COMPUTER SYSTEMS SERVICING COMPETENCY-BASED LEARNING MATERIALS

List of Competencies

GENERAL

1) Certification - Is the process of verifying and validating the competencies of a person through assessment.

2) Certificate of Competency (COC) – Is a certification issued to individuals who pass the assessment for a single unit or cluster of units of competency.

3) Common Competencies - Are the skills and knowledge needed by all people working in a particular industry.

4)  Competency - Is the possession and application of knowledge, skills and    attitudes to perform work activities to the standard expected in the workplace.

5)  Competency Assessment - Is the process of collecting evidence and making judgments on whether competency has been achieved.

6) Competency   Standard (CS) -   Is   the   industry-determined   specification   of competencies required for effective work performance.

7)  Context of Assessment - Refers to the place where assessment is to be conducted or carried out.

8)   Core Competencies -   Are the specific skills and knowledge needed in a particular area of work - industry sector/occupation/job role.

9)  Critical aspects of competency - Refers to the evidence that is essential for successful performance of the unit of competency.

10) Elective Competencies - Are the additional skills and knowledge required by the individual or enterprise for work.

11)  Elements - Are the building blocks of a unit of competency. They describe in outcome terms the functions that a person performs in the workplace.

12) Evidence Guide - Is a component of the unit of competency that defines or identifies the evidences required to determine the competence of the individual.   It provides information on critical aspects of competency, underpinning knowledge, underpinning skills, resource implications, assessment method and context of assessment.

13) Level - Refers to the category of skills and knowledge required to do a job.

14)  Method of Assessment - Refers to the ways of collecting evidence and when, evidence should be collected.

15) National Certificate (NC) – Is a certification issued to individuals who achieve all the required units of competency for a national qualification defined under the Training Regulations.  NCs are aligned to specific levels within the PTQF.

16)  Performance Criteria - Are evaluative statements that specify what is to be assessed and the required level of performance.

17) Qualification - Is a cluster of units of competencies that meets job roles and is significant in the workplace.    It is also a certification awarded to a person on successful   completion   of   a   course   in   recognition   of   having   demonstrated competencies in an industry sector.

18) Range of Variables - Describes the circumstances or context in which the work is to be performed.

19) Recognition of Prior Learning (RPL) – Is the acknowledgement of an individual’s skills, knowledge and attitudes gained from life and work experiences outside registered training programs.

20)  Resource Implications   - Refers to the resources needed for the successful performance of the work activity described in the unit of competency.   It includes work environment and conditions, materials, tools and equipment.

21)  Basic Competencies - Are the skills and knowledge that everyone needs for work.

22) Training Regulations (TR) – Refers to the document promulgated and issued by TESDA consisting of competency standards, national qualifications and training guidelines for specific sectors/occupations.  The TR serves as basis for establishment of qualification and certification under the PTQF.   It also serves as guide for development of competency-based curricula and instructional materials including registration of TVET programs offered by TVET providers.

23)  Underpinning Knowledge - Refers to the competency that involves in applying knowledge to perform work activities.    It includes specific knowledge that is essential to the performance of the competency.

24) Underpinning Skills - Refers to the list of the skills needed to achieve the elements and performance criteria in the unit of competency.  It includes generic and industry specific skills.

25) Unit of Competency – Is a component of the competency standards stating a specific key function or role in a particular job or occupation; it is the smallest component of achievement that can be assessed and certified under the PTQF.

SECTOR SPECIFIC

1.         Computer System - The complete computer made up of the CPU, memory and related electronics (main cabinet), all the peripheral devices connected to it and its operating system. Computer systems fall into two broad divisions: clients and servers. Client machines fall into three categories from low to high end: laptop, desktop and workstation. Servers range from small to large: low-end servers, midrange servers and mainframes.

2.   Computer Network, or simply a Network, is a collection of  computers and other hardware interconnected by communication channels that allow sharing of resources and information. Where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network. It is a group of devices connected to each other. Networks may be classified into a wide variety of characteristics, such as the medium used to transport the data,  communications protocol used, scale,  topology, benefit, and organizational scope.

3.    Configuration - The makeup of a system. To "configure" is to choose options in order to create a custom system. "Configurability" is a system's ability to be changed or customized.

4.    Connector - Any plug and socket that links two devices together. Although taken for granted and rarely in the limelight, connectors are a huge industry, and the quality of these components is more critical than most people would imagine. When not designed or constructed properly, they often become the weakest element in an electronic system.

5.   Display Adapter - A plug-in card in a desktop computer that converts the images created in the computer to the electronic signals required by the monitor. It determines the maximum resolution, refresh rate and number of colors that can be displayed, which the monitor must also be able to support. On many PC motherboards, the display adapter circuits are built into the chipset, and an AGP or PCI card is not required.

6.    Expansion Board - A printed circuit board that plugs into an expansion slot and extends the computer's capability to control a peripheral device. All the boards (cards) that plug into a computer's bus are expansion boards, such as display adapters, disk

controllers, network adapters and sound cards.

7.    Expansion Bus - An input/output bus typically comprised of a series of slots on the motherboard. Expansion boards (cards) are plugged into the bus. ISA and PCI are the common expansion buses in a PC.

8.    Graphical User Interface - A graphics-based user interface that incorporates movable windows, icons and a mouse. The ability to resize application windows and change style and size of fonts are the significant advantages of a GUI vs. a character-based interface. GUIs have become the standard way users interact with a computer, and the major GUIs are the Windows and Mac interfaces along with Motif for Unix and the GNOME and KDE interfaces for Linux.

9.   LAN - a local area network (LAN) is a  computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. The defining characteristics of LANs, in contrast to  wide area networks (WANs), include their usually higher  data-transfer rates, smaller geographic area, and lack of a need for  leased telecommunication lines.

10.  Motherboard - Also called the "system board," it is the main printed circuit board in an electronic device, which contains sockets that accept additional boards. In a desktop computer, the motherboard contains the CPU, chipset, PCI bus slots, AGP slot, memory sockets and controller circuits for the keyboard, mouse, disks and printer. It may also have built-in controllers for modem, sound, display and network, obviating the need to plug in a card.

11.   Networks – See Computer Network.

12.  Operating System - The master control program that runs the computer. The first program loaded when the computer is turned on, its main part, the "kernel," resides in memory at all times. The operating system sets the standards for all application programs that run in the computer. The applications "talk to" the operating system for all user interfaces and file management operations.

13.  Peripheral -Any hardware device connected to a computer, such as a monitor, keyboard, printer, disk, tape, graphics tablet, scanner, joy stick, paddle or mouse.

