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Networking Basics for Beginners

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NETWORKING BASICS Lesson 1: Introduction Lesson 2: Cable Types Lesson 3: Connector Types Lesson 4: Addressing Lesson 5: Bandwidth Lesson 6: Network Protocols Lesson 7: Network Topologies Lesson 8: Network Models Lesson 9: Network Technologies Lesson 10: Summary 1
Transcript
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Lesson 1:     Introduction

What is a Network?

Linking two or more computing devices together, usually for sharing data (files or folders) or resources (mail servers, file server, printers, Scanners etc.) is popularly known as a Network.

If there are a number of computers at home or in an organization, connecting them together can bring substantial benefits. For example, you can share printers, internet connections and files such as photos or music etc.

Networks are built using both computer hardware and software. Networks can be categorized into different types like LAN, WAN and MAN according to the geographic area they span.LAN

In a Local Area Network (LAN), computers are close together, say, in the same building, home, or an office.

MANIn a Metropolitan Area Network (MAN), computers in the network are spread over just one city or metropolitan area.

WAN

In a Wide Area Network (WAN), computers in the network are far apart and are connected by telephone lines or cables etc to cover entire states, or even across the world. The Internet can be considered as the world's largest public WAN.

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Lesson 2:     Cable Types

What is Network Cabling?

Cable is the medium through which data is transmitted from one network device to another. There are several types of cables, which are commonly used with LANs. The growth of Local Area Networks (LANs) and client server computing has produced a great increase in the amount of cabling used.

In many cases, a network will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Also the common transmission losses such as attenuation have to be taken care of while choosing the type of cable used.

A cable is a group of insulated conductors enclosed within an Insulator. The main function of a cable is transmitting signal from one point to another. They can be broadly categorized into 5 types depending on their attenuation, cost, immunity to EMI, skilled labor required for installation etc.

Given below is the list of cable types used in networking.

1. Coaxial a. RG6 b. RG8 c. RG58 d. RG59

2. Plenum/PVC

3. UTP a. CAT3 b. CAT5/e c. CAT6

4. STP

5. Fiber a. Single-mode b. Multi-mode

Let us learn more about each of these cable types.

What is a Coaxial Cable?

Coaxial cable is commonly used in the cable television industry. This has also gained popularity in use for computer networks, such as Ethernet networks. Coaxial cable is highly resistant to signal interference and can support greater distance between network devices than twisted pair cable.

Coaxial cable consists of a single core copper wire surrounded by an insulator and enclosed in a copper mesh, finally covered inside an outside insulation.

The Coaxial Cable consists of the following types:

RG (Radio Guide) 6: These are high quality and low transmission loss Cables generally used in areas where over-the-air signals may cause interference for Digital Cable and Satellite TV applications.

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RG8: These cables are used in "10base5" "Ethernet" networks because of its great flexibility with low transmission lossesRG58: RG58/U Coaxial Patch Cables are used for ThinNet.

RG59: RG59/U BNC Patch cables are used for video applications such as CCTV, home theatre, and much more.

The main features co-axial cable:

When compared to twist pair cable a coaxial cable can support greater cable lengths between network devices.

They are highly resistant to signal interference.

It costs less that other cables.

Not flexible and it is more difficult to terminate

Plenum/PVC

What is Plenum Cable?

Plenum grade cable is a cable that uses fire resistant material such as Teflon for insulation. This type of material in the insulation minimizes the amount of smoke in case of fire. However, plenum cabling are more expensive and less flexible than a PVC cable. This type of cable is generally used in space reserver for air circulation in air conditioning and heating systems.

PVC

PVC (Polyvinyl Chloride) is a form of plastic, which is widely being used in the manufacture of cable insulation.

The advantages of PVC cables are that they are flexible, and economical. However when it burns, it produces poisonous Halogen gases such as fluorine, chlorine, bromine, and iodine.

Twisted Pairs

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TWISTED PAIR CABLES :The twisting of two insulated wires around each other is known as twisted pair cables. Cables that use twisted pair of wires reduce the Crosstalk between them to a great extent.

As shown in the image, the pair of wires may be surrounded either by a shield, or similar pairs of wires. Each pair is uniquely color coded when packaged in multiple pairs. Different uses such as Analog, Digital, and Ethernet require different pair multiples.

