Networks and the effects of using them (chapter 4)

Networks

Network Interface Card (NIC)

  • A NIC is needed to allow a device to connect to a network

  • NIC converts binary data into electrical signal which allows access to a network

  • The NIC is usually integrated inton the motherboard on most modern computers.

  • Each NIC is given a unique hardwired MAC address at the manufacturing stage, this uniquely identifies a device.

  • WNICs are the same as NICs, they are also used to connect devices to a network, but the use wireless connectivity, using an antenna to communicate with networks via microwaves

Media Access Control (MAC) Address

  • The MAC address uniquely identifies a device when it is connected to a network

  • It is made up of 48 bits, shown as 6 groups of hexadecimal digits - the first 6 hex digits are the manufacturers code,and the second group of hex digits are the unique serial number of the device itself. (eg: 00 - 1C - B3 - 4F - 25 - FF)

  • Also known as the physical address as it uniquely identifies a device

  • MAC addresses are reliable for identifying data senders and receivers on a network, as they never change, making them useful for identifying network faults.

  • If NIC replaced then the MAC address will also change

Internet Protocol (IP) Addresses

  • Whenever a computer connects to a network it is given an IP address,which is usually assigned by the ISP

  • Internet Protocols define the rules agreed upon by senders and receivers of data communicating through the network

  • An IP address essentially identifies the location of a device on a network

  • The IP address changes every time you login at different locations.

  • IPv4: Based on 32 bits, written as 4 groups of eight bits ( eg: 254.25.28.77 )

  • IPv6: Uses a 128-bit address, written as 8 groups of hex digits

Data Packets

  • Data is moved around networks in the form of data packets

  • The data is split into packets for network transmission and ressembled at the destination.

  • Packet Header contains: 1. Senders and receivers IP address, 2. Sequence number, 3. Packet size, 4. Total number of packets in the message

  • Router Role: 1) It checks the destination IP address to determine the next step. 2) PAckets pass through multiple routers before reaching their final destination. 3) Headers ensure correct reassemble at the receiving station

Hubs

  • Hubs are hardware devices that can have a number of other devices connected to them

  • They are used to connect devices to form a LAN

  • A hub will take a data packet received at one of its ports and broadcast it to every device connected to it, because the data packets are delivered to every device connected - 1) hubs are not very secure as all the devices connected will receive each data packet. 2) There will be unnecessary traffic, which results in reduced bandwidth

Switches

  • Switches are the ‘intelligent’ versions of hubs

  • They also connect devices together to form a LAN

  • Unlike a hub, a switch stores the MAC address of all devices connected

  • A switch matches the MAC address of an incoming data packet arriving at one of its ports , and directs it to the correct device

  • None of the other device will see the this data packet

    Bridges

  • They are devices that connect one LAN to another LAN that uses the same protocol

  • They are often used to connect different parts of LAN so that they can function as a single LAN

Routers

  • They are used to route data packets from one network to another network, based on IP addresses

  • Each router has its own IP address

  • Routers are used to join a LAN to the internet

  • Routers know where to send data packets by consulting a routing table (stored on the routers RAM)

  • The routing table will contain information about the routers immediate network.

Wi-Fi and Bluetooth

  • Both Wi-FI and Bluetooth offer wireless communication between devices

  • Both use electromagnetic radiation as the carrier of data transfer

    • Bluetooth is useful:

      1. when transferring data between two or more devices which are very close together (less than 30 metres)

      2. when the speed of data transmission is not critical

      3. for low-bandwidth applications (eg: using hardware audios like headsets)

    • Wi-Fi is best suited to:

      1. operating full scale networks because it offers much faster data transfer rates, better range and better security than bluetooth

Cloud Computing (Storage)

  • Cloud Storage:

    1. Data is stored on remote servers

    2. Thousands of servers in may different locations

  • Data Redundacy:

    1. Same data is stored on more than one server in case of maintenance or repair

    2. Allowing clients to access data at any time

  • Types of Cloud Storage Systems

    1. Public Cloud:

      • storage environment where the client and cloud storage provider are different companies

    2. Private Cloud:

      • The client and cloud storage provider are a single organization

    3. Hybrid Cloud:

      • combination of the two previous environments

      • some data resides in the private cloud

      • less-commercial data can be accessed from a public cloud storage provider

  • Advantages:

    • files stored in the cloud can be accessed at any time, any device, anywhere in the world

    • no need for client to carry an external storage device with them

    • provides the user with remote backup of data

    • unlimited storage capacity

  • Disadvantages:

    • Problems accessing or downloading their data with slow or unstable internet connection

    • Failure of the cloud storage company is always posssible which poses a risk of loss of all backup

    • Expansive

Computer Networks

  • What is a Network? : Networking takes place when two or more computers connect together via wires, satelite, telephone line or through Wi-Fi

