Networks Flashcards

Question

Servers on LANs and WANs

Answer 1

1. One or more servers may be part of a LAN 2. A server may also be part of a WAN, e.g. 3. Google has massive servers in several different countries 4. Websites are stored on web servers

Answer 2

• A peer-to-peer network has no central server • All the nodes/devices are equal to one another

Answer 3

• Each computer stores files and acts as a server • If one peer has a printer connected to it, the other peers can access • Or another peer is connected to the router, and therefore provides internet connectivity to the other peers In this sense, the peers acts as both clients and servers.

Answer 4

• Most commonly used for sharing files, especially large ones. • In the client-server model, many users trying to access a large file, e.g. a film, would put strain on one server. • In the P2P model, many peers could store the same file. Each computer can then send sections of the file, sharing the workload P2P is ideal for sharing files. It wouldn't work for a service such as booking tickets where one server needs to keep track of how many tickets are left

Answer 5

• Easier to set up – computers can simply be cabled together • No special software or staff is required to run the network • Individual computers can share a printer, router, modem and other hardware • Users can communicate directly with each other and share each others’ files

Answer 6

• Viruses and malware are easily transferred over this type of network • Data recovery and backup is not done centrally, so each computer has to have its own backup system • Files are not centrally organised, but stored on individual computers and may be hard to locate if the computer’s owner does not have a logical filing and naming system

Answer 7

To connect a computer or device to a network, several hardware components are required: • The device must contain a network interface controller (NIC) • A transmission medium, either wired or wireless • A point to connect to such as a router, switch or wireless access point (WAP)

Answer 8

When data is sent across a network, it is split into packets (smaller chunks). Each packet has some additional information attached in a header such as the IP address of where the data came from, and its destination IP address

Answer 9

What is its purpose? • To connect a device to a network • Every NIC has a unique MAC address - it is allocated by the manufacturer and cannot be changed Tasks performed by a NIC: • At the sending end: Converts data sent by the device into the appropriate format to be sent across the transmission medium (wired or wireless) • At the receiving end: Converts signals received by the device into the corresponding digital data

Answer 10

Transmission Media carry data signals from one computer to another. Media are either wired (physical cable) or wireless.

Answer 11

What is its purpose? • To connect wired devices together in a network (don't need if using wireless devices) • Smart device as only sends packets to the intended recipient therefore minimising network traffic Tasks performed by a switch: • Receives packets • Sends packets only to its intended destination • Know which devices to send packets to as it records the addresses of devices as they are accessed - it has to look for the correct MAC address before sending it on • Uses the devices’ MAC addresses

Answer 12

What is its purpose? Connects different types of network together MUST have in order to be able to access the internet. At home it connects your home network to the internet via your ISP. Tasks performed by a Router: • Receives packets • Forwards packets on • To do this it maintains a routing table so that it can…. • Send data packets along the most efficient path to their destination using IP addresses • Assign IP address to nodes in a network

Answer 13

A wireless access point What is its purpose? Enables devices to connect wirelessly to a LAN/wired network (the WAP itself will be connected to the LAN via a cable) Tasks performed by a WAP: Provides a wireless network radio signal for wireless devices to connect to (NB: It is not the device that provides internet access) So…to connect wirelessly to the internet you need a WAP and a Router. However, at home, they are likely to be built into the same device

Answer 14

• The devices in a LAN can be arranged in different ways • Two of these topologies are: • Star • Mesh • A topology diagram will show the layout of devices (often referred to as nodes) and the connections between them

Answer 15

● One central switch ● All computers /devices connected to this central switch [Can have variations of this, e.g. Switch or Hub (not recommended) or INCORRECTLY..a server!]

Answer 16

Higher performance / fast data transfer as there are fewer data collisions as data is only passed on to the intended recipients If one cable / device fails the other devices are not affected Easy to add new nodes to the network - just need to be connected to the central switch

Answer 17

Requires additional hardware at the centre of it, ie. the central switch If the central switch fails the whole network goes down = SINGLE POINT OF FAILURE

Answer 18

Star topologies tend to be found in large organisations, such as educational establishments and businesses, where high performance is a must. They are also found in home networks, especially those that are wireless. In this case, a switch is combined with a wireless access point (WAP) to provide the central connection for all nodes. A router provides access to the internet

Answer 19

N/a For these, the fastest route is calculated before sending data

Answer 20

No single point of failure Resilient - if one link fails, then there will always be an alternative route Expansion and modification can be done without disrupting the network Work well under high load - multiple devices can transmit data at the same time which will travel via different routes

