ASN.1), with capabilities such as converting an EBCDIC-coded text file to an ASCIIcoded file, or serialization of objects and other data structures from and to XML. Layer 7: Application Layer The application layer is the OSI layer closest to the end user, which means both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application-layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication are available.

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Network layer -Provides the same functionality as the physical, the data link and network layers in the OSI model. -Mapping between IP addresses and network physical addresses. -Encapsulation of IP datagrams, e.g packets, in format understandable by the network. Internet layer -Lies at the heart of TCP/IP. -Based on the Internet Protocol (IP), which provides the frame for transmitting data from place A to place B. Transport layer -Based on two main protocols: TCP (Transmission Control Protocol) and UDP (User Datagram protocol) Application layer -Combines the functions of the OSI application, presentation, and session layers. -Protocols involved in this layer: HTTP, FTP, SMTP etc.

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CHAPTER-3 Network Topology

A network topology is the arrangement of a network, including its nodes and connecting lines. There are two ways of defining network geometry: the physical topology and the logical (or signal) topology. The physical topology of a network is the actual geometric layout of workstations. There are several common physical topologies, as described below and as shown in the illustration.

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Figure 3.1 Network Topology BUS In the bus network topology, every workstation is connected to a main cable called the bus. Therefore, in effect, each workstation is directly connected to every other workstation in the network. STAR In the star network topology, there is a central computer or server to which all the workstations are directly connected. Every workstation is indirectly connected to every other through the central computer. RING In the ring network topology, the workstations are connected in a closed loop configuration. Adjacent pairs of workstations are directly connected. Other pairs of workstations are indirectly connected, the data passing through one or more intermediate nodes. TOKEN If a Token Ring protocol is used in a star or ring topology, the signal travels in only one direction, carried by a so-called token from node to node. MESH The mesh network topology employs either of two schemes, called full mesh and partial mesh. In the full mesh topology, each workstation is connected directly to each of the others. In the partial mesh topology, some workstations are connected to all the others, and some are connected only to those other nodes with which they exchange the most data. TREE

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The tree network topology uses two or more star networks connected together. The central computers of the star networks are connected to a main bus. Thus, a tree network is a bus network of star networks. Logical (or signal) topology refers to the nature of the paths the signals follow from node to node. In many instances, the logical topology is the same as the physical topology. But this is not always the case. For example, some networks are physically laid out in a star configuration, but they operate logically as bus or ring networks.

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3.2 CATEGORIES OF NETWORK

One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common types of area networks are:     

LAN - Local Area Network WAN - Wide Area Network WLAN - Wireless Local Area Network MAN - Metropolitan Area Network SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network



CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network PAN - Personal Area Network



LAN and WAN are the two primary and best-known categories of area networks, while the others have emerged with technology advances Note that network types differ from network topologies (such as bus, ring and star). (See also - Introduction to Network Topologies.) LAN: Local Area Network A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet. In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring. WAN: Wide Area Network As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth. A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address.

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A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances. LAN, WAN and Home Networking Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem, and all of the computers on the home network use LAN (so-called private) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central network gateway, typically a broadband router, to reach the ISP. Other Types of Area Networks While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others:  

Wireless Local Area Network - A LAN based on Wi-Fi wireless network technology Metropolitan Area Network - A network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned and operated by a single entity such as a government body or large corporation.



Campus Area Network - A network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus. Storage Area Network - Connects servers to data storage devices through a technology like Fibre Channel. System Area Network (also known as Cluster Area Network) - Links high-performance computers with high-speed connections in a cluster configuration.

 

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3.3 VLAN

A VLAN is a group of devices on one or more LANs that are configured to communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible. VLANs define broadcast domains in a Layer 2 network. A broadcast domain is the set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains are typically bounded by routers because routers do not forward broadcast frames. Layer 2 switches create broadcast domains based on the configuration of the switch. Switches are multiport bridges that allow you to create multiple broadcast domains. Each broadcast domain is like a distinct virtual bridge within a switch. You can define one or many virtual bridges within a switch. Each virtual bridge you create in the switch defines a new broadcast domain (VLAN). Traffic cannot pass directly to another VLAN (between broadcast domains) within the switch or between two switches. To interconnect two different VLANs, you must use routers or Layer 3 switches. See the "Overview of Layer 3 Interfaces" section for information on inter-VLAN routing on Catalyst 4500 series switches. Figure 10-1 shows an example of three VLANs that create logically defined networks.