14.  Server - A computer system in a network that is shared by multiple users. Servers come in all sizes from x86-based PCs to IBM mainframes. A server may have a keyboard, monitor and mouse directly attached, or one keyboard, monitor and mouse may connect to any number of servers via a KVM switch. Servers may be also be accessed only through a network connection as well.

15.   Sound Card - Also called a "sound board" or "audio adapter," it is a computer expansion board that records and plays back sound, providing inputs from a microphone or other sound source and outputs to speakers or an external amplifier. The de facto standard for sound card compatibility in PCs is Creative Labs' Sound Blaster.

16.  User Interface - All graphics based today, the user interface includes the windows, menus and method of interaction between you and the computer. Prior to the Mac, Windows and Motif (UNIX) interfaces, all interaction was based on commands entered by the user. Operating systems may support optional interfaces and allow a new shell or skin, to be used instead.

17.  Virus - Software used to infect a computer. After the virus code is written, it is buried within an existing program. Once that program is executed, the virus code is activated and attaches copies of itself to other programs in the system. Infected programs copy the virus to other programs.

18.  WAN - A Wide Area Network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, or national boundaries) using private or  public network transports. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers

from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location.

 19.   WEEE Directives - The prevention of waste electrical and electronic equipment (WEEE), and in addition, the reuse, recycling and other forms of recovery of such wastes so as to reduce the disposal of waste. It also seeks to improve the environmental performance of all operators involved in the life cycle of electrical and electronic equipment, e.g. producers, distributors and consumers and in particular those oper. 

ADDITIONAL TERMS

1.  Active Hubs – Amplify or boost signals.

2.    Anti-Static – A product that prevents the buildup of static electricity.

3.   BIOS – Basic Input/output System, chip that controls the most basic functions of the computer and performs a self-test every time you turn it on.

4.      Flash drive– RAM that can retain data without electrical power. It is widely used for BIOS chips and for digital camera and digital music storage.

5.     Graphic tablet – Objects are drawn using a pen or a puck.  The puck is technically a tablet cursor, not a mouse.

6.   Goggles –    A large spectacles, with shields around the rims, for protecting the eyes from dust, excessive light, wind, etc.

7.   Hard-disk drive – Is a storage device that stores billions of characters of data on a nonremovable disk.

8.     Hardware- Refers to the tangible (things you can touch) components of a computer system hardware components are further divided into three groups namely.

9.      Host – Any computer whether mainframe, server, or even PC that acts as an information source on a network.

10.     Intelligent Hubs – Select which path a specific signal will travel.

11.     Joy Stick - A hand-held control stick that allows a player to control the movements of a cursor on a computer screen or a symbol in a video game.

12.     LAN Card – Local area network interface card.

13.     Laptop computer - A small, portable computer -- small enough that it can sit on your lap.

14.     Local Area Network- The smallest of the three network types, consist of PCs connected together within a limited area, such as within the same building, floor or department.

15.     Mainframe- A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.

16.     Metropolitan Area Network – Are network that spans no more than.   

 17.        50 miles - It is design to connect LANs spanning a town or city.

18. Minicomputer - A multi-user computer capable of supporting up to hundreds of users simultaneously.

19.     Metropolitan Area Network – Is a network that spans no more than.

20.     50 miles - It is design to connect LANs spanning a town or city.

21.     Motherboard – Contains the CPU, BIOS, Memory, mass storage interfaces, serial and parallel ports, expansion slot and all the controllers required to control standard peripheral devices such as the display screen, keyboard and disk drive.

22.     Modem - (MOdulator-DEModulator) The modem is a device that allows a given computer to share data or otherwise a device which let computers exchange information.

23.     Modular Hubs – Are popular in networks because they are easily expanded and always have management option. It is purchased as chassis, or card cage, with multiple card slots, each of which accepts a communication card, or module.

24.     Multimedia - Is the combination of different types of communication media (sound, print, video, and so on).

25.     Multitasker- Is an instrument use to measure voltage, current and resistance.

26.     NIC – Network Interface Card – The PC expansion board that plug into a personal computer or server and works with the network operating

system to control the flow of information over the network.

27.     Network – Is a communications system connecting two or more computers.

28.    Network Bridge – Divides network into smaller, more manageable sections helping reduce network traffic.

29.     Network Hub - A hardware device that all PCs on a network are connected to by cabling.  The hub manages receiving and transmitting data from networked services.

30.     Network Server- Is a powerful computer whose sole purpose is to serve network clients.

31.     Network Switch – It helps determine how data moves over large networks.

32.     Notebook computer – An extremely lightweight personal computer that weighs weigh less than 6 pounds and are small enough to fit easily in a briefcase.

33.     OHS – Occupational Health and Safety.

34.     Operating System (OS) - Software that controls the allocation and use of programs and data that a computer uses.

35.     Passive Hubs – Simply connects various cables.

36.     Personal computer:  A small, single-user computer based on a microprocessor.

37.     Port hub /Port – Is a connector on the back of a computer or other device.  A port is either a serial port or a parallel port.

38.     Peers- Mean any computer sharing the same protocol layer with another computer.

39.     Protocol – Refers to the specific standards governing the sending and receiving of data.

40.     Repeater– A device that strengthen signals and allow them to stay clear over longer distances.

41.     Printer - It is a piece of hardware that produces a paper copy (also known as ‘hardcopy’) of the information generated by the computer.

42.     RAM – Random Access Memory, is a primary memory.  This memory is used inside the computer to hold programs and data while it is running.

43.     RJ 45 – Is the connector plugged into the NIC ports on computers and often connecting the main networking hardware together.

44.     Router – A device that forwards data packets between Local or Wide Area Network groups.

45.     Scanner- It is an input device that read text or illustration printed on paper, translates the information into a form that a computer can use.

46.     Server – Is a part of a network.  It is a special computer that users on the network can assess to carry out a particular job.

47.     Software – Programs and data that a computer uses.

48.     Software applications- Enables you to perform specific tasks- solve problems, perform work, or entertain yourself.

49.     Sound Device Driver Installer / Sound and Audio Devices – A windows XP Control Panel applet, called Sounds, and Multimedia in Windows 2000, for configuring the system’s sound card.

50.     Stackable Hubs – Work just like standalone hubs, except that several of them can be “stacked” (connected) together, usually by short lengths of cable.

51.     Standalone Hubs – Are single products with a number of ports.  It is usually including some method of linking them to other standalone hubs for network expansion.

52.     Static – The discharge of electricity between two objects with different electrical potential.

53.     Sub-notebook computer - A portable computer that is slightly lighter and smaller than a full-sized notebook computer. Typically, sub-notebook computers have a smaller keyboard and screen, but are otherwise equivalent to notebook computers.

