Unit 6 Communications Flashcards

Question

What is a star topology?

Answer 1

Star topology: an arrangement where a central node or hub provides a common connection point for all other nodes

Answer 2

All nodes are connected to a single backbone cable Each end of the backbone is connected to either a terminator or a computer which stops signals ‘bouncing back’ Each node is passive Data is sent in one direction at a time only Only one computer can transmit successfully at any one time Carrier Sense Multiple Access (CSMA/CD) technology is used to enable nodes to transmit on the same cable

Answer 3

Inexpensive to set up. Devices can be easily added. Good for small networks.

Answer 4

Main cable is a port of failure. Limited cable length. Performance degrades with heavy use, owing to data “collisions” Poor security

Answer 5

Computers are connected to a central node. This is often either a hub or a switch

Answer 6

A switch sends each communication to the specific computer it is intended for. A hub broadcasts the message to every computer on the LAN

Answer 7

Every networked device contains a Network Interface Card (NIC) Each NIC is attributed a unique Media Access Control (MAC) address hardcoded in manufacture A switch holds all of the MAC addresses for each device connected to it and uses these to direct packets of data to the correct device

Answer 8

Easy to isolate problems Good performance More secure if a switch is used as data is sent only to the recipient

Answer 9

Can be expensive to set up because of the length of cable required Central device is point of failure

Answer 10

The physical topology of a network defines how the devices are physically connected

Answer 11

The logical topology defines how the devices communicate across the physical topologies

Answer 12

The logical topology defines how the devices communicate across the physical topologies

Answer 13

Client server Peer-to-peer

Answer 14

The server is a powerful computer which provides services or resources required by any of the clients A client is a computer which requests the services or resources provided by the server

Answer 15

The client sends requests to the server Waits for a reply Receives the reply

Answer 16

The server waits for requests from the clients It may need to pass the request (e.g. for a web page) to another server – in which case, it becomes the “client”

Answer 17

Features of a client-server network include: A central server is used to manage security Some files are held on the central server Some processing tasks are performed by the server Clients issue requests to the server for services such as email, file storage, backup and printing Suitable for many different types of organisation, small and large Can require specialist IT staff to administer the network

Answer 18

Web server Print server Mail server File server Database server

Answer 19

A peer-to-peer network has no central server

Answer 20

Features of a peer-to-peer network include: Suitable for a small companies with fewer computers No central server controls files or security All computers can easily see files on all other computers All computers can communicate with each other without going through a server If a computer is switched off, data cannot be retrieved

Answer 21

The P2P configuration can also be used for file-sharing websites BBC iPlayer, for example, uses P2P networking This means that with thousands of people downloading, data can be passed between computers rather than just from the server Peer-to-peer networks are often used for the illegal distribution of copyright material such as music and films, as they are very difficult to close down

Answer 22

A file request can return several parts of the same file from multiple copies on multiple computers

Answer 23

“The cloud” is simply an imaginative term for Internet computing, using remote servers run by organisations such as Dropbox, Microsoft, or thousands of other specialist software companies Instead of maintaining their own networks, many organisations now rely on cloud computing to share both software and files at different sites

Answer 24

Some software does not have to be downloaded to the user’s computer. All the software and data files are held by the software manufacturer “in the cloud” Software and data is accessible from any computer anywhere in the world The data is automatically backed up so there is no danger of losing it The software and data does not occupy space on the user’s hard drive

Answer 25

Wi-Fi is a wireless networking technology providing high-speed Internet and network connections Devices connect to the Internet via a Wireless network Access Point (WAP)

Answer 26

ISP (Internet Service Provider) Modem and wireless router (Often combined) Device with a network interface card (NIC), also known as a network interface controller

Answer 27

A station consists of a computer and an NIC Stations share a radio frequency channel

Answer 28

Identifies each network by a unique name Must be used by all devices on that network Can be set manually or automatically Can be hidden to make it harder to detect Can be set to broadcast to wireless devices in range of an access point

Answer 29

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a network protocol designed to manage how data packets are transmitted over a shared communication medium. It operates in the Medium Access Control (MAC) layer and is particularly important for wireless networks

Answer 30

The CSMA/CA protocol is needed to prevent this from happening

Answer 31

The hidden node problem is a problem that occurs in wireless networking when a node can communicate with a wireless access point (AP), but cannot directly communicate with other nodes that are communicating with that AP. This can happen when two nodes in a wireless network can communicate with a third node, but cannot communicate with each other directly due to obstacles or being out of range.

Answer 32

It can lead to collisions at the third node when both nodes transmit simultaneously.

Answer 33

RTS/CTS is an additional method to implement virtual carrier sensing in carrier sense multiple access with collision avoidance (CSMA/CA). By default, 802.11 relies on physical carrier sensing only, which is known to suffer from the hidden node problem. RTS stands for Request To Send, and the sending device uses it to tell the other end to get ready to receive, and to set its CTS line when ready. CTS stands for Clear To Send, and the receiving end uses it to tell the far end to start sending the characters

Answer 34

Wireless encryption: Scrambles data into a secret code that only authorized users can read. Authentication: Verifies the identity of users and devices trying to connect. Access control: Set rules on who can connect and what they can do. Device security: Protects devices through updates and restricted access. Intrusion detection: Watches for suspicious activity and blocks threats.

