Computer Networking

What is cloud computing?

( A recent use for internet hosting) storing files online e.g. on emails, social networking.

Advantages of LAN

- Able to share hardware devices like printers, CD-ROM drives,... - can share one internet connection - it is easy to install and update software. - required less hassle to set us and less advanced infrastructure

What is a Client-Server Network?

A Client-Server network is when one, main centralised server (that controls and access and hosts programs) is accessed from multiple client computers. This means that client machines can be relatively low specification, as most of the processing workload, security and user access is carried out by the central server. I'm he

TCP/IP

A collection of rules arranged in layers

Whats a client

A computer that acts as a desktop for users and which relies on a server for its operations.

Local Area Network (LAN)

A local area network consists of computers and peripheral devices connected in a single or local area. Each computer can work independently but can exchange information through switches.

NIC's, Switches and Routers

A network Interface Controller (NIC) is an internal piece of hardware that allows a device to connect to a network. It is usually connected to the motherboard. NICs exist for both wired and wireless connections. Switches connect devices on a LAN. Switches receive data (in units called frames) from one device and transmit data to the device on the network with the correct MAC address. Routers are responsible for transmitting data between networks - they're always connected to at least 2 different networks. Routers direct data (in units called packets) to their destination. Most home 'home' routers are in fact a router, switch and a WAP (wireless access point)

What's the internet?

A network of networks. WWW is the content on the internet that we want to access/ share.

What is a virtual network?

A network that is entirely software based to divide devices on a LAN into smaller groups.

What does the term 'layers' mean?

A set of protocols with specific functions

Network Protocol definition

A set of rules or procedures for transmitting data between electronic devices. (Needed to exchange information)

What is the internet?

A worldwide network of interconnected networks

What 2 other things do you need to connect to the internet

Access to cable infrastructure An IP address - Every computer needs a unique address in order to communicate over a network

Know the frequency band that a network uses can also affect the WiFi performance

Advantages of 2.4GHz is that it has a greater range, so it can cover a wider area. Better at getting through solid objects/ walls Advantages of 5GHz is that it is much faster when communicating over a short distance. There are more non- overlapping channels, so there's less chance of interference from other devices.

What is a Peer-to-Peer Network?

All computers within a peer-to-peer network act as both clients and a server - they share files, programs and network access. Security permissions are shared across the network, and a user can access the contents of any other user's computer on the same network.

Star Topology

All nodes are connected to a central switch or server that controls the network. Star networks may be wired or wireless. Pros: if a device fails or 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 central device so all devices can transmit data at once (unlike ring topology) and there are few data collisions (unlike bus topology). Management of network done centrally Cons: in Wired connections, every device needs a cable to connect to the central switch or server. This can be expensive. If there is a problem with the switch/server the whole network is affected

IMAP (Internet Message Access Protocol)

Allows access to email server but, rather than downloading messages, they're simply read. Allows synchronised access from multiple devices, unlike POP

Wireless - Security

Anyone within range can see network and use it. Need encryption or password Where as in wired, need to physically connect to cable

Name the 1st layer

Application layer - where requets are made to the web servers and emails

What affects the performance of a Network?

Bandwidth, measured in bits per second. It is the amount of data transferred between two network devices per second. Also: The quality of transmission either by wired or wireless. There can be interference from external factors e.g. distance or other electronic devices e.g. microwaves. The bandwidth is shared between all the users of a network, meaning more users, the lower the connection speeds.

Wide Area Network (WAN)

Connecting 1 LAN to another, or multiple LANs over a large distance, forming a wide area network (WAN). A WAN may be used across the globe by using telephone lines, undersea fibre optic cables, and even satellites. The largest WAN is the internet.

FTP (File Transfer Protocol)

Connects clients and servers across a network to exchange files.

4th layer

Data link layer - concerned with physical data transfer over cables - includes Ethernet.

What are channels?

Each 14 channels Transmit data Two adjacent channels will be subject to interference. Choice of channel allows users to reduce or minimise interference with other devices.

Advantages of layering

Each layer is specified for a particular function. Makes it easier to identify and correct networking errors A layer can be taken out, edited and replaced without affecting other layers Provides universal standard for hardware and software to manufacturers to follow - able to communicate with eachother.

HTTPS (Hypertext Transfer Protocol Secure)

Encrypts communication between server and client. Makes secure banking and online shopping possible.

Types of Cables

Ethernet cables are used to connect devices to LANs. Most common Ethernet cables are CAT 5e and CAT 6. The copper wires are twisted in pairs to reduce internal interference. 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 can transmit data as light. They are high performance (therefore expensive) cables. They don't suffer interference and can transmit data over very large distances without loss of signal quality.

What is Ethernet?

Ethernet is a protocol within the TCP/IP stack. It governs the connection of devices within the office using cables to transmit data between devices.

What affects transmission of data

External/ electrical interference e.g. microwaves slow down transmission of data. More people, same bandwidth. Walls slow or stop transmission of data Using adjacent channels. More data being transmitted - more data collisions

Disadvantages of web hosting from home:

If there's a power failure due to unavoidable circumstances for a period longer than your inverter backup, your website will be down. Website more prone to hacking due to poor security. More expensive to host own website. You will have to manually monitor your server to see if it's working

Bus and Ring topology

In a bus topology, all devices are arranged in a line, connected to a single backbone cable. Devices send data in both directions. This causes data collisions, which slows the network. In a ring topology, data moves in one direction around the ring, preventing collisions. But only one device can send data at a time and data passes through many devices before reaching its destination.