54.     UTP – (Unshielded Twisted Pair) least expensive and most popular network media.

55.     USB – Universal Serial Bus, a hardware interface for low-speed peripherals such as the keyboard, mouse, joystick, scanner, printer and telephony devices.

56.     Video Camera - Camera using videotape: a camera that records onto videotape.

57.     Wide Area Network – Used to distribute information thousands of miles among thousands of users.

58.     Wireless Hubs– Are hubs designed for the home.

59.     Workstation- Is any network computer that connects to and request resources from a network.

NETWORK DESIGN

LEARNING OBJECTIVES:

After reading this INFORMATION SHEET, YOU MUST be able to understand computer network.

COMPUTER NETWORK

A computer   network or data  network is a telecommunications network  which allows computers to exchange data. In computer networks, networked computing devices exchange data with each other using a data link.  The  connections  between  nodes  are  established  using  either cable media or wireless media. The best-known computer network is the Internet.

Network computer devices that originate, route and terminate the data are called network    nodes. Nodes    can    include hosts such    as    personal computers, phones, servers as  well  as networking  hardware.  Two  such devices can be said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other.

Computer networks differ in the transmission medium used to carry their signals,  the communications  protocols to  organize  network  traffic,  the network's size, topology and organizational intent.

Computer networks support an enormous number of applications such as access to the World Wide Web, video, digital audio, shared use of application and  storage servers, printers, and fax machines, and use of email and instant messaging applications as well as many others. In most cases, application-specific communications protocols are layered (i.e. carried as payload) over other more general communications protocols.

A computer network facilitates interpersonal communications allowing users to communicate efficiently and easily via various means:  email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing. Providing access to information on shared storage devices is an important feature of many networks. A network allows sharing of files, data, and other types of information giving authorized users the ability to access information stored on other computers on the network. A network allows sharing of network and computing resources. Users may access and use resources provided by devices on the network, such as printing a document on   a shared   network   printer.   Distributed   computing uses computing resources across a network to accomplish tasks. A computer network may be used by computer crackers to deploy computer viruses or

computer worms on devices connected to the network, or to prevent these devices from accessing the network via a denial of service attack.

NETWORK PACKET

Computer communication links that do not support packets, such as traditional point-to-point telecommunication links, simply transmit data as a bit stream. However, most information in computer networks is carried in packets. A network packet is a formatted unit of data (a list of bits or bytes,  usually  a  few  tens  of  bytes  to  a  few  kilobytes  long)  carried  by a packet-switched network.

In packet networks, the data is formatted into packets that are sent through the network to their destination. Once the packets arrive, they are reassembled into their original message. With packets, the bandwidth of the transmission medium can be better shared among users than if the network were circuit switched. When one user is not sending packets, the link can be filled with packets from others users, and so the cost can be shared, with relatively little interference, provided the link isn't overused.

Packets consist of two kinds of data: control information, and user data(payload). The control information provides data the network needs to deliver   the  user   data,   for   example:   source  and   destination network addresses, error  detection codes,  and  sequencing  information.  Typically, control  information  is found  in packet  headers and trailers,  with payload data in between.

Often the route a packet needs to take through a network is not immediately available. In that case the packet is queued and waits until a link is free.

NETWORK TOPOLOGY

The physical layout of a network is usually less important than the topology that connects network nodes.  Most diagrams that describe a physical network are therefore topological, rather than geographic. The symbols on these diagrams usually denote network links and network nodes.

NETWORK LINKS

The transmission media (often referred to in the literature as the physical media) used to link devices to form a computer network include electrical cable (Ethernet, Hommen, power line communication, G.hn), optical fiber (fiber-optic communication), and radio waves (wireless networking). In the OSI model, these are defined at layers 1 and 2 — the physical layer and the data link layer

A widely adopted family of transmission media used in local area network (LAN) technology is collectively known as Ethernet. The media and protocol standards that enable communication between networked devices over Ethernet  are defined  by IEEE 802.3.  Ethernet  transmits  data over both copper and fiber cables. Wireless LAN standards (e.g. those defined by IEEE

802.11) use radio waves, or others use infrared signals as a transmission medium. Power line communication uses a building’s power cabling to transmit data.

WIRED TECHNOLOGIES

The orders of the following wired technologies are, roughly, from slowest to fastest transmission speed.

  Coaxial cable is  widely  used for cable television systems, office buildings, and other work-sites for local area networks.  The cables consist of copper or aluminum wire surrounded by an insulating layer (typically a flexible material with a high dielectric constant), which itself is surrounded by a conductive layer. The insulation helps minimize interference and distortion. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.

  ITU-T G.hn technology   uses   existing home   wiring (coaxial   cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network

  Twisted   pair wire is   the   most   widely   used   medium   for   all telecommunication. Twisted-pair cabling consist of copper wires that are twisted into pairs.  Ordinary telephone wires consist of two insulated copper    wires    twisted    into    pairs.    Computer    network    cabling (wired Ethernet as defined by IEEE 802.3) consists of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use    of   two   wires   twisted        together   helps   to reduce crosstalk and electromagnetic induction. The transmission speed ranges  from 2 million bits per second to 10 billion bits per second. Twisted pair cabling comes in two forms: unshielded twisted pair (UTP) and shielded twisted-pair (STP). Each form comes in several category ratings, designed for use in various scenarios.

An optical fiber is a glass fiber. It carries pulses of light that represent data. Some advantages of optical fibers over metal wires are very low transmission loss and immunity from electrical interference. Optical fibers can simultaneously carry multiple wavelengths of light, which greatly increases the rate that data can be sent, and helps enable data rates of up to trillions of bits per second. Optic fibers can be used for long runs of cable carrying very high data rates, and are used for undersea cables to interconnect continents.

Price is a main factor distinguishing wired- and wireless-technology options in a business. Wireless options command a price premium that can make purchasing wired computers, printers and other devices a financial benefit.  Before making the  decision  to purchase hard-wired technology products, a review of the restrictions and limitations of the selections is necessary. Business and employee needs may override any cost considerations.

Terrestrial  microwave –  Terrestrial  microwave  communication  uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low-gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately 48 km (30 mi) apart.

Terrestrial  microwave –  Terrestrial  microwave  communication  uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low-gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately 48 km (30 mi) apart.

 Communications  satellites –  Satellites  communicate  via  microwave radio waves, which are not deflected by the Earth's atmosphere. The satellites  are  stationed  in  space,  typically  in  geosynchronous  orbit 35,400 km (22,000 mi) above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.

 Cellular  and    PCS    systems use    several    radio   communications technologies. The systems divide the region covered into multiple geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.

