Network Essentials Notes

It is an interconnection of computers to share resources (H/w & S/w). There are many types of networks.
• LAN (Local Area Networks)
• MAN (Metropolitan Area Networks)
• WAN (Wide Area Networks)

LAN : - When the computers connected with in a building or in a campus is called LAN. This type of networking used up to 1 Km. Mostly we used twisted wire to connect computers.
MAN : - When the computers connected in a big city or which connect two LAN's is called MAN. We use coaxial or fiber optic to connect.
WAN : - When the computers all over the world are connected to each other is called WAN. It has wireless connection it is generally used to communicate with other countries and at long distances. We use satellites to communicate with each other.

Topology

It is a geometric representation of computer networks. There are many topologies in computer networks.
• Bus Network Topology
• Ring Network Topology
• Star Network Topology
• Tree Network Topology
• Mesh Network Topology
• Hybrid Network Topology

Bus Network Topology

In bus topology all the computers are connected with a single wire for a network. The message is broadcast on the network. There is a T-connector to attach wires. To attach each computer with network there is a BNC (Barrel Knack Connector, Bottle Knack Connector, British Nabel Connector) connector. In this we use coaxial cable .
We use 2 50 ? connectors called terminators at both ends to stop the data signal. If the signal travels continuously on the network it is called bouncing .


Advantages
1. The main advantage of a broadcasting network is the reduction of physical lines.
2. The reliability of the network is high because the failure of a computer in the network does not affect the network functioning for other computers.
3. Addition of new computers to the network is easy.
Limitation
1. Each computer connected to the line must have good communication and decision making capability.
2. If the communication line fails, the entire system breaks down.

Star Network Topology

In star topology all the computers are connected to each other through a centralized device called HUB . Maximum distance of a client from a hub is 100 m. In star network we use RJ – 45 connector and Twisted Pair cable.
There are two types of twisted pair:-
• STP (Shielded Twisted Pair)
• UTP (Unshielded Twisted Pair)

Normally we use UTP cable but in area, where the EMI is more, we use STP cable. For example in Factories and Industries, where data wires and electricity wires are wired together. There are five categories of STP/UTP cable. Those are from cat -1 to cat -5. In telephone lines we use cat -3 cable, which is three twisted per feet and its speed is 10 Mbps and the connector is RJ – 11 . To data transfer we use cat -5 cable because its speed is 100 Mbps .


Advantages
1. This topology has minimal line cost because only n-1 lines are required for connecting n nodes.
2. Transmission delays between two nodes do not increase by adding new nodes to the network because any two nodes may be connected via two links only.
3. If any of the local computers fail, the remaining portion of the network is unaffected.
Limitation
1. The system crucially depends on the central node. If the host computer fails, the entire network fails.

Networking Media

To do networking we need to use some type of media. There are many types of media.
(i) Twisted pair cable
(ii) Coaxial Cable
(iii) Fiber optic cable
(iv) Microwave
(v) Satellite

Twisted Pair Cable

There are two wires, which are twisted with each other to avoid EMI. There are two types of twisted pair. This cable comes in 7 categories. We generally use the Cat 5 cable of speed 100 Mbps in networking.

SHIELD TWISTED PAIR CABLE (STP) : - In this an extra wire which is called shielded wire is wrapped over the inner cover which holds copper in pairs.
UNSHIELDED TWISTED PAIR CABLE (UTP) : - In this type of wire no shielded cover is there for extra protection from noise.

Coaxial Cable

Coaxial cable consists of an insulated copper conductor surrounded by a tube shaped copper braid outer copper tune and the inner conductor have the same axis of curvature hence it called coaxial cable. It is basically of two types
• BROADBAND SIGNAL CABLE (RG – 59)
• BASEBAND SINGLE CABLE (RG – 58)
We used Baseband signal cable in Networking of Computers. Its speed is 10 Mbps and impedance is 50 ?.

Fiber Optical Cable

Fiber optic cable consists of a very fine fiber made from two types of glass, one for the inner core and the other for the outer layer. That is transmitted as light through it. It is a costly but more secure transmission media.

Types of HUB/Switch

Hub/Switch is a device, which is used to connect more than two computers with each other to use resources and to communicate. There are many types of Hub/Switch

• Passive Hub : - In this type of hub, there is no electricity in hub, this hub does not regenerate/amplify the data. It simply pass the data.
• Active Hub : - It is a combination of passive hubs and repeater. In this type of hub, we need to give electricity. This hub is also called Multiport repeater . This hub also regenerates the signals.
• Switch : - Switch is actually hardware based.
Standard ports of HUB/SWITCH are 8/16/24/48/72 ports.

Difference between HUB & Switch

HUB

1. It use broadcast message.
2. It has no memory.
3. It is a slow device.
4. It is not a sensitive device.
SWITCH

1. It use point to point message.
2. It has small memory in KB.
3. It is a fast device.
4. It is a sensitive device.

NIC

NIC is Network Interface Card. It is also called LAN card or Ethernet card . It is inserted in extension slots of motherboard. In old NIC both BNC and RJ-45 connector attached, so it is called COMBO . If we attach NIC of different speed on a network, then there is Bottle Neck Problem .

Mac Address

MAC is Media Access Control. It is a 48 bit unique number which is given by the company in the time of manufacturing. Switches work on Mac address. The Mac address of each network card is stored in MAC- Table of switch.