Figure 3.2 VLAN

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VLANs are often associated with IP subnetworks. For example, all of the end stations in a particular IP subnet belong to the same VLAN. Traffic between VLANs must be routed. You must assign LAN interface VLAN membership on an interface-by-interface basis (this is known as interface-based or static VLAN membership). You can set the following parameters when you create a VLAN in the management domain:

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•

VLAN number

•

VLAN name

•

VLAN type

•

VLAN state (active or suspended)

•

Maximum transmission unit (MTU) for the VLAN

•

Security Association Identifier (SAID)

•

VLAN number to use when translating from one VLAN type to another

CONNECTING DEVICES CONNECTING LANs and VIRTUAL LANs

Hubs             

Active central element of star layout Each station connected to hub by two lines Transmit and receive Hub acts as a repeater When single station transmits, hub repeats signal on outgoing line To each station Line consists of two unshielded twisted pairs Limited to about 100 m High data rate and poor transmission qualities of UTP Optical fiber may be used Max about 500 m Physically star, logically bus Transmission from any station received by all other stations If two stations transmit at the same time, collision

Figure 3.3 HUB

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Bridges         

Ability to expand beyond single LAN Provide interconnection to other LANs/WANs Use Bridge or router Bridge is simpler Connects similar LANs Identical protocols for physical and link layers Minimal processing Router more general purpose Interconnect various LANs and WANs

Functions of a Bridge 

Read all frames transmitted on one LAN and accept those address to any station

on the other LAN  

Using MAC protocol for second LAN, retransmit each frame Do the same the other way round

Figure 3.4 Bridge

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SWITCH In a telecommunications network, a switch is a device that channels incoming data from any of multiple input ports to the specific output port that will take the data toward its intended destination. In the traditional circuit-switched telephone network, one or more switches are used to set up a dedicated though temporary connection or circuit for an exchange between two or more parties. On an Ethernet local area network (LAN), a switch determines from the physical device (Media Access Control or MAC) address in each incoming message frame which output port to forward it to and out of. In a wide area packet-switched network such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination.

Figure 3.5 Switch

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HUB VS SWITCH

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Routers Routers are small electronic devices that join multiple computer networks together via either wired or wireless connections. How Routers Work In technical terms, a router is a Layer 3 network gateway device, meaning that it connects two or more networks and that the router operates at the network layer of the OSI model. Routers contain a processor (CPU), several kinds of digital memory,and input-output (I/O) interfaces. They function as special-purpose computers, one that does not require a keyboard or display. The router's memory stores an embedded operating system (O/S). Compared to general-purpose OS products like Microsoft Windows or Apple Mac OS, router operating systems limit what kind of applications can be run on them and also need much smaller amounts of storage space. Examples of popular router operating systems include Cisco Internetwork Operating System (IOS) and DD-WRT. These operating systems are manufactured into a binary firmware image and are commonly called router firmware. By maintaining configuration information in a part of memory called the routing table, routers also can filter both incoming or outgoing traffic based on the addresses of senders and receivers. Routers for Business Networks and the Internet Before home networking became popular, routers could be found only the closets of businesses and schools.Each cost thousands of dollars and required special technical training to set up and manage. The largest and most powerful network routers form the Internet backbone. These routers must manage many terabits of data flowing through and between Internet Service Provider (ISP) networks

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Figure 3.6 Router

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REPEATERS

A repeater is a network device that is used to regenerate or replicate signals that are weakened or distorted by transmission over long distances and through areas with high levels of electromagnetic interference (EMI). The purpose of a repeater is to extend the LAN segment beyond its physical limits (e.g. Ethernet is 500m for 10Base5). It is a simple hardware device that moves all packets from one local area network segment to another. The main purpose of a repeater is to extend the length of the network transmission medium beyond the normal maximum cable lengths. Typically, repeaters are used to connect two physically close buildings together (when they are too far apart to just extend the segment). They can be used to connect floors of a building that would normally surpass the maximum allowable segment length. Repeaters operate at the physical layer, i.e., the bottom layer of the seven-layer OSI reference model. They can only operate on the same type of physical layer, i.e., tthernet-to-tthernet, or token ring-to-token ring. They can connect 10Base5 to 10BaseT because they both use the same 802.3 MAC layer. Because repeaters provide no isolation between segments, and the repeater is transparent to both sides of the segment, both sides of the repeater appear as one long network segment. Analog repeaters frequently can only amplify signals. Digital repeaters can additionally reconstruct signals to close to their original quality. In a data network, a repeater can relay messages between subnetworks that use different protocols or cable types. Hubs can operate as repeaters by relaying messages to all connected computers. A repeater cannot perform the intelligent routing performed by bridges and routers, because it only repeats the signals without understanding the packets, including their sources and destinations. Unlike bridges and switches, repeaters do not have physical addresses on the network. It is not permitted to create a loop between two network segments by using two repeaters. Repeaters provide a simple way to solve the Ethernet distance limitations, but they have some disadvantages. For example, if numerous collisions are occurring in one part of the network, they will be forwarded to other parts of the network. A hub is essentially a repeater that has multiple ports (i.e., connection points) and can connect more than two network segments.

