Networking Basic

Computer network is a group of interconnected computer that allows to communicate or exchange files and information. A typical computer network compose of Modem, Router, Switch, Work Stations and Network Printer as shown in fig1.

fig1. Typical Computer Network

Classification of Networks
Computer networks are often classified based on their connection type, topology, scale and technology that used to connect them.  

Connection Method
There are two common connection method that were used in computer networks, wireless and wired connection.  These two connection method differs on their structure.  A typical wired network used cables such as UTP (Unshielded Twisted Pair), Coaxial cables and Fiber Optics while wireless network doesn't used any cables they used radio signals or frequency to communicate to each other.  These two connection method each have advantages and disadvantages depending on your needs. One may serve you better and faster than the other. Always remember that in building a network you may need to consider the ease of installation, security, cost, reliability and performance.

WIRED NETWORK TECHNOLOGY

Wired network also known as Ethernet is a combination of cables and software that used to connect computer and other peripherals. It is typically more faster than wireless network and they can be very affordable but the cost of cables may add up to your expenses.

There are three basic things that you need to set-up wired network.

• Cables
• Hardware components
• Network Interface Card (NIC)

CABLES
Cables are very essential in setting up wired network.  This will serve as medium for communication.  It will connect all the components in your network.  The following are the commonly used cables for wired networks,

Unshielded Twisted Pair (UTP) - The most commonly used cable in computer networking. It is used in 10Base-T and 100Base-T networks, as well as in home and office telephone wiring. CAT 5 UTP was the standard cable for use with Ethernet 100Base-TX.

fig2. Unshielded Twisted Pair (UTP)  cable

The standard connector for UTP is RJ-45. This is a plastic connector that looks like a large telephone cable connector.  RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry.  As you can see on fig3, this connector has a  designated pin which wire goes inside the connector correspond to each color. 

fig3. Pin assignment for T-568B and T-568A

A standard CAT 5 UTP cable has two popular cabling scheme, Straight-through and Crossover. Straight-through cable is a CAT 5 UTP cable that has similar wiring in both ends. Both cable ends follow either T-568A or T-568B. It is also used to connect a computer to a hub or a switch.

fig4. Straight-through cable

Crossover cable is a CAT 5 UTP cable that has one end following T-568A and the other T-568B. A crossover cable is used to connect two computers directly and two hubs or switches.

fig5. Crossover cable

Shielded Twisted Pair (STP) - A type cable that is suitable for environments with electrical interference.  It protects cable from external EMI (Electromagnetic Interference).  Shielded twisted pair is often used on networks ing Token Ring topology. 

fig6. Shielded Twisted Pair (STP)

Coaxial Cable -  A type of cable that has single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield. The metal shield serve as a protector from outside interference such as EMI (Electromagnetic Interference). It is often used as a transmission line for radio frequency signals, computer networks and distributing cable television signals. 

There are two types of coaxial cable a thick and thin coaxial cable. The thick coaxial cable can support segment length of 500 meters. It is also known as 10base5. On the other hand, the thin coaxial cable can support segment length of 200 meters and it is also known as 10base2.  The most popular connector for this type of cable is Bayone-Neill-Concelman (BNC).

fig7. Coaxial cable

  

fig8. BNC connector

Fiber Optics Cable - It consists of a center glass core surrounded by several layers of protective materials. Optical fiber carries light on its transmission instead of electrical signals that makes it  more advantageous for long-distance communications.  This allows long distances to be spanned with few repeaters. The transmission is said to be high-speed, it can send information at higher data rates (bandwidth). For fiber optics cable that is specified for Ethernet communication also known as 10BaseF.
 

fig9. Fiber Optic Cable

 
HARDWARE COMPONENTS
A typical wired network consist of the following hardware components:


Router  - It is a networking device whose software and hardware are usually designed to the tasks of routing and forwarding information. It determines the next network point to which a packet should be forwarded toward its destination. The router joins two networks and decides which way to send each information. A router is located at any gateway (where one network meets another), including each point-of-presence on the Internet. A router is often included as part of a network switch.


Switch / Hub - Although hub and switch use to connect multiple Ethernet devices together and making them act as a single network segment,  there still big difference between those two network device. Hub doesn't control any network activity or traffic. If the packet was sent to a particular destination, it sent throughout the network until the correct recipient receive it.  Unlike switch, once a packet was sent it will go directly to the recipient. Technically speaking, switch is more intelligent than hub.