Twisted pair wiring is commonly used to connect telephones and in computer network technology and are classified according to their maximum transmission frequencies. Today, there are basically only two types used and they are Cat3 and Cat5.

Some features of Twisted pair cabling are:

It is flexible and easy to terminate. For Cat 5e/6/7 UTP the maximum segment length is 100 meters.

10BaseT refers to the specifications for unshielded twisted pair cable (Category 3, 4, or 5) carrying Ethernet signals. Category 6 is relatively new and is used for gigabit connections.

Twisted pair cables are available in two variants:

1. Shielded Twisted Pair (STP) and2. Unshielded Twisted pair (UTP)

Let us look into the details of these two variants. STP

Shielded Twisted Pair (STP) :

In STP each of the two copper wires are twisted together and coated with a dielectric insulator which functions as ground for the wires. The extra shielding in STP wiring protects the transmission line from the leaking of electromagnetic interference from and into the cable. STP

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cabling is often used in Ethernet networks, especially fast data rate Ethernets with Speeds in the range of 10 to 1000 Mbps.

The notable features of STP are:

It prevents interference efficiently than UTP, but it is more expensive and difficult to install.

The attenuation of UTP cable is much higher than co-axial or shielded twisted pair cable.

The drawbacks are:

If the metallic shielding is not grounded properly at both ends, the shield behaves as an antenna and picks up unwanted signals.

Because of its cost and difficulty with termination, STP is rarely used in Ethernet networks.

UTP (Cat 3, Cat 5/e, Cat 6)

Unshielded Twisted Pair (UTP) :

UTP using the 10BaseT specification is the most used type of twisted pair cable in Category 5 cabling. In this cable though each individual wire is not insulated, each wire is twisted around each other.The main disadvantage of UTP is that it is more susceptible to electrical noise and interference than other types of networking media, and the signal needs to be boosted at shorter distances than that of coaxial and fiber optic cables. The maximum cable length is 100 meters or 328 feet (10BaseT).Let us see the commonly used types of UTP cabling:

Category 3/Voice is commonly used in 10BaseT networks; it can transmit data at speeds up to 10 Mbps.

Category 5e/Data can transmit data at speeds up to 1000 Mbps (1 Gbps).

Category 6/Data is currently the fastest standard for UTP. Fiber (Single, Multi-mode)

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What is Fiber-Optic Cable?

It is a cabling technology that uses optical fibers to carry digital data signals in the form of modulated pulses of light. The core of fiber-optic cable is made of glass or plastic and the cladding that are enclosed by a protective coating. Outer insulating jacket is made of Teflon or PVC. Kevlar fibers are used to strengthen the cable and prevent from breakages.

A brief overview of the advantages of fiber-optic cable over coaxial and twisted pair:

Speed: Fiber optic networks operate at high speeds in the gigabits range. Bandwidth: High-capacity data transmission.

Distance: Due to lack of attenuation Signals can be transmitted over long distances without using repeaters.

Resistance: Greater resistance to outside interferences such as radios, motors and electromagnetic noise.

Expensive and very fragile.

Let us look at the 2 types of fiber-optic cables.

Single-mode Fiber Optic Cables:

The Single-mode Fiber (SMF) is a single strand of glass fiber with core diameter less than 10 microns and has one mode of transmission.

It carries higher bandwidth of data, approximately 50 times more than Multimode Fiber and has speeds up to 25,000 Gbps on paper.

The SMF is more expensive than the Multimode Fiber Optic Cables and requires a light source with a narrow spectral width for propagation.

These are normally used for local area networks.

Multi-mode Fiber Optic Cables

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Multi-mode fiber (MMF) is made of glass fibers with core diameter in the range of 50 to 100 microns and can carry data of more than 5 Gbps, which equals a million megabits.

It meets the bandwidth needs of the new high performance applications such as Streaming Audio/video, Multimedia, and Networking.

The industry has come up with next generation of fiber optic patch cable, 10 Gigabit (10GigE). The 10 Gigabit fiber which has a 50um fiber core and provides nearly 3 times more bandwidth than the conventional 62.5um fiber optic patch cables. It is typically used in installations up to 2000 meters in length.

These are normally used for wide area networks. RS-232

RS-232 :

RS (Recommended Standard) - 232 is a standard for serial binary data interconnection. It is commonly used in computer serial ports.