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Figure 3.7 Repeaters

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CHAPTER-4 TRANSMISSION MEDIA 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. An electrical signal is in the form of current. An electromagnetic signal is series of electromagnetic energy pulses at various frequencies. These signals can be transmitted through copper wires, optical fibers, atmosphere, water and vacuum Different Medias have different properties like bandwidth, delay, cost and ease of installation and maintenance. Transmission media is also called Communication channel. Types of Transmission Media Transmission media is broadly classified into two groups. 1. Wired or Guided Media or Bound Transmission Media 2. Wireless or Unguided Media or Unbound Transmission Media

Wired or Guided Media or Bound Transmission Media: Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. Popular bound transmission mediain use are twisted pair cable, co-axial cable and fiber optical cable. Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc. Wireless or Unguided Media or Unbound Transmission Media: Unbound transmission media are the ways of transmitting data without using any cables. These media are not bounded by physical geography. This type of transmission is called Wireless communication. Nowadays wireless communication is becoming popular. Wireless LANs are being installed in office and college campuses. This transmission uses Microwave, Radio wave, Infra red are some of popular unbound transmission media.

Figure 4.1 Transmission Medium

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The data transmission capabilities of various Medias vary differently depending upon the various factors. These factors are: TWISTED PAIR A type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. While twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable, most networks contain some twisted-pair cabling at some point along the network. Other types of cables used for LANs include coaxial cablesand fiber opticcables.

Figure 4.2 TWISTED PAIR

COAXIAL CABLE

Coaxial cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses. Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along 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.

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Coaxial cable is sometimes used by telephone companies from their central office to the telephone poles near users. It is also widely installed for use in business and corporation Ethernet and other types of local area network. Depending upon the carrier's technology and other factors, twisted pair copper wire and optical fiber may be used instead of coaxial cable. Coaxial cable was invented in 1880 by English engineer and mathematician Oliver Heaviside, who patented the invention and design that same year. AT&T established its first crosscontinental coaxial transmission system in 1940. See also: coaxial cable (illustrated) A coaxial cable, sometimes called a coax cable, provides an interference-free transmission path for high-frequency electrical signals. Coax cables were once prevalent in computers, but were replaced by digital links, such as Ethernet and other types of local area network cabling. Coaxial cables are used by telcos to carry signals from a central office to telephone poles and by cable TVproviders for service in communities. Twisted pair copper wire and optical fiber may be used instead of coaxial cable. Coax cables have concentric layers of electrical conductors and insulating material. This construction ensures that signals are enclosed within the cable and prevents electrical noise from interfering with the signal. It also yields the name "coaxial," referring to its two physical channels running along the same axis. The center layer is a thin conducting wire, either solid or braided copper. A dielectric layer, made up of an insulating material with very well-defined electrical characteristics, surrounds the wire. A shield layer then surrounds the dielectric layer with metal foil or braided copper mesh. The whole assembly is wrapped in an insulating jacket. The outer metal shield layer