Modem -  Derived from the words Modulator - Demodulator. Modem is a network device that modulates digital information into analog signal and demodulates analog signal to digital information. It is used to connect a home or small network to internet.


NETWORK INTERFACE CARD (NIC)
A Network Interface Card (NIC) is used to connect computers to Ethernet.  They often called LAN card or Ethernet card.

 

fig10. Network Interface Card (NIC)

Network Topology
Network Topology is a physical interconnection or layout of computers and other elements on a network. Network topologies are categorized into following  basic types:

• Bus
• Start
• Ring
• Mesh
• Tree

Bus topology - It is a type of network topology that use a common backbone to connect all computer and device on a network. The backbone serve as a shared communication medium. A typical Bus network use coaxial cable, it can be thinNet (10base2) or thickNet (10base10).

fig11. Bus Topology

Star Topology  - Is a type of network topology where a central connection (hub, switch or router) was used to connect all the computer and device in the network. It is very popular in small and home networks. This type of topology used CAT5 UTP cable.

fig12. Star Topology

Tree Topology -  This type of topology integrates a multiple star topologies together onto a bus.  It is a combination of star and bus topology that allows you to expand your network.

fig13. Tree Topology

Ring Topology  - It is a type of network topology where all the computer and device are connected and form a circle like shape. Each packet was sent around the ring until it reaches its destination. If there is a cable or device failure the loop breaks and it will cause network connection failure.

 fig15. Ring Topology 

Mesh Topology -  A type of network topology where all the computers and devices are connected to one another. It allows full distribution of message around the network and it can take several possible paths from source to destination.

 

fig15. Mesh Topology

TYPES OF NETWORK


Pear-to-Pear  - A type of computer network that has no intended client or host.  Both computer can be host and can be client at the same time.

Local Area Network (LAN) - A computer network that covers small area such as home, office, small business and small building. They are widely used in connecting personal computers, printers and other network devices. A LAN is useful in sharing resources like files, games and other applications.



Wide Area Network (WAN) -  A computer network that covers large geographical area like country and continent.  It also use transmission facilities provided by telephone companies.



Metropolitan Area Network (MAN) -  A computer network that connects two or more Local Area Networks but not extend beyond city limits.



Virtual Private Network (VPN) - A computer network that uses public network to connect remotely and securely to remote site or private networks. VPNs are frequently used by businesses and home offices. It is commonly used by people traveling or working from their home who want to connect to their company's network to check email or access business applications.





WIRELESS TECHNOLOGY
Wireless network is said to be the easiest and less expensive way to connect computer and other network device. The most popular among those wireless technology is wireless LAN (WLAN). 

Wireless LAN connects computer and network device without the aide of cables it uses radio signals or frequency.  A typical WLAN use WiFi communication standard, among them are:

• 802.11b
• 802.11a
• 802.11g
• 802.11n

802.11b - It is the first standard to be widely used in WiFi. It support maximum data rate of 11 Mbps and it has operating frequency of 2.4 GHz. The maximum range for indoor use is 150 ft or 45 meters and for outdoor use is 300 ft or 90 meters.


802.11a - It is more faster than 802.11b and commonly found in most business networks. It supports maximum data rate of 54 Mbps. It has operating frequency of 5 GHz.  The maximum range for indoor use is 50 ft or 15 meters and for outdoor use is 100 ft or 30 meters.

802.11g - The third WiFi standard that was ratified in 2003. It extend and improve 802.11b. It supports maximum data rate of 54 Mbps and operating frequency of 2.4 GHz. The maximum range for indoor use is 150 ft or 45 meters and for outdoor use is 300 ft or 90 meters.

802.11n -  It improves upon the previous 802.11 standards.  It has a multiple-input multiple-output (mimo).  It has an operating frequency of 5 GHz or 2.4 GHz and a throughput 144 Mbps.  It supports maximum data rate of  600 Mbps.  The maximum range for indoor use is 300 ft or 91 meters and for outdoor use is 600 ft or 182 meters.


There are two configuration of WiFi that is widely used today, ad-hoc and infrastructure.  

Ad-hoc mode is a wireless configuration that allows connection in pear-to-pear mode.

Infrastructure mode allows to communicate wireless device with a central base station (access point). It bridges communication between wireless network and wired network.

