3. Computer networks, connections and protocols Flashcards
What is a network?
A network is a system that allows computer systems to communicate and share resources with each other
What are the advantages of using networks
- Data and files can be exchanged and shared between computers on a network
- Resources & Hardware can be shared (such as printers, scanners and internet connections)
- Communication
- Roaming Profile
Disadvantages of Networking
- Hacking
- Expensive Hardware
- Need specialised staff
What are the advantages of big organisations using large networks?
- Centralised maintenance & updates
- Centralised security
- User monitoring
- Levels of Access
What are the characteristics of a LAN
- A local area network has computers that are connected together over a small geographical area such as a single building or site
- LAN usually has its own dedicated infrastructure and hardware that is owned and maintained by the individual
Where are LAN networks typically found?
LAN networks are typically found in homes, schools, universities
What are the characteristics of a WAN
- A Wide Area Network is where the computers are connected over a large geographical area, over a mile apart
- The owners of the WAN do not own the infranstructure as it is a 3rd party infranstructure
What is the largest WAN?
The Internet
Factors that affect the performance of networks
- Number of devices or users
- Bandwith
- Signal Strength
There are other factors that require you to use your common sense
COME BACK HERE
What are the two types of network models
- Client-Server model
- Peer-to-Peer model
Describe what the client server network is?
- A client is a computer that sends requests to the server for services and resources
- A server is a computer which manages access to a resource or service and provides the services and resources required by the client
In a client server network:
- The network relies on a central server
- All clients (devices) request services from the server (e.g. print services/file services or web hosting).
Give 5 examples of the services that servers may provide in a client server model
- File servers - hold and maintain user files
- Web servers - hold and share web pages
- Print servers - manage printing across a network
- Mail servers - handle emails between users
What are the advantages of a client server network?
- Central File Storage - users can access them from any computer
- Centralised security - Security can be managed centrally using antivirus software on the server
- Software can be installed or upgraded centrally without having to manually update each client machine
- Backups can be done centrally on the file server
What are the disadantages of a client-server network?
- High initial cost for server as they are expensive
- Specialist required to setup client-serve
- If the server goes down, then the whole service goes down for the network and it becomes inaccessible for all devices and users
- Too many client requests to the server can degrade server performance, bottleneck and overload it
What is the peer-to-peer network?
A peer-to-peer network is a network with no central server, where each computer is directly connected together and they can act as both a client and a server.
Furthermore, each peer has equal responsibility in the functioning of the network.
What are the advantages of a peer-to-peer network?
- Less initial cost / maintenance as no server or dedicated hardware is required
- No specialist required
- Easier to setup and add new devices
- If any device fails/is removed the remainder of devices can continue to function as normal
What are the pieces of hardware required to connect to a Local Area Network?
- Wireless access points
- Routers
- Switches
- NIC (Network Interface Controller/Card)
- Transmission media
What does a Wireless Access Point (WAP) do?
- Creates a wireless network using radio waves to allow network access and connectivity for wireless Wi-Fi devices
- They can also be used to extend the range of a wireless network
- Allows connections through wifi and bluetooth
What are the functions of a router?
- Routers work by inspecting the destination IP address of a data packet and determining if it is on the network or not. It then directs the packets/data to another network or to the destination
- They sit between LANs and WANs to connect the two different networks together - for example, joining a home network to Internet
- Has (public) IP address for LAN
- Designates (private) IP addresses to network nodes
When do data collisions occur?
Data collisions occur when two or more packets send data at the same time
What is the purpose of a switch?
- Switches are used to connect devices on a LAN together
- It recieves data packets and sends them only to the destination device, using the MAC addresses of the connected devices
What is a network interface card (NIC) required for?
A Network Interface Card is a hardware component used to connect a device to a wireless network.
Nearly all new computers have a NIC built directly into the motherboard
Define Transmission media
Transmission media are the ways of physically transferring data along a network, from one computer to another.
What are the types of transmission media that can be used?
Transmission media can be wired or wireless and include:
- Fibre optic cable
- Coaxial cable
- Twisted copper wire cable
What is the internet?