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of the coax cable is typically grounded in the connectors at both ends to shield the signals, and as a place for stray interference signals to dissipate. A key to coaxial cable design is tight control of cable dimensions and materials. Together, they ensure that the characteristic impedance of the cable takes on a fixed value. High-frequency signals are partially reflected at impedance mismatches, causing errors. Characteristic impedance is sensitive to signal frequency. Above 1 GHz, the cable maker must use a dielectric that doesn't attenuate the signal too much, or change the characteristic impedance in a way that creates signal reflections. Vendor specs should provide guidance. Electrical characteristics of coax are application dependent and crucial to good performance. Two standard characteristic impedances are 50 Ohm, used in moderate power environments, and 75 Ohm, common for connections to antennas and residential installations. Simple coax cables carry only one connection. There are variations, such as twinax, that place multiple connectors at the center and take advantage of transmission line properties to pass the signal. Applications sometimes bundle multiple separate coax cables inside a protective plastic outer layer applied to prevent mechanical damage. Connectors for coax range from simple single connectors used on cable TV systems to complicated combinations of multiple thin coax links, mixed with power and other signal connections, housed in semi-custom bodies. These are commonly found in military electronics and avionics. Mechanical stiffness can vary tremendously, depending on the internal construction and intended use of the coaxial cabling. For example, high-power cables are often made with thick insulation and are very stiff. Some cables are deliberately made with thick center wires, resulting in skin-effect resistance. It results from high-frequency signals traveling on the surface of the conductor, not throughout. If the center conductor is larger, it results in a stiff cable with low loss per meter.

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Coaxial cable was invented and patented in 1880 by English engineer and mathematician Oliver Heaviside. AT&T established its first cross-continental coaxial transmission system in 1940.

OPTICAL FIBERS Fiber optics, or optical fiber, refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic strand or fiber. A fiber optic cable can contain a varying number of these glass fibers -- from a few up to a couple hundred. Surrounding the glass fiber core is another glass layer called cladding. A layer known as a buffer tube protects the cladding, and a jacket layer acts as the final protective layer for the individual strand RADIOWAVES Radio waves are part of a larger group of waves classified all together as electromagnetic radiation. This large group of waves is broken down into smaller groups based upon their frequencies and wavelengths. Two examples of electromagnetic radiation (other than radio waves) are:  

Light -- which is the group of electromagnetic radiation you can see with your eyes X-rays -- which are a group from a higher frequency and they are what is used by doctors to see inside of you

MICROWAVES The virtualized network poses challenges to network management systems -- and as more hardware components become virtualized, that challenge becomes even greater. This handbook discusses the steps IT must take to both build and corral their virtualized infrastructure. Start Download Microwave signals propagate in straight lines and are affected very little by the troposphere. They are not refracted or reflected by ionized regions in the upper atmosphere. Microwave beams do not readily diffract around barriers such as hills, mountains, and large human-made structures. Some attenuation occurs when microwave energy passes through trees and frame

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houses. Radio-frequency (RF) energy at longer wavelengths is affected to a lesser degree by such obstacles. The microwave band is well suited for wirelesstransmission of signals having large bandwidth. This portion of the RF electromagnetic radiation spectrum encompasses many thousands of megahertz. Compare this with the so-called shortwave band that extends from 3 MHz to 30 MHz, and whose total available bandwidth is only 27 MHz. In communications, a large allowable bandwidth translates into high data speed. The short wavelengths allow the use of dish antennas having manageable diameters. These antennas produce high power gain in transmitting applications, and have excellent sensitivity and directional characteristics for reception of signals.

INFRARED

Infrared radiation is a type of electromagnetic radiation, as are radio waves, ultraviolet radiation, X-rays and microwaves. Infrared (IR) light is the part of the EM spectrum that people encounter most in everyday life, although much of it goes unnoticed. It is invisible to human eyes, but people can feel it as heat. IR radiation is one of the three ways heat is transferred from one place to another, the other two being convection and conduction. Everything with a temperature above about 5 degrees Kelvin (minus 450 degrees Fahrenheit or minus 268 degrees Celsius) emits IR radiation. The sun gives off half of its total energy as IR, and much of its visible light is absorbed and re-emitted as IR, according to the University of Tennessee. According to the Environmental Protection Agency, incandescent bulbs convert only about 10 percent of their electrical energy input into visible light energy; about 90 percent is converted to infrared radiation. Household appliances such heat lamps and toasters use IR radiation to transmit heat, as do industrial heaters such as those used for drying and curing materials. These appliances generally emit blackbody radiation with a peak energy output below the wavelength of visible, though some energy is emitted as visible red light. A TV remote control uses IR waves to change channels. In the remote, an IR light-emitting diode (LED) or laser sends out binary coded signals as rapid on/off pulses, according to NASA. A detector in the TV converts these light pulses to electrical signals that instruct a microprocessor to change the channel, adjust the volume or perform other actions. IR lasers can be used for point-to-point communications over distances of a few hundred meters or yards.