RS-232 also has relatively poor control of signal rise and fall times, which leads to crosstalk problems.

RS-232 is good for short connections below 15 meters. Because of the unbalance circuits, RS-232 interface cables are usually not constructed with twisted pair.

The usage of unbalanced circuits is responsible for RS-232 being susceptible to problems due to ground potential shifts among two devices.

Lesson 3:     Connector Types

BNC

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The BNC (British Naval Connector) is a standardized connector used with Thinnet and coaxial cable.

It is used to connect a computer to a coaxial cable in a 10BASE-T Ethernet network. The 10BASE-2 is a 10 MHz baseband cable network extending up to 180 meters the 2 is the rounding up to 200 meters without using a repeater.

The wire in this type of Ethernet is a thin 50-ohm, base-band coaxial cable.

The BNC connector is simpler to use and less expensive than other types of coaxial connectors.

Some of the important components in the BNC family are:

1. The BNC cable connector: It is either soldered or crimped to the end of a cable.2. The BNC T connector: It joins the network interface card in the computer to the network

cable.

3. The BNC barrel connector: It is used to join two lengths of thinnet cable to make one longer length.

4. The BNC terminator: It closes each end of the bus cable to absorb unwanted signals. Without BNC terminators, a bus network will not function.

RJ-45

What does RJ-45 mean?

RJ (Registered Jack)-45 also known as Cat 5e jacks or Cat 5e plugs is the standard connector used for Unshielded Twisted-Pair cable.

It is most commonly used for 10Base-T (10 megabit baseband over twisted-pair copper wire) and 100Base-TX Ethernet connections. Also used in network cabling and in telecommunication applications.

RJ-45 jacks and plugs have 8 pins. It is also referred to as 8P8C connectors. This stands for 8 Position that describes the width 8 Conductor.

AUI

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AUI (Attachment Unit Interface)

AUI is a 15-pin connector that is used to attach coaxial, fiber optic, or twisted pair cables that are found on Ethernet cards.

In a network the AUI is the physical interface between a network card and Ethernet cable.

AUI using a D-shape connector is an interface from a computer to an Ethernet. The AUI Interface that plugs into an AUI cable, which can be up to 50m long is fitted to the computer or the client in a 10Base5 Ethernet installation.

In 10Base-5 Ethernet networks, a short cable is used to connect the AUI with a transceiver on the main cable. In 10Base-2 Ethernet, the NIC connects directly to the Ethernet coaxial cable

ST/SC

ST and SC connectors

There are many types of plugs and sockets available to connect optical fibers; the most common connector used with fiber optic cable are:

ST (Straight Tip) connector: It is barrel shaped and is similar to a BNC connector. SC (Subscriber Connector or Standard Connector): Easier to connect in a confined

space and it is squared faced.

Attaching a connector to an optical fiber takes much effort than copper wire connectors because the ends of the fiber usually have to be carefully cemented and then polished in order to let the

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maximum light pass through.

The SC and ST connectors are field-installable, multimode fiber optic connectors. The ST connector is used only on NICs for fiber optic networks such as 10BaseFL or 100BaseFX

IDC/UDC

What are IDC/UDC connectors?

The Insulation Displacement Connector refers to the way by which the connection is made with the ribbon cable.

UDC connectors are used to terminate 2-pair STP cable; there is no jack (female end) or plug (male end) as it is neutral and both are identical.

The connector and ribbon cable are placed in position and pressed. The pins on the connector are designed to pierce the insulation on the cable and make contact with the wire conductor.

An Insulation Displacement Connector or Universal Data Connector (IDC or UDC) has two rows of 25 pins on 0.1-inch centers.

Lesson 4:     Addressing

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Addressing

What is Network Addressing?

To communicate across a network, terminals within the system should be able to identify one another. An identifier generally is in the form of a name or an address.

All types of networks such as LAN, MAN and WAN use Internet addresses.

An Internet address, mostly referred to as the IP address can be divided into two parts:

Network address. Host address.

The network address part is used for the network identification. The host address is used to identify a node within the network. To form the internet address, a network address is concatenated with a host address and it identifies a node within a network uniquely .

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Internet Address Formats:

Internet address format is an addressing scheme for identifying computers over the internet. Just like postal address uniquely identifies a house, the internet addressing identifies a computer.

