5 Fundamentals Of Computer Networks Flashcards
What is a network?
A network is a collection of connected computers. These computers can communicate by sending data between themselves
What are the benefits of networks?
Resources can be shared. E.g. Printers and Scanners
A network manager can manage other computers over a network. E.g. Updating Software and Fixing Problems
Data can be sent between computers without the need for external storage
What are the factors that can affect network performances?
Choice of Hardware
Bandwidth
Topology
Wired or Wireless networks
How does the choice of Hardware affect network performances?
The choice of cabling and other networking hardware can have a big impact on the speed of a network.
How does Bandwidth affect network performances?
Bandwidth is the amount of data that can be transferred in a given time.
The greater the bandwidth, the better the network’s performance potential.
Bandwidth is shared between all active users, so performance can decrease if there are too many users.
How does the Topology of the network affect network performances?
The topology of the network (how the computers are laid out and connected together) can have a large impact on the network performance
How does having a wired network affect network performances?
Wired networks are usually much faster and more reliable.
Wireless performance depends on how well a computer can pick up the signal but is rarely better than a wired connection would be
What is Transmission media?
Transmission media are different ways of physically transferring data along a network
What are the different types of Transmission media?
Fibre-Optic cables
Twisted-pair copper cables
Coaxial Cables
Radio Waves
What are Twisted-pair copper cables often referred to as?
This is often referred to as ‘Ethernet cable’.
What are Twisted-pair copper cables made of?
Inside the cable, there are eight wires which are twisted into pairs. This is to reduce interference from other signals and improve transmission speed.
What do twisted cable ratings indicate?
Twisted cables have different ratings to indicate how quickly data can be transferred.
E.g. Cat-5e can transmit at 1 Gbps.
E.g. Cat-6 can transmit at 10 Gbps.
What are Fibre-optic cables made up of?
Fibre-optic cables are made of thin strands of glass which transmit binary data as pulses of light.
What are the advantages of Fibre-optic cables?
Fibre-optic cables have many advantages:
Do not suffer interference.
Very high bandwidth (100 TBps).
Because of the lack of interference, fibre-optic cabling is appropriate for long distance communication such as undersea cabling
What are Coaxial cables?
Coaxial cable is a wired transmission media where an insulated copper wire is surrounded by a metal mesh to protect it from interference.
This is most often used for cable television
Why does WiFi signal lose strength as you get further away from the router?
The amplitude (strength) of a radio wave decreases as it moves further from its transmitter. This is why WiFi signal loses strength further away from a Wireless Access Point (WAP)
What does WAN stand for?
WAN stands for Wide Area Network
What is a WAN (Wide Area Network)?
A WAN is a collection of computers connected over a large geographical area.
WANs are used by multinational organisations that have international offices they need to connect to.
A WAN is usually rented from a large telecommunications company because WANs are expensive to set up
What is an example of WAN (Wide Area Network)?
The Internet - It is the largest WAN in the world
What does PAN stand for?
PAN stands for Personal area network
What is a PAN (Personal area network)?
A personal area network (PAN) is a network used to connect a single user’s devices in their workspace
What is an example of PAN (Personal area network)?
An example of a PAN would be connecting your phone to a headset via Bluetooth
What does LAN stand for?
LAN stands for Local area network
What is a LAN?
A LAN is a collection of computers connected over a small geographical area.
The LAN is set up and maintained by the organisation that uses it.
Where is LAN (Local area network) usually found?
LAN is typically found in homes, schools, universities, and small companies
What is WiFi?
WiFi is a set of protocols that define how network devices can communicate wirelessly over radio waves.
What is the official name of WiFi?
The official name of WiFi is IEEE 802.11x
What does WiFi’s official name (IEEE 802.11x) define?
IEEE 802.11x defines several rules such as:
What frequency should the radio waves be?
How powerful should the transmitter be?
How can data be secured?
What should happen if data is lost in transmission?
What are some examples of WiFi standards?
- 11g which operates at 54Mb/s
- 11n which operates at 600Mb/s
- 11ac which operates at 3.2Gb/s
Why do devices use the same WiFi standards?
By creating devices which use the same standards, we can guarantee that devices from different manufacturers will be compatible
Why do we split frequencies into bands?