 Radio   and  spread   spectrum  technologies –   Wireless   local   area networks use a high-frequency radio technology similar to digital cellular and  a  low-frequency  radio  technology.  Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. IEEE 802.11 defines a common flavor of open- standards wireless radio-wave technology known as WIFI.

 Free-space optical communication uses visible or invisible light for communications. In most cases, line-of-sight propagation is used, which limits the physical positioning of communicating devices.

 EXOTIC TECHNOLOGIES

·   There have been various attempts at transporting data over exotic media:

·   IP  over  Avian  Carriers was  a  humorous  April  fool's Request  for Comments,  issued  as RFC 1149.  It  was  implemented  in  real  life  in 2001. Extending the Internet to interplanetary dimensions via radio waves.

·   Both cases have a large round-trip delay time, which gives slow two-way communication, but doesn't prevent sending large amounts of information.

Apart from any physical transmission medium there may be, networks comprise additional basic system building blocks, such as network interface controller    (NICs),    repeaters,   hubs, bridges, switches, routers, modems, and firewalls.

NETWORK INTERFACES

An ATM network interface in the form of an accessory card. A lot of network interfaces are built-in.

A typical home or small office router showing the ADSL telephone line and Ethernet network cable connections

A router is an internetworking device that forwards packets between networks by processing the routing information included in the packet or datagram (Internet protocol information from layer 3). The routing information is often processed in conjunction with the routing table (or forwarding table). A router uses its routing table to determine where to forward packets. A destination in a routing table can include a "null" interface, also known as the "black hole" interface because data can go into it, however, no further processing is done for said data, i.e. the packets are dropped.

MODEMS

Modems (MOdulator-DEModulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this  one  or  more carrier  signals are modulated by  the  digital  signal  to produce an analog signal that can be tailored to give the required properties for transmission. Modems are commonly used for telephone lines, using a Digital Subscriber Line technology.

FIREWALL

A firewall is a network device for controlling network security and access rules. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in cyber-attacks.

NETWORK STRUCTURE

Network topology is the layout or organizational hierarchy of interconnected nodes of a computer network. Different network topologies can affect throughput, but reliability is often more critical. With many technologies, such as bus networks, a single failure can cause the network to fail entirely. In general, the more interconnections there are, the more robust the network is; but the more expensive it is to install.

Common layouts 

Common network topologies

Common layouts are:

·   A bus network: all nodes are connected to a common medium along this medium.  This  was  the  layout  used  in  the  original Ethernet, called 10BASE5 and 10BASE2.

·   A star network: all nodes are connected to a special central node. This is the typical layout found in a Wireless LAN, where each wireless client connects to the central Wireless access point.

·   A ring network: each node is connected to its left and right neighbour node, such that all nodes are connected and that each node can reach each other node by traversing nodes left- or rightwards.  The Fiber Distributed Data Interface (FDDI) made use of such a topology.

·   A mesh network: each node is connected to an arbitrary number of neighbours in such a way that there is at least one traversal from any node to any other.

·   A fully connected network: each node is connected to every other node in the network.

·   A tree network: nodes are arranged hierarchically.

Note that the physical layout of the nodes in a network may not necessarily reflect the network topology.  As an example,  with FDDI,  the  network topology is a ring (actually two counter-rotating rings), but the physical topology is often a star, because all neighboring connections can be routed via a central physical location.

 OVERLAY NETWORK

A SAMPLE OVERLAY NETWORK 

An overlay network is a virtual computer network that is built on top of another network. Nodes in the overlay network are connected by virtual or logical links. Each link corresponds to a path, perhaps through many physical links, in the underlying network.  The topology of the overlay network may (and often does) differ from that of the underlying one. For example,   many peer-to-peer networks   are  overlay  networks.   They  are organized  as  nodes of a virtual system of links  that run on top  of the Internet.

Overlay networks have been around since the invention of networking when computer  systems  were  connected  over  telephone  lines  using modems, before any data network existed.

The most striking example of an overlay network is the Internet itself. The Internet   itself   was   initially   built   as   an   overlay   on   the telephone network.[11] Even today, each Internet node can communicate with virtually any other through an underlying mesh of sub-networks of wildly different topologies and technologies. Address resolution and routing are the means that allow mapping of a fully connected IP overlay network to its underlying network.

Another example of an overlay network is a distributed hash table, which maps keys to nodes in the network. In this case, the underlying network is an IP network, and the overlay network is a table (actually a map) indexed by keys.

Overlay networks have also been proposed as a way to improve Internet routing, such as through quality of service guarantees to achieve higher- quality streaming   media.  Previous  proposals  such  as Insert, Differ, and IP Multicast have not seen wide acceptance largely because they require modification of all routers in the network.[citation needed]On the other hand, an overlay network can be incrementally deployed on end-hosts running the overlay   protocol   software,   without   cooperation   from Internet   service providers. The overlay network has no control over how packets are routed in the underlying network between two overlay nodes, but it can control, for

example, the sequence of overlay nodes that a message traverses before it reaches its destination.

For   example, Akamai   Technologies manages   an   overlay   network   that provides reliable, efficient content delivery (a kind of multicast). Academic research includes end system multicast, resilient routing and quality of service studies, among others. 

COMMUNICATIONS PROTOCOLS

The TCP/IP model or Internet layering scheme and its relation to common protocols often layered on top of it.

Figure 4. Message flows (A-B) in the presence of a router (R), red flows are effective communication paths, black paths are the actual paths.

A communications protocol is a set of rules for exchanging information over network links. In a protocol stack (also see the OSI model), each protocol leverages the services of the protocol below it. An important example of a protocol    stack    is HTTP (the World    Wide    Web    protocol)    running over TCP over IP (the Internet    protocols)    over IEEE    802.11 (the    Wi-Fi protocol).  This  stack  is  used  between  the wireless  router and  the  home user's personal computer when the user is surfing the web.

Whilst the use of protocol layering is today ubiquitous across the field of computer networking, it has been historically criticized by many researchers for two  principal reasons.  Firstly,  abstracting the protocol stack in this way may cause a higher layer to duplicate functionality of a lower layer, a prime example being error recovery on both a per-link basis and  an  end-to-end  basis. Secondly,  it  is  common  that  a  protocol implementation  at  one  layer  may  require  data,  state  or  addressing information that is only present at another layer, thus defeating the point of separating the layers in the first place. For example, TCP uses the ECN field in   the IPv4  header as   an   indication   of   congestion;  IP  is   a network layer protocol whereas TCP is a transport layer protocol.

Communication   protocols have   various   characteristics.   They   may be connection-oriented or connectionless,   they   may        use circuit mode or packet switching, and they may use hierarchical addressing or flat addressing.

