1.3 Computer networks, connections and protocols Flashcards
What are the advantages of networks?
- File-sharing
- Peripheral-sharing
- File-accessing from anywhere
- Centralised security, software updates and backup data
- Communication e.g. email & social networking
- Access Levels - different users can be given different access rights.
- user monitoring - network managers can monitor what users do on a network
What is a Network?
Networks
A network is two or more computers (or other electronic devices) that are connected together for the purpose of communication. They are connected by a wired medium such as cables, or by a wireless medium such as Wi-Fi.
A computer or device that is not connected to a network is called a stand-alone.
What is LAN?
Local Area Networks(LAN), It is a network:
- Covers a small geographical area located on a single site
- All the hardware for a LAN is owned by the organisation using it
- LANs are wired with UTP cable, Fibre optic or wireless using Wi-Fi
What is WAN?
Wide Area Network(WAN), it is a network which:
- Covers a large geographical area, connecting LANs together
- Infrastructure between the LANs is leased from telecommunication companies who own and manage it.
- WANs are connected with telephone lines, fibre optic cables or satellite links
What are disadvantages of Networking?
- Cost of hardware
- Increased security risks as Malware and viruses spread easily
- Reliance on Server - if the server fails the computer might not run
- The computer may run more slowly if there is a lot of data travelling on the network.
- Specialist staff required
What are the Factors which affect the performance of Networks?
Bandwidth
Latency
Error Rate
Number of Users
Transmission Media
BLENT
Factors that affect the performance of networks: Bandwidth
Bandwidth is a measure of the amount of data that the medium can transfer over a given period of time.
Each transmission medium has a different bandwidth. Measure in bits per second, often called bit rate
Each connected device requires bandwidth to be able to communicate. The bandwidth of the medium is shared between each connected device. For example, a home Wi-Fi network with one device would allocate 54 Mb per second to that device. If a second device joins the network, the bandwidth would be split between the two, giving 27 Mb per second to each, and so on.
Factors that affect the performance of networks: Number of Users
Too many users can cause the network to slow down if there is an insufficient bandwidth for the data as it has to be shared.
Factors that affect the performance of networks: Transmission media
- Wired connections have a higher bandwidth than wireless connections
- Fibre optic cables have a higher bandwidth than copper cables.
Factors that affect the performance of networks: Error Rate
Less reliable connection increase the number of errors that occur when data is transferred. This means data has to be resent until it arrives correctly
- The signal quality of wireless connections is dependant on the range of devices from the wireless access point and other environmental factors.
- The signal quality of copper cables is determined by the grade of material used which reduces interference
- The length of the cable is also a factor.
Factors that affect the performance of networks: Latency
What is the benifit of using switches
- The delay from transmitting data to receiving it
- Latency is caused by bottlenecks in the infrastructure of the network
- For example, by not using switches to appropriately segment traffic on a network.
- Hardware such as switches and transmission media may not operate at the same speed.
A network with low latency experiences few delays in transmission, whereas a high latency network experiences many delays. The more delays there are, the longer it takes to transmit data across a network.
Latency is affected by the number of devices on the network and the type of connection device. A hub-based network will usually experience higher latency than a switch-based network because hubs broadcast all messages to all devices. Switch-based networks transmit messages only to the intended recipient.
What is Client-Server model?
What does the Client do?
What does the Server do?
A server is a computer that manages and stores files, whereas a client is a computer that relies on other computers(servers) to provide and manage data.
server is a computer that manages and stores files, or one that provides services to other computers on the network. They control the network and allow other computers to share and communicate. In effect, they serve other computers.
Servers tend to be quite powerful machines. They need the processing power because many other computers connect to them.
Clients do not usually store data. Furthermore, they have no control over the network as a whole or over individual computers. Clients send requests to the server asking for data and the server processes this request and responds. This is client server relationship.
Client-server networks are best suited to organisations with many computers, or to situations where many computers need access to the same information. Many schools use this type of model.
Typical servers include:
- file servers - hold and maintain user files
- applications servers - allow programs to be run over a network
- web servers - hold and share web pages
- print servers - manage printing across a network
- mail servers - handle emails between users
What are disadvantages and advantages of the client-server model?
ADvantages:
- Centralised backups, security and operating system updates
- Easier software updates
- Easier File and user management
Disadvantges:
- Expensive to set up and requires It specialists
- Server Dependence
What is the Peer-to-Peer Model?
What do Peers do?
- A peer is a computer on a network, and is equal to all other peers
- Peers serve their own files to each other
- Each Peer is responsible for its own security & its own backup
- Peers usually have their own peripherals
- You can send print jobs to another peer to process, but that peer would need to be switched on to be able to communicate with the connected printer.
