Networks Flashcards
What is a network
A network is more than one computer system connected together allowing for communication and sharing of resources.
LAN
A local area network (LAN) has computer systems
situated geographically close together, usually
within the same building or small site, like a school
or office.
The network infrastructure of a LAN (such as servers
and routers) is usually owned and managed by the
network owner.
WAN
A wide area network (WAN) has computer systems
situated geographically distant to each other,
possibly across a country or even across the world.
WANs often use third party communication
channels, such as connections by internet services
providers like BT or Virgin Media.
Alternative network types
Other network types do exist, such as a Metropolitan Area Network (MAN) for computer systems connected across a town or city or a
Personal Area Network (PAN) for devices connected and used by an individual.
Client server network
Clients make requests to a server, the server manages that request and responds. For
example, if the user (client) makes a request to access www.bbc.co.uk to a web server.
Large services like Amazon and Google will need very powerful servers to handle millions
of requests a second.
The client is completely dependent on the server to provide and manage the
information. The server controls network security, backups and can be upgraded to
manage higher demand
Advantages of client-server networks
The network can be controlled centrally from the server to easily backup data and update software
Hardware, software and resources can be shared
across the network, such as printers, applications and data files.
The network allows for improved scalability, meaning more clients can be easily added to the central server.
Disadvantages of client-server networks
Large amounts of traffic congestion will cause the
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.
Malware, such as viruses, can spread quickly across the network.
Peer-to-Peer Network
For peer-to-peer networks, data is shared directly between systems without
requiring a central server. Each computer is equally responsible for providing data.
Peer to peer is optimal for sharing files that can then be downloaded.
Advantages of Peer-to-Peer Network
This is a simpler network than client-server to set up as no server is required.
Clients are not dependent on a server.
Perfect for quickly sharing files between systems, such as downloading media files.
Disadvantages of Peer-to-Peer Network
Without a dedicated server there is 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, especially if other machines are slow.
Data Packets
When sending data across a network, files are broken down into smaller parts called data packets.
Whole files are too large to transfer as one unit so data packets allow data to be transferred across a
network quickly.
Each packet of data is redirected by routers across networks until it arrives at its destination. Data
packets may split up and use alternative routes to reach the destination address.
When all the packets have arrived at the destination address the data is reassembled back into the
original file.
Contents of a data packet
Header -
Source address
Destination address
Packet number
Protocol
Payload -
The data itself
Trailer -
A checksum - this is a calculation on the data to see if any errors or
corruption have occurred during transmission.
What is a network topology
Network topology refers to layout of computer systems on a local network.
Devices in a network topology diagram are often called ‘nodes’. Two types of typology are star and mesh
Star topology
Each computer system is connected to a central device, usually a hub or switch.
How it works:
Each computer system is connected to the central hub or switch and transfers its data packets there.
The hub or switch looks at the destination address and transfers the packets directly to the intended computer.
Advantages of the Star Topology
A star topology has improved security because data packets are sent directly to and from the hub / switch in the Centre and not necessarily all devices like in a bus or ring topology.
New systems can be attached directly to the central system so the network doesn’t need to be shut down. System failures of attached computers won’t usually cause complete network failure.
Transfer speeds are generally fast in a star topology as there are minimal network collisions