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1. Bandwidth. It refers to the data carrying capacity of a channel or medium. Higher bandwidth communication channels support higher data rates. 2. Radiation. It refers to the leakage of signal from the medium due to undesirable electrical characteristics of the medium. 3. Noise Absorption. It refers to the susceptibility of the media to external electrical noise that can cause distortion of data signal. 4. Attenuation. It refers to loss of energy as signal propagates outwards. The amount of energy lost depends on frequency. Radiations and physical characteristics of media contribute to attenuation.

Figure 4.2 Types of frequency bands

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CHAPTER-5 MULTIPLEXING

Networks use multiplexing for two reasons: To make it possible for any network device to talk to any other network device without having to dedicate a connection for each pair. This requires shared media; To make a scarce or expensive resource stretch further -- e.g., to send many signals down each cable or fiber strand running between major metropolitan areas, or across one satellite uplink. In analog radio transmission, signals are commonly multiplexed using frequency-division multiplexing (FDM), in which the bandwidth on a communications link is divided into subchannels of different frequency widths, each carrying a signal at the same time in parallel. Analog cable TV works the same way, sending multiple channels of material down the same strands of coaxial cable. Similarly, in some optical networks, data for different communications channels are sent on lightwaves of different wavelengths, a variety of multiplexing called wave-length division multiplexing (WDM). These techniques are all basically use the same concept. FDM describes fields that traditionally discuss frequencies (like radio and television broadcasting). WDM is used in fields that traditionally talk about wavelengths, like telecommunications and computer networks that use laser systems (which generate the signals sent over fiber opticcables). Variations include coarse WDM (CWDM) and dense WDM (DWDM), which put relatively fewer or more channels of information, respectively, on the medium at the same time. Other variations use light polarization to multiplex. In digital transmission, signals are commonly multiplexed using time-division multiplexing(TDM), in which the multiple signals are carried over the same channel in

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alternating time slots. For example, TDM is used on SONET links that used to be a mainstay of enterprise WAN and Internet connectivity. Code Division Multiplexing (CDM) uses identifying codes to distinguish one signal from another on a shared medium. Each signal is assigned a sequence of bits called the spreading code that is combined with the original signal to produce a new stream of encoded data; a receiver that knows the code can retrieve the original signal by subtracting out the spreading code (a process called dispreading). CDM is widely used in digital television and radio broadcasting and in 3G mobile cellular networks. Where CDM allows multiple signals from multiple sources, it is called Code-Division Multiple Access (CDMA).

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5.1 TYPES OF MULTIPLEXING The different types of multiplexing technologies are as below        

Wavelength Division Multiplexing (WDM) Frequency Division Multiplexing (FDM) Dense Wavelength Division Multiplexing (DWDM) Conventional Wavelength Division Multiplexing (CWDM) Reconfigurable Optical Add-Drop Multiplexer (ROADM) Orthogonal Frequency Division Multiplexing (OFDM) Add/Drop Multiplexing (ADM) Inverse Multiplexing (IMUX)

Frequency Division Multiplexing Frequency Division Multiplexing is a technique which uses various frequencies to combine many streams of data for sending signals over a medium for communication purpose. It carries frequency to each data stream and later combines various modulated frequencies to transmission.Television Transmitters are the best example for FDM, which uses FDM to broad cast many channels at a time. Wavelength Division Multiplexing Wavelength Division Multiplexing (WDM) is analog multiplexing technique and it modulates many data streams on light spectrum. This multiplexing is used in optical fiber. It is FDM optical equivalent.Various signals in WDM are optical signal that will be light and were transmitted through optical fiber.WDM similar to FDM as it mixes many signals of different frequencies into single signal and transfer on one link.Wavelength of wave is reciprocal to its frequency, if wavelength increase then frequency decreases.Several light waves from many sources are united to get light signal which will be transmitted across channel to receiver.

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Wavelength Division Multiplexing The main principle in using prisms is that they bend a light beam depending on angle of incidence and frequency of light wave or ray. At receiver end the light signal is split into different light waves by demux. This type of merging and breaking of light wave made by a prism. Single prism is used at the end of sender for multiplexing and other prism is used at receiver end for demultiplexing as shown in fig.

Figure 5.2 Usage of PRISM in WDM WDM used in Synchronous Optical Network (SONET). It utilizes various optical fiber lines that are multiplexed and demultiplexed. Time Division Multiplexer TDM is one of types of multiplexers which join data streams by allotting every stream different time slot in a set. It frequently transfers or sends various time slots in an order over one transmission channel. TDM attaches PCM data streams.