There are many communication protocols, a few of which are described below.

IEEE 802

The complete IEEE 802 protocol suite provides a diverse set of networking capabilities.  The protocols have a flat addressing scheme.  They operate mostly at levels 1 and 2 of the OSI model.

For example, MAC bridging (IEEE 802.1D) deals with the routing of Ethernet packets  using  a Spanning  Tree  Protocol. IEEE  802.1Qdescribes VLANs, and IEEE  802.1X defines  a  port-based Network  Access  Control protocol, which forms the basis for the authentication mechanisms used in VLANs (but it is also found in WLANs) – it is what the home user sees when the user has to enter a "wireless access key".

ETHERNET

Ethernet,  sometimes  simply called LAN, is a family of protocols used in wired   LANs, described   by   a   set   of   standards   together   calefied 802.3 published by the Institute of Electrical and Electronics Engineers.

WIRELESS LAN

Wireless LAN, also widely known as WLAN or WIFI, is probably the most well-known member of the IEEE 802 protocol family for home users today. It is standardized by IEEE 802.11 and shares many properties with wired Ethernet.

 INTERNET PROTOCOL SUITE

The Internet Protocol Suite,  also  called  TCP/IP,  is  the foundation of  all modern networking. It offers connection-less as well as connection-oriented services over an inherently unreliable network traversed by data-gram transmission at the Internet protocol (IP) level. At its core, the protocol suite defines the addressing, identification, and routing specifications for Internet

Protocol Version 4 (IPv4) and for IPv6, the next generation of the protocol with a much-enlarged addressing capability.

SONET/SDH

Synchronous    optical    networking (SONET)    and    Synchronous   Digital Hierarchy   (SDH)   are   standardized multiplexing protocols   that   transfer multiple digital bit streams over optical fiber using lasers. They were originally designed to transport circuit mode communications from a variety of different sources, primarily to support real-time, uncompressed, circuit switched voice encoded in PCM (Pulse-Code Modulation) format. However, due to its protocol neutrality and transport-oriented features, SONET/SDH also  was  the  obvious  choice  for  transporting Asynchronous  Transfer Mode (ATM) frames.

Asynchronous   Transfer   Mode

Asynchronous   Transfer   Mode (ATM) is   a   switching   technique   for telecommunication     networks.     It uses asynchronous time-division multiplexing and encodes data into small, fixed-sized cells. This differs from other  protocols  such  as  the Internet  Protocol  Suite or Ethernet that  use variable sized packets or frames. ATM     has     similarity with both and packet switched networking. This makes it a good choice for a network that must handle both traditional high-throughput data traffic, and  real-time, low-latency content  such  as  voice  and  video.  ATM  uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins.

While the role of ATM is diminishing in favor of next-generation networks, it still  plays  a  role  in  the last  mile,  which  is  the  connection  between an Internet service provider and the home user.

 GEOGRAPHIC SCALE

A network can be characterized by its physical capacity or its organizational purpose. Use of the network, including user authorization and access rights, differ accordingly.

NANO SCALE NETWORK

A nanoscale communication network has key components implemented at the nanoscale including message carriers and leverages physical principles that differ from macroscale communication mechanisms. Nanoscale communication extends communication to very small sensors and actuators such as those found in biological systems and also tends to operate in environments that would be too harsh for classical communication.

PERSONAL AREA NETWORK

A personal   area   network (PAN) is   a   computer   network   used   for communication among computer and different information technological devices close to one person. Some examples of devices that are used in a PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even video game consoles. A PAN may include wired and wireless devices. The reach of a PAN typically extends to 10 meters. A wired PAN is usually constructed with USB and FireWire connections while technologies such as Bluetooth and infrared communication typically form a wireless PAN.

LOCAL AREAS NETWORK

A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as a home, school, office building, or closely positioned group of buildings. Each computer or device on the network is a node. Wired LANs are most likely based on Ethernet technology. Newer standards such as ITU-T G.hn also provide a way to create a wired LAN using existing wiring,  such  as  coaxial cables,  telephone lines,  and power lines.

The   defining   characteristics   of   a  LAN,   in  contrast   to   a wide   area network (WAN), include higher data transfer rates, limited geographic range, and lack of reliance on leased lines to provide connectivity. Current Ethernet or other IEEE 802.3 LAN technologies  operate  at data transfer rates  up to 100  Gbit/s,  standardized  by IEEE in  2010. Currently, 400  Gbit/s Ethernet is being developed.

A LAN can be connected to a WAN using a router.

HOME AREA NETWORK

A home area network (HAN) is a residential LAN used for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices. An important function is the sharing of Internet access, often a broadband service through a cable TV or digital subscriber line (DSL) provider.

STORAGE AREA NETWORK

A storage area network (SAN) is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices to the operating system. A SAN typically has its own network of storage devices that are generally not accessible through the local area network by other devices. The cost and complexity of SANs dropped in the early 2000s to levels allowing wider adoption across both enterprise and small to medium-sized business environments.

CAMPUS AREA NETWORK

A campus area network (CAN) is made up of an interconnection of LANs within a limited geographical area. The networking equipment (switches, routers) and transmission media (optical fiber, copper plant, Cat5 cabling, etc.) are almost entirely owned by the campus tenant / owner (an enterprise, university, government, etc.).

For example, a university campus network is likely to link a variety of campus buildings to connect academic colleges or departments, the library, and student residence halls.

BACKBONE NETWORK

A backbone network is  part  of a computer network infrastructure that provides a path for the exchange of information between different LANs or sub-networks.  A backbone can tie together diverse networks within the same building, across different buildings, or over a wide area.

For example, a large company might implement a backbone network to connect departments that are located around the world. The equipment that ties together the departmental networks constitutes the network backbone. When  designing  a  network  backbone, network  performance and network congestion are critical factors to take into account. Normally, the backbone network's capacity is greater than that of the individual networks connected to it.

Another example of a backbone network is the Internet backbone, which is the set of wide area networks (WANs) and core routers that tie together all networks connected to the Internet.

METROPOLITAN NETWORK

A Metropolitan area network (MAN) is a large computer network that usually spans a city or a large campus.

WIDE AREA NETWORK

A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances. A WAN uses a communications channel that combines many types of media such as telephone lines, cables, and air waves. A WAN often makes use of transmission facilities provided by common carriers, such as telephone companies.  WAN  technologies  generally  function  at  the  lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

ENTERPRISE PRIVATE NETWORK

An enterprise private network is a network that a single organization builds to  interconnect  its  office  locations  (e.g.,  production  sites,  head  offices, remote offices, shops) so they can share computer resources.

