NETWORKING I (SS3 FIRST TERM)

NETWORKING

Definition of Network and Networking

A computer network consists of a collection of computers, printers and other equipment that are connected together so that they can communicate with each other. It is also defined as a group of two or more

computer systems linked together.

Computer Networking is the scientific and engineering discipline concerned with communication between computer systems.

Types of Networks

Depending upon the geographical area covered by a network, it is classified as:

1.  Personal Area Network (PAN). PAN is a computer network organized around an individual person (typically within 10 meters).  PAN may be wired with computer such as USB and Fire wire. A wireless Personal Area Network (WPAN) can be made possible with network technology such as infrared Data Association (irDA) and Bluetooth.

2.  Local Area Network (LAN). A local area network is a computer network covering a small local area, like a home, office, or school. LAN has the following elements:

i. Server: It is the main computer that acts as a host and provides data, software, etc. to the other terminal linked with it.

ii. Work station: These are the computers attached to the server on the LAN

iii. Network Interface Unit: This provides the communications between the server and the work station

iv. Communication Channel: It is the medium through which the packets travel. The packets generally travel through cables which are of three types: Twisted pair cables, Co-axial cables and Fiber optic cables

3.  Metropolitan Area Network (MAN). MANs are large computer network usually spanning a large campus.

4.  Wide Area Network (WAN). WAN is a computer network covering a broad geographical area.

5.  Internet. The internet is a worldwide network of computers that share information

Network Topology 

Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer network. Network topology refers to the physical or logical layout of a network.

Types of Topologies

1.  Bus Topology

2.  Star Topology

3.  Ring Topology

4.  Mesh Topology

5.  Tree Topology

6.  Hybrid Topology

Bus Topology

 

 

 

All the nodes (file server, workstations, and peripherals) on a bus topology are connected by one single cable. A bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable. It is popular on LANs because they are inexpensive and easy to install.

Advantages of bus topology

1.     It is Cheap, easy to handle and implement.

2.     It is easy to install.

3.     Requires less physical lines hence less costly.

4.     It is independent i.e. any single computer can’t affect communication between other computers.

5.     Easy to expand, just need to add the new computer on the line.

Disadvantages of bus topology

1.     Only one node can transmit signals at a time.

2.     Failure or fault in the transmission line affects the whole communication network.

3.     Troubleshooting a cable fault is difficult.

4.     There is a limit to the number of computers that can be connected to the cable. Increasing the number of computers results in an increased collision as machines compete for transmission.

Ring Topology 

 

 

 

In a ring network, every device has exactly two neighbours for communication purposes. All messages travel through a ring in the same direction. A failure in any cable or device breaks the loop and can take down the entire network. To implement a ring network, we use the Token Ring technology. A token, or small data packet, is continuously passed around the network. When a device needs to transmit, it reserves the token for the next trip around, and then attaches its data packet to it.

Advantage of Ring Topology

Advantages of ring topology are:

1.     They use short length cables – less costly.

2.     Simple to install.

3.     Very effective where there is distributed data processing.

4.     More reliable because of alternate routing if one computer breaks down.

5.     Very orderly network where every device has access to the token and the opportunity to transmit.

6.     Easier to manage than a Bus Network

7.     The packet delivery time is fixed and guaranteed.

Disadvantages of Ring Topology

1.     The failure of a single node of the network can cause the entire network to fail.

2.     The movement or changes made to network nodes affects the performance of the entire network.

3.     Installation requires sophisticated software.

4.     Delays in communication are directly proportional to the number of nodes the message has to pass through.

5.     Requires a lot of reconfiguration when new nodes are added.

6.     Troubleshooting can be difficult.

7.     Token management must be robust because loss or corruption of the token can cause chaos.

8.     Modification may be difficult because adding or removing a device can disrupt the entire network.

Star Topology 

• In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub.

The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. The star topology reduces the chance of network failure by connecting all of the systems to a central node.

Advantages of Star Topology

1.      Easy to manage

2.      Easy to locate problems (cable/workstations)

3.      Easier to expand than a bus or ring topology.

4.      Easy to install and wire.

5.      Easy to detect faults and to remove parts.

Disadvantages of Star Topology

1.      Requires more cable length than a linear topology.

2.      If the hub or concentrator fails, nodes attached are disabled.

3.      More expensive because of the cost of the concentrators.

Tree Topology 

A tree topology (hierarchical topology) can be viewed as a collection of star networks arranged in a hierarch. This tree has individual peripheral nodes which are required to transmit to and receive from one other only and are not required to act as repeaters or regenerators. The tree topology arranges links and nodes into distinct hierarchies in order to allow greater control and easier troubleshooting.

