Computer networks, connections and protocols

What are standalone computers?

Not connected to any network

What are networks?

A system connecting two or more computers

What are the advantages to networking?

• can share files

• can share hardware eg printers

• The internet connection can be shared between the devices

• Updates on software can be installed into all computers at once

• Can communicate with users cheaply and easily

• User accounts can be stored centrally, so users can log in from any device on the network

What are the disadvantages to networking?

• increased security risks to data

• malware and viruses spread very easily between computers

• if a servers fails, the computer connected to it may not work

• computers may run more slowly if there is a lot of data travelling on the network

What are local area networks (LAN)?

• covers a small geographical area located on a site

• all the hardware for LAN is owned by the organisation using it

• LANS are wired with UTP cable, fibre optic or wireless using Wi-Fi

• often found in businesses, schools or universities

What are wide area networks (WAN)?

• covers a large geographical area, connecting LANS together

• infrastructure is hired (the underlying facilities that support this) from telecommunication companies who own and manage it

• WANS are connected with telephone lines, optic cables or satellite links

What is the function of a switch?

• connects devices on a LAN

• recieves data from one device and transmits it to the device on the network with the correct mac adress

What is the function of a router?

• connects the LAN to the internet

• responsible for transmitting data between networks

• crucial role for directing data packets to their destination

• assigns a unique IP address to each device

How do wireless networks work? What are there advantages?

• Uses radio waves to transmit data

• A wireless access point (WAP) is needed to connected devices wirelessly

Advantages:

• Convenient as you can move around while still being connected

• Cheaper as you need fewer wires

Describe the features of Bluetooth

• A direct connection between two devices so data can be shared

• Connection range is low

• Low bandwidth

• Often used in mobiles/wearing devices

Describe the features of Wi-fi

• Can be used by multiple devices to connect to a LAN at the same time

• Has a high connection range

• High bandwidth compared to Bluetooth

• Often used in homes

What is wireless access point (WAP)?

A WAP is a switch that allows devices to connect wirelessly

What do wireless network interface controllers (NIC) do?

• An internal piece of hardware that allows a device to connect to a network

What are dongles?

• USB dongles can be plugged into computers to allow them to connect wirelessly to the internet

• HDMI dongles can use wireless networks to stream high-quality video to TV

What are ethernet networks?

Uses different types of ethernet cables to connect devices to a LAN

Transmission data - copper cables (UTP)

• wired connections assure maximum, bandwidth, security and reliability

• with twisted pair cables the wires are twisted around each other to reduce interference

Transmission data - coaxial cables

• Made of single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interface

Transmission data - fibre optic cables

• Uses light to transmit data

• Covers much longer distances and don’t suffer interference

• Are expensive

What is bandwidth?

• The amount of data that can be sent and receive successfully in a given time

• This is not a measure of how fast data travels, but how much data can be sent in transmission media(the physical or wireless transfers of data)

• Measured in bits per second

What is the impact of the numbers of users have on a network?

• Too many users or devices on the same network can cause the network to slow down if there is a insufficient bandwidth for the data

Do wireless or wired connections have more bandwidth?

• Wired connections have a higher bandwidth than wireless as it is less susceptible to interference

Do fibre optic cables or copper cables have more bandwidth?

• Fibre optic cables have a higher bandwidth than copper cables

What is the error rate?

• Less reliable connections = increased number of errors during data transfer

• This means data will be resent until it arrives correctly

• The quality of the wireless connections is dependant on the range of devices from the wireless access point and other environmental factors

What is latency?

• The delay from transmitting data to receiving it

• Caused by bottlenecks (when main components cant keep up with demands)

What is the client-server model?

• A network that uses a server

• A client makes a request to the server and the server processes the request and responds

• The server stores:

  • Passwords

  • User profiles

  • Access information

• This so it does not accept the wrong request

What are advantages of a client-server model?

• Easier to keep track of files

• Easier to perform backups

• Easier to install software updates on all computers

• Reliable and always on

• Easier to manage network security

What are disadvantages of a client-server model?

• Can be expensive to set up and maintain

• Requires IT specialist to maintain

• The server is a single point of failure

• Users will loose access if the server fails

• Server may become overloaded if too many clients access it at once

What is a peer to peer model?

