3.4 Network Hardware

(a) Computer Network:

A Computer Network is a communication system with interconnected computing devices that exchange data and share resources with each other.

These networked devices use a system of rules, called communication protocols, to transmit information over physical or wireless technologies.

(b) Components of a computer network:

• Node: A Node refers to any device that is connected to a network.
• Client: A Client is a node that requests and uses resources available from other nodes.
• Network Server: A powerful computer that provides various shared resources to workstations and other servers on a network. The shared resources can include disk space, hardware access and email services.
• File Server: A Server that provides access to files and folders. It acts as a central file storage location.
• Application Server:
  • A Server that manages the distribution of applications software.
  • Hosts Web Apps.
  • Network users may run and use applications without having to install a copy.
  • May be a part of the world wide web or a local network.
• Proxy Server:
  • A Server that sits between client computer and the web server.
  • It accepts incoming traffic from the client and sends it to the web server using its own IP-address, hiding the IP-address of client.
  • It filters the internet traffic against set criteria to allow or block access to a website.
  • It protects direct attack on web-server by hackers.
  • It improves web performance by storing a copy of frequently used web-pages in its cache.

(c) Advantages and disadvantages of a Network:

(a) Network Interface Card (NIC):

• NIC is a hardware that allows a device to connect to the internet or a network.
• It contains Media Access Control (MAC) address generated at the time of manufacturing.
• It could be on a separate card, built into the motherboard or plugged into USB port.
• NICs exist for both wired and wireless connections.
• Wired NIC relies on an input jack and wired LAN technology. Wireless NIC (WNIC) relies on an antenna to communicate through radio frequency waves (or microwaves) on a Wi-Fi connection.

(b) Network Switch:

• Switch is a hardware that connects devices on a LAN (Local Area Network).
• Switches receive data in units called frames or data packets, identify the destination MAC address of the device and transmit it only to the device it is intended to reach.

(c) Router in a network:

• Router is a hardware used to connect at least two different networks, like a LAN (home or office) network to a WAN (Internet) network.
• Router receives data transmitted in one format from a network, and converts the data to another format understood by another network using its particular protocol.
• A Router would typically have an Internet cable plugged into it and several cables connecting to computers and other devices on the LAN.
• Router sits behind a firewall that protects the computers on a network.
• Routers can be wired or wireless devices.
• Since every computer on the same network has the same part of an IP-address, the router is able to send the data packet to the appropriate switch, and the data will then be delivered to the correct device using the destination MAC-address.
• If the MAC address doesn't match any device connected to the switch, it passes on to another switch on the same network until the appropriate device is found.

(a) ISP (Internet Service Provider):

• Internet Service Provider (ISP) is the company that provides access to the internet to the user.
• The ISP creates a user account for their client in their system, secured by Username and Password for providing Internet services.
• A monthly fee is usually charged for this service.

(b) Protocol:

• A protocol is a set of rules that determines how data is transmitted between different devices on a computer network or internet.
• It allows the devices to communicate with each other, regardless of any differences in their internal process, structure or design.
• Protocols are built into device software and hardware to perform primary network tasks of communication, management and security.

(a) MAC address:

• MAC address is a unique 48-bits hardware identification number assigned to a Network Interface Card (NIC) by its manufacturer.
• It contains 6-pairs of hexadecimal digits separated by colon (:) or hyphen (-). The first 3-pairs of hex-digits represents the manufacturer-ID and the last 3-pairs of hex-digits is the serial number of the device (e.g. A6-1C-B3-09-85-15).
• MAC address of each network device should be unique all over the world.

(b) Difference between UAA and LAA:

(c) Three reasons why the MAC address needs to be changed using LAA:

1. Certain software used on mainframe systems need all the MAC addresses of devices to fall into a strict format; it is necessary to change the MAC address of some devices to ensure they follow the correct format.
2. It may be necessary to bypass a MAC address filter on a router or a firewall; only MAC addresses with a certain format are allowed through, otherwise the devices will be blocked if their MAC address doesn't adhere to the correct format.
3. Changing the MAC Address can help you bypass certain network restrictions by emulating an unrestricted MAC Address that is authorized.

(a) IP address:

• IP address is a unique location address that identifies a device on a local area network (LAN) or on the internet or a wide area network (WAN).
• It allows information to be sent between devices on a network and makes devices accessible for communication.
• It is assigned automatically by ISP using DHCP server or manually configured by the user.