The internet address format consists of Network address and host address. There are five internet address classes, each accommodating a different number of network and host addresses.

The five classes are:

1. Class A 001.x.x.x to 126.x.x.x255.0.0.0 used for very large networks.

2. Class B 128.1.x.x to 191.254.x.x255.255.0.0 For medium size networks.

3. Class C 192.0.1.x to 223.255.254.x255.255.255.0 For small networks.

4. Class D 224.x.x.x to 239.255.255.255 used to support multicasting.

5. Class E 240.x.x.x to 247.255.255.25 reserved for future use.

Here the character 'x' is used to denote the numbers ranging from 0 to 255.

Benefit of Network Addressing:

Network addressing basically organizes hosts into groups. This will improve the security by isolating critical nodes and can reduce network traffic by preventing transmissions between the nodes that does not need to communicate. When launching subnetting or supernetting network addressing can become even more useful.

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Lesson 5:  Bandwidth

Bandwidth

What is Bandwidth?

The term bandwidth is used to refer the data transmission capacity of the network. The greater the bandwidth the more the information can be transferred over that network at one time.

In the internet, which is connected by a group of more than one computer, It is the size of each network connection that determines how much bandwidth is available. For example, if you use a DSL connection to connect to the internet, you have 1.5 Mega bits (Mb) of bandwidth. Bandwidth therefore is measured in bits. Bits are grouped into bytes that form text, and other data that is transferred between the computer and internet.

For analog devices, the bandwidth is expressed in cycles per second, or Hertz (Hz) and for digital devices; it is expressed in bits per second (BPS) or bytes per second.

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Lesson 6:     Network Protocols

Network Protocols

Network Protocol Levels:While talking about networking you might have noticed that the word "protocol" is used several times. This is because protocols are the special set of rules that allow computers with dissimilar operating systems, network topologies, hardware, etc. to communicate with each other.Protocols operate at many layers of the network models described below. There are protocols considered to be transport protocols such as TCP and UDP. Other protocols work at the network layer of the OSI network model and some protocols work at several of the network layers.

Protocols can be implemented either in hardware or software, or a mixture of both. Typically, only the lower layers are implemented in hardware, with the higher layers being implemented in software.

Network protocols :

Network communication is defined by network protocols. A network protocol is a set of guidelines that governs how computers communicate over a network. In other words, it is a standard procedure and format that two data communication devices must understand and accept to be able to talk to each other.

The Internet uses a suit of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol). Other popular computer protocols include AppleTalk, used in many Apple Macintosh computers, IPX used on networks made by Novell Corporation, and NetBEUI used in many Microsoft networks.

Let us now see how a network protocol works:

Signals are sent over computer networks in chunks of information called packets. A network packet

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mainly consists of two components.

Header information that includes the network addresses, type of data being sent, and timing information.

Trailing information that includes error-checking information to verify that a packet of information was received correctly

TCP/IP

Overview of TCP/IP Protocol Suite

TCP/IP model was created by the U.S. Department of Defense (DoD). The TCP/IP protocol suite forms the foundation of the Internet. The main protocols in this suite are the TCP and IP protocols that are described below, along with the UDP protocol.

IP - Internet Protocol It is the most basic underlying protocol for communication over the Internet. It provides "Addressing" over the Internet. Just like a postman needs house address to deliver

mail. Internet needs IP address to deliver data (packets) to your computer.

TCP - Transmission Control Protocol

TCP provides connection-oriented reliable transmission of data over a network. It ensures that information that is sent to a destination, reaches the destination. Incase some parts of the information are lost along the way due to network congestion or losses, TCP detects missing parts and re-transmits them.

UDP- User Datagram Protocol

UDP is another important protocol in the TCP/IP protocol suite . It offers best effort (unreliable) delivery of data but has less transmission overhead than TCP.

IPX/SPX (NWLINK)

IPX/SPX

The IPX (Internetwork Packet Exchange/SPX(Sequenced Packet Exchange) protocols were developed by Novell and were used with Novell Netware operating systems to route packets in within a network. IPX is a connectionless datagram-based network protocol and it is the fastest routable protocol, whereas SPX is connection oriented.

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Novell IPX network addresses are unique and are represented in hexadecimal format that consist of two parts:

Network number. Node number.