Radio wave communications are subject to interference if another transmitter is transmitting at a similar frequency. We try to split the frequencies into bands and channels to avoid this interference
What are the two main frequency bands used for WiFi?
2.4 GHz
5 GHz
How many channels are there in the 2.4 GHz frequency band?
13 channels
Why is the 2.4 GHz band not effective at supporting many networks?
Only three of the 13 channels do not interfere with each other in the 2.4 GHz band
This means that the 2.4 GHz range is not effective at supporting many networks
How many non-overlapping channels are there in the 5 GHz band?
24 non-overlapping bands
Why is the 5 GHz band effective for supporting a high number of networks?
There are 24 non-overlapping bands in the 5 GHz band
This makes the 5 GHz band much more effective compared to the 2.4 GHz band for supporting a high number of networks
Why do we subdivide frequencies into bands and channels?
To reduce the effects of interference
What are the three common security measures on the internet?
Wired Equivalent Privacy (WEP)
WiFi Protected Access (WPA)
WiFi Protected Access version 2 (WPA2)
What is the Wired Equivalent Privacy (WEP)?
WEP is a type protection on the internet but is the weakest form of protection
WEP only needs a password to enter the network
WEP doesn’t encrypt any data
What is WiFi Protected Access (WPA)?
WPA requires a password to join the network
WPA uses encryption to scramble the data being sent:
This means that only devices with the correct key can decode the data
WPA is much stronger than WEP
What is WiFi Protected Access version 2 (WPA2)?
WPA2 is the successor of WPA.
WPA2 uses a stronger encryption algorithm. compared to WPA, to prevent unauthorised parties from accessing the encrypted data
What is star topology?
A star topology is when each computer is connected to a central switch or server
What are the pros and cons of a star topology?
Pros:
Reliable - If a single client fails, all others can continue as normal
Multiple devices can access the server simultaneously
The network is easily scalable
Cons:
Expensive
What is Bus Topology?
Each computer is connected to a main cable called a bus in a Bus Topology
What are the pros and cons of a Bus topology?
Pros:
Bus topology is easy to build and expand
Many cables aren’t required
Cons:
Unreliable since the network is shut down if the main cable is broken
Problems can be difficult to find as a break could happen anywhere in the cable
What does IP (address) stand for?
Internet Protocol Address
What are IP addresses used for?
Internet Protocol (IP) addresses are used to identify where data packets need to be sent to and where they have come from
What do IP addresses need to be?
IP addresses must be unique within the same local area network.
IP addresses do not need to be universally unique
What happens when a packet reaches the router?
When a packet is received by the router, the router looks at the head of the packet to find the destination IP address
What are the two types of IP address?
Static or Dynamic
What is a Static IP address?
A static IP address will have the same IP address every time it connects to the network
What is a dynamic IP address?
A device with a dynamic IP address will be allocated a new IP address every time it connects to the network
How are Dynamic IP addresses provided?
Dynamic IP addresses are provided by the Dynamic Host Configuration Protocol (DHCP) server
What happens when the Destination IP address is on the current network?
If the packet is meant for a device on the current device, then the router will pass it to the network switch
What happens if the destination IP address in on a different network?
If the packet is mean for a different network, then the router will pass it onto a wide area network (WAN) so that it can be routed to the correct network
What are the two types of IP addresses?
IPv4 (version 4) and IPv6 (version 6)
How are IPv4 displayed?
IPv4 are 32-bit numbers often displayed as 4 numbers separated by dots (.).
For example: 74 . 124 . 131 . 67 .
How are IPv6 displayed?
IPv6 are 128-bit numbers, often displayed as 8 groups of 4 hex digits
For example: 2001 : 0db8 : 85a3 : 0000 : 0000 : 8a2e : 0370 : 7334
Which devices have a public IP address?
Routers have public IP addresses
What are the uses of MAC addressing?
MAC addresses can be used to exchange data on the same local area network (LAN).
MAC addresses are also used by switches and NICs to send data to the intended recipient
How are MAC addresses formatted?
MAC addresses originally used to be 48-bit numbers, although some 64-bit versions were introduced
They are now represented as hexadecimal numbers
For Example, B8:8D:12:58:77:32
The first half of the address relates to the manufacturer of the device.
