Computer Networks & Hardware Essentials
Network Communication
- A kilobit is comprised of one thousand bits. It is used to measure the amount of data transferred per second.
- 1 kp/s=1000 bits per second
- 1 KB/s=1024 bytes per second
- People tend to get confused by the similarity of KBps and kbps regarding the internet bandwidth and download speeds. Data transfer speeds are always calculated in kilobits per second (kbps).
- On the other hand, file size measures are always in Kilo Bytes and thus download speed is always calculated based on how many Bytes per second are downloaded hence Kilo Bytes and kilo bits are not interchangeable.
Components of Networks
- Hardware components
The network interface card (NIC) provides a computer with a dedicated, full-time connection to a network. It implements the physical layer circuitry necessary for communicating with a data link layer standard, such as Ethernet or Wi-Fi.
NIC is a hardware component attached to the circuit board that is installed on a computer so it can connect to a network.
Network Medium refers to the cable (metallic or fibre-optic) that links computers on a network. Since wireless networking is possible, it can also describe the type of wireless communications used to permit computers to exchange data via some wireless transmission frequency.
Interconnecting device is a widely used term for any hardware that connects different network resources. The key devices that make up a network are switches, routers, bridges, repeaters, and gateways.
- Software Components
Network client software requests info stored on another network computer or device and runs on a client computer and allows it to establish connectivity with services running on server computers.
Network server software allows a computer to share its resources. It is a powerful computer used to store files and run programs.
Protocols define the rules and formats a computer must use when sending information across the network.
NIC driver receives data from the protocol and forwards this data to the physical NIC.
Layer of Network Communication Process
Steps:
- User Application: An application tries to access a network resource.
- Network Software: Client software detects the attempt to access the network and passes the message on to the network protocol.
- Network protocol: The protocol packages the message in a format suitable for the network and sends it to the NIC driver.
- Network Interface: The NIC driver sends the data in the request to the NIC card, which converts it into the necessary signals to be transmitted across the network medium.
Broadcast IP address
The broadcast address can be used to send data packets in IP networks to all participants of a local network. The individual addresses of each party in the network do not have to be known for this to work.
How two Computers Communicate on Lan
Transmission Control Protocol(TCP)/IP is the common protocol used on the network. It uses 2 addresses to identify devices that is the logical address (IP address) and the Physical address (MAC address).
1. A user at Comp A types ping 10.1.1.2 at a command prompt
2. Network software creates a ping message
3. The network protocol packages the message by adding IP address of the sending and destination computers and acquires the destination computer’s MAC address
4. The network interface software adds MAC addresses of sending and destination computers
5. Comp B receives the message, verifies that the addresses are correct and then sends a reply to Comp A using Steps 2 – 4
Network Terminology
An internetwork is a networked collection of LAN tied together by devices such as routers.
A personal area network (PAN) interconnects technology devices, typically within the range of a single user, which is approximately 10 meters or 33 feet. This type of network is designed to enable devices in a small office or home office environment to communicate and share resources, data and applications either wired or wirelessly.
PAN
PANs typically consist of laptops, smartphones, tablets, wearables, printers and entertainment devices. These devices are generally interconnected using some form of wireless technology. This kind of PAN could also be connected to the internet or other networks without wires.
LAN
LAN. A local area network connects devices within a relatively close proximity. A LAN can be deployed inside a home, office suite, building or corporate campus. The organization typically owns and maintains the network hardware and cabling. Ethernet -- 1 gigabit per second to 100 Gbps -- is often used and can consist of twisted-pair copper cabling, as well as single- or multimode fibre interconnects.
MAN. Metropolitan area networks are most often used when an organization maintains multiple buildings or locations within a city or municipality. Buildings are typically connected using fibre optic cabling. In most cases, the organization partners with a telecommunications company to provide and manage the MAN service on the client's behalf.
WAN
WAN. A wide area network connects business locations that are dispersed throughout a state, country or even globally. The organization purchases WAN services from a telecommunications provider that manages the operational status of each WAN link. In most cases, only network traffic that must be transported back and forth between business locations is moved over the WAN. 
Internet: a worldwide public internetwork. Uses protocols such as TCP/IP and HTTP to transfer and view information.
Intranet: a private internetwork in which devices and servers are only available to those users connected to the internal network
Extranet: allows limited and controlled access to internal resources by outside users.
Private IP Address and Public IP Address
A public IP address identifies you to the wider internet so that all the information you’re searching for can find you.
A private IP address is used within a private network to connect securely to other devices within that same network.
Packet and Frames
Reasons data is transferred this way:
1. Pause between bursts allows other computers to transfer data during pauses
2. Allows the receiving computer to process received data
3. Allows the receiving computer to receive data from other computers at the same time
4. Gives the sending computer an opportunity to receive data from other computers and perform other processing tasks
5. If an error occurs during the transmission of a large file, only the chunks of data involved in the error have to be sent again
Packets: In networking, a packet is a small segment of a larger message. Data sent over computer networks, such as the Internet, is divided into packets. These packets are then recombined by the computer or device that receives them.
Frames: A frame is a digital data transmission unit in computer networking and telecommunication. In packet-switched systems, a frame is a simple container for a single network packet.
Client and Server
- A client is a program that runs on the local machine requesting service from the server. A client program is a finite program means that the service is started by the user and terminates when the service is completed.
- A server is a program that runs on the remote machine providing services to the clients. When the client requests a service, then server opens the door for the incoming requests, but it never initiates the service.
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