section 3 - networks Flashcards
A LAN is a Local Area Network
- A LAN covers a small geographical area located on a single site i.e. businesses, schools/universities
- All the hardware for a LAN is owned by the organisation that uses it.
- LANs are either wired (e.g., with Ethernet cables) or wireless (e.g., using Wi-Fi®)
Why Use A LAN?
- Sharing files is easier — network users can access the same files, work collaboratively on them (at the same time) and copy files between machines.
- You can share the same hardware (like printers) on a LAN.
- The Internet connection can be shared between every device connected to the LAN.
- You can install and update software on all computers at once, rather than one-by-one.
- User accounts can be stored centrally, so users can log in from any device on the network.
WAN
1) WAN stands for Wide Area Network.
2) A WAN connects LANs that are in different geographical locations. E.g. a business with offices in three different countries would need a WAN for all their devices to connect together.
3) Unlike a LAN, organisations hire infrastructure (e.g. communication lines) from telecommunications companies. This is because a WAN is much more expensive to set up than a LAN.
4) WANS may be connected using fibre or copper telephone lines, satellite links or radio links.
5) The Internet is one big WAN
Network Interface Controller
A Network Interface Controller (NIC) is an internal piece of hardware that allows a device to connect to a network. These used to be on separate cards, but nowadays they’re built into the motherboard. NICs exist for both wired and wireless connections.
To connect wirelessly, devices need a wireless NIC. This is often built in, but if not, you can use a dongle.
* USB dongles can be plugged into computers to allow them to connect wirelessly to the Internet.
* HDMI dongles can use wireless networks to stream high-quality video to a TV.
switches
Switches connect devices on a LAN. Switches receive data (in units called frames) from one device and transmit this data to the device on the network with the correct MAC address
Routers
Routers are responsible for transmitting data between networks. they’re always connected to at least two different networks.
Routers have a crucial role on the Internet, directing data (in units called packets) to their destination.
Routers are used in homes and offices to connect the LAN to the Internet.
ethernet connections
Ethernet (wired) networks can use different types of Ethernet cables to connect devices on a LAN.
CAT 5e and CAT 6 Ethernet cables
The most common Ethernet cables are CAT 5e and CAT 6. They are ‘twisted pair’ cables, containing four pairs of copper wires which are twisted together to reduce internal interference.
Coaxial cables
Coaxial cables are made of a single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference.
Fibre optic cables
Fibre optic cables transmit data as light. They are high performance (and therefore expensive) cables they don’t suffer interference and can transmit over very large distances without loss of signal quality.
Bluetooth®
- Usually a direct connection between two devices so that data can be shared.
- Connection range varies, but mobile devices are typically 10 meters.
- Low bandwidth compared to Wi-Fi®.
- Often used in mobile/wearable devices - smartphones/watches, headphones, etc.
Wi-Fi®
- Can be used by multiple devices to connect to a LAN at the same time.
- Connections have a range between 40 and 100 metres.
- High bandwidth compared to Bluetooth®.
- Often used in the home-routers, desktops, laptops, smartphones, etc.
Wireless networks
1) Like mobile phones and TVs, wireless networks use radio waves to transmit data.
2) Wireless networks are more convenient than wired networks as you can move around while still being connected - they are also cheaper as you need fewer wires.
3) Bluetooth® and Wi-Fi® are two common wireless technologies:
4) To set up a Wi-Fi® network, you need a Wireless Access Point (WAP) device. The WAP is basically a switch that allows devices to connect wirelessly.
Many Factors can affect the Performance of Networks
1) Bandwidth is the amount of data that can be transferred in a given time, e.g. 500 Mbps.
2) Available bandwidth is shared between the devices on a network too many devices or heavy use (e.g. streaming video) may cause congestion and slow the network. You can limit the bandwidth available to individual users to address this.
3) Wired connections are generally faster and more reliable than wireless.
4) Wireless performance depends on signal quality so is affected by the range of the device, the amount of interference from other wireless networks and physical obstructions like thick walls in buildings.
client servers and peer to peer networks are about…
the roles of individual devices on the network
client-server network
1) A client-server network is managed by a server. The devices connected to the server are clients.
2) Files and software are usually stored centrally on the server rather than on individual client devices.
3) Clients send requests to the server, e.g., asking for data. The server processes the request and responds. This is the client-server relationship.
4) The server stores user profiles, passwords, and access information - it may request a password before fulfilling certain requests or deny requests to users without the right access level.
client-server network - pros
-Easier to keep track of files as they are stored centrally.
-Easier to perform back-ups.
-Easier to install and update software.
-Easier to manage network security (e.g. anti-malware software and user access levels).
-Servers are very reliable and are always on.
client-server network - cons
-Expensive to set up and needs IT specialists to maintain the network and server.
-Server dependence - if the server goes down all clients lose access to their work.
-The server may become overloaded if too many clients are accessing it at once.
peer to peer networks
1) In Peer-to-Peer (P2P) networks all devices are equal, connecting directly to each other without a server.
2) You store files on individual devices and share them with others.
3) You may use a P2P network at home to share files between devices or connect devices to a printer.
peer to peer networks - pros
-Easy to maintain -you don’t need any expertise or expensive hardware.
-No dependence on server - if one device fails the whole network isn’t lost.
peer to peer networks - cons
-No centralised management - devices need their updates and security installed individually.
-Copying files between devices creates duplicate files - it’s easy to lose track of what’s stored where and which files are up to date.
-Peer machines are less reliable, and data may be lost if one fails.
-Machines are prone to slow down when other devices access them.
network topologies
Layout of the network
star topology
-In a star topology, all the devices are connected to a central switch or server that controls the network.
-The central switch allows many devices to access the server simultaneously.
-Star networks may be wired or wireless.
star topology - pros
-If a device fails or a cable is disconnected, the rest of the network is unaffected.
-It’s simple to add more devices to the network.
-Better performance than other setups data goes straight to the central device so all devices can transmit data at once and there are few data collisions.