The IPX network number is 32 bits long. The node number, generally the Media Access Control (MAC) address for one of the system's network interface cards is 48 bits long. IPX/SPX (NWLINK) (Cont...) - Extra Information

The NetWare IPX Packet Header:8 16 bit

ChecksumPacket Length

Transport control Packet TypeDestination Network (4 bytes)

Destination node (6 bytes)Destination socket (2 bytes)

Source network (4 bytes)Source node (6 bytes)

Source socket (2 bytes) Protocol Structure - Novell IPX: Internetwork Packet Exchange Packet Header

Checksum - when this 16-bit field is set to 1s (FFFF) it indicates that the checksum is not used.

Packet length - specifies the length of a complete IPX datagram, in bytes. Packet fragmentation is not allowed in IPX. Packets can be of any length, up to the media maximum transmission unit (MTU) size.

Transport control - indicates the number of routers from which the packet has passed. When the value reaches 16, assuming that a routing loop might be occurring the packet will be discarded.

Packet type- specifies the upper-layer protocol that should receive the packet's information. It has two common values:

o 5- Specifies Sequenced Packet Exchange (SPX). o 17- Specifies NetWare Core Protocol (NCP).

Destination network, Destination node, and Destination socket - Specify destination information.

Source network, Source node, and Source socket - Specify source information.

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NetBEUI

NetBEUI: NetBIOS Enhanced User Interface

NetBEUI is an extended version of NetBIOS that enables the computers to communicate within a LAN. NetBEUI introduces the frame format that was not specified as part of NetBIOS. NetBEUI protocol is often called as NetBIOS frame (NBF) protocol.

NetBEUI works at the Transport and Network layers for LAN. It is the fastest protocol of all. It is a non-routable transport protocol but provides data transportation. For transmission within a single LAN, NetBEUI is a good choice keeping performance in

mind. Its interface must be adapted to other protocols such as IPX or TCP/IP for Internet routing,

Generally, both NetBEUI and TCP/IP are installed in each computer and the server is set up to use NetBEUI for communication within the LAN and TCP/IP for communication beyond the LAN.

NetBIOS and NetBEUI were developed by IBM and have been adopted by Microsoft for its Windows NT, XP and 2000, and Windows for Workgroup products. Novell, Hewlett-Packard and DEC too use it in similar products.

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Lesson 7:     Network Topologies

Network Topologies

Topology refers to the way in which the computers are connected in a network. Each topology is suited for specific tasks and has its own advantages and disadvantages.

The choice of topology is dependent upon the number and type of equipment being used and the cost.

There are 5 major network topologies:

1. Bus2. Ring

3. Mesh

4. Star

5. Hybrid

Bus network

A bus network is set up by connecting all of the nodes to a single line, and the nodes connect only to the bus. However, most bus networks later began to use a specialized central node called a

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"hub" to make the practice of attaching nodes easier. The major disadvantage is that any break in the cable will cause all nodes on the cable to loose connection to the network.

Ring

The easiest way to add more computers into a network is by connecting each computer in series to the next. If a message is intended for a computer is passed, each system bounces it along in sequence until it reaches the destination. By connecting the computers at each end, a ring topology can be formed.

An advantage of the ring is that the number of transmitters and receivers can be cut in half, since a message will eventually loop all of the way around. This potentially results in a doubling of travel time for data, but since it is traveling at a significant fraction of the speed of light, the loss is usually negligible. The major disadvantage is that a single workstation going down can break the entire ring in this topology.

MeshIn a mesh topology, there are at least two nodes with two or more paths between them. This is similar in some ways to a grid network, where a linear or ring topology is used to connect systems in multiple directions. In a true mesh topology (also known as full mesh) every node has a connection to every other node in the network. However, since a full mesh is expensive to implement, partial mesh is more commonly found. The main advantage of mesh topology is that alternate connections or routes exist between nodes incase one does down.

Star

The star topology reduces the chance of network failure by connecting all of the systems to a central node. When applied to a bus-based network, this central hub rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node.

All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected.

Hybrid

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Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not have one of the standard forms.

For example, a tree network connected to a tree network is still a tree network, but two star networks connected together exhibit hybrid network topologies. A hybrid topology is always produced when two different basic network topologies are connected.

Lesson 8:  Network Models

Networking Models

Network Models

Network models provide a standard framework to use when designing complex communication systems.

