Networking Devices

Introduction

• A typical computer network either LAN or WAN is consist of a large number of the communication devices along with communication medium or channels.
• To build a typical LAN especially, we need to have computers, communication mediums or channels, NOS(Network Operating System) and networking devices such as Hubs, Switches, Network Adapters, NICs, Repeaters, Amplifiers, Bridges, Gateways, Internal/External Modems, different types of Connectors, Cable testers, clipping tools etc. 

Definition

• Networking devices are those basic hardware components which are used and helps for creating a typical computer network.

Features

• Networking devices help to organize data transmission successfully. 
• Examples of networking devices are –  NIC adapter card, Hubs, Switches, Repeaters, Amplifiers, internal/external Modems, Gateway, Routers, cable connectors, cable testers, clipping tools

Types

There are two types of networking devices – 

(a) Intra Networking Devices and (b) Inter Networking Devices

(a) Intra Networking Devices:

• The networking devices which are used within a network to connect the components of the network and make it as a typical network.
• These devices are typically components of LANs.
• Examples are – NIC adapter card, Hubs, Switches, Repeaters, Amplifiers, internal/external Modems, Gateway, cable connectors, cable testers, clipping tools etc.

(b) Inter Networking Devices:

• The networking devices that are used between two/more networks to connect it and make it a larger network .
• Examples are – Routers etc.

(1.) NIC(Network Interface Card) Adapter Card/Network          Card/Network Interface Controller

• The network interface card (NIC) provides the physical connection between the network and the computer.
• NIC is the simplest intra-networking device that is used in the data communication.
• The most common network interface connection today is Ethernet cards. Ethernet cards Ethernet cards that contain connections for twisted pair cables have a RJ-45 connection. The Ethernet card is sometimes also called as network adapter card.
• Each Ethernet card is identified by a unique number called the Media Access Control (MAC) address.
• NIC adapter card is attached with the every computer that takes part in data communication.
• Most NICs are internal, with the card fitting into an expansion slot inside the computer. 
• A NIC is a piece of computer hardware (recently inbuilt with motherboard or early controllers are attached in motherboard expansion cards/ slots that plugged into a computer bus) to allow computers to communicate over a computer network.
• Network interface cards are a major factor in determining the speed and performance of a network.
• It allows users to connect to each other, either by using cables or wirelessly.
• The network controller implements the electronic circuitry required to communicate using a specific physical layer and data link layer standard such as Ethernet, Wi-Fi, or Token Ring.
• NIC provides a base for a full network protocol stack, allowing communication among small groups of computers on the same LAN and large-scale network communications through routable protocols, such as IP.
• The NIC follows one or more of four techniques to transfer data :-
  • Polling – In this method, the CPU examines the status of the peripheral under program control.
  • Programmed I/O – In this method, the microprocessor alerts the designated peripheral by applying its address to the system’s address bus.
  • Interrupt-Driven I/O – In this method, the peripheral alerts the microprocessor that it is ready to transfer data.
  • Direct Memory Access – In this method, an intelligent peripheral assumes control of the system bus to access memory directly. This removes load from the CPU but requires a separate processor on the card.

(2.) Repeater

• • Actually, when a signal travels through a medium in a network they lose its strength gradually, degrade and finally become distorted (called attenuation)which is now not able to propagates further with proper speed, hence a repeater is required.
  • A repeater is a electronic device that electrically amplifies the signal it receives and re-broadcasts/re-transmits it so that the signal can cover longer distances without degradation.
  • It works with the actual physical signal, and do not attempt to interpret the data being transmitted,
  • They operate on the Physical layer, the first layer of the OSI model.
  • In telecommunication sector, It is an analog device that amplifies an input signal regardless of its nature (analog or digital).
  • Typically, it is a digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.
  • The purpose of a repeater (as the name suggests) is simply to receive the digital signal, reform it, and retransmit the signal ahead.
  • This has the effect of increasing the maximum length of a network, which would not be possible due to signal deterioration if, a repeater were not available.
  • The repeater, simply regenerates cleaner digital signal so it doesn’t have to understand anything about the information it is transmitting, and processing on the repeater is non-existent.

(3.) Amplifier

• An amplifier is an electronic device or circuit that increases the magnitude of voltage, current, or power of a signal applied to its input.
• Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds.
• Amplifier is the generic term used to describe a circuit which produces and increased version of its input signal.
• They can be categorized as either weak-signal amplifiers or power amplifiers.
• The purpose of an amplifier is to amplify or increase the input signal to produce an output signal which is much larger than that of the input, with a similar waveform as that of the input. The main change in the output signal will be the increase in the power level.