The internet is a worldwide connection of computer networks
What is a Domain Name Service made up of?
A Domain Name Service (DNS) is made up of multiple Domain Name Servers
What is the purpose of the Domain Name Service (DNS)?
The purpose of DNS is to keep a record of the IP address of each web server that is associated with a particular domain name, so that the website address/URL can be converted into an IP address
Describe the DNS’s role in the conversion of a URL to an IP address
- When the client enters the URL, the browser sends a request to the ISP’s (Internet Service Provider’s) DNS server, with the URL
- The ISP’S DNS looks up and finds the database for the IP address matching the URL
- The ISP’s DNS then returns the IP address to the browser on the client machine
- If the IP address is not found, the DNS passes the request to a higher level authoratative DNS and the process repeats until it is found.
- If no IP address match is found, an error is returned
What is the benefit of having DNS?
The benefit of having DNS is that users only need to remember or enter the website’s domain name or URL rather than needing to remember or enter the whole destination IP address
Web Hosting
What does URL stand for?
Uniform Resource Locator
What are the parts of a URL?
Define the Cloud
The Cloud refers to the remote provision of services such as storage, software and processing, that are accessible via the internet - and exist in a remote server that is located in giant data centres
Not needed: Generically, it refers to remotely accessed storage
What are the advantages of using the cloud?
- Storage is more flexible so it is easier to buy and increase the storage space when it runs out
- There is no need to buy or maintain any expensive hardware or infranstructure
- Can access files from anywhere where there is an internet connection
- Do not have to backup manually as automatic backups are provided
- Security from 3rd party cloud providers may be better and and more reliable
What are the disadvantages of using the cloud?
- You cannot access the data without a reliable internet connection
- There is little to no control over the security of your data, so you are reliant on 3rd party providers and are vunerable to hacking and theft
- Issues regarding data ownership
What are the two types of network topologies?
Star Networks
Mesh Networks
What is a network topology?
- A network’s topology is the organisation of the connections between the devices.
- In other words, how the network is ‘laid out’ and how the devices should connect to one another
Describe the star network topology
- In a star network topology, all of the devices on the network are connected to a central switch
- Every packet of data has to go through the central switch, which directs packets of data only to the destination device using their unique MAC address
What is the difference between a star network topology and a client-server model
Star network refers to how they’re physically connected and client server refers to how they communicate and share resources
What are the advantages of a star network topology?
- Easier to add or remove devices
- Easy to troubleshoot and detect faulty parts
- Needs fewer cables
- Fewer data collisions can occur
- If a node or device fails it does not affect the rest of the network
- A signal does not need to be transmitted to all computers in the network
What is the disadvantage of a star network topology?
- If the switch fails, then the whole network connection fails (there is a single point of failure)
- A cable is required to connect every compuer, which can be expensive
Describe the mesh network topology
In a the mesh topology, all devices are connected either directly or indirectly to each other without a central switch
Describe the mesh network topology
In a the mesh topology, all devices are connected either directly or indirectly to each other without a central switch
Explain the difference between the two types of mesh network topologies
In a full mesh network, every device is directly connected to every other device. In a partial mesh, direct connections only exist between some devices, but they can all communicate with each other indirectly by finding different routes
What is the best example of a mesh network
The Internet
What are the advantages of a mesh network topology?
- It is highly robust as if there is a failure between the connection of two nodes, the network will automatically find a different route
- Data can be transmitted from several devices simultaneously, so the network can cope with high traffic
What are the disadvantages of a mesh network topology?
- Wired mesh networks are very expensive as every device needs to be wired to every other device. This is also very impractical in terms of the number of network interfaces required on every device
- Difficult to add or remove devices
- Maintenance and security practices become harder to do as there is no central point through which data travels through and nodes are connected to
Why may a partial mesh network be better than a full mesh network?
Less wires, so less costly
What are the different ways of connecting devices?
Devices can be connected through:
- Wi-Fi
- Ethernet
- Bluetooth
Describe how Wi-Fi works
Wi-Fi uses radio waves to transmit data
