ITGS Chapter 4 quesitons

What are the similarities and differences between hubs, routers and switches?

Hub, routers and switches are all devices that let you connect one or more computers to other computers, network devices, or even other networks and include a number of ports, but the way in which they operate in different. Hub and switch are both used to connect a number of devices to form a LAN. But switch does more efficiently. Switch learns the location of the devices that they are connected to almost instantaneously. Routers have a slightly different task: they connect two or more separate networks. It reads the address information to determine destination of data packets and enables data packets to be routed between networks, connects LAN to WAN.

What are the advantages and disadvantages of allowing remote access to computers?

Pros: Can be accessed from far away, you don't need to be physically there to perform the task. Cons: Has to be set up which might be time consuming and people with low IT skills might not be able to carry out the task.

Explain what is meant by the term bandwidth?

Bandwidth is the bit rate of available or consumed information capacity expressed typically in metric multiples of bits per second. It measures how much data can be sent over a specific connection in a given amount of time. Bandwidth does not however measure how fast bits of data move from one location to another.

What is bit rate? How is it calculated?

Bitrate describes the number of bits that are transferred or processed per unit of time. Network speeds are measured in bits per second (bps) not bytes per second. A 1 Mbps internet connection is not 1MB per second, but 128 kilobytes (there are 8 bits in a byte). Kbps is kilobits per second etc. Bitrate can also describe the quality of an audio or video file, higher is better quality. Wi-Fi is typically up to 108 Mbps with Fibre Optic connections reaching over 40 Gbps. Cable and DSL connections are typically 10 - 100 Mbps, but home connections are often capped.

Explain the four main wireless technologies of connecting computers

Bluetooth: used for short distances (PANs - personal area networks). Used to connect computers to mobile phones, cameras, and other peripheral devices. Wi-Fi: (Wireless Fidelity) standard for wirelessly connecting devices in a small area (e.g. office). Devices are connected to a wireless router, then to the internet. WiMax: (Worldwide Interoperability for Microwave Access) wireless technology designed to transfer data over distances up to 50km. Suited to provide internet access to homes in areas where laying cables would be difficult - providing hotspot access to large areas. 3G/4G: are standards for wireless communication that operate using the mobile phone network. Smart phones and the MODEMS in laptop computers use these standards.

How do client/server networks different from peer-to-peer networks?

Client-server network : network organized around one or more servers. The server maintains a database of authorized users, passwords, and access rights. Peer-to-peer network : a simple network that provides shared resources, such as printers and storage, and some other additional facilities (file storage, etc). Peer-to-peer network has no central server. Each workstation on the network shares its files equally with the others. This can be operated on a basic PC operating system. However, there are separate dedicated servers and clients in a client/server network. Through client workstations, users can access most files, which is generally stored on the server. Moreover it needs a special operating system.

What is meant by the term 'cloud computing'?

Cloud computing is using web-based programs that are stored remotely rather than local server to store data. The examples of cloud computing are Google Drive and Dropbox where you can save any data using these programs and then you can access to these data anywhere you are. Cloud computing is beneficial because it provides you much lower cost than licensing software do.

What are the similarities and differences between LANs, WLANs and PANs?

LANs, WLANs and PANs are all similar in the way that they are all local networks. This means that all the devices used in the network are all situated relatively close to each other. The differences between these networks are the scale of the network and the way that data is distributed. The difference between LANs and WLANs is the physical way that data is transferred. A WLAN is a type of LAN that uses wireless technology (nearly always Wi-Fi) to connect some or all computers and devices to the router whereas a LAN network needs physical cables attaching each node or client to the router. The difference then between these two networks in comparison with PANs is that PANs are personal devices such as tablets, phones and personal computers. The scale of the data sharing and transferring is on a much smaller scale.

What are the key features of MANs, WANs and SANs?