Advantages of a Tree Topology

1.   Point-to-point wiring for individual segments.

2.   Supported by several hardware and software vendors.

3.   All the computers have access to the larger and their immediate networks.

Disadvantages of a Tree Topology

1.   Overall length of each segment is limited by the type of cabling used.

2.   If the backbone line breaks, the entire segment goes down.

3.   More difficult to configure and wire than other topologies.

Mesh Topology 

In this topology, each node is connected to every other node in the network. Implementing the mesh topology is expensive and difficult. In this type of network, each node may send message to a destination through multiple paths. While the data is travelling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route.

Advantages of Mesh Topology

1.   No traffic problem as there are dedicated links.

2.   It has multiple links, so if one route is blocked then other routes can be used for data communication.

3.   Point-to-point links make fault identification easy.

Disadvantages of Mesh Topology

1.   There is mesh of wiring which can be difficult to manage.

2.   Installation is complex as each node is connected to every node.

3.   Cabling cost is high.

The other variation is the tree with a hybrid topology

Hybrid Topology 

Hybrid topology is a combination of any two or more network topologies. A hybrid topology always accrues (results) when two different basic network topologies are connected. It is a mixture of above mentioned topologies.

Advantages of a Hybrid Topology

1.   It is extremely flexible.

2.   It is very reliable.

Disadvantage of a Hybrid Topology

1.      Expensive

Transmission medium

·          Wired medium (guided medium) : physical cables (coaxial, twisted pairs, fiber optic cables)

·          Wireless medium (unguided medium): infrared (IrDA), Wi-Fi, Bluetooth, Li-Fi, Satellite, Microwave

Twisted pair (TP) cables

Characteristics

•        A twisted pair cable consists of two insulating copper wires arranged in a regular spiral pattern.

•        A number of these pairs are bundled together into a cable by wrapping them into a tough protective sheath.

•        Twisting decreases crosstalk interference between adjacent pairs in the cable

•        Susceptible to interference and noise because of its easy coupling with electromagnetic fields.

•        The standard connector is RJ45 (Register Jack 45)

•        Most common in the telephone network

•        Can either be Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP)

Coaxial cable

Characteristics

•        It consist of hollow outer cylindrical conductor that surround only a single inner wire conductor

•        A single coaxial cable has a diameter of from 1 to 2.5cm

•        Can be used over long distances

•        Less susceptible to interference and crosstalk than TP.

•        More expensive than twisted pair cable

•        Connectors include BNC, BNC-T

•        Used in Television distribution – cable TV, long distance telephone lines –NITEL wire, LAN – bus topology

Fiber optics

Characteristics

•        Made up of glass or plastic and transmit signals in form of light.

•        Glass or plastic core is surrounded by a cladding of less dense glass or plastic

•        Can be single mode or multi-mode

•        Outer jacket is made of Teflon or Polyvinylchloride (PVC)

•        Best in terms of performance – can span longer distance and very low attenuation

•        Immune to electromagnetic interference (it’s not made of copper wire)

•        Connectors include Subscriber channel (SC) connector, Straight –tip (ST) connector, MT-RJ connector

•        They are used in long distance telecommunication link, found in backbone network and LAN.

Wireless Media

·          Infrared (IrDA): This type of transmission is used for communication over short distances between sender and receiver that are within the line of sight.

 

·          Bluetooth: Bluetooth technology uses radio waves to connect mobile devices such as phones, PDAs, computer etc. It has a limited transmission range of 10 meters.

·          Wi-Fi (Wireless Fidelity): This is a technology that uses radio waves to provide high speed wireless connection between electronic devices based on the IEEE 802.11x standards.

·          Li-Fi (Light-Fidelity): LI-Fi is a form of visible light communication system that uses common household LED (light emitting diode) light bulbs to enable data transfer, boasting speeds of up to 224 gigabits per second.

·          Microwave: microwave signals are sent through space in the form of electromagnetic waves. Just like radio signals, they also must be sent in straight lines from one microwave station to another. To avoid interference, most microwave stations are built on mountain tops or placed on top of buildings.

·          Satellite: communication satellites are placed in orbit 22300 feet above the earth surface. This allows the satellite to maintain a constant position above one point on the earth surface by rotating at the same speed as the earth.

Network architecture

Peer-to-peer: In this network, the computers connected together are called peers and each handles its security. Peer-to-peer networks are designed to satisfy the networking needs of home networks or of small companies that do not want to spend a lot of money on a dedicated server but still want to have the capability to share information or devices.

Client/Server: Computers (clients) are connected to a server. The server takes responsibility of storing clients’ data and managing other computers (clients) in the network.