Figure 5.3 Time Division Multiplexer Dense Wavelength Division Multiplexer In Dense Wavelength Division Multiplexing, an optical technology used to expand bandwidth onto fiber optic. Bit rate and protocol are independent and these are the main advantage of DWDM. Dense Wavelength Division Multiplexing (DWDM) operated by combining different signals simultaneously at different wavelengths. On fiber is changed to multiple fibers. By increasing the carrier capacity of fiber from 2.5Gb/s to 20 Gb/s, an eight OC 48 signals can be multiplexed into single fiber.Single fibers are able to transfer data at a speed upto 400 GB/s due

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to DWDM.DWDM transfers data or information in IP, SONET, ATM and Ethernet It also carries different type of traffic at a range of speeds on an optical channel.

Figure 5.4 Dense Wavelength Division Multiplexer Statistical Multiplexer It allows to share a single line of data for multiplexer RS-232 devices. Error correction will be performed in order to ensure the transmission an error-free one. The word “Statistical” refers to its capability to receive advantage of statics of many RS-232 devices means terminal and PC users.Each PC averages less than 5% of its potential data rate. This type of multiplexer permits the sum of terminal and PC rates in which it extends composite link speed between multiplexers. This is due the reason that the keyboards are idle. These types of multiplexers requires buffer.

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CHAPTER-6 NETWORK SECURITY (i) TYPES OF ATTACKS:

Figure 6.1 Types of Attacks (a) Spoofing : Spoofing is a type of scam where an intruder attempts to gain unauthorized access to a user's system or information by pretending to be the user. The main purpose is to trick the user into releasing sensitive information in order to gain access to one's bank account, computer system or to steal personal information, such as passwords. BREAKING DOWN 'Spoofing' There are several kinds of spoofing including email, caller ID, and uniform resource locator (URL) spoof attacks.

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Email spoofing (or phishing), used by dishonest advertisers and outright thieves, occurs when email is sent with falsified “From:” entry to try and trick victims that the message is from a friend, their bank, or some other legitimate source. Any email that claims it requires your password or any personal information could be a trick. In a caller ID attack, the spoofer will falsify the phone number he/she is calling from. URL spoofing is when scammers set up a fraudulent website to obtain information from victims or to install viruses on their computers. For instance, targets might be directed to a site that looks like it’s from their credit card company and be asked to log in. If one falls for it and actually logs in, the scammer could then log onto the real site and commit mishap by using the account information the victim used to log in. (For more, see: 6 Ways To Protect Yourself From Cybercrime) Be extremely cautious whenever you receive a message asking for personal information and only download files from trusted sources. Install firewalls to block suspicious inquiries and keep antivirus software installed and up-to-date on any computer you use. If you get an inquiry seeking personal information, don’t provide it. Hang up (or log off) and then independently look up the phone number or customer service email address from the entity purportedly contacting you for your personal information. If you think you’ve been spoofed, contact the FCC at 1-888CALL-FCC or via email at www.fcc.gov/complaints.

(b) Cyber Attack : A cyberattack is any type of offensive manoeuvre employed by nation-states, individuals, groups, or organizations that targets computer information systems, infrastructures, computer networks, and/or personal computer devices by various means of malicious acts usually originating from an anonymous source that either steals, alters, or destroys a specified target by hacking into a susceptible system.[1] These can be labelled as either a cyber campaign, cyberwarfare or cyberterrorism in different context. Cyberattacks can range from installing spyware on a PC to attempts to destroy the infrastructure of entire nations. Cyberattacks have become increasingly sophisticated and dangerous as the Stuxnetworm recently demonstrated.[2] User behavior analytics and SIEM are used to prevent these attacks. Legal experts are seeking to limit use of the term to incidents causing physical damaage, distinguishing it from the more routine data breaches and broader hacking activities.

