Networks

Networks

1. LAN is a Local Area Network and it covers a small geographical area on a single site. It can either be wired (Ethernet) or wireless (Wi-Fi).

   • Sharing files and communicating is easier. You can share the same hardware and the same Internet connection and can be shared between every device connected to the LAN.

2. WAN stands for Wide Area Network and it connects LANs in different geographical locations and they hire infrastructure. A WAN is more expensive than a LAN. The Internet a example of a WAN.

3. Bandwidth is the amount of data in a given time and is measured in Mbps (Megabytes per second). Too many users ore heavy use may cause congestion and it slows the network. Wired connections are generally faster and more reliable than wireless. Wireless performance depends on signal quality by the range and interference such as thick walls.

4. Hardware include NICs, Switches and Routers. NICs which is a network interface controller which allows a device to connect to a network. Switches connect devices on a LAN and receive data called frames. The data is transmitted to another device on the network using the correct MAC address. Routers transmitting data between networks. these data (called packets) are directed to their destination. They also connect a LAN to the Internet.

   • Ethernet cables are used to connect devise in a LAN. The most common are CAT 6. They are twisted pair which are containing four pairs of copper wires twisted together to reduce internal interference Coaxial cables are made of single copper wire surrounded by a plastic layer for insulation. Fibre optic cables transmit data as light. They are expensive but they are high performance and they don't suffer interference and the signal quality doesn't change.

5. Client-server network is managed by a server and the devices connected are clients. Files and software are stored centrally and clients have to send a request to access the information they require.

   • Easier to keep track of as they are stored centrally. They can preform backups, install and update software and manage security more easily. They are expensive to set up and have server dependence though. They can also be overloaded too.
   • Peer to peer networks are all equal and are connected directly to each other.
     • Peer to peer networks are easier to maintain and there isn't any server dependence but there aren't any centralised management. Copying files is also harder and peer machines are less reliable.

6. There are different topologies such as Star, Mesh, Bus and Ring.

7. Protocols are a set of rules for how devices communicate and how is data transmitted accoss a netwok.

   • All devices contain a unique identifier so it can be found in a network. All network-enabled devices have a MAC address that cannot be changed.
     • MAC addresses are 48 or 64 bit binary to be made easier, they are converted into hexadecimals.
   • IP addresses are used when sending data between TCP/IP networks. IP addresses aren't linked to any hardware and are assigned manually (static) or automatically (dynamic).
     • IP addresses that are static are permanent but dynamic IP addresses are always changing. It is assigned by either a 32 bit or 128 bit binary number.

8. Data is sent between networks and they each have a packet number, a source code, a destination address and a payload.

   • They contain a checksum number to validate if the payload data has been corrupted. The packets may take different routes but the receiving device always orders the packets and resemble them in the right number

9. There are several protocols such as Hyper Text Transfer Protocol which is used by web browse to access websites and communicate with web servers. There is a secure version of HTTP too which encrypts all information. File Transfer Protocol ace edit and move files between devices on a network. Post Office Protocol version 3 retrieve emails from a server ad is held until it is deleted. Internet Message Access Protocol retrieve emails from a server. The server holds the email until you delete it manually. A Simple Mail Transfer Protocol is used to send emails and transfer emails between servers.

10. A layer is a group of protocols which have similar functions. each layer serves the layer above it. It breaks the network o manageable pieces and each layers are self-contained and can be changed without other layers being affected. Having set rules means devices are compatible and universal.

    • Layer 1- Data Link Layer passes data over a physical network and is responsible for how bits are sent as electrical signals over cables. Ethernet.
      • Layer 2- Network Layer makes connections between networks, directing data and handling traffic. Used by routers. IP (Internet Protocol).
        • Layer 3- Transport Layer controls data flow splitting data into packets and checking are correctly sent and delivered. TCP (Transmission Control Protocol).
          • Layer 4- Application Layer turns data into websites and other applications. HTTP, HTTPS, FTP and SMTP

11. The Internet is a network of networks. The WWW is a collection of websites that are hosted on web servers. A URL is a uniform resource locator contains a protocol, a domain name that will be changed, using a DNS, into an IP address and a path to a s file.

    • A clouds stores files and while it easier to increase the amount of storage available without the need to provide your own security and backups or require IT staff and hardware, It needs connection to the Internet to access files. It end on the host and is vulnerable to hackers. It is also unclear who has ownership.

12. A virtual network is a network that is software based and ity partitions off a ophysical network's bandwidth frm a separate network.

    • A Virtual Private network sends data securely over a large network

13. A passive attack is where someone gains information by using packet sniffers and they a hard to detect. The best defence is to use encryption. Active attacks are easier to detect and is when someone attacks a network using malware. The best defence against them is a firewall. An insider attack is when someone in an organisation exploits their network access. A brute force attack is when a software tries to guess passwords through trial and error. The best defence against them is to use strong passowrds. A denial of service attack is where a ahcker floods the network inaccessible by filling it with useless traffic.

    • Malware genrally delete or modify files, scare users intfollowing malicious links, locking files, spying keyboard presses, altering permissions and opening backdoors
      • Viruses attach by copying themselves to certain files,wo self replicate and are activated by opening the file and trojans lure users into installing them

14. Social Engineering is gaining sensitive information by influencing people. Phishing genrally takes place over a telephone but it can be pretending to be from well-known business. A SQL injection is inputing pieces of coide to access other peoples accounts if the code doesn't have a strong form of validation. If the code is insecue, then it is an easy way to get past a firewall.

    • A good policy will regularly test the netwoto find security weaknesses. Use passwords and enforce user access levels. They will also install anti-malware and firewalls. They must crypt all data sent.
      • Pentesting is when companies employ hackers to simulate an attack and show potential weaknesses in a system.
        • User access levels allow people to access the information needed and teep sensitive information unknown. This helps prevent insider attacks.
          • Encryption requires a key to access the information preventing passive attacks. Enpted text is called cypher text while text thisn't encryoted is called plaintext.