Basic PC Troublesooting and Repair

Troubleshooting and Repair are basically a method of finding the problem that causes the system not to work properly and later applying the possible solution. Successful troubleshooting requires a logical, consistent approach that seeks to narrow down the source of a problem by figuring out what is and what's not working until a single cause is identified.You cannot fix a problem by changing two or three object at once. It can cause serious damage to your computer. Patience is one characteristic of a good technician.

Boot Failure

Boot failure is one of the common problem in computer system. One possible cause of this issue is power supply and sometimes, each computer components can contribute more than we expected.

The Computer is dead set

Dead Set, in electronics, is basically no power or not enough power to make a device functional. The possible cause of this is power supply, groundings and busted components. The best way to deal with this is to check whether the computer has enough power. To do these check the following:

• Power cable
• Power supply
• Soft power ON
  

The Computer is ON but no system activity

The possible cause of this issue is component failure. Basically, computer has a built in program, known as POST (Power ON Self Test), designed to test all component before boot process start. Normally, POST stops the boot process when a hardware problem occurs and the BIOS (Basic Input Output System) will issue an error message or a series of beep codes. Try the following to resolve that issue:

• Restart computer and observe the POST. Usually, an indication that a computer has no problem is one short beep. If the technician will hear an abnormal beef codes there might be a problem with your system unit. Please refer to the list of beep codes in table 1.1.
• Check motherboard for short.
• Check CMOS reset jumper is on SET setting. Sometimes CMOS reset jumper can make the computer to stop from any system activity.
• Test voltage output of the power good pin. This power good pin is usually used for resetting purposes so that the motherboard reset signal is kept active until the power good signal is raised to +5V. This keeps the motherboard not trying to do anything before the operating voltages have stabilized.

INDICATION	BEEP CODE	ERROR
Good	1 short beep	No Error
Bad	1 Long, then 2 Short Beeps	Video Error
Bad	1 Long, then 3 Short Beeps	Video Error
Bad	1 Long Beep	Memory
Bad	Continuous Beeping	Memory or Video Error
Bad	1 Long Beep	Memory

Table 1.1 - Common POST beep Codes

The Computer is ON but has error message disk boot error, replace and Strike any key when ready boot error, replace and Strike any key when ready

The main cause of this problem is booting on a non-bootable disk. If you encounter this error please try the following:

• Check the floppy disk drive if there is any inserted disk.
• Check if there's any USB flash drive that is connected in computer.
• Check the boot sequence in Advance CMOS set-up. Make sure that the boot sequence is C:, CD-ROM, A: or the first boot device is Hard Disk Drive, second boot device is floppy drive and the third boot device is CD-ROM.
  
• Make sure that you are booting in a valid system disk.
• If none those steps resolve that issue, clone your Hard disk to a reliable source or make a clean installation of your Operating System. There might be a problem on the boot record of your operating system.

Display Section Issue

Display section may be divided into two areas – video card and monitor. Video Card is the component that is responsible for producing the visual output from your computer. It is also a piece of hardware that takes the visual output and tells the monitor which of the dots on the screen to light up (and in what color) to allow you to see it. The most common problem that you may encounter in display section is no video display. In order to deal with this we need to check the following areas:

1. Check the Monitor

• Make sure that the monitor has enough voltage or plugged into wall socket or to a computer power supply.
• Check the monitor if it is turned ON. A LED Power indicator will indicate whether the monitor is turned ON or OFF. The LED Light will be ON if the monitor is turned ON.
• Check if the video cable was connected to the video adapter port at the back of your computer.
• Replace the suspected monitor with the good one.
• If the following did not solve that issue check the video card and the rest of the components in your computer.

2. Check the Video Card

• If the POST beep code pertains to video card, remove the video card. Examine carefully. Look for signs of burn. Remove the dust in the slot carefully by blowing air directly to the slot then reseat the video card. Restart the computer and observe the POST. For some reason, video card fails because of the dust inside the computer and sometime those dust stick to the expansion slot.
  
• If the above procedure does not fix the problem, replace the suspected video card with good one. Otherwise there is a serious problem in your system unit that can cause video card not to work properly. One possible cause is the motherboard. The video card slot (PCI, PCIE, AGP) in the motherboard may be busted and cannot recognize it.
  
