#Devices  #Computer-Networks  
# Topic covered
* Network Devices
  * Repeater, Hub, Bridges, Switch, Router Modem
* Client, Server, Host, Noise, Distortion
* Who governs the Internet?
* Internet, Intranet and Extranet

3.1 Network Devices

  • Cable, Repeaters, Hubs –> Pure Hardware
  • Bridges, Switches, Routers –> Hardware + Software
  • Gateway –> just a term
  • IDS + Firewall –> Security purpose

Repeater

A repeater operates at the physical layer. It is a 2-port device. Its job is to regenerate the signal if the signal becomes weak.

Repeater cannot filter data, so data packets are sent to all connected devices. It copies the signal bit by bit and regenerate it at the original strength, repeaters do not amplify the signal.

Points: PL device, 2 port Device, Forwarding, No filtering, N collision domain

Hub

A Hub operates at the physical layer. It is a basically multi-port repeater. A hub connects multiple wires coming from different branches.

Hubs cannot filter data, so data packets are sent to all connected devices. The process used by the Hub consumes more bandwidth and limits the amount of communication.

Active Hub: They are smarter than the passive hubs. They not only provide the path for the data signals in fact they regenerate, concentrate and strengthen the signals before sending them to their destinations. Active hubs are also termed as multi-port repeaters.

Passive Hub: They are more like point contact for the wires to built in the physical network. They have nothing to do with modifying the signals.

Points: PL device, Multiport Repeater, Forwarding, No filtering, N collision domain

Bridges

A bridge operates at the data link layer. A bridge is a repeater, with add on the functionality of filtering content by reading the MAC addresses of the source and destination.

It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device.

Collision is less due to store-and-forward buffer.

Static Bridges: Manual routing configuration by admin should be done

Transparent Bridges: No Manual routing configuration required, it uses bridge forwarding and bridge learning

Points: DLL device, 2 port Device, Forwarding, Filtering, Low collision

Switch

A bridge operates at the data link layer. A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance.

It supports unicast, multicast as well as broadcast communications.

A switch transfers data only to that port which is connected to the destination device. Switch delivers the message to the correct destination based on the physical address(MAC addresses) present in the incoming message. It increases the speed of the network.

Points: DLL device, Multiport Bridge, Full duplex, Traffic is min, Collision domain is Zero

Router

A router works in a Network layer, used to connect a LAN with an internet connection. It is used to receive, analyze and forward the incoming packets to another network.

Routers normally connect LANs and WANs and have a dynamicallyupdating routing table based on which they make decisions on routing the data packets.

It determines the best path from the available paths for the transmission of the packet.

Points: NL device, Multiport, Forwarding, Filtering, Routing, Collision domain is Zero.

Modem

A modem is a hardware device that allows the computer to connect to the internet over the existing telephone line. A modem is not integrated with the motherboard rather than it is installed on the PCI slot found on the motherboard.

It stands for Modulator/Demodulator. It converts the digital data into an analog signal over the telephone lines.

What is a Client?

A client is a computer hardware device or software that accesses a service made available by a server. The server is often (but not always) located on a separate physical computer.

What is a Server?

A server is a physical computer dedicated to run services to serve the needs of other computers. Depending on the service that is running, it could be a file server, database server, home media server, print server, or web server.

What is a Host?

A host is a computer, connected to other computers for which it provides data or services over a network. In theory, every computer connected to a network acts as a host to other peers on the network. In essence, a host reflects the logical relationship of two or more computers on a network.

What is Noise? Types of Noises in Network?

Noise is any undesired signal in a communication circuit. Another definition calls noise unwanted disturbances superimposed on a useful signal, which tends to obscure its information content.

There are many varieties of noise; however, the four most important to the telecommunication/data communication technologist are thermal noise, inter modulation noise, crosstalk and impulse noise.

In contrast, noise is an external random signal added to the original signal.

Distortion

Distortion is a term used to describe an interruption of transmitting signals that cause an unclear reception. Distortion is commonly found in sound generated or received by a computer, video or display signals and data cables such as network cables.

Distortion in a signal is the alteration or change of the shape or some other characteristic of the waveform.

The Internet vs Web

https://www.geeksforgeeks.org/the-internet-and-the-web/

The Internet is a global network comprised of smaller networks that are interconnected using standardized communication protocols.

The Web is the only way to access information through the Internet. It’s a system of Internet servers that support specially formatted documents.

The documents are formatted in a markup language called HTML, which supports a number of features including links and multimedia. These documents are interlinked using hypertext links and are accessible via the Internet.

Who governs the Internet?

The Internet is not governed and has no single authority figure. The ultimate authority for where the Internet is going rests with the Internet Society, or ISOC. ISOC is a voluntary membership organization whose purpose is to promote global information exchange through Internet technology.

ISOC appoints the IAB- Internet Architecture Board. They meet regularly to review standards and allocate resources, like addresses. IETF- Internet Engineering Task Force. Another volunteer organization that meets regularly to discuss operational and technical problems.

Internet, Intranet and Extranet

Internet

  • The network formed by the co-operative interconnection of millions of computers, linked together is called Internet.
  • Internet comprises of:
    • People : People use and develop the network.
    • Resources : A collection of resources that can be reached from those networks.
    • A setup for collaboration : It includes the member of the research and educational committees worldwide.

Intranet

https://www.javatpoint.com/intranet

The intranet is a private network that belongs to a particular organization. Users on the intranet can access the internet, but the internet users can’t access the intranet if they are not authorized for it.

Extranet

It is the type of network that allows users from outside to access the Intranet of an organization without giving access to the company’s entire network.