Identify network hardware and protocols Identify network hardware and protocols



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7.2  Network devices


  • Networks require a variety of different devices, each with a particular function, in order to provide connectivity and data forwarding. In a home network, the router provided by your ISP will provide all these functions, but in larger networks within businesses and schools, discrete devices are required.

7.2.1  Switches


  • Switches provide connectivity points within a network, allowing you to add a large number of devices to a network, typically using UTP cabling. Because the most common network access protocol is Ethernet, most switches will support it and are thus referred to as Ethernet switches. Ethernet switches have now largely replaced the older and much slower Ethernet hubs.

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Figure 10

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  • Switches provide multiple Ethernet NICs, which are referred to as ports. You can use a UTP cable to connect multiple computing devices to the ports:

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Figure 11

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  • The term used to describe the layout of your devices is ‘network topology’. The simple layout shown above is referred to as a star topology, as it resembles a multi-pointed star. Note that each of the UTP cables shown must be no longer than 100m.

  • The number of computing devices you can connect using a single switch is limited to the number of ports that are available. If you need to add more devices, or you wish to extend the size of your network, you can connect two switches together. This topology is referred to as an extended star:

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Figure 12

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  • The Ethernet network access protocol was originally designed to support data rates of 10Mbps. This is too slow to support modern networks, so the protocol has evolved to support greater data rates.

  • Most Ethernet switches are capable of supporting several Ethernet variants on each port. Although it is possible to configure each port to operate at a particular data rate, most Ethernet switches will negotiate with the connected computing device and set themselves to the highest data rate that they both support. It is best practice to connect switches together using the fastest data rate port available.

  • Switches forward data between computers using the destination MAC addresses contained in the frames they receive. This means that switches have no knowledge of the IP addresses of the packets contained within the frames, so they cannot be used to join together different IP networks. Referring to the diagram below, all the PCs are addressed within the same IP network and the switches will successfully forward data between them.

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Figure 13

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  • The diagram below shows the same topology, but this time the PCs have been placed in different IP networks. While the switches will forward data between the PCs based on the MAC addresses in the Ethernet frames, the PCs will refuse to communicate with devices outside their own IP network.

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Figure 14

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Start of Activity

Activity: Data rates

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Research the data rates supported by the following Ethernet variants:

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Protocol

Data rate

Ethernet

10Mbps

Fast Ethernet

Provide your answer...

Gigabit Ethernet

Provide your answer...

10 Gigabit Ethernet

Provide your answer...

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End of Question



End of Activity

7.2.2  Routers


  • Routers provide connectivity between different IP networks and are responsible for forwarding IP packets based on their destination IP addresses. It is the job of the router to connect many different networks – this is how the internet operates. Routers provide multiple Ethernet NICs, which are referred to as interfaces. Typical routers do not have many interfaces, as they are not designed to provide connectivity between different IP networks rather than for individual hosts.

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Figure 15

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  • Each router interface must be addressed with an IP address within the network to which they connect. This IP address will act as the default gateway address configured on all the host devices within the IP network:

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Figure 16

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  • Although Ethernet is the most common network access protocol you will meet in LANs, there are many other types of protocols available, especially within Wide Area Networks (WANs). Because routers are designed to connect networks together, they must be capable of supporting multiple network access protocols. Some routers are specifically designed to connect to particular types of WANs, whereas others are modular in design, allowing you to add the correct NIC for the WAN network access protocol in use.

7.2.3  Wireless Access Points (WAP)


  • You can send data directly between two devices using WiFi provided that the devices have compatible wireless NICs fitted. This is very useful if you wish create a temporary connection between the devices, but it can prove difficult to manage as you try to connect more devices.

  • Using a wireless access point in your network provides a central WiFi connection point to which all WiFi capable devices must connect in order to exchange data. In effect, you have created a star topology without wires:

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Figure 17

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  • While a single star topology WiFi network can be useful, you are more likely to meet WAPs connected to Ethernet switches, allowing the network to provide both wired and wireless network access:

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Figure 18

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7.2.4  Modem


  • The function of a modem is to MOdulate and DEModulate data to and from a transmission media. In the early days of the Internet, computers sent binary bits, which alternated between 0 and 5v, towards an ISP using the telephone system, which was (and still is) designed to process audio signals from telephones.

  • The modem was required to convert the binary electrical signal from the computer into an audio signal suitable for transmission over the telephone system, and vice versa. So it was used to modulate data onto the phone line, and demodulate data received from the phone line:

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Figure 19

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  • You will not see many individual modems in modern networks as they are now integrated within other devices, such as home routers. They are still needed as home Internet access via Digital Subscriber Line (DSL) utilises the telephone system, albeit using different frequencies. Cable Internet providers also utilise modems, as the binary electrical signal from a computer has to be converted into the radio frequencies used within the cable transmission system.

  • There are also some legacy systems that still require modems, such as some older chip and pin systems. Network engineers also use modems as a secret back door into their networks, just in case the main connection fails and they need to remotely find the cause of the issue.

7.2.5  Home router


  • If you have an Internet connection at home, you are probably using a home router given to you by your service provider. Although it is often referred to as a router, it is actually a combination of all the devices that we have discussed so far:

    • Wireless Access Point: provides wireless connectivity for WiFi devices.

    • Switch: provides Ethernet ports for the connection of devices using UTP cables.

    • Router: provides routing between the home and ISP IP networks. Also performs Network Address Translation (NAT) and firewall security.

    • Modem: converts the router output to a format suitable for transmission over the link used to connect to the ISP, usually DSL or cable.

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Figure 20

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