1.3 Computer networks, connections and protocols Flashcards
Which network topology best describes The Internet?
The Internet is a great example of a partial mesh network. Packets on The Internet often take different routes to get to their destination. However, not all routers are connected to each other on The Internet.
The difference between a star network and a mesh network is that…
With a mesh network switches or routers are connected so there is more than one route to the destination.
What is a router
a piece of network hardware which sends data between networks
What is the purpose of the SMTP protocol?
sends email to an email server.
What does the internet protocol do (IP)
responsible for routing data across networks
What is the purpose of a Domain Name Server?
to maintain an index of mapped URLs to IP addresses and serve web pages
Which statement best describes ‘Ethernet’?
data is transmitted in frames on a local area network
what is latency
Which factor affecting the performance of a network is described as, ‘the delay from transmitting data to receiving it.’
what does a switch do and how is it specialised
.
What is a LAN
Local Area Network - a network of computers located over a small geographical area on a single site where all the hardware for the LAN is owned by the organisation using it
Common examples of a LAN
- school
- hospital
- offices
- flats
what are computers which are not connected to a network called
stand alone computers
what is a WAN
a WAN is created when LANs are connected. It spans over a large geographical area and the infrastructure between LANs is leased from telecommunication companies who own and manage them
common examples of a WAN
- mobile broadband
- internet
- a network of bank cash dispensers
What are the factors that affect the performance of networks
- number of users
- error rate
- transmission media
- bandwidth
- latency
How does error rate affect the performance of a network
less reliable connections mean that more errors occur when data is sent which then means that data needs to be resent until it arrives correctly.
what is latency
the delay from transmitting the data to receiving it
what is bandwidth
the amount of data that the medium can successfully send and receive over a given period of time
How does transmission media affect the performance of a network
Wired connections have a higher bandwidth than wireless
Fibre optic cables have a higher bandwidth than copper cables
how does having too many users affect the performance of a network
too many users or devices can cause the network to slow down if there is insufficient bandwidth for the data
what is the role of a server in a client-server network
- control access and security to one shared file store
- manages printing jobs and access to the internet
- runs a backup of data
- provides email services
what is the role of a client in a client-server network
- make requests to the server for data and connections
advantages of a client-server network
- easier to manage security file
-easier to take backups of shared data - easier to install software updates
disadvantages of a client-server network
- can be expensive to setup and maintain
- requires specialists to maintain
- server is a single point of failure
- users lose access if the server fails
what is a peer responsible for in a peer-to-peer network
- peers server their own files to each other
- responsible for their own backup and security
- usually have their own printers
advantages of a peer-to-peer network
- very easy to maintain
- specialist staff not required
- cheaper to set up
- no expensive hardware required
disadvantages of a peer to peer network
- less secure
- users need to manage their own backups and security
- can be difficult to maintain a well ordered file store
what 5 bits of hardware are needed to connect stand-alone computers into a LAN
- wireless access points
- routers
- switches
- Network Interface Card
- Transmission media
what does a router do
Uses IP addresses to route traffic between networks. Routers work by collecting knowledge of available routes to transmit data. They then determine the most suitable route for sending data.
You CANNOT connect to a WAN without a router
what does a switch do
- sends data between computers on a LAN
It learns the MAC addresses of all the devices connected and forwards the traffic in an intelligent way to the correct location only
what does a NIC do
- use a protocol to determine how the connection should work and allow devices to connect to either a wired or wireless network
what does a WAP do
allows wireless enabled devices to connect to a network
advantages of fibre optics
- cover much longer distances
- has a greater bandwidth than copper
how do fibre optic cables work
use light to transmit data
advantages of copper cables
- lightweight
- inexpensive
- easily installed
what does the DNS do
Domain Name Server - it takes the human friendly URL (www.abc.co.uk) and maps it to its IP address which the computer can then use.
It is a store of which IP addresses match up to which URLs.
2 advantages of having a DNS
- humans do not have to remember numerical addresses
- if the IP address change, the DNS servers can update their databases and the users can continue using the same URL
what is the domain name service
made up of multiple domain name servers
what is hosting
when websites are stored on servers dedicated to this purpose.
what is the internet
a collection of interconnected computers which span the world
what is cloud storage
when data is saved in an off-site storage system maintained by a third party.