In a peer-to-peer (P2P) network, all computers have equal status - no computer has control over the network. Instead, each computer is known as a peer. Peers store their own files, which can be accessed by other peers on the network. Therefore, a peer is both a client and a server.
P2P networks are best suited to smaller organisations that have fewer computers, or where fewer computers need access to the same data.
Peer to Peer model advantages and disadvantages?
Pros:
- Easy to maintain
- No specialist staff
- No dependency
- Cheaper
- No expensive hardware
Cons:
- Network is less secure
- will need to manage their own backups
- difficult to maintain a well ordered file store
What does a NIC do?
An NIC connects a device to a wireless or wired network connection. and it uses a protocol.
What is the internet?
Most known WAN
What do web servers do?
How are webpages stored?
How does a URL request pull up the requested webpage?
Web servers host sites and deal with client requests.
The web page is stored as text
- First a URL Request is made from browser
- Browser sends domain name to a Domain Name Server
- DNS maps Domain name to an IP address and sends it back to browser
- GET request for webpage/resource is sent to the web server using the IP address
- Requested webpage/resource is returned to the clients web browser
How does a domain turns a human readable URL into a IP address
What is hosting
Hosting is the storing of files and data on a web server.
The web server is referred to as a host .
What is Bus topology?
What is Ring topology?
What is Star topology?
Each computer is connected to a central switch(which segments traffic) however the switch is still a central point of failure.
What are the advantages and disadvantages of using a star topology?
Pros:
- If a node fails the other nodes still work increasing reliability
- New nodes can be added easily
- Have higher performance as they use a switch which only sends data to where it needs to go.
- Less data collisions
Cons:
- The whole network fails if the switch fails
- Requires Hardware which is expensive
What is a Mesh topology?
A mesh topolgy is when every device is connected to every other device so if one node fails there are still multiple pathways for the data to travel but there is a lot more cabling and switch hardware required.
What is the advantages and disadvantages of Mesh topology?
Advantages:
- messages should always get through as they have many possible routes on which to travel
- multiple connections mean (in theory) that no node should be isolated
- multiple connections mean each node can transmit to and receive from more than one node at the same time
- new nodes can be added easily
However, mesh topologies also have their disadvantages:
- full mesh networks can be impractical to set up because of the high number of connections needed
- many connections require a lot of maintenance
- Expensive and IT specialist staff required.
- More power consumption
What are the two types of connection?
Wired
Wireless
What is Mac Address?
What is an IP Address?
MAC addresses are used to route packets on a LAN and is unique to every NIC.
IP addresses are used to route packets on a WAN and have 2 versions
An IP address is the location of your device on the internet, whilst a MAC address identifies the actual device.
What is TCP
TCP provides error free transmission between two routers
What is a NIC?
What is a Switch?
What is a Router?
Network interface controllers
A network interface controller (NIC) provides a method of connecting to a network. A NIC offers an interface port for a wired connection. A wireless NIC provides a radio transceiver for connecting wirelessly.
Most modern PCs come with a NIC and wireless NIC built in, providing the option of either connection method. However, mobile devices such as tablets, smartphones and many embedded devices only feature a wireless NIC, giving only wireless connection.
Switches
Switches are similar to hubs, with one important difference - a switch records which computers are connected to which ports. When traffic is received, the switch forwards the traffic to its intended recipient only. This improves network performance by cutting down on unnecessary transmissions.
A hub broadcasts messages to all devices on the network. A switch sends the message to the intended recipient only.
Routers
Routers are one of the most commonly used connection devices. They are used to send data signals across the internet. Routers work by collecting knowledge of available routes to transmit data. They then determine the most suitable route for sending data.
Routers are also commonly used in homes. These types of router usually contain a hub and a WAP, enabling a small peer-to-peer network to be formed. Additionally, they contain a modem, which allows users to connect to the internet.
What is a Domain Name Server?
A domain name server translates a domain name into an internet address.
Domain names are much easier for users to remember.
What are Virtual Networks?
A virtual network is a network of geographically unrelated computers connected together via the internet.
Virtual networks form their connections through the internet. Virtual network servers create a network that has no direct physical connection, but one that allows file sharing and communication.
Some organisations use virtual networks to enable users at home to connect to the organisation’s data and facilities. Users can then work at home as if they were at their place of work or study.
What are IP addresses?
What is the difference between a static and dynamic IP address?
IP Addressing
When connected to a network each device is given a unique IP address. This address consists of four sets of up to three digits, each with a maximum value of 255, which are separated by dots. An example is:
192.168.0.254
When a node wants to send a message to another node, it uses the recipient node’s address as the destination. A switch on the network knows where the node with this address is and routes the message to it accordingly.I
What is the Cloud and its Pros and cons?