Answer 21

• Full Mesh Topology: • Every device is connected to every other device • Multiple communication paths between the devices • Partial mesh Topology: • Each device is connected to at least one other device • There is a minimum of one path between every pair of devices • Usually used, often in conjunction with star topologies to create larger networks The internet is a classic example of a mesh topology

Answer 22

Can involve redundant connections - inefficient use of hardware Expensive to install cabling if using wired connections (hence wired mesh networks are not very common) Network maintenance and management is more complicated than other topologies

Answer 23

Mesh topologies are used where the reliability of network communication is very important: ● military organisations often use mesh topologies to avoid breakdowns in communication ● cities are increasingly using wireless mesh networks to help monitor traffic flow, sewage treatment and to help control street lighting ● emergency services, such as police and fire services, also use wireless mesh networks to ensure that communication is reliable

Answer 24

Transmission media transmits data from one device to another. Two main categories: ● Wired ● Wireless

Answer 25

Wired transmission media is a physical cable that connects one device to another. This is often shown as a solid or a long dashed line in a graph or a diagram. N/a

Answer 26

Wireless transmission media doesn’t require a physical cable. Wireless signals are sent through the air. A wireless connection is often shown using a short dotted line or a wave symbol. N/a

Answer 27

A protocol is a set of rules for how data is transmitted on a network • The Ethernet protocol is used in wired transmission between devices and between networks • WiFi is a suite of protocols used for wireless transmission over longer distances • Bluetooth is a protocol used for wireless transmission over a short distance

Answer 28

• WiFi - enables you to connect your device to a network • Bluetooth - enables you to connect different devices together Both use radio signals

Answer 29

In modern networks, wired media use either twisted copper wiring, or fibre-optic cable. Both use the Ethernet protocol: Twisted Copper Wire: Cost: cheap Maximum transmission speed: fast Maximum distance for reliable communication: up to 100m Form of signal: uses electrical signal Fibre-optic cable: Cost: expensive Maximum transmission speed: very very fast Maximum distance for reliable communication: over 2km Form of signal: uses light pulses

Answer 30

1. A Wifi Enabled Device - Built into the device, either a wireless NIC / Adapter (typically in PCs) or a wireless Antenna (tablets, smartphones) 2. Access to a WAP

Answer 31

The internet is a global network of networks. It is an infrastructure that is used to share data and resources on a global scale.

Answer 32

Your Internet Service Provider (ISP) connects you to the billions of devices that are connected to the internet. Each, with their own unique IP address. IP addresses allow a device to be located and data to be sent to the intended recipient.

Answer 33

It is the World Wide Web. The internet can be used to access the World Wide Web (WWW). The WWW is a collection of web pages.

Answer 34

In order to navigate the WWW you need a web browser. The most widely used web browsers are: ● Google Chrome ● Safari ● Firefox ● Microsoft Edge

Answer 35

To access a web page on the WWW you enter a website address into the address bar at the top of your browser. This website address is known as a Uniform Resource Locator (URL). A website address is a user friendly way of writing the IP address location of the server that stores the website. It would be very hard to remember the IP address of every website that you wish to use, so a naming system is used instead.

Answer 36

DNS is a domain name system that associates a website address with the IP address of its web server (ie. the server hosting the website)

Answer 37

First, it will check if you have visited the website before. If you have, then your computer will already know the IP address. It will be stored in the browser's cache If not there it will use the DNS to find the IP address for the website.

Answer 38

DNS = thousands of DNS servers all around the world arranged in a hierarchy. If your computer doesn’t know the IP address for the website that you need then it will try and find that IP address in the fastest way possible. There is a process for this.

Answer 39

1. URL is sent to DNS. Firstly DNS checks your ISP’s DNS server (e.g Sky Broadband) 2. On it, DNS looks for the URL in its table of URLs to find the corresponding IP address of the web server 3. If it is found there, the IP address is returned to the browser Otherwise, If the website’s IP address can not be found here then it sends the URL / Request to a higher-level DNS Server in the hierarchy. Either: ● The URL is found, and the IP address of its web server is returned to the Browser, or ● The URL and corresponding IP address is not found, so an error is returned to the browser

Answer 40

The web browser establishes a connection with the web server at the IP location specified by the DNS. The web browser then makes a request for the web page. The server will then check what has been requested and start to build a response. Web pages are typically built using a markup language known as HTML. The server will prepare the HTML required to build the web page in your browser. It will then send that HTML page and any other files, like images to your computer. The browser then takes the HTML and builds the web page within your browser. This is then displayed as a fully functioning web page.