MANs are Metropolitan Area Network which covers very large area such as a town or city and is owned by a single person or company (local council or large company). WANs stands for Wide Area Network which covers a broad area like communication links that cross metropolitan, regional, or national boundaries. It contains multiple LANs and MANs. It uses satellites and microwave relays and the best example is the Internet. SANs are Storage Area Network connects servers directly to devices which store amounts of data without relying on a LAN or WAN network to do so. This connects servers to data storage devices via fiber optic cables.

Outline the main ICT methods of protecting data on a network.

Main methods of protecting data on a network include firewall, proxy server and using a antivirus software. A firewall acts as a filter and it protects a LAN from a WAN. It only allows websites that are not suspicious and block data sent from other programs. Proxy server is an intermediate between the computers in a LAN and the internet. It works by having a user sending requests to the proxy and the proxy retrieve data from the internet. By this it prevents any unwanted packets of data entering the LAN. Antivirus software works by searching for viruses and remove them.

In what ways can firewalls and proxy servers improve the effectiveness of networks?

Proxy servers and firewalls are used to improve the security and safety of networks and users' data within the network. Firewalls work as a filter and it protects a LAN from a WAN. Firewalls allow websites to pass through without problems or any suspicious content and block data that is sent from other programs. Proxy server can be used to improve a user's authentication and security by hiding IP address. It is used to block unwanted website types (e.g pornography) and view blocked websites that are blocked by ISP.

What is a RAID system and when would you recommend its use?

RAID stands for redundant array of inexpensive disks. This means that there is a set of hard drive units used as one single mass storage unit. By using two or more disks to hold the same data, a disk drive fault will be unlikely to have any effect on the operation of the whole system. If fragments of data are stored on each number of disks, the storage and retrieval of data will be much faster. RAID systems should usually be used with companies or firms that require mass storage of data as it will be more efficient for these companies to store all their data on one RAID system.

What is meant by the terms grid computing and supercomputers?

Supercomputers are optimised for high computation speed and are typically used for scientific applications that handle very large databases or do a great amount of computation. Supercomputers use centralisation, where the computer is located in a large room where it can be managed and maintained. Users access the power indirectly via terminals. Grid computing is an example of decentralised computing. Hundreds, if not thousands of computers perform complex scientific calculations and communicate over the internet, to become the supercomputer. Grid computing is more cost-effective than supercomputers, but is not suitable for all types of calculation and can cause network bottlenecks.

What are the common network protocols?

TCP/IP (Transmission control protocol/Internet protocol) HTTP (Hypertext transfer protocol) HTTPS (Secure hypertext transfer protocol) POP3 (Post office protocol 3) FTP (File transfer protocol)

Explain the four main wired methods of connecting computers.

The four main wired methods of connection are fibre optic cables, cable, dialup and Ethernet. Fibre Optic transfers data by sending light down a thin glass tube at speeds of over 40 Gbps, but cost around $70 per metre. Cable internet access uses existing cable television networks or DSL which uses telephone networks. Dialup is old technology using a standard telephone line and a modem, having slow transfer speeds (56 Kbps). They charged per minute and monopolised the phone line. Ethernet cables are the standard cables used for many local area networks, for high speed data transfer over short distances.

How do VPNs and VLANs work?

VPN (virtual private networking) is a way of implementing a virtual private network (used to protect information being shared). It ensures two-way secure communications between stations. VPN system allows a client station to communicate using the internet, with a server, to verify the authenticity of the remote computer. Data is encrypted during transmission. VLAN (virtual local area network) is part of a local area network that appears as a separate network and is separated from the rest by the use of sophisticated switches. This allows a local area network to be split into several virtual networks that work independently.

Explain the difference between synchronous and asynchronous communication.

Within a computer, there is a clock providing the timing for that computer. Between 2 computers, 1 computer's clock will be chosen as a master clock. Synchronous communication is when data transfer is timed to coincide with a clock pulse from the computer clock whereas Asynchronous communication transfer data as soon as it is available with a start bit marking the beginning of a character and 1 or 2 end bits marking the end of a character.