A network is a collection of computers and mobile devices connected together via communication devices and transmission media, often wirelessly allowing computers to share resources(hardware, software & data and information)
1)Sharing an internet connection among several users.
2)Sharing application software, printers and other resources.
3)Exchanging files among network users and over the internet.
Hardware component that enables a computer to send (transmit) and receive data, intructions, and infornation to and frorm one or more computers.
NIC Adapters:
NIC is Network Interface Card; this is the most important device in building network.These adapters are the most common part of computers which are used in our homes and offices.Nic is also referred to LAN, i.e. is Local area network card. Communication mediums (cables) are attached to this card to build network. This device has unique Mac address. To build network unique IP address is assign to this LAN card to begun communication.In case of developing WLAN, instead of LAN card we use Wireless card. Its functionality is same as simple LAN card; it is just wireless communication device which connects to router for communication.
Routers:
Router is intelligent device which routes data to destination computers. It helps in connecting two different logical and physical networks together. In small network server is connected to router along with clients for communication. With routers network communication is not possible; it is soul of network without which distribution if internet and other network data to entire network is impossible. It works very same when it comes to use wireless network using wireless network router. It performs all functions similarly without using any medium like cables etc.Router uses software known as routing table. Routing table is used to store source and destination address. Major companies which know for manufacturing routers and wireless routers are Tp Link, Cisco systems, Nortel, D link etc.
Hubs:
If we talk about networks on larger scale hub(s) are required to build network. All computers are connected directly to the hub as hub performs as centralized device the network. When data is sent to the hub it broadcasts the data to all the ports of the hub and then it is sent to destination computer on the network. If hubs fails to perform its routine functions it will halt the working of the entire network until it is put back in normal condition.
Switches:
Switch is another important device when we talk about computer network on broader spectrum.It is used at the same place as hub is but the only difference between the two is that switch possess switching table with in it. Switching tables store the MAC addresses of every computer it is connected to and send the data to only requested address unlike hub which broadcasts the data too all the ports. Switches can be considered advance form of hubs.
Gateways:
As name suggests it some kind of passing through to some thing. Interestingly gateways can be software or it can also be device. Gateway device connects LAN with internet. Its basic functionality is to provide security to the network. By using gateways incoming/out going traffic can be monitored for any malicious activity within the network which can be harmful to network integrity.
Modems:
Modems can be of two types. One modem is very common in every computer which we use to connect to internet using our telephone line by dialing to our ISP and the other one is used to connect to DSL. Functions however are same for both types of modems; they are used for modulation and demodulation, they are used to convert analog signals into digital and digital signals into analog so that signals can be travelled on telephone lines.
Cables:
Cables are obviously used to connect communication devices with each other to form network. There different types of cables, commonly used cables are 10baseT/CAT5 , coaxial cable, Ethernet and fiber optical cable. Fiber optical is the most expensive as it enables the data transfer at speed of light. It is costly solution which is mostly get adopted by corporate sector. However in recent developments optical fiber cable is now being used in home networking and also used as medium to connect to internet.
PHYSICAL: Send signals through cable, wire or tangible materials.
WIRELESS:Send signals through the air or space.
BOUNDED MEDIA:
Bounded media are the physical links through which signals are confined to narrow path. These are also called guide media. Bounded media are made up o a external conductor (Usually Copper) bounded by jacket material. Bounded media are great for LABS because they offer high speed, good security and low cast. However, some time they cannot be used due distance communication. Three common types of bounded media are used of the data transmission. These are
- Coaxial Cable
- Twisted Pairs Cable
- Fiber Optics Cable
COAXIAL CABLE:
Coaxial cable is very common & widely used commutation media. For example TV wire is usually coaxial.
Coaxial cable gets its name because it contains two conductors that are parallel to each other. The center conductor in the cable is usually copper. The copper can be either a solid wire or stranded martial.
Outside this central Conductor is a non-conductive material. It is usually white, plastic material used to separate the inner Conductor form the outer Conductor. The other Conductor is a fine mesh made from Copper. It is used to help shield the cable form EMI.