The remaining half relates to the individual device that has been produced
How unique are MAC addresses?
MAC addresses are unique globally
What are network protocols?
A network protocol is a set of rules that define how data is transmitted between connected devices.
Protocols exist for any data exchange between two devices
What is in a Protocol?
Common decisions made in a protocol are:
How communication should start and end
How data should be structured
Which network port communication should be over
How to check if the received data is correct
What to do if something goes wrong
What is the Transmission Control Protocol?
Transmission Control Protocol (TCP) splits data from applications into small pieces called ‘packets’
Each packet has a header and a payload
The header is data about how the packet should reach its destination
The payload is the actual data that needs to be sent
What is Ethernet?
Ethernet is a protocol that defines how data should be physically transmitted between network hardware
Ethernet is used in wired networks
What is Internet Protocol?
Internet Protocol (IP) defines how data packets should be sent between networks An IP header is added to each packet with the source and destination IP address Routers use this information to deliver the packet to the correct network
What is WiFi?
WiFi (802.11x) is a set of protocols defining how data should be transmitted using radio waves
WiFi is used in wireless networks
What is User Datagram Protocol?
User datagram protocol (UDP) is an alternative to transmission control protocol (TCP)
UDP performs all of the same functions, but skips the stages which ensure that a packet has arrived, and checks that the packet is correct
UDP is faster than TCP, but less reliable
UDP is useful when reliability of data is less important than achieving fast transfer, for example in online gaming
What is Hypertext Transfer Protocol?
Hypertext transfer protocol (HTTP) defines how data should be exchanged between web browsers (clients) and web servers
HTTP relies on the idea of requests and responses
HTTP is mainly used to access websites from servers
What is Hypertext Transfer Protocol Secure?
Hypertext transfer protocol secure (HTTPS) is a secure version of HTTP
HTTPS uses secure socket layer (SSL) to encrypt the data that is sent between the client and the server
What is File Transfer Protocol?
File transfer protocol (FTP) defines how binary and text data can be requested from a server and transmitted back to the client
FTP is used to download or transfer files over a network
What is Post Office Protocol?
The Post Office Protocol (POP) is a common e-mail protocol which defines how emails can be retrieved from a mail server
Inboxes are not kept in sync:
Once a user has downloaded their mail from the server, the server deletes their copy
Only a local copy remains
What is Simple Mail Transfer Protocol?
Simple Mail Transfer Protocol (SMTP) defines how e-mail messages are sent from an e-mail client to a mail server
Almost all e-mails are sent using SMTP
What is Internet Message Access Protocol?
Internet Message Access Protocol (IMAP) is another protocol for retrieving e-mails from a mail server
IMAP allows e-mails to be kept in sync:
Actions on your local machine are synced with the server
Inboxes remain consistent across multiple devices
IMAP is becoming more popular than Post office Protocol because of the ability to sync multiple devices
What is a protocol layer?
a protocol layer is simply a group or collection of network protocols that work at a similar level within the networking process
What are the properties of layers in a protocol layer model?
Layers of a protocol layer model should be independent of each other.
Layers should only interact with each other by considering the inputs and outputs of that layer, not how it works
What are the two best known protocol layer models?
The four-layer Transmission Control Protocol model
Seven-layer Open Systems Interconnection model
What is the difference between the TCP and OSI models?
Nothing apart from the grouping
What are the advantages of Layering?
Specialists can be employed
Can improve layers for efficiency without affecting other layers
Applications can be developed without knowledge of networking
Can fix issues in individual layers
What is the order of layers for the Transmission Control protocol model?
Application layer - Creates and interprets data
Transport layer - Splits and joins data
Internet layer - Adds addresses to data
Network Access layer - Converts data into electrical signals
What is the order of layers for the Open Systems Interconnection protocol model?
Application Presentation Session Transport Network Data Link Physical
What are the comparisons between the two protocol models?
The two models describe the exact same network system:
The first three layers of the OSI model are grouped into TCP’s ‘Application’ layer.
The ‘Transport’ layers are the same in both models.
OSI’s ‘Network’ layer is called ‘Internet’ in the TCP model.
OSI’s bottom two layers are grouped into TCP’s ‘Network Access’ layer.