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CHAPTER-7 FIREWALL

Figure 7.1 Firewall

A firewall is a network security device that monitors incoming and outgoing network traffic and decides whether to allow or block specific traffic based on a defined set of security rules. Firewalls have been a first line of defense in network security for over 25 years. They establish a barrier between secured and controlled internal networks that can be trusted and untrusted outside networks, such as the Internet. A firewall can be hardware, software, or both. 7.1 TYPES OF FIREWALL Proxy firewall An early type of firewall device, a proxy firewall serves as the gateway from one network to another for a specific application. Proxy servers can provide additional functionality such as content caching and security by preventing direct connections from outside the network. However, this also may impact throughput capabilities and the applications they can support. Stateful inspection firewall Now thought of as a “traditional” firewall, a stateful inspection firewall allows or blocks traffic based on state, port, and protocol. It monitors all activity from the opening of a connection until it is closed. Filtering decisions are made based on both administrator-defined rules as well as context, which refers to using information from previous connections and packets belonging to the same connection.

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Unified threat management (UTM) firewall A UTM device typically combines, in a loosely coupled way, the functions of a stateful inspection firewall with intrusion prevention and antivirus. It may also include additional services and often cloud management. UTMs focus on simplicity and ease of use. See our UTM devices. Next-generation firewall (NGFW) Firewalls have evolved beyond simple packet filtering and stateful inspection. Most companies are deploying next-generation firewalls to block modern threats such as advanced malware and application-layer attacks.

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According to Gartner, Inc.’s definition, a next-generation firewall must include: Standard firewall capabilities like stateful inspection

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Integrated intrusion prevention

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Application awareness and control to see and block risky apps

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Upgrade paths to include future information feeds

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Techniques to address evolving security threats While these capabilities are increasingly becoming the standard for most companies, NGFWs can do more. Threat-focused NGFW These firewalls include all the capabilities of a traditional NGFW and also provide advanced threat detection and remediation. With a threat-focused NGFW you can:

    

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Know which assets are most at risk with complete context awareness Quickly react to attacks with intelligent security automation that sets policies and hardens your defenses dynamically Better detect evasive or suspicious activity with network and endpoint event correlation Greatly decrease the time from detection to cleanup with retrospective security that continuously monitors for suspicious activity and behavior even after initial inspection Ease administration and reduce complexity with unified policies that protect across the entire attack continuum

CHAPTER-8 BLUETOOTH

Figure 8.1 Bluetooth Bluetooth is a radio communication technology that enables low-power, short distance wireless networking between phones, computers and other network devices. The name Bluetooth is borrowed from King Harald Gormsson of Denmark who lived more than 1,000 years ago. The king's nickname meant "bluetooth," supposedly because he had a dead tooth that looked blue. The Bluetooth logo is a combination of the two Scandinavian runes for the King's initials. Using Bluetooth Bluetooth technology was designed primarily to support networking of portable consumer devices and peripherals that run on batteries, but Bluetooth support can be found in a wide range of devices including:      

Cell phones Wireless headsets (including hands-free car kits) Wireless keyboards Printers Wireless speakers Computers

How Bluetooth Works Two Bluetooth devices connect to each other by a process called pairing. When you press a button or select a menu option on the unit, a Bluetooth device initiates a new connection. Details vary depending on the type of device. Here are some examples:  

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How to Pair or Connect a Bluetooth Device to the iPad Bluetooth Car Kits

 

Pairing a Bluetooth Headphone With a Phone How to Pair Your Laptop With Bluetooth Devices

Many mobile devices have Bluetooth radios embedded in them. PCs and other devices can also be enabled through the use of Bluetooth dongles. Bluetooth networks feature a dynamic topology called a piconet, which contains a minimum of two and a maximum of eight Bluetooth peer devices. Devices communicate using network protocols that are part of the Bluetooth specification. The Bluetooth standards have been revised over many years starting with version 1.0 (not widely used) and 1.1 on up to version 5. Radio signals that are transmitted with Bluetooth cover only short distances, typically up to 30 feet until the most recent standard. Bluetooth was originally designed for lower-speed wireless connections, although technology advancements over the years have increased its performance considerably. Early versions of the standard supported connections below 1 Mbps while modern versions are rated up to 50 Mbps. Bluetooth vs. Wi-Fi Although Bluetooth utilizes the same standard signal range as conventional Wi-Fi, it cannot provide the same level of wireless connectivity. Compared to Wi-Fi, Bluetooth networking is slower, more limited in range and supports fewer peer devices. Bluetooth Security As with other wireless protocols, Bluetooth has received its fair share of scrutiny over the years for network security weaknesses. Popular television dramas sometimes feature criminals pairing their Bluetooth phone to an unsuspecting victim's, where the criminal can then eavesdrop on conversations and steal private data. In real life, of course, these attacks are highly unlikely to happen and sometimes even not possible in the way they are portrayed. While Bluetooth technology incorporates its fair share of security protections, security experts recommend turning off Bluetooth on a device when not using it to avoid any small risk that exists.