  

Hard Disk Drive (HDD)

Hard Disk Drive (HDD) is a non-volatile data storage device that stores data on a magnetic surface layered onto hard disk platters. It can save large amount of data at minimum time compare to a typical floppy disk. The most common problem that you may encounter with hard disk drive is failed to detect by your computer. The following are the possible causes.

• Power supply is unplugged or not connected to the drive.
  
• Busted Drive electronics.
  
• Damaged or unplugged IDE Cable.
  
• Busted IDE Controller.
  
• Disabled in CMOS set-up.
  
• No hard disk is present.

Try the following solution in an effort to resolve that issue:

• Check CMOS set-up. In some instances, HDD may be disabled in CMOS Setting. To access CMOS set-up, restart computer press Del simultaneous to enter CMOS set-up. Go to Standard CMOS set-up check the status of your primary master, primary slave, secondary slave and secondary master and change their setting to Auto. Exit and save setting.
  
• Check the HDD configuration. If possible try to change the present configuration of HDD if you suspected bad configuration. Sometimes, there are some HDD that can be detected to slave set-up only or master set-up only.
  
• Check if the power supply is present and connected properly to HDD
  
• Check if the IDE cable is properly connected. If the drive still undetected replace the suspected IDE Cable with good one.
  
• Replace the suspected HDD with good one. This action can save time and can easily determine whether the HDD is defective or not.
  
• If all of those solutions don’t fix the problem, we can conclude that the problem is in motherboard. The IDE Controller that was built in to the motherboard was defective.Replace the mother board with good one.
• If your motherboard support SATA you can use SATA compliant HDD.
  

Floppy Disk Drive (FDD)

Floppy disk is the cheapest storage media that is available in the market. It is made of a magnetic disk enclosed in a plastic rigid container. In order to access the data that was stored in floppy disk a floppy disk drive (FDD) is needed. This two are very useful in our everyday computing but it can give inconvenience when trouble start. Most of the common FDD trouble is caused by floppy disk and the more serious comes from the drive it self.The following section will discuss some of the common FDD problems with its possible solution.

Undetected Floppy Disk Drive

The system fails to detect FDD because of the following:

• Power supply is unplugged or not connected to the drive
  
• Busted Drive electronics
  
• Damage or unplugged FDD interfaces cable
  
• Busted FDD IDE Controller
  
• Disabled to CMOS set-up
  
• No floppy Disk Drive
  

In order for us to deal with that problem, we must consider all of its possible causes.Try to do the following solution:

• Check the power supply connection of FDD. Turn On the computer and observe the POST as well the LED indicator at the FDD’s front panel. That LED will light for a short time once the FDD is detected and if enough power was establish to have system activity.
  
• Check the FDD cable interface. Replace the suspected FDD interface cable with the good one to determine whether it is damage or not.
  
• Check the CMOS set-up.In standard CMOS set-up look at the floppy disk tab. Check the status.The normal status is 3.5 inches floppy disk drive.
  
• Replace the suspected FDD with good one before concluding that the FDD is defective. Doing this can save time and can easily determine whether the FDD is defective or not.
  
• If all of those solutions don’t fix the problem, we can conclude that the FDD IDE Controller that was built in the motherboard is defective. Replace the motherboard with good one.
  

Floppy Disk Issue

More often, the cause of FDD problem is not with the drive but with the disk. As we all know floppy disk is made of plastic and the materials that was used in manufacturing it is not class A as we think off. The following are some Floppy Disk issue that you may encounter during computer operation.

