Unit 09 Computer Networks

Gain a knowledge about network devices.

Discuss what network devices are required to create a basic network

Draw a bespoke network drawing using Visio

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In order to setup a network a variety of devices are required.

The network devices differ according to what network you intend to setup.

A network segment is a portion of a computer network where every device communicates using the same physical layer.

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A simple network can be created between two computers (peer to peer). In order to create this connection each computer

must have an NIC network interface card.

A Network card, Network Adapter, LAN Adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network.

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An NIC provides physical access to a networking medium and provides a low-level addressing system through the use of MAC (Media Access Control) addresses.

It allows users to connect to each other either by using cables or wirelessly.

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Cross-Over cables are used to connect two computers directly through NICs

without the use of a Hub or Switch or routers.

A crossover cable is a cable that maps all output signals on one electrical

connector to the input signals on the other connector, allowing two electronic

devices to perform full-duplex communication.

Most commonly, the term refers to the Ethernet crossover cable, but other cables

follow the same principle. It also allows devices to communicate without a switch,

hub, or router.

The Pins of the RJ-45 Connectors at both ends of a cross-over cable are

connected as follows:

Pin 1 ----------- Pin 3 Pin 2 ----------- Pin 6

Only two pairs of wires in the eight-pin RJ-45 connector are used to carry Ethernet

signals. Both 10BASE-T and 100BASE-T use the same pins, a crossover cable

made for one will also work with the other.

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Compare a crossover cable to a standard Cat 5e lead.

Discuss and make notes on the purpose of the crossover cable.

Find out more about MAC Addresses

Using the internet find out what a Modem is used for.

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•HNC COMPUTING - Network

Concepts •9•Network Concepts & Devices •9

There are a variety

of different network devices that are

available, each of which has a

specific role within the network.

Switch

Hub

Router

Bridge

Gateway

Repeaters

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A network switch connects network segments.

A switch is intelligent, it can recognise what cable has been inserted into it and adapt to allow the network to communicate.

It maintains a table of destination address and its port.

When the switch receives a packet:

It reads the destination address from the header information in the packet

Establishes a temporary connection between the source and destination ports

Sends the packet on its way, and then terminates the connection.

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A network hub is a device

for connecting multiple

devices together, making

them act as a single network

segment.

When a hub receives a

packet at one of its ports

from a PC on the network, it

transmits (repeats) the

packet to ALL of its ports

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What is the difference between a Hub and a Switch?

A hub receives a packet at one of its ports from a PC on the network, it transmits the packet to all of its ports (broadcast) thus, to all of the other PCs on the network.

A hub does not use any intelligence to determine the destination of a packet, whereas a switch does.

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What problems could occur as a result of using a hub?

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This is a device that forwards and routes data packets along networks.

A router is often included as part of a network switch.

A router is located where one network meets another.

It prevents the traffic on one from unnecessarily spilling over to the other. This process is known as routing.

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A bridge is a device that connects two networks so that they

act as if they’re one network.

A key feature of a bridge is to enable a large network to be

partition into two smaller, more efficient networks.

A bridge directs frames according to hardware assigned MAC

addresses while a router makes its decisions according to

assigned IP Addresses.

Bridges work best in networks that are highly segregated.

A bridge directs frames based on hardware assigned MAC

addresses while a router uses IP Addresses. •Network Concepts & Devices •16

A gateway converts protocols between different communications networks.

A gateway can accept a packet formatted for one protocol (e.g. AppleTalk) and convert it to a packet formatted for another protocol (e.g. TCP/IP) before forwarding it.

A gateway can be implemented in hardware, software or both, but they are usually implemented by software installed within a router.

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Watch the video – Switches, Routers & Hubs! Oh my!

Using the internet look into the various other available network devices/terms:

What is DSL and ADSL?

Also including repeaters, multiplexers, Analogue and digital frequencies.

Do you agree with the following descriptions of DSL and ADSL?

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Asymmetric Digital Subscriber Line (ADSL) is a form of DSL.

A data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide.

Utilizing frequencies that are not used by a voice telephone call.

A splitter - or micro filter - allows a single telephone connection to be used for both ADSL service and voice calls at the same time.

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DSL or xDSL, is a family of technologies that provide

digital data transmission over the wires of a local

telephone network.

DSL originally stood for digital subscriber loop, although

in recent years, the term digital subscriber line has been

widely adopted as a more marketing-friendly term for

ADSL.

DSL uses high frequency, while regular telephone uses

low frequency on the same telephone line.

DSL is the most popular version of consumer-ready DSL.

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Bandwidth is the amount of data that can be transmitted within a fixed time period.

Bandwidth is measured in bits per second and is usually denoted by the following:

•bps - bits per second

•Kbps - kilobits per second

•Mbps - megabits per second

Latency is the amount of time it takes data to travel from source to destination.

Data is transmitted in one of three modes:

• Simplex (Unidirectional transmission) is a single, one-way transmission.

• Half-duplex allows data to flow in one direction at a time.

• Full-duplex allows data to flow in both directions at the same time.•Network Concepts & Devices •21

Gained knowledge about network devices

Discuss what network devices are required to setup a network

Create a bespoke network diagram in Visio

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