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Network Communication Media. Chapter 3. This presentation will:. Help you understand what kind of communication media is available to run a network and how they effect bandwidth including: Cables Optical and Wireless. Introduction.
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Network Communication Media Chapter 3
This presentation will: • Help you understand what kind of communication media is available to run a network and how they effect bandwidth including: • Cables • Optical and • Wireless
Introduction • In the previous lesson we looked at what bandwidth was and how bottlenecks can effect performance. • We also looked at the importance of choosing the right bandwidth speed for your needs. • Once you have decided on your needs you need to think about the kinds of communications media you require and the hardware to support it.
Communication Media • It is important to consider the type of interconnection when building a network. • Factors to consider include: • The predicted bandwidth. • The environment. • The distance between clients. • The level of security needed. • The cost of the interconnection. • Computers can be connected to a network through different media. Sample media include: • Twisted pair. • Coaxial cable. • Fibre optics. • Wireless connections.
Unshielded twisted pair (UTP) • Many networks use this cable. • It is light, flexible and cheap and has been around a long time which means network engineers are familiar with it. • Used extensively at home to connect computers to the telephone system. • Consists of pairs of conductors covered in insulation material and then twisted together. • Within one cable you might have 4 pairs but there are different designs, each with their or characteristics. • Twisting the wire reduces the effects of electrical interference at minimal costs. • You can further reduce this electrical interference by covering the cables in silver foil.
Unshielded twisted pair (UTP) • Many people have debated the ups and downs of UTP over STP (Shielded Twisted Pair) and these discussions can be found on the net. • It is important to note that the bandwidth of UTP is slower then coaxial and fibre optic cable and you need repeaters more often with UTP also. • i.e. It has more resistance and a higher level of data degradation over longer distances.
Coaxial • Made up of a central conducting core wrapped in protection within a cable. • Wrapped around the installation is a think metal sheath that provides the electrical interference protection. • Finally, the cable has an outer covering. • It is the cable of choice when connecting a television to an aerial. • It is heavier and less flexible compared to a UTP and also more expensive too. • Cable lengths can be longer than UTP but still not as long as fibre optic cables. • You need less repeaters than a UTP too and is mechanically strong and has a high level of resistance to electrical interference.
Fibre optic cable • Consists of glass cores surrounded in protective material. • Signals are sent via light sources. As signals are not electrical they do not suffer from electrical interference. • Also, the cables do not suffer from the effects of moisture as they are non-metallic (like most cables). • The cables are extremely brittle compared to metallic cables and need to be well protected.
Fibre optic cable • They are high bandwidth compared to UTP cables and are often used for networks were video conferencing is needed. • The cost of these cables are relatively cheap compared to metallic ones but they require specialists to install them which makes them expensive overall. • Often used as the backbone for LAN networks to connect servers to switches and located in places where there are clusters of computers. • After the switches UTP and coaxial cables tend to be used. • The bandwidth is so impressive that speeds of up to 1Gbit/sec is easily reached.
Fibre optic cable • Note: the angle of the acceptance cone. If the cable is bent too much the light will not be able to travel through it.
Activity • Complete this table:
Wireless LAN • We now have the ability to connect up networks without the need for wires. • Data can be fired using lasers across a network or use radio signals to send information across a LAN. • Lasers are useful for connecting two building together. You must have a clear line between the equipment that sends and receives the equipment or else the signals will get blocked. • A school might use wireless technology if they have no space for a fixed computer room. They may use laptops with wireless technology to allow for a roaming classroom. • Also, it can allow teachers to take electronic registers and work in areas of the school away from noisy pupils! • You need wireless access points which relay information from the main server. They can often be seen attached to walls.
Wireless LAN • Draw backs include low bandwidth which means generic software will work fine but high bandwidth applications such as video conferencing is sometimes impossible. • Electrical interference is a big problem and also it is potentially more insecure. • Signals are easily intercepted and if data has not been encrypted then it is easily viewed. • Companies wanting to send data over large distances should look at satellite technology, cellular technology and microwave technology.
Ethernet • A widely used design for baseband LANs, which can work at 10Mbps, 100Mbps and 1Gbps. • Works by connecting stations together using coaxial cables. • Ethernets make use of data collision avoidance and detection strategies. • As traffic increases on an Ethernet data collisions become more likely. This is because each station is broadcasting information to other stations. • The more stations the more traffic. • When a computer sends out data it waits for a reply. If it does not receive a reply it assumes the data packet was lost. • In the event of a collision data packets will be sent out again.
Reducing data collisions • Look again at switches and what they do. • Switches can be used to split large networks into segments to reduce traffic. • Also, stations can be given temporary communication links using a switch.
Activity • Describe how wireless networks can be used to improve the speed and delivery of medical care at the scene of an emergency, perhaps in an ambulance. • Describe the use and the technology behind the wireless network used to deliver education to children in remote parts of the Australian outback. You will need to research this.
Activity • Discuss the problem of balancing ‘over engineering’ with ‘future proofing’ in a new network. • Use the Internet and define the term Wi-Fi. Describe its benefits in the business environment. • What is UTP and list the reasons why it is commonly used for LANs. • Discuss in what circumstances a company might select • Coaxial Cable or • Fibre Optics for its network. • Define Ethernet.
Activity • Explain what is meant by ‘collision avoidance’ and ‘collision detection’. • How does an Ethernet deal with data collision? • What is meant by a ‘switched Ethernet LAN’? • Why do communications slow down when there are many users connected to a LAN? • Describe how a switch can reduce the number of collisions in a LAN and therefore improve communications.
