topic 4 Flashcards
what is a network
A network is an arrangement of two or more computing devices connected together in order to communicate with each other and share resources.
reasons for connecting computers on a network
to share data and software
to share printers, hard drives and other hardware peripherals.
to share internet connections and services.
to provide centralised support and backup services.
to enable the rabid deployment of new software and updates
to enable people to communicate with each other using services.
to support collaborative working
LAN and WAN
LAN (Local Area Network)
a network that covers a relatively small geographical area.
WAN (Wide Area Network)
a network that covers a large geographical area and connects together multiple LANs.
IP address
internet protocol address
a unique identifier assigned to each device connected to a network.
- most devices use a dynamic IP address
- this is allocated to them from a communal pool when they connect to the internet and returned when they disconnect.
- next time they connect, the IP address will be different.
a device such as a router, is permanently connected to the internet with a static IP address that never changes.
Packet switching
1) the senders large file is broken up into smaller packets.
2) packets are directed to their destination by routers.
routers inspect the packets and decide the most efficient path to the next router.
3) packets take different routes across the network.
they may nit arrive in the correct order.
4) the receiving computer reassembles them in the correct order using information in the packet headers.
wired vs wireless
transmission speed is faster for wired.
latency is very low for wired (good)
network speed
file size = time x data transfer rate
time (s) = file size (bits) / data transfer rate (bps)
data transfer rate = file size / time
speed (data transfer rate) = size / time (time)
email protocol: POP
Post Office Protocol
Internet –. Mail server → client
used by client to retrieve emails from a main server.
all of the emails are downloaded when there is a connection between client and server.
messages are deleted from the email server once they have been downloaded.
- get email from a mail server
- emails are removed, once downloaded to a client
email protocol: SMTP
Simple Mail Transfer Protocol
provides the rules for sending email messages from client to server and then from server to server until it reacges its destination.
- used to send email between email servers
- it is not to receive emails
Email uses these protocols to communicate with mail servers.
SMTP is used to send the email
email protocol: IMAP
Internet Message Access protocol
messages do not have to be deleted.
they can be read and stored on the message server.
- a set of rules that email client programs use to download emails from a mail server.
- this protocol leaves the emails on the server so they can be accessed by a different application.
TCP/IP Model (simple VERY)
Application: user interface
Transport: create a channel and packets
Internet: addressing
Link: physical transmission
After Tea I Link
Describe the process of sending information from client A to client B
From client A, the information that needs to be sent from an application in the application layer, is sent down to the transport layer.
It is then split into packets.
The packets are sent to the internet layer.
Addresses are added to the packets.
They are sent to the link layer.
There, they are converted into signals and sent across the transmission medium.
At the receiving end, the signals are converted to data and sent to the internet layer.
There, the addresses are removed.
The data is sent up to the transport layer, where the many packets are joined back up together in the right order.
The data is sent up to the corresponding application on the application layer.
The data is processed for client B.
star topology
in a star network, each computer or client is connected individually to a central point or node, which can be a hub or switch.
+ data is only sent to the intended computer directly
+ network traffic is kept to a minimum
+ if one fails, all of the others will continue to operate,
+ it is easy to add new devices without disrupting the network.
- if the central point fails, then so will the entire network.
- requires a lot of cable because each computer connects individually to the central component.
firewalls
Firewalls are software.
They are designed to monitor and block incoming and outgoing connections to a network.
Firewalls protect a system from hackers.
If a hacker is already inside the system, they may be prevented from doing extra damage by the firewall blocking outgoing traffic
- a firewall protects a network connected to a WAN such as the internet.
it can be provided by hardware or software.
firewalls can be configured to prevent communications from entering the network and also programs and users from accessing the internet from within the netwokrk.
TCP/IP protocols
application - HTTP, HTTPS, SMTP, POP, IMAP
Transport - TCP
Internet - IP
Link - Ethernet, Wi-Fi