  • Advantages of Networking

    • Communicate with other network users (eg: email,instant messaging)

    • Sharing of hard resources such as printers and internet connections

  • Disadvantages of Networking

    • Viruses can spread when the computers are connected

    • Loss of data can also take place

  • Local Area Network (LAN)

    • A LAN is a private network within a single building or site

    • A LAN will consist of a number of computers and devices that are connected to hubs or switches

      • Advantages:

        1. Sharing of resources

        2. EAsy communication between users

      • Disadvantages:

        1. Slower access to internet

        2. Spread of viruses throughout the whole network

  • Wireless Local Area Network (WLAN)

    • Similar to LANs but no wires or cabels

    • Provide wireless network communications over fairly short distances using radio or infrared signals

      • Advantages:

        1. Adding new computers and device is very easy

        2. SInce no cabling, there is safety improvement

      • Disadvantages:

        1. Data transfer rate is slower compared to LAN

        2. Security is a big issue, since anyone can access the network

  • Wide Area Network (WAN)

    • A WAn is a network that extends over a large area

    • A WAN is created by using several LANs together using a router

    • Connection technologies like radio link, cables, satellites are used for WAN

      • Advantages:

        1. Files and data can be shared over a large area

        2. Computers can be connected over a large area accross countries

      • Disadvantages:

        1. Data transfer rate is slower compared to LAN

        2. Security can be an issue

Netork Issues and Communications

  • How to protect passwords? :

    • Run anti-spyware software

    • Change passwords on regular basis

    • Passwords should not be easy to crack

  • Zero login and Biometrics: Allows users to login to computer systems without the need to type in a password

    • Zero login recognises a user by a number of features based on:

      1. biometrics

      2. behavioral patterns

    • Biometrics - Fingerprint and Face recognition

    • Behavioral Patterns - your typing speed, your normal location, how you swipe the screen, how you walk

    • Adavnatages:

      1. enhanced security

      2. easier and quicker way to login

  • Magnetic Stripe Cards:

    • Cards have a magnetic stripe on the revious side

    • The stripe is read by swiping it through a card reader

    • Access only allowed if the scanned data matches the data in a data base

  • How to secure magnetic stripe cards

    • Holographic image is designed to make the forgery of the card more difficult

    • Holographic images change color or appear to have a moving object as the image is viewed from different angles

    • Holographic images are difficult to copy

    • Photographic image of the card user is printed onto the card surface

  • Smart Cards

    • By inserting a tag ( chip and antenna) into a security card,it can act as a smart contactless card

    • The chip on the smart card can store data like name, security number, sex, date of birth and a PIN

  • Physical Tokens

    • Form of authentication in the form of a physical, solid object

    • They contain internal clocks and when a PIN and other authentication details are entered , then an OTP is generated

  • Types of Physical Tokens

    • Disconnected physical token: key in data manually

    • Connected physical token: No need to key in data manually

  • Electronic Tokens

    • Software installed on a users device, like a smartphone

    • When the website requests the user to authnticate who they are, the user opens the app on their device, the app will gnerate a one time OTP which is valid for less than a minute

  • Virus (Malware): A computer virus is designed to spread from one computer to another and interfere with other computer operations

  • Anti-Virus Software

    • Protects devices against a potential virus attack

    • Features:

      1. Check softwares before they are run or loaded on a computer

      2. Allows the virus to be automatically deleted

      3. allows the user to make the decision about deletion

Video Conferencing

  • It is a communication method that uses both video and sound,

  • It is a substitute for face-to-face conferences

  • It is carried out in real time and makes use of some form of network

  • Basic hardware includes:

    • webcams

    • large monitors

    • microphones

    • speakers

  • Advantages

    • Easier to access important documents when people are in their own building

    • Possible to hold conferences on a short notice

    • Very convenient, doesnt require travel time and is sustainable

  • Disadvantages

    • There is potential lag in responses whne talking

    • Images can jerk due to poor network

    • Can be expansive to set it up

  • Audio Conferencing

  • Audio conferencing refers to meetings held between people using audio equipment, it can be done over the standard telephone network

  • Basic Hardware Needed:

    • a computer

    • external microphones or speakers

    • standard phone

    • internet phone

    • Using VoIP allows an organiser to create a group of people to ttake part in the conference call

    Web Conferencing

  • Uses the internet to permit conferencing to take place

  • As with video conferencing, it is also carried out in real time and allows the following types of meetings to take place:

    1. bussiness meeting

    2. online education

    3. presentations

  • Feautures:

    1. Slide presentations using presentation software can be posted on the conference website in advance

    2. Sharing of live presentations,or other live demonstrations

    3. Draw or write on a whiteboard using their mouse or keyboard