These models outline standard issues associated with network design and allow the designer to solve each issue separately, modularizing the solution.

A network model is a framework to use, not a concrete method. It is up to the implementers

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to decide which parts of the model are relevant to accomplish their goals.

Different networks can be described functionally as belonging to one of these three broad categories:

1. Peer-to-peer networks,2. Client/server networks, and

3. Wireless.

Let us look into the details of each of these models now.

Peer-to-peer

Peer-to-peer:

Peer-to-peer network is also known as Workgroup. All the computers in a peer-to-peer network acts as both client as well as server. There are no dedicated servers in this type of network. All the computers can act as a resource, providing printers, files or even disk storage to the others. At the same time, all the terminals can work independently, as they have the internal resources like memory, and processing power. Peer-to-peer networks are recommended for small to medium local area networks i.e. networks with 10 or fewer computers.

Advantages of Peer-to-peer Network:

Easy to install and setup costs are relatively low.

Disadvantages of Peer-to-peer network are:

They do not expandability and centralized management. There is no central repository for files and applications.

It does not provide the security as available in a client/server network.

Client-Server

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Client-Server:

The Client/server network model lets the network to centralize the functions and applications in one or more dedicated servers. These servers then become the heart of the system and provide applications and services to other computers in the network. The clients have access to the resources available on the servers. Placing resources on a central server also provides security to the network.Advantages:

Centralized - Resources and data security can be controlled through the server. Interoperability - All components (client/network/server) work together.

Accessibility - Server can be accessed remotely and across multiple Operating systems, such as Windows 95/98, Windows NT, and Macintosh.

Disadvantages:

Maintenance - They can support thousands of clients, hence requires a staff to ensure efficient operation.

Dependence - When server goes down, operations across the network will be affected

Lesson 9:     Network Technologies

Network Technologies

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What are Connectivity Technologies?

There are different types of technologies that connect a computer to other computers through any network, which are known as Connectivity Technologies.

Let us look at the basic types of networks:

1. LAN 2. MAN 3. WAN 4. DSL 5. ISDN 6. Cable 7. Wireless

8. Satellite

LAN

Local Area Networks (LAN):

It is a network of computers and other networking devices that spans a relatively small area. Most LANs are confined to a single building or group of buildings. They are connected using different cabling standards, hardware, and protocols.

A typical LAN setup has a computer with a dedicated CPU of its own and also a computer is designated as the file server. All the related software controlling the network as well as those that can be shared by the computers attached to the network is stored here.

Workstations are the computers connected to the server. However, these workstations are less powerful when compared to the file server, and they are allowed to have additional software on

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their hard drives. There are many different types of LANs Ethernets being the most common for PCs. Most Apple Macintosh networks are based on Apple's AppleTalk network protocol, which is built into Macintosh computers.

LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN MAN (Metropolitan Area Networks )

MAN (Metropolitan Area Networks)

Metropolitan Area Networks (MANs) are networks that connect LANs together within a city.

The main criterion for a MAN is that the connection between LANs is through a local exchange carrier generally the local phone company.

The protocols that are used for MANs are quite different from those used for LANs.

Examples of MAN protocols are:

RS232, V35. Asynchronous Transfer Mode (ATM).

ISDN (Integrated Services Digital Network) PRI and BRI.

XDSL (many different types of Digital Subscriber Lines).

WAN (Wide Area Network)

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WAN (Wide Area Network):

When we need to connect larger geographic areas like two states or few different countries together, we use what is called a Wide Area Network or WAN. This connection can be established over any distance via telephone lines or satellite uplinks.

The main difference between a MAN and a WAN is that the WAN uses cabling or radio waves over long distance. Otherwise the same equipment and protocols are used as a MAN. The main difference between a LAN and WAN is that while LAN typically covers a single office, WAN covers a much wider area.

Using a WAN, an office at New York can communicate with places like Singapore in a matter of minutes, economically. A WAN uses multiplexers to connect local and metropolitan networks to global communication networks like the Internet. To users, however, a WAN will not appear to be much different than a LAN or a MAN.

The Internet can be considered as the world's largest public WAN. DSL

What is DSL?