VIRTUAL PRIVATE NETWORK

A virtual private network (VPN) is an overlay network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The data link layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.

VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point.

GLOBAL AREA NETWORK

A global area network (GAN) is a network used for supporting mobile across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is handing off user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial wireless LANs.

ORGANIZATIONAL SCOPE

Networks are typically managed by the organizations that own them. Private enterprise networks may use a combination of intranets and extranets. They may also provide network access to the Internet, which has no single owner and permits virtually unlimited global connectivity.

 INTRANET

An intranet is  a  set  of  networks  that  are  under  the  control of a  single administrative entity. The intranet uses the IP protocol and IP-based tools such  as web  browsers  and file transfer applications.  The administrative entity limits use of the intranet to its authorized users. Most commonly, an intranet is the internal LAN of an organization. A large intranet typically has at least one web server to provide users with organizational information. An intranet is also anything behind the router on a local area network.

EXTRANET

An extranet is a network that is also under the administrative control of a single organization, but supports a limited connection to a specific external network. For example, an organization may provide access to some aspects of its intranet to share data with its business partners or customers. These other entities are not necessarily trusted from a security standpoint.

Network connection to an extranet is often, but not always, implemented via

WAN technology.

Internetwork

An internetwork is the connection of multiple computer networks via a common routing technology using routers.

Internet

Partial map of the Internet based on the January 15, 2005 data found on opte.org.  Each  line  is  drawn  between  two  nodes,  representing  two IP addresses. The length of the lines are indicative of the delay between those two nodes. This graph represents less than 30% of the Class C networks reachable.

The Internet is the largest example of an internetwork. It is a global system of interconnected governmental, academic, corporate, public, and private computer   networks.  It  is  based   on  the  networking  technologies   of the Internet Protocol Suite.  It is the successor of the Advanced  Research Projects  Agency  Network (ARPANET)  developed  by DARPA of  the United States  Department of  Defense.  The Internet is  also the communications backbone underlying the World Wide Web (WWW).

Participants  in  the  Internet  use  a  diverse  array  of  methods  of  several hundred documented, and often standardized, protocols compatible with the Internet   Protocol   Suite   and   an   addressing   system   (IP   addresses) administered   by   the Internet  Assigned   Numbers   Authority and address registries.  Service  providers  and  large  enterprises  exchange  information about the reachability of their address spaces through the Border Gateway Protocol (BGP), forming a redundant worldwide mesh of transmission paths.

DARKNET

A Darknet is an overlay network, typically running on the internet, that is only accessible through specialized software. A darknet is an anonymizing network where connections are made only between trusted peers  sometimes called "friends" (F2F) — using non-standard protocols and ports.

Darknets are distinct from other distributed peer-to-peer networks as sharing is anonymous (that is, IP addresses are not publicly shared), and therefore users can communicate with little fear of governmental or corporate interference.

Routing

Routing calculates good paths through a network for information to take. For example, from node 1 to node 6 the best routes are likely to be 1-8-7-6 or 1-8-10-6, as this has the thickest routes.

Routing is the process of selecting network paths to carry network traffic.

Routing is performed for many kinds of networks, including circuit switching networks and packet switched networks.

In packet switched networks, routing directs packet forwarding (the transit of  logically  addressed network  packets from  their  source  toward  their ultimate destination) through intermediate nodes. Intermediate nodes are typically        network   hardware        devices   such   as routers, bridges, gateways, firewalls,   or switches.   General-purpose computers can also forward packets and perform routing, though they are not specialized hardware and may suffer from limited performance. The routing process usually directs forwarding on the basis of routing tables, which maintain a record of the routes to various network destinations. Thus, constructing routing tables, which are held in the router's memory, is very important for efficient routing.

There are usually multiple routes that can be taken, and to choose between them, different elements can be considered to decide which routes get installed into the routing table, such as (sorted by priority)

1. Prefix-Length: where longer subnet masks are preferred (independent if it is within a routing protocol or over different routing protocol)

2. Metric: where a lower metric/cost is preferred (only valid within one and the same routing protocol)

3. Administrative distance: where a lower distance is preferred (only valid between different routing protocols)

Most routing algorithms use only one network path at a time. Multipath routing techniques enable the use of multiple alternative paths.

Routing, in a more narrow sense of the term, is often contrasted with bridging in its assumption that network addresses are structured and that similar addresses imply proximity within the network. Structured addresses allow a single routing table entry to represent the route to a group of devices. In large networks, structured addressing (routing, in the narrow sense) outperforms unstructured addressing (bridging). Routing has become the dominant form of addressing on the Internet. Bridging is still widely used within localized environments.

NETWORK SERVICE

Network services are applications hosted by servers on a computer network, to provide some functionality for members or users of the network, or to help the network itself to operate.

The World   Wide   Web, E-mail, printing and network   file   sharing are examples of well-known network services. Network services such as DNS (Domain  Name  System)  give  names  for IP and MAC  addresses (people remember  names  like  “nm. An”  better  than  numbers  like “210.121.67.18”), and DHCP to   ensure   that   the   equipment   on   the network has a valid IP address.

Services are usually based on a service protocol that defines the format and sequencing of messages between clients and servers of that network service.

NETWORK PERFORMANCE

QUALITY OF SERVICE

Depending on the installation requirements, network performance is usually measured by the quality of service of a telecommunications product. The parameters that affect this typically can include throughput, jitter, bit error rate and latency.

The following list gives examples of network performance measures for a circuit-switched network and one type of packet-switched network, viz. ATM:

Circuit-switched   networks:   In circuit  switched networks, network performance is synonymous with the grade of service. The number of rejected calls is a measure of how well the network is performing under heavy traffic loads. Other types of performance measures can include the level of noise and echo.

ATM: In an Asynchronous Transfer Mode (ATM) network, performance can be measured by line rate, quality of service (QoS), data throughput, connect time, stability, technology, modulation technique and modem enhancements.

There are many ways to measure the performance of a network, as each network is different in nature and design. Performance can also be modelled instead of measured. For example, state transition diagrams are often used to model queuing performance in a circuit-switched network. The network planner uses these diagrams to analyze how the network performs in each state, ensuring that the network is optimally designed.

NETWORKING CABLES

Networking cables are networking hardware used to connect one network device to other network devices or to connect two or more computers to share printer, scanner etc.  Different  types  of  network  cables  like Coaxial cable, Optical fiber cable, Twisted Pair cables are used depending on the network's topology, protocol and size. The devices can be separated by a few meters (e.g.  via Ethernet)  or  nearly unlimited distances  (e.g.  via the interconnections of the Internet).