Outside the copper mesh is the final protective cover. (as shown in Fig)
The actual data travels through the center conductor in the cable. EMI interference is caught by outer copper mesh. There are different types of coaxial cable vary by gauge & impedance.
Gauge is the measure of the cable thickness. It is measured by the Radio grade measurement, or RG number. The high the RG number, the thinner the central conductor core, the lower the number the thicker the core.
Here the most common coaxial standards.
- 50-Ohm RG-7 or RG-11 : used with thick Ethernet.
- 50-Ohm RG-58 : used with thin Ethernet
- 75-Ohm RG-59 : used with cable television
- 93-Ohm RG-62 : used with ARCNET.
CHARACTERISTICS OF COAXIAL CABLE
- Low cost
- Easy to install
- Up to 10Mbps capacity
- Medium immunity form EMI
- Medium of attenuation
ADVANTAGES COAXIAL CABLE
- Inexpensive
- Easy to wire
- Easy to expand
- Moderate level of EMI immunity
DISADVANTAGE COAXIAL CABLE
- Single cable failure can take down an entire network
Twisted Pair Cable
The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mps. Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are done to reduce vulnerably to EMI and cross talk. The number of pairs in the cable depends on the type. The copper core is usually 22-AWG or 24-AWG, asmeasured on the American wire gauge standard. There are two types of twisted pairs cabling
1. Unshielded twisted pair (UTP)
2. Shielded twisted pair (STP)
1. Unshielded twisted pair (UTP)
UTP is more common. It can be either voice grade or data grade depending on the condition. UTP cable normally has an impedance of 100 ohm. UTP cost less than STP and easily available due to its many use. There are five levels of data cabling
Category 1
These are used in telephone lines and low speed data cable.
Category 2
These cables can support up to 4 mps implementation.
Category 3
These cable supports up to 16 mps and are mostly used in 10 mps.
Category 4
These are used for large distance and high speed. It can support 20mps.
Category 5
This is the highest rating for UTP cable and can support up to 100mps.
UTP cables consist of 2 or 4 pairs of twisted cable. Cable with 2 pair use RJ-11 connector and 4 pair cable use RJ-45 connector.
Characteristics of UTP
- low cost
- easy to install
- High speed capacity
- High attenuation
- Effective to EMI
- 100 meter limit
Advantages of UTP
- Easy installation
- Capable of high speed for LAN
- Low cost
Disadvantages of UTP
- Short distance due to attenuation
2. Shielded twisted pair (STP)
It is similar to UTP but has a mesh shielding that’s protects it from EMI which allows for higher transmission rate.
IBM has defined category for STP cable.
Type 1
STP features two pairs of 22-AWG
Type 2
This type include type 1 with 4 telephone pairs
Type 6
This type feature two pairs of standard shielded 26-AWG
Type 7
This type of STP consist of 1 pair of standard shielded 26-AWG
Type 9
This type consist of shielded 26-AWG wire
Characteristics of STP
- Medium cost
- Easy to install
- Higher capacity than UTP
- Higher attenuation, but same as UTP
- Medium immunity from EMI
- 100 meter limit
Advantages of STP:
- Shielded
- Faster than UTP and coaxial
Disadvantages of STP:
- More expensive than UTP and coaxial
- More difficult installation
- High attenuation rate
Fiber Optics
Fiber optic cable uses electrical signals to transmit data. It uses light. In fiber optic cable light only moves in one direction for two way communication to take place a second connection must be made between the two devices. It is actually two stands of cable. Each stand is responsible for one direction of communication. A laser at one device sends pulse of light through this cable to other device. These pulses translated into “1’s” and “0’s” at the other end.
In the center of fiber cable is a glass stand or core. The light from the laser moves through this glass to the other device around the internal core is a reflective material known as CLADDING. No light escapes the glass core because of this reflective cladding.
Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second)
Characteristics Of Fiber Optic Cable:
- Expensive
- Very hard to install
- Capable of extremely high speed
- Extremely low attenuation
- No EMI interference
Advantages Of Fiber Optic Cable:
- Fast
- Low attenuation
- No EMI interference
Disadvantages Fiber Optics:
- Very costly
- Hard to install
