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Networking (Devices), Exams of Computer science

Computer science

This contains networking topologies an networking devices.

Typology: Exams

2019/2020

Uploaded on 09/18/2020

Shivam53
Shivam53 🇮🇳

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Chapter 1
1. Introduction to networks (Period-02, Marks 08)
1.1. Hardware
1.1.1. Topologies , Routers, bridges, gateways, switches,
1.1.2. wired /wireless media ,Selection criteria for the devices
Network:-
A network consists of two or more computers that are linked in order to share
resources (such as printers and CDs), exchange files, or allow electronic
communications. The computers on a network may be linked through cables,
telephone lines, radio waves, satellites, or infrared light beams.
Types of networks include:
Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Networks (MAN)\
Wireless LAN (WLAN)
Wireless WAN (WWAN)
Need for Computer Networks:-
Computer networks help users on the network to share the resources and
in communication
The following are the important uses and benefits of a computer network.
File sharing: Networking of computers helps the network users to
share data files.
Hardware sharing: Users can share devices such as printers,
scanners, CD-ROM drives, hard drives etc. Without computer
networks, device sharing is not possible.
Application sharing: Applications can be shared over the network,
and this allows to implement client/server applications
User communication: Networks allow users to communicate using
e-mail, newsgroups, and video conferencing etc.
Network gaming: A lot of network games are available, which
allow multi-users to play from different locations.
Voice over IP (VoIP): Voice over Internet Protocol (IP) is a
revolutionary change in telecommunication which allows to send
telephone calls (voice data) using standard Internet Protocol (IP)
rather than by traditional PSTN.
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Chapter 1

1. Introduction to networks (Period-02, Marks 08) 1.1. Hardware 1.1.1. Topologies , Routers, bridges, gateways, switches, 1.1.2. wired /wireless media ,Selection criteria for the devices

Network:-

A network consists of two or more computers that are linked in order to share

resources (such as printers and CDs), exchange files, or allow electronic

communications. The computers on a network may be linked through cables,

telephone lines, radio waves, satellites, or infrared light beams.

Types of networks include:

 Local Area Network (LAN)

 Wide Area Network (WAN)

 Metropolitan Area Networks (MAN)\

 Wireless LAN (WLAN)

 Wireless WAN (WWAN)

Need for Computer Networks:-

Computer networks help users on the network to share the resources and

in communication

The following are the important uses and benefits of a computer network.

 File sharing: Networking of computers helps the network users to

share data files.

 Hardware sharing: Users can share devices such as printers,

scanners, CD-ROM drives, hard drives etc. Without computer

networks, device sharing is not possible.

 Application sharing: Applications can be shared over the network,

and this allows to implement client/server applications

 User communication: Networks allow users to communicate using

e-mail, newsgroups, and video conferencing etc.

 Network gaming: A lot of network games are available, which

allow multi-users to play from different locations.

 Voice over IP (VoIP) : Voice over Internet Protocol (IP) is a

revolutionary change in telecommunication which allows to send

telephone calls (voice data) using standard Internet Protocol (IP)

rather than by traditional PSTN.

Elements of Computer Network:-

Computer Network is a system in which multiple nodes are connected to each other

to share information and resources. Computer network allows to share resources

between different nodes connected within it.

Computer Network Elements: The objects basically used in computer network are

known as Computer Network Elements (CNEs). There are basically 4 computer

networking elements:

 Computers  Transmission medium (wired or wireless)  Protocols  Network software Centralized network:-

A centralized network architecture is built around a single server that handles all the

major processing. Less powerful workstations connect to the server and submit their

requests to the central server rather than performing them directly. This can include

applications, data storage, and utilities.

Decentralized network:-

In computing terms, a decentralized network architecture distributes workloads

among several machines, instead of relying on a single central server. This trend has

evolved from the rapid advancements of desktop and laptop computers, which now

offer performance well beyond the needs of most business applications; meaning the

extra compute power can be put to use for distributed processing.

Line configuration: - Line configuration refers to the way two or more communication devices attach to a link. A link is a physical pathway that transfers data from one device to another. There are two possible line configurations:-  Point-To-Point:- This line configuration provides a dedicated link between two devices. The entire capacity of the channel is reserved for transmission between those two devices. Eg.:- Mesh Topology, Star Topology.  Multi Point : - This line configuration is one in which more than two specific devices share a single link.The entire capacity of the channel is always shared. Eg.:- Bus Topology.

1.1.1Topology:-

Topology refers to the geometrical arrangement & connection of the network nodes. There are five basic topologies and one hybrid topology.

