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OCR GCSE Computer Science 1.3 revision - Coggle Diagram
OCR GCSE Computer Science 1.3 revision
Network
- A connection between 2 nodes (which just means devices)
Local Area Network
- It's a network within a small geographical area e.g. homes or offices
Wide Area Network
- A network that covers a large geographical area e.g. the internet is a WAN
Bandwidth
- How much data can be transmitted within a given time. Can affect network performance.
Topology
- The physical layout of the network and how the nodes are connected
Client-Server
- when at least one computer is a central server on a network and is providing data to other computers on the network.
Disadvantages
Expensive
If the server fails, all clients lose the work.
Server can be overwhelmed if there's a lot of network traffic
Advantages
Easy to manage security
Easy to perform software updates
Easy to perform backups
Easy to keep track of files
Peer-to-Peer
- When all connected nodes have "equal status" and can share data with each other without a server.
Disadvantages
No centralized management (each device has to do it individually).
Copying files between devices creates duplicates and you can lose track of them.
Advantages
Easy to maintain
If one device fails, everything else on the network runs smoothly.
Cheap
Wireless Access Point
- Hardware that connects your nodes to wireless network.
Router
- Sends data across the internet
Switches
- Takes data and sends it to a certain computer on the network. this is better for the network performance as there is less unnecessary traffic.
Hub
- Sends data to all nodes on the network, it causes unnecessary traffic
Network Interface Card/Controller (NIC)
- Embedded in a computer and used to connect it to a network. NIC is wired; NIC wireless connects the node to wireless networks
Transmission Media
- Methods of carrying data signals from one node to another
Fibre Optic cables
- Data transmitted using light
Types of Commonly used Cables
Fibre Optic Cable
Price - Expensive
Max distance for reliable communications - over 2k meters
Max transmission speed - 40000000 Gigabits/40000 terabits per second
Twisted Copper Wire
Price - Cheap
Max distance for reliable communications - 100 meters
Max transmission speed - 1 Gigabit per second
The Internet
- A network for networks
Websites are made up of webpages, which are stored on a server
Server
- A piece of hardware that sends and responds to requests
Hosting
- Storing files/data/webpages on a server
Host
- The web server it's stored on
World Wide Web (WWW.)
- A collection of websites hosted on web servers
Key point:
The internet refers to the network of networks, the world wide web is the web pages stored on the individual networks (hosts).
URL
-
Uniform Resource Locator
. We type this in, but behind the scenes the computer uses the DNS to take us back to where we want to go
IP
-
Internet Protocol
. Unique address that is used to identify a local network and connect it to the internet.
MAC Address
-
Media Access Control Address
. A unique identifier for a device, made by the manufacturer.
Key point:
The IP address is the whole network whereas the MAC address is for each device
DNS
-
Domain Name Server
. When we type a URL into the search browser, the DNS compares this to its lots of corresponding IP addresses and gives the computer the right IP addresses.
Key point:
We need the IP address because the computer communicates with the host server, which is identified by the IP. (The URL is just easier for us humans to remember).
"
http://www.website.ac.uk
" explained
http
is the protocol,
www.website.ac.uk
is the domain name: easier for us to remember compared to
IP
addresses.
website
is the third level (organization name)
ac
is the second level (type of organization)
uk
is the first level/top level
the
DNS
uses the hierarchy levels in reverse order (3rd is checked first) to retrieve the
host
's
IP
.
What happens when you enter a
URL
The
DNS
returns the
IP
and the client use this to communicate with the
host
.
Keep in mind that this happens in less than a second.
The client sends a request to the
DNS
for the corresponding
IP
address of the website
host
.