Flashcards in The Internet Deck (39):
How do search engines fill their database with sites?
Program called a web crawler which looks for new sites.
What is a meta tag?
A list of keywords the website owner has chosen and put in the header of the html document so the web crawlers know what the site contains.
What factors can increase your website ranking (aside from PageRank)?
Using searched for keywords in the title tag
Age of site
Last or frequency of updates
Number of keywords appearing in specific tags
Relevancy of domain name
What is the PageRank algorithm?
PR(A) = (1-d) + d( sum of PR(Tn)/C(Tn)) where PR(A) is the PageRank of the site, d is a damping factor (~0.85), C(Tn) is the number of links from site Tn to A.
What does URL stand for?
Uniform Resource Locator.
What is the purpose of a URL?
To show where the location of the required resource is on the internet (it is the web address).
What does DNS stand for?
Domain Name System.
What is the DNS?
They are designed to be easy to remember strings of text which point to the domain an internet resource resides in, for example .uk shows the resource is in the UK.
What is an IP address?
Internet Protocol (IP) address's are the unique string of numbers assigned to a network/device, it shows where the data needs to be sent.
What is a WAN?
Wide Area Networks (WANs) are collections of LANs spanning more than a single location, the internet is an example of a WAN.
What is a LAN?
Local Area Networks (LANs) are several computing devices connected together on a single site.
Describe a bus topology.
All devices are connected to a central main cable which has the server at one end.
Describe a star topology.
All devices have their own dedicated connections to the central server.
Advantages and disadvantages of a bus topology?
Is cheaper as it requires less cable and dedicated hardware
Will fail if the main cable breaks
Is much slower with heavy traffic
Has lower security as PC's can see all data on the cable
Advantages and disadvantages of a star topology?
Cable failures only affect one machine
Fairly consistent performance
No chance of data collisions
Easy to add new devices
May be very expensive
If central server goes down the whole network is down.
What is a WAP?
Wireless Access Points are devices which connect devices via Wi-Fi to the network.
What is a Mesh network topology?
Where every device is directly connected to every other (often via Wi-Fi) with one device connected to an external network like the WWW.
What is circuit switching?
When a direct link is created between two devices on a network for time taken for a message to be sent.
What is packet switching?
When data packets are sent to adjacent nodes on a network at each stage sending a packet to the local optimum for sending the packet to the required location.
Circuit switching vs packet switching?
Circuit switching is faster for a single user but often uses unnecessary bandwidth as the route is locked for the duration of the message, used now for telephone calls.
Packet switching is often slower but allows more users to use the network, also packets may not appear in order.
What is a MAC address?
A Media Access Control (MAC) address is a 12 (hex) digit that uniquely identifies any single device for the purpose of transmitting information.
What is TCP/IP?
Transmission Control Protocol / Internet Protocol is a set of standards for transmitting data.
What are the four layers of the TCP/IP stack?
Application, transport, network and link layers.
What is the application layer of the TCP/IP stack?
It is the layer that deals with displaying and receiving information from the device (could be from user or sensor).
What is the transport layer of the TCP/IP stack?
Creates or splits packets given port information and and packet number
What is the network layer of the TCP/IP stack?
Adds the IP address of destination and sender to packets.
What is the link layer of the TCP/IP stack?
Adds the MAC address. this could change on route if the target computers MAC address is not known.
What is a firewall?
A security feature designed to prevent unauthorised access between two networks, may also act as proxy server.
What is a proxy server and what are they used for?
It is a server that intercepts all data entering/leaving a network, hides true network address, can store cache of commonly visited sites for other users of the networks and can filter content.
What is a worm?
A worm is malicious software that can self-replicate.
What is a virus?
Malicious software that replicates and hides itself inside other programs.
What is a Trojan?
Malicious software which pretends to be something else so that you install and run it.
What is malware?
Unwanted and harmful software, a worm, virus or Trojan.
What is a client-server network?
Where several devices are connected to a central server.
Advantages and disadvantages of a client-server network?
Higher security since files are stored centrally and access is managed by server
Easier to manage backups
Data and resources (like printers) can be shared
But is expensive
And requires IT staff to maintain
What is a peer-peer network?
Where individual computers are connected directly to each other.
Advantages of a peer-peer network?
Cheap to set up
enables resource sharing
Easy to maintain
What is the difference between client-side and server-side processing?
The location where code is executed or databases are read/changed.