Studied by 16 people
what is a network?
two or more computers connected together that have the ability to transmit data between each other
what is a Local Area Network (LAN)?
a network which is spread over a small geographical area or a single site
what is a Wide Area Network (WAN)?
a network which is spread over a large geographical area
often a combination of many LANs
usually, a WAN will require extra hardware (e.g telephone lines, satellite links)
infrastructure used in WANs is rented from third-parties such as telecommunication companies
what is a physical topology?
the physical layout of the wires and components which form the network (e.g bus, star and mesh)
what is a bus topology?
a topology where all the terminals (devices) are connected to a backbone cable, the ends of which are plugged into a terminator
what are the benefits of using a bus topology?
relatively inexpensive to set up
doesn’t require much additional hardware
what are the drawbacks of using a bus topology?
if backbone cable fails, the entire network gets disconnected (central point of failure)
as traffic increases, performance decreases
all computers can see the data transmission
what is a star topology?
a topology that uses a central node, often a switch, to direct data through the network
a MAC address is used to identify each device on the network
what are the benefits to using a star topology?
performance is consistent even with heavy network traffic
if one cable fails, only that single terminal is affected
transmits data faster than bus topology
easy to add new terminals
no data collisions
what are the drawbacks to using a star topology?
expensive due to switch and cabling
if the central switch fails, the rest of the network fails (central point of failure)
what is a mesh topology?
each node is connected to every other node, most commonly found with wireless technology such as Wi-Fi
what are the benefits to using a mesh topology?
if using a wireless network, there is no cabling cost
as the number of nodes increase, the reliability and speed of network becomes better
nodes don’t go through a central switch, improving speed
what are the drawbacks to using a mesh topology?
if using a wireless network, devices with wireless capability (which increases cost) must be purchased
if using a wired network, a large quantity of cable is required compared to other network topologies, this is expensive
maintaining the network is difficult
what is a network protocol?
a set of rules defining how two computers communicate with each other
why are network protocols standard?
so that all devices have a designated method of communicating with each other, regardless of manufacturer
describe the HTTP protocol.
used for web page rendering
clients and servers can send and receive requests and deliver HTML web pages
describe the HTTPS protocol.
encrypted version of HTTP protocol
describe the TCP/IP protocol.
a networking protocol used in the routing of packets through networks
TCP provides error-free transmission between two routers
IP routes packets across a WAN
describe the IMAP and POP3 protocols.
both are mailing protocols used to retrieve emails from a mail server
describe the SMTP protocol.
a mailing protocol that transfers outgoing emails between servers or from email client to mail server
describe the FTP protocol.
protocol used for the transmission of files over networks
what is the Internet?
a network of networks which allows computers on opposite sides of the globe to communicate with each other
what is the TCP/IP stack?
a stack of networking protocols that work together passing packets during communication
why is protocol layering used?
to apply protocols one after the other
layers are self-contained
each layer does a specific job
improved troubleshooting (as it is easier to identify the layer that causes the issue)
simplifies interfacing as each layer only communicates with adjacent layer
what is the function of the application layer?
the data is encoded
specifies what protocol needs to be used in order to relate the application that’s being sent
e.g. if the application is a browser then it would select a protocol such as HTTP or FTP
what is the function of the transport layer?
uses TCP to establish an end-to-end connection between the source and recipient computer
splits data into packets and labels these packets with…
their packet number
the total number of packets the original data was split up into
the port number being used for communication
if packets get lost, the transport layer requests retransmissions of these lost packets
what is the function of the network layer?
adds the source and destination IP addresses
routers operate on the network layer and use the IP addresses to forward the packets
the combination of IP address and port number is called a socket address
the sockets are then used to specify which device the packets must be sent to and the application being used on that device
what is the function of the link layer?
adds the MAC addresses identifying the NICs of the source and destination computers
for devices on the same network, the destination MAC address is the address of the recipient computer
otherwise, it will be the MAC address of the router
what is the Domain Name Server (DNS)?
the system used to name and organise internet resources
it is a hierarchy, in which each smaller domain is separated from the larger domain by a full stop
the role of the domain name system server is to translate these domain names into IP addresses when a user requests access to a website
what is a data packet?
packets are segments of data
each packet consists of three sections: the header, the payload and the trailer
what data is held in the header of a packet?