Answer 35

Wireless Router Wireless Access Point (WAP) or Access Point (AP) Wireless Adaptors or NICs Wireless Bridge Wireless Controller

Answer 36

This device allows wireless and even wired devices to connect to the internet. Most modern wireless routers integrate a wireless access point, router, and ethernet switch into one device. This allows the three functions of these components to be configured and managed in the router. This is done through the router’s management interface and hardware. A wireless router can thus permit a wireless or wired device to access the internet through a cable, DSL, or ADSL modem. Some advanced wireless routers have a parallel port to allow them to function as print servers.

Answer 37

An access point is a device that contains a radio card that communicates with individual user devices on a wireless local area network or WLAN. Access points also have a wired NIC that interfaces to a network distribution system such as Ethernet. System software installed in the access point bridges the WLAN and wired distribution side. Therefore, the access point provides a wireless connection to the remaining wired LAN, receiving and transmitting data to all the wireless devices in a particular area. Access points also manage multiple connections within the wireless network. However, if one WAP gets overloaded with numerous devices, the network’s overall performance will drop. One or more access points are typically enough for a small office or building. Most access points look like a small box with multiple aerials, synonymous with the looks of a router. And despite modern routers also integrating a wireless access point, some devices serve this role exclusively.

Answer 38

Wireless adaptors, also known as wireless network interface cards (NICs), act as the radio receiver and transmitter for the computer or device connected to a wireless network. This component is coupled with the computer’s operating system using a software driver. Many modern computers and laptops come with Wi-Fi capability built-in. You may have to install this feature using a network card connected to your computer’s motherboard or externally through a USB interface for older generation computers. NICs are designed chiefly to connect to an access point. However, some NICs allow a peer-to-peer connection. This type of connection allows computers with compatible network cards within range to communicate. Peer-to-peer connections are helpful for a small roaming workgroup of devices that don’t need LAN or the internet to operate.

Answer 39

A wireless bridge aims to improve your Wi-Fi coverage or extend it. Their primary purpose is to receive an existing Wi-Fi signal, relay requests, and respond back and forth between your device and the main access point or Wi-Fi router. Wireless bridges are at times referred to as wireless repeaters. They can double the range of the WLAN. Thus, a wireless bridge provides a high-speed, long-range, outdoor link between buildings. Most bridges have a range of about twenty-five miles. They’re not usually affected by water bodies, railroads, or physical obstacles since they’re based on line-of-sight. However, the range of most WLANs will typically be affected by the access points in the network. Most WLANs have access points with omnidirectional aerials or antennae which transmit the signal in all directions. On the other hand, some WLANs use access points with directional antennae that produce a more concentrated signal covering a narrower area. You may thus need to replace the antennae on your wireless access point to get a better range.

Answer 40

Wireless controllers are necessary when a wireless network needs many wireless access points. The job of a wireless controller is to provide a centralized Wi-Fi management platform that manages all the access points in the network. With wireless controllers, you get advanced features and management capabilities such as access control, centralized authentication, and the ability to restrict bandwidth on a group or user basis. You can also perform traffic and Quality of Service (QoS) prioritization

Answer 41

Developments in communications technology mean that organisations can: Monitor behaviour Collect and analyse personal information Distribute, publish, communicate and disseminate personal information

Answer 42

Internet trolling Cyberbullying Anonymous blogs Hate sites

Answer 43

Decisions and choices previously made by humans are now often delegated to algorithms Profiling algorithms determine what information can be accessed Online advertisements may be delivered according to perceived ethnicity, interests or pages viewed Algorithms give users directions about how and when to exercise, what to buy, what route to take An algorithm may be used for bail and sentencing decisions, to identify potential crime hotspots and to predict the likelihood of people reoffending

Answer 44

Algorithms are based on complex rules that make it difficult to predict or explain the decision-making logic The ethics of an algorithm may be ethically questionable because of this complexity Machine-learning algorithms, given new training data, can define or modify their decision-making The human operator does not need to understand how or why the algorithm makes a particular decision

Answer 45

Algorithms may give rise to ethical concerns because of: Inconclusive evidence – the algorithm may not be infallible and this limitation has to be recognised Inscrutable evidence – the human operator may not know what data and what reasoning a decision is based on Inadequate algorithm or data – the conclusions can only be as reliable as the data they are based on

Answer 46

Enforcement is difficult and the criminals are often very hard to trace There may not be suitable laws in place to deal with new types of behaviour on the Internet that could be viewed as criminal The Internet is international but laws vary in different countries, so what is illegal in one country may be legal in others New uses of technology arise so fast that the law cannot keep up – e.g. types of wearable technology