• Does not use a server

• A peer is a computer on a network connected to all other peers and is equal to all other peers

Peers:

-Serve their own files to each other

-Responsible for its own security

-Responsible for its own backup

What are the advantages of a peer to peer model?

• Easy to maintain

• Specialist isn’t required

• No dependency on a single server

• No expensive hardware

What are the disadvantages of a peer to peer model?

• Network is less secure

• Users will need to manage their own backups

• Can be difficult to maintain a well ordered file store as duplicates are made when copying files between devices

Describe star topology

All the devices are connected to a central switch or server that control the network

What are the advantages of star topology’s?

• If a device fails or a cable is disconnected it does not affect the rest of the network

• It is simple to add more devices to the network

• Better performance - data goes straight to the central device so all devices can transmit data at one and there are fewer collisions

What are the disadvantages of star topology’s?

• In a wired network every device needs a cable to connect to the central switch or server which can be expensive

• If there is a problem with the switch the whole network will be affected

Describe the bus topology

What are the disadvantages?

• All devices are connected to a single backbone cable

• Devices sent data in both directions

Disadvantages:

• Data collisions which slows the network

Describe the ring topology

What are the disadvantages?

• Data moves in one direction around the ring, preventing collisions

Disadvantages

• Only one computer can send of data at a time

• Data passes through many computers before reaching its destination

Describe mesh topology

• It is decentralised

• Networking devices are either directly or indirectly connected to every other one so do not need a switch

• Work by sending data along the faster route from one device to another

Describe a full mesh topology

Every device is connected to every other device

Describe a partial mesh topology

Not all devices are fully connected

What are advantages of full mesh topology?

• No single point of failure

  • When one device fails then data is sent along a different route to get to its target

What are the disadvantages of mesh topology’s?

• Expensive

What is a network standard?

• A set of agreed requirements for hardware and software

• Important as it allows manufactures to create products and programs that will be compatible with products and programs from other manufactures

What are network protocols?

A set of rules for how devices communicate an how data is transmitted

What are communication protocols?

Specify how communication between two devices must start and end, how data must be organised and what devices must do if data goes missing

Describe MAC addresses

• Every device needs a unique identifier so it can be found on a network

• Mac addresses are assigned to all network-enabled devices by the manufacturer

• Unique to each device and cannot be changed

• Mac addresses are 48-64-bit binary numbers and are converted to hexadecimal

• Mainly used in LANS

Describe IP addresses

• IP addresses are used when sending data between networks

• Assigned automatically or manually before devices enter a network

• IPv4 - 32 bits 162.0.88.7

• IPv6 - 128 bits 65F8:49A4:… 8 times

• 32 bit binary IP address is translated into four denary numbers

What does the protocol TCP/IP do?

• Dictates how data is sent between networks

What does the TCP (transmission control protocol) do?

• Sets the rules for how devices connect on the network and is in charge of splitting data packets and ressembling the packets back into its original data once they reach the recieving device

What does the IP (internet protocol) do?

• Responsible for directing packets to their destination across the network

What are the other key protocols and what do they do?

What are layers? What are the features?

A group of protocols which have similar functions

• Self contained - dont need to know whats happening in each layers

• Serves the layer above

What are the advantages of layers?

• Breaks down network communication in manageable pieces

• Layers can be chnages without other layers being affected

• Standards for each layers forces companies to make compatible hardware and software to different brands

• Data can only be passed between adjacent layers

What do layers do?

Does hidden work for an action on the layer above

Describe the internet

• A network of networks - a WAN which connects devices

• Based around the protocol TCP/IP

What are URLs?

Adresses used to access web servers and resources on them

What is domain name service (DNS)?

Used to translate website domain names into IP addresses so you dont have to remember a IP address to access websites

What is hosting?

When a business uses its servers to store files of another organisation ..

What is the cloud?

Data and programs stored over the internet

What are the advantages of the cloud?

• Users can access files and applications from any connected device

• Easy to increase storage

• No need to buy expensive hardware

• No need for IT staff

• Cloud hosts provide security and back-ups

• Software is updated automatically

What are the disadvantages of the cloud?

• Need connection to the internet

• Dependent on host

• Data can be vulnerable to hackers

• Unclear who has ownership over data

• Subscription fees may be expensive