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CHAPTER-9 WI-FI

Wi-Fi is the name of a popular wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections. A common misconception is that the term Wi-Fi is short for "wireless fidelity," however this is not the case. Wi-Fi is simply a trademarked phrase that means IEEE 802.11x.

Figure 9.1 Wi-fi How Wi-Fi Networks Works Wi-Fi networks have no physical wired connection between sender and receiver by using radio frequency (RF) technology -- a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space. The cornerstone of any wireless network is an access point (AP). The primary job of an access point is to broadcast a wireless signal that computers can detect and "tune" into. In order to connect to an access point and join a wireless network, computers and devices must be equipped with wireless network adapters. The Wi-Fi Alliance The Wi-Fi Alliance, the organization that owns the Wi-Fi registered trademark term specifically defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards." Initially, Wi-Fi was used in place of only the 2.4GHz 802.11b standard, however the Wi-Fi Alliance has expanded the generic use of the Wi-Fi term to include any type of network

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or WLAN product based on any of the 802.11 standards, including 802.11b, 802.11a, dual-band and so on, in an attempt to stop confusion about wireless LANinteroperability. Wi-Fi Support in Applications and Devices Wi-Fi is supported by many applications and devices including video game consoles, home networks, PDAs,mobile phones, major operating systems, and other types of consumer electronics. Any products that are tested and approved as "Wi-Fi Certified" (a registered trademark) by the Wi-Fi Alliance are certified as interoperable with each other, even if they are from different manufacturers. For example, a user with a Wi-Fi Certified product can use any brand of access point with any other brand of client hardware that also is also "Wi-Fi Certified". Products that pass this certification are required to carry an identifying seal on their packaging that states "Wi-Fi Certified" and indicates the radio frequency band used (2.5GHz for 802.11b, 802.11g, or 802.11n, and 5GHz for 802.11a).

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CHAPTER-10 BLUETOOTH VS WI-FI Bluetooth and Wi-Fi are both methods that provide wireless communication, but the difference between the two mainly stems from what they are designed to do and how they are used. The main difference is that Bluetooth is primarily used to connect devices without using cables, while Wi-Fi provides high-speed access to the internet.

Bluetooth is a wireless technology standard that is used to exchange data over short distances (less than 30 feet), usually between personal mobile devices. This means that a Bluetoothenabled device such as a smartphone is able to communicate with other Bluetooth devices, such as a wireless headset, MP3 player or printer. Bluetooth, therefore, acts much like a cord between the two devices by creating a secure, wireless personal area network in which these devices can communicate. Bluetooth has a wide variety of applications, and has boosted the convenience and functionality of portable devices by providing a simple way for them to interact with other Bluetooth-enabled devices. Bluetooth is considered a proprietary protocol because device manufacturers must license a number of patents in order to make and market a Bluetooth device. (Read about a different Bluetooth standard that emerged in 2011 in From Bluetooth to New Tooth: A Look at Bluetooth 4.0.) Wi-Fi has some similar applications to Bluetooth, such as setting up a network or printing and transferring files. It is also a wireless standard, but rather than being designed to communicate between devices, it serves to wirelessly connect devices to the internet or Ethernet networks such as a corporate local area network (LAN). Its range is quite a bit larger than the very short range within which Bluetooth devices communicate, as a Wi-Fi signal can be accessed up to 300 feet away. This means that a Wi-Fi-enabled device, such as a PC or smartphone, can connect to the internet wirelessly when in a Wi-Fi "hotspot," or area in which a Wi-Fi signal may be accessed.

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(For more on the different types of Wi-Fi out there, see 802.What? Making Sense of the 802.11 Family.) This hotspot can be a small area such as a single room, or may cover several miles if hotspots are allowed to overlap. Wi-Fi is a trademark name used to refer to devices that employ IEEE 802.11 standards. Product manufacturers must complete Wi-Fi interoperability certification testing, as conducted by the Wi-Fi Alliance, in order to label devices as Wi-Fi devices. Wi-Fi is available in most devices, and Wi-Fi hotspots continue to proliferate across companies, university campuses, restaurants, airports and other public locations.

Figure 10.1 Bluetooth vs wi-fi

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