While wireless networks are much easier deployed when total throughput is not  an  issue,  most  permanent  larger computer  networks use  cables  to transfer signals from one point to another.

TWISTED PAIR

Twisted pair cabling is a form of wiring in which pairs of wires (the forward and  return  conductors  of  a  single circuit)  are  twisted  together  for  the purposes of canceling out electromagnetic interference (EMI) from other wire pairs and from external sources. This type of cable is used for home and corporate Ethernet networks.

There are two major types of twisted pair cables: shielded, unshielded.

UNSHIELDED/SHIELDED

There are two major types of optical fiber cables: short-range multi-mode fiber and long-range single-mode fiber.

The most common use for coaxial cables is for television and other signals with a bandwidth of several hundred megahertz to gigahertz. Although in most homes coaxial cables have been installed for   transmission   of TV signals,   new   technologies   (such   as   the ITU- T G.hn standard) open the possibility of using home coaxial cable for high- speed home networking applications (Ethernet over coax).

In the 20th century they carried long distance telephone connections.

TERMINAL

In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters and/or leaves a network. Examples of equipment containing network terminations are telephones, fax  machines, computer  terminals and  network  devices, printers and workstations.

CABALE RACEWAY

Surface raceway is used to route wires through a discreet cable track that will improve the aesthetics in just about any room, and is a great and affordable way to conceal and protect cables in both home or office. Plastic cable raceway is available in many different styles including latching (1- piece), sliding cover, and J channel versions, and installation is simple. Many styles have self-sticking adhesive backing, can be cut to any desired size, and are paintable to match your decor. Accessories can help you add power and data ports, or junctions to change direction and/or split your cable runs.

There are also several varieties of specialty raceway for industrial, commercial or outdoor applications: wire guards for utility poles, solid cable trays for sensitive fiber optic cables, ADA compliant over floor raceways, and many more!

Because of their low cost and ease of use, tie-wraps are ubiquitous, finding use in a wide range of other applications. Stainless steel versions, either naked or coated with a rugged plastic, cater for exterior applications and hazardous environments.

The common tie-wrap, normally made of nylon, has a flexible tape section with teeth that engage with a pawl in the head to form a ratchet so that as the free end of the tape section is pulled the tie-wrap tightens and does not come undone. Some ties include a tab that can be depressed to release the ratchet so that the tie can be loosened or removed, and possibly reused.

Generically, an NID  may also be called a network interface unit (NIU),  telephone network

interface (TNI), system network interface (SNI), or telephone network box. Australia's National Broadband

Network uses the term network termination device or NTD. A smart jack is a type of NID with capabilities beyond simple electrical connection, such as diagnostics. An optical network terminal(ONT) is a

type of NID used with fiber-to-the-premises applications.

Network cable connector

However, as far as the original router or access point is concerned, only the repeater MAC is connected, making it necessary to enable safety features on the wireless repeater. Wireless repeaters are commonly used to improve signal range and strength within homes and small offices. It is used if the devices that you are going to network are far from each other.

TOOLS, EQUIPMENT AND TESTING DEVICES

 INFORMATION SHEET 2.1-3

                    Personal Protective Equipment and OHS Policies and Procedures

Learning Objective:

After reading this INFORMATION SHEET, YOU MUST be able to Identify Personal protective equipment and understand OHS policies and procedures.

Personal protective equipment (PPE) refers to protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, electrical, heat, chemicals, biohazards, and airborne particulate matter. Protective equipment may be worn for job-related occupational safety and health purposes, as well as for sports and other recreational activities. "Protective clothing" is applied to traditional categories of clothing, and "protective gear" applies to items such as pads, guards, shields, or masks, and others.

The purpose of personal protective equipment is to reduce employee exposure to hazards when engineering and administrative controls are not feasible or effective to reduce these risks to acceptable levels. PPE is needed when there are hazards present. PPE has the serious limitation that it does not eliminate the hazard at source and may result in employees beingexposed to the hazard if the equipment fails.

Occupational health and safety (OHS)

Occupational safety and health (OSH) also commonly referred to as occupational health and safety (OHS) or workplace health and safety (WHS) is an area concerned with the safety, health and welfare of people

engaged in work or employment. The goals of occupational safety and health programs include to foster a safe and healthy work environment. OSH may also protect co-workers, family members, employers, customers, and many others who might be affected by the workplace environment. In the United States the term occupational health and safety is referred to as occupational health and occupational and non- occupational safety and includes safety for activities outside work.

General Safety

Safe working conditions help prevent injury to people and damage to computer equipment. A safe workspace is clean, organized, and properly lighted. Everyone must understand and follow safety procedures.

Follow the basic safety guidelines to prevent cuts, burns, electrical shock, and damage to eyesight. As a best practice, make sure that a fire extinguisher and first-aid kit are available in case of fire or injury. Poorly

placed or unsecured cables can cause tripping hazards in a network installation. Cables should be installed in conduit or cable trays to prevent hazards.

This is a partial list of basic safety precautions to use when working on a computer:

• Remove your watch and jewelry and secure loose clothing.

• Turn off the power and unplug equipment before performing service.

• Cover sharp edges inside the computer case with tape.

• Never open a power supply or a CRT monitor.

• Do not touch areas in printers that are hot or that use high voltage.

• Know where the fire extinguisher is located and how to use it.

• Keep food and drinks out of your workspace.

• Keep your workspace clean and free of clutter.

• Bend your knees when lifting heavy objects to avoid injuring your back.

Follow electrical safety guidelines to prevent electrical fires, injuries, and fatalities in the home and the workplace. Power supplies and CRT monitors contain high voltage.

Do not wear the antistatic wrist strap when repairing power supplies or CRT monitors. Only experienced technicians should attempt to repair power supplies and CRT monitors.

Some printer parts become hot during use, and other parts might contain high voltage. Check the printer manual for the location of high-voltage components. Some components retain a high voltage even after the printer is turned off. Make sure that the printer has had time to cool before making the repair.

Electrical devices have certain power requirements.

For example, AC adapters are manufactured for specific laptops. Exchanging power cords with a different type of laptop or device may cause damage to both the AC adapter and the laptop.

Fire Safety

Follow fire safety guidelines to protect lives, structures, and equipment. To avoid an electrical shock and to prevent damage to the computer, turn off and unplug the computer before beginning a repair.

Fire can spread rapidly and be very costly. Proper use of a fire extinguisher can prevent a small fire from getting out of control. When working with computer components, be aware of the possibility of an accidental fire and know how to react. Be alert for odors emitting from computers and electronic devices. When electronic components overheat or short out, they emit a burning odor. If there is a fire, follow these safety procedures

• Never fight a fire that is out of control or not contained.

• Always have a planned fire escape route before beginning any work.