Instead of saving data on your computer’s hard drive or other local storage device, you save it to a remote storage facility and access it via the internet
3 advantages of the cloud
- you can access data and software from anywhere in the world with internet access
- data can be shared with others in different locations
- backup is not an issue as it is the responsibility of the provider
2 disadvantages of the cloud
- you are dependent on whether or not you have an internet connection in order to access the data
- some users are concerned that it would be more of a target to hackers so their data is unsafe
1 advantage of a star topology
- if there is a break in one of the connections then only the device use that connection will be affected
2 advantages of a full mesh topology
- data can be sent and received quickly as every device is connected to every other device
- if there is a break in one of the connections then your data can still arrive via a different route
2 disadvantages of a full mesh topology
- much more hardware required
- meaning that the cost of large networks will be high
1 disadvantage of a star topology
- if the switch breaks, every computer loses connection
why doesn’t data get broadcast to all devices connected in a star network topology
because the switch is intelligent and makes sure traffic only goes where it is intended rather than being broadcasted to all connections
what is a partial mesh topology
when multiple routes exist between different devices but every device is not connected directly
disadvantage of a partial mesh topology
every computer still needs its own switch
what is a network topology
a given arrangement of all the elements needed for networking
what are the two types of wireless connection
- Wi-Fi
- Bluetooth
advantages of WiFi compared to wired connections
- users can move around freely
- can easily handle large numbers of users
- easier to set up and less expensive than wired connections
disadvantages of WiFi
- relies on signal strength to the WAP
- signal can be obstructed
- less secure than wired networks
advantages of Bluetooth compared to wifi
- ideal for connecting to personal devices
- lower power consumption than Wi-Fi
Disadvantages of Bluetooth
- only has a short range of about 10m (Wi-Fi has 100m)
- lower bandwidth than Wi-Fi
what wired connection would be used for communicating on a wired LAN
ethernet
what is an advantage of an ethernet connection
provides an error free connection between two points on a network
disadvantages of an ethernet connection
- user’s location is limited by the need for a physical cable connection
- a set up that uses ethernet requires a lot of hardware which increases the overall cost dramatically
what is an SSID
Service Set Identifier
A unique identifier given to all wireless networks. These have to be used by all devices which want to connect to the network
how can SSIDs be adapted to make them more secure
- make the SSID hidden in order to make it harder to detect
- protect it with a password so that even if it is found, users still won’t be able to gain access
which 3 protocols are used for wireless encryption
- WEP
- WPA
- WPA2
how does wireless encryption work
- the data is scrambled into cipher text using a master key created from the network’s SSID and its password
- the data is sent and then decrypted by the receiver using the same master key
- a handshaking protocol is then used to make sure the receiver has the correct master key before transmission begins
what is an IP address
the unique identification number given to every device that is connected to the internet. it represents the unique location on which you are connected to the internet.
what does IP in IP address stand for
Internet Protocol
what are the two formats of an IP address
IPv4 and IPv6
how is an IPv4 address formatted
four 8bit fields separated by full stops
eg
65.123.217.14
how is an IPv6 address formatted
8 groups of 4 hexadecimal digits separated by semicolons
128 bits long, arranged in eight groups of 16 bits each. each group is four hexadecimal digits separated by colons
eg
BC43:71A6:0000:044C:3879:0000:55FD:286B
what is a MAC address
a unique serial number assigned to each Network Interface Card. This allows a network to uniquely identify any device each time it connects to a network
how is a MAC address formatted
the first 6 digits are used to identify the manufacturer of the device (eg. apple), the second set give the serial number of the device
eg
00-1C-B3-F1-F7-85
WHAT IS A PROTOCOL
a set of rules that allows two devices to communicate
why are standards needed
because without them, devices on LANs and WANs wouldn’t be able to communicate successfully
what are standards
a set of specifications for hardware and software
they make it possible for manufacturers and producers to create products which are compatible with each other
what is a communication protocol
a set of rules for transferring data
what does HTTP stand for and what does it do
HYPERTEXT TRANSFER PROTOCOL
a way for a client and server to send and receive requests, and to deliver HTML web pages.
this is the fundamental protocol of the WWW
what does TCP/IP stand for and what does it do
TRANSMISSION CONTROL PROTOCOL/INTERNET PROTOCOL
it organises how data packets are communicated and makes sure packets have the following information:
source
destination
packet sequence
data
error check
what does HTTPS stand for and what does it do
HYPERTEXT TRANSFER PROTOCOL SECURE
(a way for a client and server to send and receive requests, and to deliver HTML web pages.)
effectively the same as HTTP nut it adds in encryption.
it is used when websites need to deal with sensitive details (eg passwords)
what does FTP stand for and what does it do
FILE TRANSFER PROTOCOL
for sending files between computers (usually on a WAN)
what does POP stand for and what does it do
POST OFFICE PROTOCOL
used by mail clients (eg, mobiles, laptops) to manage the remote mailbox on servers and retrieve emails from it.
it removes the email from the server when complete
what does IMAP stand for and what does it do
INTERNET MESSAGE ACCESS PROTOCOL
used by mail clients (eg, mobiles, laptops) to manage the remote mailbox on servers and retrieve emails from it.
this is similar to POP except that it stores a copy of the email on the server. this prevents different devices from becoming out of synch
what does SMTP stand for and what does it do
SIMPLE MAIL TRANSFER PROTOCOL
USED TO SEND AN EMAIL FROM A DEVICE OT AN EMAIL SERVER
what does the application layer do in the TCP/IP stack
encodes/decodes the message in a form that is understood by the sender and the recipient
what does the transport layer do in the TCP/IP stack
breaks down the message into small chunks (packets). Each packet is given a packet number and the total number of packets. The recipient uses this information to assemble the packets together in the correct order. It also allows the recipient to see if there are any missing packets.
what does the network layer do in the TCP/IP stack
adds the sender’s IP address and that of the recipient. the network then knows where to send the packet and where it came from
what does the data-link layer do in the TCP/IP stack
enables the transfer of packets between nodes on a network and between one network and another
- adds the sender and recipient’s mac addresses
what is the concept of layers
to divide the complex task of networking into smaller, simpler tasks
what is a protocol
a set of rules that allows two devices to communicate
what are the similarities between a switch and a router
- They both connect devices
*…they receive data from the devices
*…they determine the correct destination for the data
*…they transmit the data to its destination
what are the differences between a switch and a router
*A switch uses MAC addresses - A router uses IPs
*A switch corrects nodes - A router connects networks
*A router stores the addresses of devices attached - a switch has to look for correct address before sending
what are the benefits of storing data on the cloud
*She can access the program from anywhere
*… does not need to carry a storage device with her
*Security/backup is managed for her
*…does not need to manually backup her work
