Computer Science: Networks

Advantages

• Users can share files
• Peripherals can be shared e.g. Printers
• Users can access personal files from any computer on the network
• Servers can control security , software updates and make back ups of data
• Users can communicate with others e.g. via email

Disadvantages

• Increased security risks to data
• Malware and viruses spread very easily between computers
• If a server fails, the computers connected to it may not work
• The computer may run more slowly if there is a lot of data travelling along the network

• Covers a small geographical area located on a single site
• All hardware for a LAN is owned by the organisatiom using it
• LANs are wired with copper UTP cable, fibre optic cable or wirelessly using WIFI

• Covers a wide geographical area, connecting LANs together
• Infrastructure between the LANs is leased from telecommunication companies who own and manage it
• WANs are connected with telephone lines, fibre optic cables or satellite links

Bandwidth

• This is the amount of data that can be sent and received successfully in a given time
• It is not a mesure of how fast data travels but how much data can be sent on the transmission media
• It is measured in bits per second, or bit rate.

The Number of Users

• Too many users or devices on the same network can cause it to slow down if there is insufficient bandwidth for the data

Transmission Media

• Wired communications (e.g. copper cable) have a higher bandwidth than wireless connections (e.g. wi-fi)
• Fibre-optic cables have a higher bandwidth than copper cables.

The Error Rate

• Less reliable connections increase the number of errors that occur when data is transferred. This means data has to be re-sent until it arrives correctly.
• The signal quality of wireless connections is dependent on the range of the device from the wireless access point and other environmental factors
• The signal quality on copper cables is determined by the grade of material used, which reduces interference. The length of the cable is also a factor.

Latency

• This is the delay from transmitting data to receiving it. Latency is caused by bottlenecks in the infrastructure of the network. For example by not using switches to appropriately segment traffic on a network.
• Hardware such as  switches and transmission media may not opperate at the same speed.

A Client Server

• A server controls access and security to one shared file store
• A server manages access to the internet
• A server manages printing jobs
• A server provides email services
• A server runs a Back up of data
• A client makes requests to the server for data and connections

Advantages

• Easier to manage security of files
• Easier to take backups of all data that is shared
• Easier to install software updates to all computers

Disadvantages

• Can be expensive to set up and maintain and requires an IT specialist to maintain.
• The server is a single point of failure. Users will lose access if the server fails.

Peer to Peer

• A peer is a computer on the network and is equal to all other peers
• Peers serve their own files to each other
• Each peer is responsible for its own security and backup
• Peers usually have their own printers. You can send print jobs to another peer to process, but that peer would need to be switched on to be able to communicate with the connected printer.

Advantages

• Very easy to maintain. Specialist staff not required.
• No dependency on a single computer.
• Cheaper to set up. No expensive hardware required.

Disadvantages

• The network is less secure
• Users will need to manage their own backups
• Can be difficult to maintain a well ordered file store.

• A network interface controller (NIC) connects a device to a wired or wireless network connection
• An NIC uses a protocol to ensure successful communication
• Wireless access points allow wireless enabled devices to access the network
• Wireless connections are popular because it avoids the need to install cables
• Bandwidth on a wireless connection is lower than on a wired connection
• Security is more of a problem on wireless networks
• A switch sends data between computers on a LAN
• A switch uses the NIC address on a device to route traffic
• A router sends data between networks
• A router is needed to connect a LAN to a WAN
• A router uses the IP address on a device to route traffic to other routers
• Connections between desktop computers and a switch are usually made with unshielded twisted pair (UTP) copper cable
• Copper cable is cheap and flexible which means it is easy to install
• Longer distance cables and WANs are usuyally connected with fibre optic cable
• Fibre optic has a higher bandwidth than copper and suffers from less interference

• The internet is a global connection of interconnected devices
• Web addresses which are easier forhumans to remember are converted into IP addresses for routers by a domain name server
• Websites that are stored on servers are dedicated to this purpose. This is known as hosting. Hosted solutions provide for 24/7 access, multiple users and greater security.
• Servers that store data and programs remotely that can be accessed and used over the internet are reffered to as cloud storage. They provide access anytime, anywhere, automatic backup and collaboration on documents.

A virtual LAN applies a logical structure to the network independently of the physical structure.

Advantages

• Scalability: Users can be connected to different switches but appear as if they are on the same segmenr of the network. Bandwidth is used more efficiently.
• Security: Users cannot access computers in other VLANs even if they are connected to the same switch.
• Cost: You don't need to change the network infrastructure as the business changes