Identify network hardware and protocols Identify network hardware and protocols

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7  Network hardware

  • A network is made up of hardware, which can be categorised as either:

    • transmission media

    • devices.

  • Hardware devices make forwarding decisions to send data between user devices across interconnecting pathways created using copper, optical or wireless transmission media.

7.1  Transmission media

  • Most home networks use a combination of copper and wireless transmission media to interconnect devices.

  • The copper wiring normally used to support the operation of Ethernet within homes is referred to as unshielded twisted pair (UTP). This consists of four insulated twisted copper pairs within a protective outer jacket:

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Figure 7

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  • The advantages of using UTP in the home is that pre-made cables are easily available, and they are cheaper than coaxial cables, which they have largely replaced.

  • One disadvantage of UTP is that it is vulnerable to electromagnetic noise signals. Noise signals are created by other electromagnetic sources, such as power cables, lighting and power tools. Electromagnetic noise can appear on the UTP copper pair and interfere with the data signals it is carrying. This can lead to data loss or data corruption.

  • To minimise the effects of noise, the copper pairs are twisted together, which helps cancel out noise signals travelling down the pair. Additionally, UTP cable lengths are limited to 100m when carrying Ethernet to guarantee that they can support the required data rates in the presence of noise.

  • UTP cables have to be wired correctly to allow the twisted pairs to perform noise cancellation, and this is achieved using a standard plug, called an RJ45, and a particular wiring convention. A correctly built UTP cable with an RJ45 connector can be connected to the Ethernet NIC ports of most devices:

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Figure 8

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  • Wireless is a very popular transmission media within home networks, as the lack of physical cabling makes connecting new devices relatively straightforward. In a home environment, the WiFi system requires a WiFi NIC fitted to the user’s computing device, allowing it to connect to a compatible wireless access point (WAP), which will itself generally connect to the rest of the network using a UTP connection:

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Figure 9

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  • WiFi is a popular network access technology as it is derived from Ethernet, and there are many devices available that provide both Ethernet and WiFi capability. This is especially true at home, as the ‘home router’ you use to connect to your Internet Service Provider (ISP) will provide both Ethernet and WiFi connectivity, as it contains an integrated WAP.

  • WiFi wireless is also affected by noise signals, but to a far greater degree than UTP as it is impossible to protect a wireless signal from external interference. Whereas UTP will guarantee a fixed data rate over 100m, the rate achieved over wireless will steadily reduce as the user device moves away from the access point.

  • WiFi introduces another serious problem, as the signal it produces does not stop when it reaches the limits of your property. This makes it possible for other people to ‘hijack’ your network by connecting to it wirelessly. It is therefore extremely important to use some form of security, such as a password, to prevent such access.

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