(4.) Hub/Concentrator

• • A hub sends any data packet coming from one port to all other ports.
  • Hubs are typically used on small networks where the amount of data going across the network is never very high.
  • Hub is used to connect segments of a local area network (LAN), because a hub contains multiple ports.
  • A hub is typically the least expensive, least intelligent, and least complicated of the hub, router and switches.
  • Every computer connected to the hub sees everything that every other computer on the hub sees.
  • A hub is a hardware device that contains multiple ports which is used to connect multiple devices in a star topology.
  • When a packet arrives at one port in hub, it is copied to all the ports of the hub. But when the packets are copied, the destination address in the frame does not change to a broadcast address. It does this in a rudimentary way; it simply copies the data to all of the Nodes connected to the hub (broadcast).
  • Advantages :
    • Improves the performance of especially bursty/heavy traffic and  also of large files.
    • Enables optimum performance of PCI computers.
    • Use of Fast Ethernet hubs require no hardware or software settings rather just plug them in. Thus, hub offers ease of use. 
  • Disadvantages :
    • Not suitable for variable traffic because hub has fixed bandwidth and as network traffic grows, performance suffers.
    • The biggest problem with hubs is their simplicity. Since every packet is sent out to every computer on the network, there is a lot of wasted transmission. This means that the network can easily become bogged down.
    • Does not reduce collisions.
    • Requires Category 5 UTP cabling for each 100BaseTX connection.

(5.) Switch

• A switch does essentially what a hub does but more efficiently i.e. it pays attention to the traffic that comes across it and it can learn where particular addresses are.
• On busy networks this can make the network significantly faster.
• A switch (or Switching Hub) is a device that can segment a larger local area network to reduce the traffic load.
• One should implement a switch when you have a network with 20 or more users that have bogged down the network by excess traffic.
• It splits the network into two or more segments with devices that normally talk with each other.
• Conceptually – switching takes data from one interface and delivers it to another interface.

(6.) Modem (Modulator/Demodulator) 

• • Modem is a device that converts digital and analog signals, i.e. at the source, modems convert digital signals to a form suitable for transmission over analog communication facilities (public telephone lines) i.e. into analog signal. At the destination, modems again convert the analog signal back to a digital format.

(7.) Bridge

• • Like a repeater, a bridge can join several LANs.
  • However, a bridge can also divide a network to isolate traffic problems.
  • A bridge is used to connect two segment i.e., segment 1 (LAN 1) and segment 2 (LAN 2). Each segment can have several computer attached to it.
  • This intra networking device works at the data link layer.
  • Bridges are store and forward devices to provide error detection.
  • They capture an entire frame before deciding whether to filter or forward the frame, which provides a high level of error detection because a frame’s CRC checksum can be calculated by the bridge.
  • Bridges are highly susceptible to broadcast storms. A broadcast storm occurs when several broadcasts are transmitted at the same time. It can take up huge bandwidth.
  • Advantages:
    •  Reliability
    • Manageability
    • Scalability
  • Disadvantages:
    • A bridge cannot filter out broadcast traffic.
    • It introduces 20 to 30 % latency.
    • Only 2 networks can be linked with a bridge at a time.

(8.) Router

• It is one of the major inter networking device.
• Router is a device or PC(combination of both hardware and software) which is used to connect two or more IP networks logically.
• A router translates information from one network to another.
• It is similar to an intelligent bridge but works in WAN mostly and are advance structure.
• Router selects the best path from available paths to route a message, based on the destination address and origin. Thus, the router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along shortcuts.
• Routers can even listen‖ to the entire network to determine which sections are busiest. They can then redirect data around those sections until they are removed.
• If we have a LAN and we want to connect to the internet, we will need to purchase a router. In this case, the router serves as the translator between the information on your LAN and the internet.
• It also determines the best route to send the data over the internet.
• Routers maintain a map of the physical networks on a Internet (network) and forward data received from one physical network to other physical networks.
• The address of router is called Default Gateway.

(9.) Gateway

• If we are connected to the internet, we have to enter through a Gateway i.e. a gateway connects a smaller network to the internet.
• A gateway passes information from one network to another network via internet.
• Gateway Interconnects networks at higher layers than bridges or routers.
• A gateway usually supports address mapping from one network to another, and may also provide transformation of data between the environments to support end to end application connectivity.
• Gateway typically limits the interconnectivity of two networks to a subset of the application protocols supported on either one.
• Gateway, is also called protocol converters, can operate at any layer of the networking model. Typically, a gateway must convert one protocol into another. A gateway, on the other hand, accepts data formatted for one protocol and convert it to data formatted for another protocol before forwarding it.
• The job of a gateway is much more complex than that of a router or a switch.
• A router by itself transfers, accepts and relays packets only across networks using similar protocol.
• A gateway can be implemented in hardware, software or both, but they are usually implemented by the software installed within a router.
• A gateway must understand the protocols used by each network linked into the router.
• Gateways are slower than bridges, switches and (non- gateway) routers.
• The nodes that connect the networks in between are gateways. For example, the computers that control traffic between company networks or the computers used by internet service providers (ISPs) to connect users to the internet are gateway nodes.
• In a communications network, gateway is a network node equipped for interfacing with another network that uses different protocols.
• A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability.
• A protocol translation/mapping gateway interconnects networks with different network protocol technologies by performing the required protocol conversions.
• A gateway is a network point that acts as an entrance to another network.
• On the Internet, gateway is a node or stopping point node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes, while the nodes that connect the networks in between are gateways.
• In the enterprise network, a computer server acting as a gateway node is often simultaneously acting as a proxy server and a firewall server.
• A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.