(b) Difference between IPv4 and IPv6:

(c) Characteristics of IPv4 address:

1. IPv4 is a 32-bits address written in a group of four 8-bits denary numbers separated by dots (.).
2. It can be static (assigned manually) or dynamic (assigned automatically by DHCP server).
3. It can be public or private; public IP is unique globally when connected to the Internet; private IP is unique when connected in a separate private network.
4. When a router connects to the Internet it is given a unique public IP-address.
5. All the devices connected to a router have the same public IP-address as of the router.

(d) Characteristics of IPv6 address:

1. IPv6 is a 128-bits address written in a group of eight 16-bits hex-digits (between 0000 and FFFF) separated by colons (:).
2. It allows the Internet to grow with large number of devices on the network.
3. It removes the risk of IP-address collisions.
4. It contains built-in authentication checks.
5. It allows more efficient packet routing.

(e) Main advantages of IPv6 over IPv4:

1. IPv6 is thousand times (1028) larger than IPv4, so it allows the internet to grow in size.
2. Removes the risk of IP-address collisions.
3. Has built-in authentication checks.
4. Provides auto-configuration capabilities.
5. Allows more efficient and hierarchical packet routing.

(a) Private vs Public IP-address:

(b) Why we need both Private and Public IP-address:

• Private IP-address is used to communicate within the network assigned by the Router, which is unique on that network.
• Public IP-address is used to communicate over the Internet outside the LAN, which is assigned by ISP when the Router is connected to the Internet.
• All the devices connected to that router have the same public IP-address as of the router but each have their own different private IP-address on that network.

(a) Static vs Dynamic IP-address:

Note: The diagram shows the sequence of events when a Dynamic IP-address is assigned to a device and how it contacts the web-server when connected to the Internet.

• DHCP server: The device is using dynamic IP addressing; a request for an IP address is made (via the ISP) to allow Internet access. The DHCP assigns a temporary IP address and sends it back to the device.
• Device ↔ Domain Name Server (DNS): When the device wants to download a webpage, the DNS translates the required website URL into an IP address and sends it back to the device.
• Device ↔ Website server: A message is sent by the device to the IP address of the website server (given by the DNS) requesting a webpage. The website server sends the required webpage back to the device.

(b) Features of Static IP-address:

1. Static IP-addresses do not change, so they can be located from anywhere in the world.
2. It is easier to locate shared devices, like network printers.
3. Offers a stable connection, since the IP-address never resets.
4. Provides faster download/upload speed.

(c) Features of Dynamic IP-address:

1. Dynamic IP-address is automatically assigned to a device by ISP using DHCP server.
2. Provides security, since they change each time a user logs on to internet.
3. Provides privacy by the use of VPN.
4. Avoids the problem of address conflicts when new devices are added.

(d) Why we need both Static and Dynamic IP-address:

• Static IP-addresses which don't change are used to share network resources, like network servers and printers.
• Dynamic IP-addresses which often change are used by devices to communicate over the internet.

(a) DHCP Server:

• Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks.
• It automatically provides and assigns unique dynamic IP-addresses, default gateways and other network parameters to client computers/devices.
• The IP-address information assigned by DHCP is only valid for a limited period of time.

(b) Location of DHCP servers:

• DHCP server is in Router or Switch, which provides a private IP-address to each device for private LAN network.
• Internet Service Provider (ISP) has their own DHCP server that provides dynamic public IP-address to each device for public internet connection.

(a) DNS Server and how it works:

• Domain Name System (DNS) is a computer server that contains a database of public IP-addresses and their associated hostnames or website names.
• It translates human readable domain name into corresponding numeric Internet Protocol (IP) address, which is used to identify and locate the resources on the Internet.
• DNS servers run special software, and communicate with other servers at its data center using special protocols.
• When you type a website address into your browser's address bar and press Enter, the browser sends a request to the DNS server to find the IP-address of the website you typed and sends it back. The browser then requests the webserver to access the website using its IP-address.

(b) Location of DNS server:

• DNS servers are located in ISP's data centers at different remote locations all over the world.