Answer 41

'Resolving' a URL means translating the URL into the IP address of the Server hosting the website 1. Browser checks its cache for the URL, and the corresponding IP address. If not found there….. 2. The URL is sent to the ISP's DNS server. 3. Its table of URL is searched to find the URL, and its corresponding IP address 4. If it is found, it is sent back to the browser otherwise… 5. The URL/Request is sent to a higher-level DNS server in the DNS hierarchy 6. This repeats until either the URL is found, and the corresponding IP address is returned to the browser OR an error is sent back indicating that the URL can't be found

Answer 42

1. We as users don’t have to remember / type in IP addresses -> URLs are much easier for us to remember 2. The IP address of a server (eg. the web server is upgraded) can be changed seamlessly

Answer 43

= Computing services which are accessed via the internet Services include: 1. Storage 2. Software 3. Processing The services are run out of server farms - huge warehouses full of servers attached to extremely large storage devices

Answer 44

• An Internet host is a company (often an ISP) that is able to: • store your files and make them available to you or others from other Internet-connected computers • Host software which you can then run, without having it installed on your device • These include: • Website pages, images and related files • Online file hosting services such as OneDrive or DropBox • Video hosting services such as YouTube • Software such as Office 365, Gmail, Google Slides

Answer 45

• The software and storage for your account is not held on your computer – it’s on the service provider’s servers • Your device is the client, and accesses those servers via the internet • Usually, each application will have its own dedicated servers (e.g. Google Drive, Slides, Classroom, etc..)

Answer 46

• Cloud-based servers enable access to software on demand • Typically on a subscription basis • No need to have the software installed on a local machine • Can access the software (and your data) from any Internet-connected computer, including mobile phone applications • Examples include: • Word processing (e.g. Google Docs) • Graphics design (e.g. Adobe Creative Cloud)

Answer 47

• Can access applications from any device at any time (providing have internet connection) • You don’t need a powerful computer with a powerful CPU and huge hard drive – the software application is stored and run on a remote computer • Updating software is done automatically by the service provider

Answer 48

• Data is stored on 3rd party servers • Data can be accessed from any device (providing have an internet connection) • Typically need to sign into the service to retrieve their data

Answer 49

• Can access additional processing power • Computation-intensive applications (e.g. rendering animations, processing large data sets, creating 3D models) can be done with borrowed computing power from the cloud Advantage: • Can free up your own machine (for individuals) • Don’t have to invest in and maintain extra computers that might not be fully utilised all of the time

Answer 50

Advantages: • For individuals: • Can access data and files from any device at any time (providing have internet connection) • Backing up data is no longer crucial – it is done by the service provider • You don’t need as much storage space on your device -> saves money • For data, is typically easily scalable (albeit at a price) • Much of the above also applies to organisations as well Disadvantages: • Need an internet connection! • Are totally dependent on that company taking care to: • protect your data (in line with the Data Protection Act) • back it up regularly • As data is being transferred via the internet between the device and the cloud, is susceptible to interception • While you can usually store a limited amount of data for free, you typically have to pay to store more than the free allowance

Answer 51

….is all about response time - how fast a message can be sent, or how quickly a film can be streamed, or how quickly a web page can be loaded, etc Several factors affect network performance: 1. Bandwidth 2. Number of connected devices 3. Type / Amount of data being transmitted 4. Error rate 5. Transmission Medium

Answer 52

• The amount of data that can be carried at a time - Lower bandwidth means less data can be transmitted at the same time

Answer 53

- type of transmission media - number of users connected - what users are doing

Answer 54

The number of devices connected to the network will affect the performance of the network for all users due to its impact on available bandwidth: • More users/devices means more data is being transmitted at a time • The available bandwidth will need to be split between more users/devices -> means less bandwidth for each user/device

Answer 55

Ie. What the users are doing will have an impact on the network performance: E.g. streaming high definition movies -> Greater quantity of data being transmitted -> needs more bandwidth VERSUS Writing an essay using a cloud based word processing application

Answer 56

• The larger the amount of data being sent across the network, the greater likelihood of errors and collisions • When packets collide, they are corrupted or lost which means… • …more data has to be retransmitted…. (again, reducing available bandwidth) • ….Causing more corrupted packets and data to be lost

Answer 57

I.e. Wired vs Wireless For wired connections typically offer higher bandwidth. Fibre Optic offers the highest, over long distances. For wireless, there are other factors affecting the performance: • Distance from WAP • Obstacles such as walls • Interference from other electronic devices

Answer 58

• Latency is the time delay between the moment the first data packet of a communication starts and when it is received at its destination • A network with low latency -> very little delay in transmission = High Performance • A network with high latency -> many delays in transmission = Low Performance Bandwidth = the amount of data that can be transferred per second. Latency = the time that data takes to travel between its source and destination