DSL (Digital Subscriber Line) is the technology that delivers high-speed Internet access to the users across the existing twisted pair telephone lines to transport high-bandwidth data, such as multimedia and video, to service subscribers. In DSL data signals are sent as changes in voltage on the wire. It enables much higher speeds up to 2 Megabits per second.

A DSL modem on the phone line splits the single phone line into two frequencies - one for data and one for voice. This allows simultaneous voice and high-bandwidth data, such as multimedia and video services over a single pair of copper telephone wires.

ISDN

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ISDN

Integrated Services Digital Network (ISDN) is made up of digital telephony and data-transport services that are offered by local telephone carriers.

ISDN often involves digitization of telephone network that allows voice, data, text, graphics, music, video, and any other source material to be transmitted over to any existing telephone wire.

ISDN Adapter is a device that allows a computer to transmit over ISDN lines. ISDN lines are digital telephone lines that are capable of transferring speeds in the range from 57.6K to 128K. They provide two data channels, each having its own phone number that allow simultaneous voice and data as well as higher speed data transfers using both lines for data.

There are two basic types of ISDN service:

1. Basic Rate Interface (BRI): this is the basic service and is intended to meet the needs of most individual users, and

2. Primary Rate Interface (PRI): it is intended for users with greater capacity requirements.

ISDN adapters operate at the Data Link layer of the OSI model. Cable

Cable

in cable transmission a high frequency carrier signal is modulated by data. Cable networking involves distributing the data collected at a central location to users by means of a network of connecting cables such as optical fibers or coaxial cables and broadband amplifiers including a Cable modem.

A Cable modem is a device that is located at the subscriber's end that lets a computer to get connected to the Internet through an existing cable network connection. This does not require a

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phone line like a dial-up connection.

Accessing the Internet using a Cable Network is becoming popular due to greater speed it offers than through telephone-modem access.

Using Cable technology data speeds up to 4Mbps are possible. Wireless

What is Wireless Technology?

The term wireless technology is generally associated with mobile IT equipment like cellular telephones and laptops. It is a method of data transmission, which similar to wired technology. For both these technologies the range of transmission is the prime concern.

The three broad categories of wireless media are:

Radio - The frequency ranges from 3Hz to 300GHz. It is broken into many bands including AM (300-3000 KHz), FM (30�300 MHz), and microwave bands (3-30GHz).

Microwave - These frequencies can further be classified into Terrestrial and Satellite. The frequency usually falls in the range of 4-6GHz or 21-23GHz and the speed is usually between 1-10Mbps. In order to link networks over long distances, microwaves are used. However, two-microwave towers should have a line of sight between them. These signals are usually encrypted for the sake of privacy. The transmission frequencies of Satellite are generally between 11-14GHz with a transmission speed in 1-10Mbps ranges.

Infrared - This is just below the visible range of light ranging between 100Ghz and 1000Thz. In order to transmit the signal, a laser or light emitting diode (LED) is used. Light may interfere with the signal but infrared signals cannot travel through objects.

Wireless networks allow connecting computers without the need of wires or cables. In a wireless network the data may be transmitted over several different types of transmission medium such as microwave, radio, infrared light, or lasers.

The main disadvantages of wireless networking are that data transmission rates are not as high as those attainable through wired networks. Also security is a concern in the wireless medium.

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Page 29: Networking Basics for Beginners

Satellite

Satellite :

A satellite orbits at an altitude of 22,300 miles above the earth, the altitude that cause it to stay in a fixed position relative to the rotation of the earth. This is called as a Geostationary orbit.

In satellite communications a ground station on the earth will send and receive signals from the satellite. The signals will have propagation delays ranging between 0.5 to 5 seconds due to the distances involved. The transmission frequency will normally be in the ranges of 10 to 15 GHz with a transmission speed in the range of 1 to10Mbps. GEOs can cover as much as a third of the earth's surface.

Satellite Internet services can be used in locations where physical Internet access is not available and in devices that move frequently.

Internet access via satellite is available in most parts of the globe, including remote areas like forests and to ships at sea.

Lesson 10:     Summary

To summarize, you have learnt about:

The Types of Cables used for Networking. The Types of Connectors used in Networking.

Network Addressing and Bandwidth.

Network Protocols.

Cabling Network using Twisted Pair, Coaxial, Fiber Optic, RS-232.

Networking Models.

Common Network Technologies available for establishing Internet connectivity.

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