(a) Wired network:

• A wired network refers to a wire-based high-speed networking system called Ethernet to allow computer workstations, servers and printers to share data and resources.
• Examples of wired networks include telephone networks, cable television, internet access and fiber-optic communication.
• Wired networks use ethernet cables like coaxial, twisted pair, and fiber-optic to transfer data between connected computers and devices.
• Some advantages of wired network technology include enhanced speed, lack of interference, increased security, and the ability to connect systems across long distances.
• Disadvantages can include high installation and replacement costs.

(b) Types of cables used in a wired network:

1) Coaxial cable:

• 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.
• It carries high frequency electrical signals used by TV cable operators, telephone companies, and Internet providers to transmit data, video and voice communications to customers.

2) Twisted pair ethernet cable:

• Twisted pair ethernet cable contains four pairs of insulated copper wires which are twisted together to reduce internal interference.
• The most common ethernet cables are CAT 5e and CAT 6 (CAT is short for 'Category') used to connect devices in a LAN.
• Twisted pair cables provide high data transmission rates and bandwidth. They are thinner and less expensive.

3) Fiber-optic cable:

• A Fiber Optic cable contains strands of one or more flexible insulated fibers of glass, slightly thicker than a human hair.
• Each strand provides a pathway to transmit data in the form of light pulses, that reflects light inward to avoid loss of signal and allow the light to pass through bends in the cable.
• Fiber cables are capable of transmitting data over a very long distance with higher transmission rate and bandwidth, without losing quality and strength.

(a) Wireless network and how it works:

• A wireless network uses electromagnetic waves, like radio waves, microwaves or infrared to connect network nodes. Examples include Cell-phone networks, wireless local area networks (WLANs), satellite communication networks, etc.
• A computer's wireless adapter translates data into a radio signal and transmits it using an antenna.
• A wireless router receives the signal and decodes it. The router sends the information to the internet using a physical, wired ethernet connection.

(b) Types of wireless communication technologies:

1) Bluetooth:

• Bluetooth is a short-range wireless communication technology that uses radio waves in 79 different frequencies known as channels, centered at a frequency of 2.45 GHz.
• Bluetooth devices automatically detect and connect to each other, without interfering with each other since each pair uses a different channel.
• While connecting two devices called Pairing, each device is equipped with special security keys to encrypt data shared between them.
• Bluetooth creates a secure wireless personal area network (WPAN), where data transmission rate and bandwidth is not crucial, like sharing data or listening to music from mobile phone using bluetooth devices.

2) Wi-Fi:

• Wi-Fi is a wireless networking technology that allows Wi-Fi compatible devices such as laptops, smartphones and printers to connect with each other and share data using radio signals.
• Wi-Fi enabled devices can access the Internet through a wireless Router or any Wireless Access Point (WAP) or "Hot spot" from any location within the network coverage area.
• Wi-Fi offers much faster data transfer rate, better security and larger range than Bluetooth.

(c) Difference between Bluetooth and Wi-Fi:

(a) Computer Port:

• A Computer Port is an interface or a slot on the motherboard to connect peripheral devices with a computer using cables.
• The interaction of the ports with connected input and output devices is controlled by the control unit.
• Based on the type of communication, computer ports are of two types: Serial and Parallel.

Examples of Serial Ports: COM1 COM2 USB HDMI — used to connect peripherals like Mouse, Modem, game controllers, printers, projectors, etc.

Examples of Parallel Ports (used in early computers): PS/2 EPP ECP — used to connect mouse, keyboard, printer, scanner, etc.

(b) Universal Serial Bus (USB):

• USB is an external bus with a plug-and-play interface.
• It is used to connect external peripheral devices with a computer.
• It uses asynchronous serial data transmission. Allows both half-duplex and full-duplex.
• It provides power supply to the peripheral devices.

USB cable cross-section — The USB cable consists of a four-wired shielded cable, with two wires for power (red and black). The other two wires (white and green) are for data transmission:

(c) Three reasons for using USB ports over traditional Serial ports:

1. Data transfer rate of USB port is much higher (between 12 Mbps to 480 Mbps) than traditional Serial port (1 Mbps to 10 Mbps).
2. USB port is capable of supplying power to the peripheral devices.
3. USB port automatically detects the device and installs the correct driver.
4. USB ports are much more durable than serial ports because pins in serial ports are very easy to bend or break, whereas USB pins are more robust and much more difficult to damage.