Computer Networking Devices Explained with Function

This tutorial explains the functions of the most common and the essential networking devices (such as Hub, Switch, Router, Bridge, Modem, NIC, Proxy and Gateway) in detail with examples.

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Network Interface Card (NIC)

In the list of the networking devices, NIC stands on the first place. Without this device, networking cannot be done. This is also known as network adapter card, Ethernet Card and LAN card. NIC allows a networking device to communicate with the other networking device.

NIC converts the data packets between two different data transmission technologies. A PC uses parallel data transmission technology to transmit the data between its internal parts while the media that provides connectivity between different PCs uses serial data transmission technology.

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A NIC converts parallel data stream into the serial data stream and the serial data stream into the parallel data stream.

nic functions

Typically all modern PCs have the integrated NICs in the motherboards. If additional NICs are required, they are also available as add-on devices separately.

For desktop or server system, they are available in the adapter form which can be plugged into the available slots of the motherboard. For laptop or other small size devices, they are available in the PCMCIA (Personal Computer Memory Card International Association) card form which can be inserted into the PCMCIA slot.

Types of NICs

There are two types of NICs.

Media Specific: - LAN card are used according to the media type. Different types of the NICs are used to connect the different types of media. To connect a specific media type, we must have to use a NIC which is particularly made for that type of media.

Network Design Specific: - A specific network design needs a specific LAN card. For example FDDI, Token Ring and Ethernet have their own distinctive type of NIC cards. They cannot use other types of NIC cards.

Following figure illustrates some common types of NICs.

types of nics

Hub

Hub is a centralized device that connects multiple devices in a single LAN network. When Hub receives the data signals from a connected device on any of its port, except that port, it forwards those signals to all other connected devices from the remaining ports. Usually, Hub has one or more uplink ports that are used to connect it with another Hub.

There are two types of the Hub.

Passive Hub: - It forwards data signals in the same format in which it receives them. It does not change the data signal in any manner.

Active Hub: - It also works same as the passive Hub works. But before forwarding the data signals, it amplifies them. Due to this added feature, the active Hub is also known as the repeater.

networking device hub

Hubs are no longer used in the computer networks.

MAU and Patch panel

MAU and Patch Panel look like the Hub, but they are different. MAU (Multi Access Unit) is the sibling of Hub for the token ring network. Differences between Hub and MAU are the following: -

  • Hub is used for the Ethernet Network while the MAU is used for the Token ring network.
  • Hub creates logically star topology while MAU creates logically ring topology.

mau

Patch panel is used to organize the UTP cables systematically. It doesn't interfere in the data signals.

patch panel

Bridge

Bridge is used to divide a large network into smaller segments. Basic functions of the Bridge are the following: -

  • Breaking a large network into smaller segments.
  • Connecting different media types. Such as connects UTP with the fiber optic.
  • Connecting different network architectures. Such as connects Ethernet with the Token ring.

functions of bridge

A Bridge can connect two different types of media or network architecture, but it cannot connect two different types of network layer protocol such as TCP/IP or IPX. Bridge requires the same network layer protocol in all segments.

There are three types of Bridge:-

Local Bridge: - This Bridge connects two LAN segments directly. In Ethernet Implementation, it is known as the Transparent Bridge. In Token Ring network, it is called the Source-Routed Bridge.

local bridge

Remote Bridge: - This Bridge connects with another Bridge over the WAN link.

remote bridge

Wireless Bridge: - This Bridge connects with another Bridge without using wires. It uses radio signals for the connectivity.

wireless bridge

In OSI Layers /TCP-IP networking models, the functionalities of the Bridges are defined in the physical layer and data link layer.

Just like Hubs, Bridge no longer used in the computer network. Bridges have been replaced by the Switches.

Switch

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Just like Hub and Bridge, Switch is also used to connect the multiple devices together in a LAN segment. Basically, a Switch is the upgraded version of the Bridge. Besides providing all the functionalities of Bridge, it also offers several additional features.

The biggest advantage of Switch is that, it makes switching decisions in hardware by using application specific integrated circuits (ASICs).

Unlike the generic processors that we use in our PC, ASICs are the specialized processors built only to perform very few particular tasks. Usually, the ASICs in the Switches have single task and that is the switching the frames as fast as possible.

An ASIC occupied switch performs this task blazingly fast. For example, an entry level Catalyst Switch 2960 can process 2.7 million frames per second.

switch

Modem

In simple language, a Modem is the device that is used to connect with the Internet. Technically, it is the device that enables the digital data to be transmitted over the telecommunication lines.

A Telco company uses entirely different data transmission technology from the technology that a PC uses for the data transmission. A modem understands both technologies. It changes the technology that a PC uses, in the technology which Telco Company understands.

It enables communication between the PC (Known as the DTE device) and the Telecom company' office (Known as the DCE device).

functions of modem

Following figure shows some common types of the Modem.

types of modem

Gateway

Gateway is used to forward the packets which are generated from the local host or network and but intended for the remote network. If a data packet does not find its destination address in the local network then it takes the help of the gateway device to find the destination address in the remote network. A gateway device knows the path of the remote destination address. If require, it also changes the encapsulation of the packet so it can travel through the other networks to get its destination address.

gateway

Examples of the Gateway

Email Gateway: - Translates SMTP e-mail in standard X.400 format before forwarding.

GSNW Gateway: - Allows Windows clients to access resources from the NetWare server.

PAD Gateway: - Provides connectivity between LAN network and X.25 network.

Router

The router connects the different network segments. It switches the data packets between those networks which are either located in the different logical segments or built with the different network layer protocols.

When a router receives a data packet on any of its interface, it checks the destination address of that packet and based on that destination address, it forwards that data packet from the interface which is connected with the destination address.

To forward a data packet to its destination, router keeps the records of connected networks. These records are maintained in a database table known as the routing table. Routing table can be built statically or dynamically.

router

Basically routers are used: -

  • To connect different network segments.
  • To connect different network protocols such as IP and IPX.
  • To connect several smaller networks into a large network (known as the Internetwork)
  • To break a large network into smaller networks (Known as the Subnets. Usually created to improve the performance or manageability.)
  • To connect two different media types such as UTP and Fiber optical.
  • To connect two different network architectures such as Token Ring and Ethernet.
  • To connect LAN network with Telco company’ office (Known as the DTE device).
  • To access DSL services (known as the DSL Router).

Proxy

Proxy is used to hide the internal network from external world. It can be a dedicate device or can be an application software. Once it is configured, all communication goes through it. Since external devices cannot access the internal devices directly, they cannot tamper with the internal devices.

proxy

Transceiver

Transceiver is a small device that has the capability of receiving and sending both types of signals; analog and digital. Usually, it is inbuilt in network interface card. But, it is also available as an individual device. It detects the type of signal from the network wire and converts the passing signal accordingly.

For example, a transceiver is attached with a device that transmits signal in digital form. Now suppose, this device is connected with the network wire that uses analog form for data transmission. In this case, transceiver converts digital signals in the analog signals before placing them in the network wire.

transceiver

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

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