1) BUS:- In BUS one long cable acts as a backbone to link all devices in the network. The link

joining the computer and the backbone cable is called Drop Line. The Tap is the connection between the drop line and the backbone cable.

d) It is easy to install and configure than mesh. Disadvantages:- a) More cabling as compared to Bus or Ring topology. b) Central controller is required. c) The failure of server or central hub causes the entire network to fail. Example: - The following types of networks are examples of star topologies: ARCnet 10Base-T, 100Base-TX StarLAN

4) MESH:- In MESH topology, every device has a dedicated point-to-point link to every other

device in the network. A fully connected network therefore has n (n-1)/2 physical channels to link n devices, so every device in the must have n-1 input/output ports. Network:- Advantages:- a) Reliable b) If one link becomes unusable, it does not affect the entire network. i.e. it is ROBUST network. c) Fault identification and isolation is very easy.

d) Privacy and security is there. Disadvantages:- a) Lots of connections i.e. links are required. b) Due to more links it is expensive. c) Installation and reconfiguration is difficult.

5) TREE:- A tree topology is a variation of star. In TREE topology along with the central control

(Primary Hub), Secondary hubs are used which are then connected to the central controller. Network:- Advantages:- a) It is easier to add new node. b) It is easier to isolate a defective node. c) More devices can be attached to a single hub. d) Failure of one or more nodes does not affect the entire network. Disadvantages:- a) Failure of root node (Central controller) causes entire network to collapse. b) Installation is costly & complex c) Communication path can be sometimes become quite long. Example: - The following types of networks are examples of tree topologies: ARCnet 10Base-T, 100Base-TX

6) HYBRID :- This topology is formed by combination of any of the basic 5 topologies.

According to the appropriate basic topology its functioning changes. This topology is required for big networks. Network:- Advantages:- a) It is very useful in large networks. b) It can combine the advantages of any of the 5 basic topology.

2) HUB: -

a) It is a device in a star topology that connects the computers to LAN. b) Hub works on the Physical Layer of the OSI model. c) Any data packet coming from one port is sent to all other ports. d) It is then up to the receiving computer to decide if the packet is for it or not. e) If the IP address matches then the packet is given the respective computer. f) HUB prevents the collisions by implementing the CSMA/CD in it. TYPES: - I. Active HUB:- Hubs that are plugged in to the electric power are called Active hub. These regenerate the incoming signal. II. Passive HUB: - A hub that merely connects different cables on a network and provides no signal regeneration. Diagram: - Advantages: - a) More number of computers can be connected to the hub. b) Data is sent in a central format. c) Hub can subdivide the traffic on the network. Disadvantages: - a) Hubs are typically used on small networks where the amount of data going across the network is never very high. b) Since every packet is sent out to every node on the network, there is a lot of wasted transmission. This means that the network can easily become bogged down. 3) BRIDGE: -

a) A Bridge is a physical unit, typically a box with two ports in it, which connects two or more LANs or network segments. b) Bridge works on the Data Link Layer of the OSI model. c) A bridge goes one step up on a hub in that it looks at the destination of the packet before sending. d) When a frame arrives, software in the bridge extracts the destination address (MAC) from the frame header & looks it up in a table to see where to send the frame, called Packet Filtering. e) If the destination address of a frame arriving from one network segment is that of a computer on the other segment, the bridge transmits it out through the other port. f) If the destination address is that of a computer on the same network, the bridge discards the packet.

Diagram: - TYPES: - I. Cut-Through: - It forwards packets immediately by reading the destination address from data-link layer protocols header without any processing. II. Store and Forward:- It waits until an entire packet arrives before forwarding it to its destination. Advantages: - a) Switch increases the available network bandwidth. b) With switches there is reduced workload on individual computer. c) There are fewer collision as switch creates collision domains for each connection. Disadvantages: - a) Network connectivity problems can be difficult to trace through a switch. b) Switches are expensive than bridge. 5) ROUTER:- a) Router is a device used to find the shortest path in the network. b) Router work at the network layer of the OSI module. c) When a packet comes into a router, the frame header & trailer are stripped off & the packet located in the frames payload field is passed to the routing software d) This software uses the packet header to choose an output line. e) Networks connected to router are called as internetworks because they create a large network of smaller networks. Diagram: - As per class notes. TYPES:- I. Static Router: - In this router path is predefined and every packet need to take the same rout even though there is more traffic in the rout.

II. Dynamic Router: - In this router there are various paths and out of these paths only that path is selected where traffic is less. Advantages:- a) Router can choose the best path across the different network using dynamic routing. b) Routers can connect different network architecture. Disadvantages:- a) Router work only with routable protocols like TCP/IP, IPX/SPX etc. b) Routers are more expensive the bridge or repeaters. 6) GATEWAYS:- a) Gateways Provides links between two incompatible LANs. b) Router transfers, accepts & relays packets only across n/w using similar protocol. c) A gateway can accept a packet forwarded for one protocol and convert it to a packet formatted for other protocol. d) So gateway is called as Protocol converter. e) Gateways potentially operate at all seven Layers of OSI module. f) A Gateway is generally software installed in a router. Diagram: -