• Get out of the building quickly.

• Contact emergency services for help.

• Locate and read the instructions on the fire extinguishers in your workplace before you have to use them.

Be familiar with the types of fire extinguishers used in your country or region. Each type of fire extinguisher has specific chemicals to fight different.

Types of fires:

• Paper, wood, plastics, cardboard

• Gasoline, kerosene, organic solvents

• Electrical equipment

• Combustible metals

It is important to know how to use a fire extinguisher. Use the memory aid

P-A-S-S to remember the basic rules of fire extinguisher operation:

• P: Pull the pin.

• A: Aim at the base of the fire, not at the flames.

• S: Squeeze the lever.

• S: Sweep the nozzle from side to side.

INFORMATION SHEET 2.1-4 Cable splicing and crimping

Learning Objective:

After reading this INFORMATION SHEET, YOU MUST be able to splice and crimp network cable.

RJ-45 conductor data cable contains 4 pairs of wires each consists of a solid colored wire and a strip of the same color. There are two wiring standards for RJ-45 wiring: T-568A and T-568B. Although there are 4 pairs of wires, 10BaseT/100 Basset Ethernet uses only 2 pairs: Orange and Green. The other two colors (blue and brown) may be used for a second Ethernet line or for phone connections. The two wiring standards are used to create a cross- over cable (T-568A on one end, and T-568B on the other end), or a straight through cable (T-568B or T-568A on both ends). Straight-through & Cross- over cables are the two-cabling standard.

More on straight-through and cross-over connections

The RJ45 data cables we use to connect computers to an Ethernet switch is straight-through cables. As noted above, the RJ45 cable uses only 2-pairs of wires: Orange (pins 1 & 2) and Green (pins 3 & 6). Pins 4, 5 (Blue) and 7, 8.

(Brown) are NOT used. Straight-through cable, as its name suggests, connects pin 1 to pin 1, pin 2 to pin 2, pin 3 to pin 3, and pin 6 to pin 6. Cross-over cables are used to connect TX+ to RX+, and TX- to RX-, which

connects pin 1 to pin 3, pin 2 to pin 6, pin 3 to pin 1 and pin 6 to pin 2. The unused pins are generally connected straight-through in both straight- through and cross-over cables.

To network two computers without a hub, a cross-over cable is used. Cross- over cable is also used to connect a router to a computer, or ethernet switch (hub) to another ethernet switch without an uplink. Most

ethernet switches today provide an uplink port, which prevents a use of cross-over cable to daisy chain another ethernet switch. Straight through cables are used to connect a computer to an ethernet switch, or a router to an ethernet switch.

Pin Number Designations

There are pin number designations for each color in T-568B and T-568A.

MODULAR BOX

T-568 A

T-568 B

Steps in Crimping RJ45

RJ-45 connectors are normally used in telephone and network cables. Occasionally they are used for serial network connections. When the RJ-45 connectors first came into use, they were primarily used for telephones. The great advances in technology created a need for another size connector and the RJ-45 was adapted to fit. Today there are 2 different RJ-45 connector sizes available, 1 for Cat 5 cable and 1 for Cat 6 cable. The user has to make sure they have the one suited to their job. The easiest way to tell them apart

is to compare them side by side. The Cat 6 connector is larger than the Catn5 connector. Below are instructions for crimping RJ-45 connectors to a cable.

Steps

1. Purchase your cable and your RJ-45 connectors. Most ethernet able is sold on spools of varying lengths, so you might have to measure and cut the amount you need when you get home.

3. Fold each pair of wires backwards to expose the core of the cable.

4. Cut off the core and discard.

6. Arrange the untwisted wires in a row, placing them into the position, running from right to left, in which they will go into the RJ-45 connector:

o Orange with a white stripe

o Orange

o Green with a white stripe

o Blue

o Blue with a white strip

o Green

o Brown with a white stripe

o Brown

10. Follow the instructions above to crimp an RJ-45 connector to the opposite end of the cable.

How to Terminate a Patch Panel?

Step by step instructions on how to terminate solid wire Cat5, Cat5e or Cat6 cables to a respective standard rack mountable 110 style patch panel.

Steps

1. Strip the cable of its protective outside jacket about 3–6 inches (7.6– 15.2 cm) from the end. This can be done with the cabling scissors by applying pressure from the scissors to the cable and rotating the scissors

around the cable. After you have punctured the cables jacket, you should be able pull the jacket off easily leaving exposed wires.

2. Stripping the cable can cut and damage the wires at the area that we cut the cable so we want to expose about 6 more inches of fresh wires. Most twisted pair Cat5, Cat5e and Cat6 cables have a small string inside the cable to assist with this.

3. If your cable has the small string, make a small cut in the jacket of the cable, making sure not to touch any wires, and then use the string to pull towards the fresh end of the cable exposing about 6 inches (15.2 cm) of cable. Cut the string after you have enough exposed cable.

4. If your cable does not have the small string, make a small cut in the jacket described above and gently pull all of the wires together in one hand and pull the jacket in the opposite direction.

All Cat5, Cat5e and Cat6 cables follow a standard color pattern for the individual wires. Blue, Orange, Green and Brown. There are two wires per color. White/Blue and Blue, White/Orange and Orange, White/Green and Green, White/Brown and Brown. If you look at the back side of your patch panel, you will see the corresponding colors where you will terminate the cable to.

Note: There are two color patterns, T568A and T568B. Make sure to terminate both sides of the cable on the same pattern. If you have already terminated one side of the cable, look to see what pattern was used! If you have not already terminated, choose a standard that you will always use. Both patterns will produce the same results.

5. After choosing the correct pattern, choose the port on the patch panel you wish the cable to connect to. It is general practice to terminate in ascending order so start at the lowest number. First cable should be terminating to the 1st port and so on.

6. Untwist the wires completely to the jacket. Place the wires into the appropriate color slot on the patch panel. Make sure to place the wires as tightly as possible in the slots in regards to the jacket. There should be as little exposed and untwisted wire as possible to keep the signal strength as

high as possible. Make sure to place the White/Blue in the White/Blue spot and not the solid Blue spot. The White/Color wire is not the same as the solid color.

7. Terminate each wire. After all the wires are in the correct spot and double checked to make sure as little amount of exposed wires will be left as possible, use the punch down tool with the 110 blade and terminate each wire individually. The 110 blades will fully cover the wire connector on the patch panel. Push down until the tool clicks and cuts the end of the wire off. Repeat this step if the wire was not fully cut.

8. Secure the cable to the patch panel with a zip tie if there is a slot or tab for a zip tie.

9. Use a cable tester to assure that you correctly terminated all the wires.