ICT L.O.3 Flashcards
What is a Network?
Networks are connections between devices which enable resources and data to be shared.
(+) –> communication is faster and easier.
–> Resources are used more efficiently.
(-) –> Many networks are fixed in their arrangement and need cost/expertise to set up.
What are 2 types of networks based on behaviour?
1) Client-Server Networks–> Clients (devices/software) request data from servers (and servers provide data to clients).
-(Every device acts as either a client or a server)
(+)–>Provides centralized control
(-)–> can be expensive and difficult to run.
2) Peer-to-peer Networks–> Have no central servers, individual devices can switch between being clients and servers
(Each computer is equal in responsibility)
(+)–> Simpler to set up and maintain
(-)–> No managed security backups (Malware can spread quite quickly and illegal movies etc. are shared)
What is a server?
A server is a dedicated hardware or software that provides functionality for other programs or devices. (clients)
What are the different types of servers?
1) File Server
2) Printer Server
3) Application Server
4) Database Server
5) Web Server
6) Mail Server
7) Hypervisor
What is a File Server?
A file server stores data and allows clients to access their/shared files remotely.
What is a Print Server?
Manages print jobs and communicates with printers.
–>useful when there is a queue of people printing, or budgets (keeping track of what was printed and how much it cost)
What is a Database Server?
Hosts a Database (allows it to run) so is used to store large amounts of related data.
What is a Web server?
Hosts websites –> holds and supports websites (may connect to a database)
–>Allows clients to request and receive webpages through HTTP/S
What is a Mail server?
A server that sends, receives, stores, and manages emails.
-(May run the SMTP and/or POP protocols)
What is an Application Server?
A server which allows multiple users to access software.
(often used to access data from a database e.g., a central email system in a company
–>Acts as a layer of security as it will restrict certain applications to those with invalid access levels.
What is a Hypervisor?
A type of server that can create multiple virtual machines.
(The computer running the virtual machine is called the (Host) whilst the virtual machine is the (Guest)
–>The hypervisor allocates the underlying physical computing resources such as CPU and memory to individual virtual machines as required.
(Virtual machines are portable-meaning they can be moved between hypervisors)
What is Virtualisation?
Virtualisation is the act of presenting something to the user which is different to the physical reality.
-E.g.–> using one set of hardware to create multiple virtual machines
What is ‘Server Virtualisation’?
Allows one physical server to run multiple virtual servers/machines (each running separately)
What is ‘Client Virtualisation’?
A Virtual client has full desktop functionality, but processing and storage are done via a hypervisor.
What is Storage ‘Virtualisation’?
Data is stored across multiple physical devices but is presented as one/fewer devices.
What is ‘Cloud Virtualisation’?
When Data is held and processed in an off site location, either private or public
-Private–>company owns its own remote location
-Public–>remote location owned by a third party
(Hybrid virtualisation is usually a mix of public and private cloud services)
What are the Advantages and Disadvantages of Virtualisation?
(+)
–>Hardware can be used more efficiently as it can be shared to create multiple virtual machines
–>Reduced long-term cost (less hardware means reduced power consumption)
–> Easy to add new user
(-)
–>More complex (may need specialist staff)
–>If the hypervisor or host goes down, all users will be affected
–>Performance issues with high server load
What is a Client-Server Network?
Clients will make request to a server, the server manages the request and responds
(Client is completely dependent on the server to provide and manage the information)
What are the advantages and disadvantages of a Client-Server Network?
(+)
–>Network can be controlled centrally from the server to easily backup data and update software
–>Hardware, software and resources are shared e.g. printers/applications/data files
–>Improved scalability (clients can be easily added to the central server)
(-)
–>Large amounts of traffic congestion will cause network to slow down
–>If a fault occurs with the server, then the whole network will fail
–>IT technicians may be required to manage and maintain the network (costly)
–>Malware such as viruses can spread quickly across the network
What is a Peer-to-peer network?
Data is directly shared between systems without requiring a central server (each computer is equally responsible for providing data)
What are the advantages and disadvantages of a Peer-to-peer network?
(+)
–>Simpler to set up as no server is required
–>Clients not dependent on a server
–>efficient for quickly sharing flies between systems (e.g. such as downloading media files)
(-)
–>No central device to manage security or backups (backups must be performed on each individual system)
–>Computer performance will decrease with more devices connected to the network
What is a ‘Bus Topology’ and how does it work?
-The Nodes ( computers, servers, switches, routers, and even smartphones or IoT devices) are connected to a bus (a central cable which transfers all data on the network)
How it works:
1) Bus transfers data packets along the cable
2) Each computer checks the destination address contained in the packet to see if it matches its own
3) if it matches, it is accepted and processed
4) if it does not match, the computer system passes the data packet to the next system
What are the advantages and disadvantages of a Bus Topology?
(+)
–>Easy to attach another system to the main cable without disrupting the whole network
–>Quick to set up (once the main cable has been established) making it optimal for temporary networks
–>Cost effective as it contains less cabling than other topologies and requires no additional hardware (e.g. hub or switch)
(-)
–>Poor security (as data packs are passed on to each system on the network)
–>Data collisions are more likely (when 2 systems attempt to transfer data on the same line at the exact same time ) this will slow down the network
–>The main cable only has a limited length which can become crowded and slow down the network
What is a ‘Token Ring’ topology and how does it work?
-Computer systems are connected in a ring or a loop
How it works:
1) A token (small data packet) is sent around the ring in one direction, being passed from one computer system to the next.
2) A computer seizes the token and includes its own data when it transfers data
3) As the token arrives at each computer system, the system checks the destination address contained in the packet to see if it matches its own.
4) If the address matches, the computer processes the data otherwise it ignores it