sender and recipient IP addresses
allows the packet to be delivered to the correct destination
enables the recipient device to trace where the packet came from
protocol being used
allows the recipient computer to know how to interpret the packet
packet number and total number of packets
Time To Live
tells the packet when to expire so that it does not travel forever
what data is held in the payload of a packet?
raw data to be transmitted
what data is held in the trailer of a packet?
a checksum and/or cyclic redundancy check
this contains a code used to detect whether any errors have occurred during transmission
what is packet switching?
a method of communication in which data is transferred as packets across a network
packets are sent across the most efficient route, which can vary for each packet
what are the benefits of using packet switching over circuit switching?
multiple methods to ensure data arrives intact e.g. checksums and cyclic redundancy checks
multiple routes can be used between devices, so if one path breaks, another can be used
packets can be transferred over very large networks to allow communication globally
what are the drawbacks of using packet switching over circuit switching?
time is spent deconstructing and reconstructing the data packets
must wait for all packets to arrive before data can be received
what is circuit switching?
a method of communication where a direct, physical link is created between two devices
this direct link is maintained for the duration of the entire conversation between devices
what are the benefits of using circuit switching over packet switching?
data arrives in a logical order which results in a quicker reconstruction of the data
enables two users to hold a call without delay in speech
what are the drawbacks of using circuit switching over packet switching?
bandwidth wasted during the time in which no data is being sent
devices must transfer and receive data at the same rate.
using switches means electrical interference may be produced which can corrupt or destroy data
ties up sections of the network which cannot be used by others data until transmission has been completed
what is a firewall?
a device designed to prevent unauthorised access to a network
it consists of two network interface cards (NICs) between the user and the Internet
the firewall passes the packets between these two NICs and compares them against a set of rules (packet filters) set by the firewall software
monitors data going to and from a network
what are packet filters?
the preconfigured rules set up by a firewall software
they limit network access in accordance with administrator rules and policies
works by examining the source IP, destination IP and the protocols being used as well as the ports being requested
when access is denied by a firewall, the packet can either be dropped or rejected
a rejected packet sends an alert to the sender to notify them of the error whereas a dropped packet will not
what is a proxy server?
a server that acts as an intermediary, collecting and sending data on behalf of the user
what are the benefits to using a proxy server?
the privacy of the user is protected and they remain anonymous
the proxy server can cache frequently used website data making it faster to load
proxies can reduce overall web traffic
can be used by administrators to prevent access to sensitive or irrelevant information at work or at school
what is a Network Interface Card (NIC)?
a network interface card is the card required to connect a device to a network
it is usually built into the device and assigns a unique media access control (MAC) address to each device
allows wired/wireless communication between computers on a LAN or communication to a large scale network using the internet protocol (IP)
what is a switch?
a device used to direct the flow of data across a network by routing transmissions to the correct device
allows multiple devices to connect to one network
switches are frequently used in star topologies
what is the function of a Wireless Access Point (WAP)?
allows a device to wirelessly connect to a network by connecting to a wired router or switch by ethernet cable and projecting Wi-Fi signal within a designated area, used frequently in mesh networks.
what is a router?
a device used to connect two or more networks together, they allow private, home networks to connect to the Internet and route data between devices in a small home network
what is the function of a gateway?
used when protocols are not the same between networks
they translate the protocols so that networks can communicate with each other
gateways work by removing the header from packets before adding the data to packets using the new protocol
describe a client-server network.
a network that consists of terminals known as clients connected to a server
the server is a powerful, central computer that holds all of the important information and resources, and…
controls access/security for a shared file store
runs regular backups of data
has greater processing power than the terminals
manages access to the internet
a client can make requests to the server for data, connections and other services
what are the benefits of using a client-server network?
more secure as data is stored in one location
central backups are carried out so there is no need for individual backups
data and resources can be shared between clients
easier to install software updates to all computers
what are the drawbacks of using a client-server network?
relatively expensive to set up
functionality of terminals depends on the server; if this fails, performance falls
trained staff are required to maintain the server
describe a peer-to-peer network.
computers are connected to each other so that they can share files
each device effectively acts as both a server and client, as it can both provide and request resources
what are the benefits of using a peer-to-peer network?
cheaper to set up
allows users to share resources
easy to maintain
not dependent on a central server
specialist staff are not required
what are the drawbacks of using a peer-to-peer network?
impossible to trace the origin of files
backups must be performed separately
poorer security
may be difficult to locate resources
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