1. Access Denied - Your have tried to perform a write function to a read-only file. If using a floppy, make sure the disk is not write-protected. If you really want to delete the file, you can change it be a regular file, then delete it. In Windows 95, right click the file then choose Properties, then un-check the "Read-Only" box. In DOS, use the ATTRIB command.
2. Attempted Write-Protect Violation - You tried to format a write-protected floppy diskette.
3. Data Error Reading Drive X: - Usually caused by the slow misalignment of disk drives over time. Use a disk fixing utility to realign the disk's data.
4. Disk Drive 0 Seek Failure - Drive 0 and 1 refer to your a: and b: drive. Most often, if you get this error it is because your BIOS are looking for a drive that is not there. Check your setup and be sure that only the floppy drives
5. Disk Read Failure - Many potential problems. Try another disk. Make sure the cables are correctly attached to the drive. If all this is ruled out, your floppy drive is probably bad.
6. Drive Not Ready - If this is a floppy drive, make sure the disk is inserted all the way. Try another disk. Make sure the floppy drive cable is not damaged. If this doesn't pinpoint the problem, you'll have to replace the floppy drive. You may have a bad sensor, so it can't sense a disk inside it.
7. General Failure Reading Drive X: - First, press I for ignore, then use a diagnostic utility to test the disk. If this doesn't help, press A for abort, then inspect all cables related to the drive producing the error. If it a floppy, try another diskette.
8. Non-Dos Disk Error Reading (Writing) Drive X: - The computer can't find a boot track on the disk. Boot off a floppy then use SYS to recopy the system files over.
9. Not Ready Reading Drive X: - Usually, the cause of this is that the drive door of your diskette drive is not closed all the way. If it is, then you may have a bad sensor in your disk drive.
10. Target Disk Is Write Protected - Often seen when trying to do a DISKCOPY to a write protected floppy disk. If the disk is not write protected, then that part of your floppy drive that senses write protection may be broken. Best bet is to buy another diskette drive.

Keyboard Issues
keyboard is an input device that used to enter information to computer. Using a keyboard, a person can type a document, use keystroke shortcuts, access menus, play games and perform a variety of other tasks. Although keyboard is very simple device in a computer system still it has issue that is can bring inconvenience in our everyday computing. The following are some keyboard issues that some computer user experienced:

• Wrong characters appear when typing.
  
• Onscreen messages do not appear when pressing multimedia keys.
  
• Setting a multimedia button produces an illegal peration error message.
  
• Multimedia keyboard buttons not working.
  
• Internet keyboard buttons not working.
  
• Sticking keys.
  

The following are the common solution for those issues:

1. The most common problem when faced with a non-working keyboard is an improper connection. Try reconnecting your keyboard, restart your computer and see if that fixes it.
   
2. Turn off the system. Unplug the keyboard connect and inspect for any bent or broken pins. If the pins are bent, then it is possible to gently straighten them using the tip of a ball point pen or mechanical pencil. If the pins are broken, then replacement of the keyboard may be necessary.
   
3. Try updating the device driver. Visit the manufactures web site for the latest driver available for your keyboard make and model.
   
4. While at the manufactures web site. See if there are software patches or updates available for your keyboard. If there are, go ahead and install them as well as the updated driver.
   
5. If you are using a multi-media type keyboard, be sure to delete the software before installing any new drivers for this type of keyboard. Install the updated driver for the manufactures web site, then re-install the keyboard software. If any software updates or patches are available for your multi-media keyboard, install them at this time. Delete the keyboard software by using Add/Remove Programs (Start > Control Panel > Add/Remove Programs). If you receive a prompt asking if you would like to remove all shared files, answer "No to all". Then click OK.
   
6. If none of the above steps resolves your keyboard problem, it is likely that your keyboard is bad.

Mouse Issue

Mouse is a pointing device that will help you in navigating your computer screen. Your mouse senses your motion, when you click it sends them to the computer so it can respond appropriately. This section will cover some common mouse problem with its possible solution.

Mouse is slow or erratic

1. Clean the mouse.
   
2. Check that mouse surface or mouse pad is clean and flat.
   
3. Restart the computer.
   
4. Change the mouse tracking speed
   
   
   
   • In Windows, Start  > Settings > Control Panel > Mouse > Motion.
     
   • In Macs, Apple Icon > System Preferences > Keyboard and Mouse.

Mouse is not responding

1. Check cords
   
2. Unplug and re-plug the mouse.
   
3. Ensure plugged firmly into Computer
   
4. See if damaged or twisted
   
5. Restart the computer
   
6. Swap mice with another computer.
   

Cleaning Trackball Mice

1. Turn the mouse upside-down
   
2. Remove ball cover.
   
3. Remove mouse ball
   
4. Clean gunk from the 3 rollers and mouse ball, using your finger or a paper clip as needed.
   
5. Put ball in the mouse
   
6. Secure the ball cover in place.
   

Optical mice

Some Macintosh optical mice (where the whole mouse is the button) will occasionally become stuck in the down position when they are new. Gently tapping the mouse will pop it back up. If an optical mouse is jumping around the screen, have the user remove the mouse pad and attempt to use the mouse. Sometimes the colors affect the performance of the optical mice.