What are the benefits of using networking layers?

It breaks the complex process of networking down into more manageable chunks

Whats an NIC?

It formats the data sent from the computer into a required format. Every NIC has a Mac Address (48 bit and 12 digit hexadecimal)

What is a virtual private network?

It is an encrypted connection over a less secure connection e.g the internet from a device to a network. The encrypted connection helps ensure that sensitive data is safely transmitted.

How are networks formed?

Linking together computer devices so that they can communicate and exchange information which forms a network. Desktops, laptops, tablets, printers, smart TVs and smartphones can all connect to a network. The internet is a group of many networks connected together using cables and wireless technology.

What hardware do u need to connect to the internet?

Modem A Network Adapter

Mesh Topology

Network devices are either directly or indirectly connected to every other one without the need for one central switch or server. Mesh networks work by sending data along the fastest route from one device to another. Advantage: there is no single point where a network can fail. In a star network, it the central server/ switch fails server the whole network fails. Disadvantage: Very expensive (lots of wire needed to connect each device all the other devices). But now people are using wireless technology, mesh networks are a more practical option.

3rd layer

Network/Internet Layer - communicates the IP address of all devices used in data traffic between networks and routers - includes IP

What is packet switching?

Packets are split up and are in equal size. A header containing the destination address and the source, and the position of the packet in the complete message or file. The body contains part of message data (also known as payload) A footer (a.k.a trailer) informs receiving device that it has reached the end of the packet and can be used for error checking to ensure the complete packet has been delivered. Server waits to see if all packets have arrived Server reorders packets Server requests missing packets of data The router can direct the packet to the correct recipient

Pros and cons of a client to client network

Pros: Easier to perform back ups Easier to install and update software Servers are very reliable and are always on. Cons: Expensive to set up and needs IT specialists to maintain the network and server. Server dependence - it the server goes down a clients lose access to their work. Their server may become overloaded if too many clients are accessing it at once.

Pros and cons of Peer to Peer networks

Pros: They're easy to maintain and there is no dependence on any server. Cons: Management of the computers is difficult as devices need their updates and security installed individually. It's hard to keep track of Files. Peer machine are less reliable and data may be lost if one fails. Machine are prone to slow down when other devices access them.

What's a router?

Routers connect different neteoekrs together. They send data in packets.

HTTP (Hypertext Transfer Protocol)

Rules followed by web servers and web clients, or browsers, which host and present websites based on our request.

Disadvantages of cloud computing:

Security of data worry - not in charge of storing their own files. If we don't have internet access we can't update our files. It's unclear who owns the data - the company that owns the servers where the data is stored or is it the company that created the files. Dependent on host for security and backup.

What is a topology?

The layout of a network

What does frequency mean?

The rate which signal changes.

2nd layer

Transport layer - ensures that the data is sent (in packets) and received correctly between network hosts - TCP

Microwaves

Type of transition media Consist of electromagnetic radiation (frequency higher than 1 GHz) Wifi uses radio waves

What's a DNS?

Used to identity one or more IP addresses.

POP (Post Office Protocol)

Used to login into and retrieve email messages from a mail server.

SMTP (Simple Mail Transfer Protocol)

Used to send email messages to an email server only.

Advantages of Cloud Computing

We can access files whenever we want, wherever we are as long as we have an internet connection Reduced hardware costs - less processing power is needed and less hard drive space to store files. No need to buy software licenses for every employee The cloud host provides security and back ups for you Space to store servers isn't needed as the servers will be at the clouds company's site

Hosting

Web companies rent space on servers where people can develop their own websites to be accessed by users on WWW. You need to have technical knowledge You need a static internet address. Most home computers have different address every time they connect to internet Computer needs to be switched on all the time for clients to connect.

What is a layer?

Where jobs or processes are split up.

WiFi (wireless fidelity)

WiFi uses two radio frequency bands - 2.4GHz and 5GHz The bands are split into numbered channels that each cover a small frequency range. The channel was in the 2.4GHz band overlap. Wi-Fi performance is affected by interference between networks using adjacent channels. To avoid problems, only certain channels that are spaced apart tend to be used.

How Wireless Networks work/ Dongles

Wireless waves use radio waves to transmit data. Like mobile phones and TVs, wireless networks use radio waves to transmit data. To set up a wireless network, you need a Wireless Access Point (WAP). This is a switch which allows devices to connect wirelessly. WAPs are different from hotspots. Hotspots are locations where you can connect to a WAP. To connect, devices need wireless capability, but devices that don't can use a dongle. USB dongles can be plugged into the computers to allow them to connect wirelessly to the internet HDMI dongles can use wireless networks to stream high-quality videos to a TV

What is an IP address?

a unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network. Described as static if permanently assigned to a computer by an internet service provider. Dynamic if assigned by the router within a network - can change each time network is restarted. Stored as four denary numbers.

What is web hosting?

the SERVICE that provides internet users with online systems for storing information, images, video, or any content accessible via the web