Answer 59

Standards are technical specifications that specify how hardware and software components must work. Without agreed standards, hardware made by different manufacturers and software components produced by different companies would not work together. A standard: • Is used by many manufacturers / devices… • … as it allows compatibility with other devices

Answer 60

• Fit for purpose - depending on the area where it’s likely to be used it might need to be: secure, reliable, high performance • Cost effective

Answer 61

A protocol is a set of rules governing how computers communicate, ie. how they transfer data between them Many protocols are also standards, e.g. Ethernet, Wifi, Bluetooth, TCP However other protocols exist which are not standards, (e.g. HTTP, FTP).

Answer 62

- HTTP - HTTPS - FTP

Answer 63

Hypertext Transfer Protocol Purpose: - used for accessing and receiving web pages in the form of HTML files on the Internet Features: - Sends a request for a webpage from the web browser to the web servers - transfers the requested web page from the web server to the user’s browser for viewing - If the page cannot be found it will return an error code

Answer 64

Hypertext Transfer Protocol Secure Purpose: - Encrypted version of HTTP Features: - As for HTTP but sends an encrypted request for a webpage, and an encrypted page is returned

Answer 65

File Transfer Protocol Purpose - Used to upload or download a file between a device and a server via the Internet Features - Server opens a data connection over which the file is transferred

Answer 66

• Mail servers pass on or store emails until they are collected • You must log in to a mail server to collect mail • Examples of mail providers are Gmail or Yahoo sender’s computer -SMTP-> sender’s mail server -SMTP-> Internet -SMTP-> recipient’s mail server -POP/IMAP-> recipient’s computer

Answer 67

- SMTP - POP - IMAP

Answer 68

Purpose: - Used to send an email to an email server Features: - Delivers the email from the client/sender’s device to their email server - And then…delivers the email to the recipient’s email server (destination mail server)

Answer 69

Purpose: - Used to request any new emails for a specific email account from an email server Features: - Downloads any emails from an email server to the user’s device - Deletes the email from the server

Answer 70

Purpose: - Used to synchronise a client email account with an account on a mail server - Allows a user to use multiple devices to access their email account Features - Server delivers the header of any new emails to the client / user’s device(s) - Downloads the email when the email is opened on the client/user’s device - Leaves the message on the recipient’s email server (unless the user deletes the email on their client/device)

Answer 71

Transmission Control Protocol Purpose: - Splits data to be sent into packets, and reassembles packets at receiving end Features: - When data is to be sent, it is split into packets - Each packet is given a sequence number - When data packets are received, they are checked, and any missing packets are re-requested

Answer 72

Internet Protocol Purpose: - Routes Packets using IP address Features: - Adds source and destination IP addresses to packets - ….allowing packets to be routed across the internet

Answer 73

Purpose: - Manages transmission of the data along the wired (Ethernet) or wireless (WiFi) media - Uses MAC addresses Features: - Turns packets into frames (another kind of packet) - Adds source and destination MAC addresses

Answer 74

Network communication across the internet is very complex Many organisations are involved in writing the software and developing the hardware which is involved in networking To simplify the process, it is divided into layers: • Each layer has a defined responsibility • The layers are ordered so that data moves from one layer to the next in its journey from the application (ie. the user) to the point at which it is physically transmitted across a network, and vice versa at the receiving end • The specification for the interface between each layer is well documented -> means that developers and manufacturers just need to make sure that the data is in the correct format so that it can move from one layer to the next

Answer 75

• Layering means dividing up the process of sending and receiving data into different sub-parts ( = layers) • The TCP/IP stack is made up of 4 layers - each is a division of network functionality, each carrying out a different role • Different protocols operate in different layers. Therefore, protocols are used as a hierarchy that divides the tasks of communications into different layers.

Answer 76

The application you are using to send data will determine the correct protocol to use to communicate Application (computer application - HTTP/HTTPS, FTP, IMAP, POP) —> Transport (creates connection - TCP) —> Internet (sends and routes the data - IP) —> Link (physical hardware and cables - Ethernet and WiFi) —> Link —> <— Internet —> router

Answer 77

• Layers are self-contained which means: • A layer can be removed or changed without affecting any other layers • Each layer doesn’t need to consider what the other layers do • Different hardware or software operates on a particular layer providing interoperability between providers and systems, e.g. one manufacturer’s router operating on the Internet layer, will operate with another manufacturer’s NIC operating on the Link layer • Individual protocols are smaller and simpler to manage since they only need to cover a small part of the overall network functionality

Networks Flashcards

(106 cards)