Networks, internet, www, cybersec Flashcards
Purpose of a network
- To share and access data
- to store and share data
- to share physical reosurces
- to track access and implement security policies
- to communicate and collaborate
Network scopes
WAN(country), MAN(10km,city), LAN(1km,building/office), PAN(10m, bluetooth)
Topology
Ring - not used anymore, undirectional and biderectional
Star - Wired/wireless network w/a CENTRAL ACCESS POINT. more failsafe as break in connection only affects single device
Bus - A wired connection on ethernet backbone (used in QUB). Devices connected to bus through network access points. Needs terminators?
Mesh - Interconected (wired/unwired) between every computer. Failsafe as data can always be routed directly or indirectly
Bus vs star network
- Bus allows devices to DIRECTLY communicate
- Star allows INDIRECT communication through intermediary central machine (switch)
Examples of network devices
(with compatible characteristics)
Repeater - connects two buses, passes all signals back and forth
Bridge - two buses, only passes signals for other computers on the bus
Switch - acts like a bridge but connects multiple buses
(with incompatible characteristics)
Router - connects two incompatible networks resulting in a network of networks called an internet
Gateway - similar to router but connects a network to the outside world (the wider internet). includes satelite gateways
What is an IP address
- A unique address assigned to every device connected to the Internet
- 32 bit (IPv4), 128 bit(IPv6)
How do we look up websites
- Type in url
- Sent over the internet using http (protcol) to DNS SERVER
- Does DNS lookup, returns IP address
top-level domains and domain name example
.gov, .org, .com, .mil, .uk, www.google.com
People responsible for IP addresses
ICANN (Internet corporation for Assigned Names & Numbers)
- they allocate blocks of IP addresses to ISPs who then assign those addresses within their regions
Protocols
Protocols are rules by which activities are conducted on a network. for example, http.
OSI 7 layer model
7 - Application layer - human computer interaction layer
6 - Presentation layer - ensures the data is in a usable format, where data encryption occurs
5 - Session layer - Maintains connections and is responsible for controlling ports and sessions
4 - transport layer - transmits data using transmission protocols including TCP and UDP
3 - Network layer - decides which physical path the data will take
2 - Datalink layer - defines format of data on the network
1 - Physical layer - transmits raw bit stream over physical medium
OSI acronym
Open systems interconnection model (bottom up)
Please
Do
Not
Throw
Sausage
Pizza
Away
Internet protocols
At application layer (highest layer) ** contains transfer
HTTP - Hypertext transfer protocol
FTP - File transfer protocol
SMTP - Simple mail transfer protocol
NNTP - Network news transfer protocol
At transport layer (important) ** does not contain transfer
TCP/IP - Transmission control protocol/Internet protocol
UDP - User datagram protocol
What does the transport layer do?
Handles end-to-end connections
TCP and UDP protocols package data into small packets to be sent onto another device
TCP
Transmission control protocol
Before a message is sent between client and server there is request, acknowledgement, acknowledgement
known as three-way handshake
