Data and Network Communication Fundamentals

Data Communication

• Refers to the exchange of data or information through a computer network between devices via transmission mediums like cables, optical fibers, or wireless.
• Involves the transfer of text, numbers, images, audio, and video.
• It serves as a fundamental component for modern information technology.

Network Communication Components

• Data communication involves transferring information from one point to another within a network environment.
• Network communication consists of five basic components:
  • Sender
  • Message
  • Medium
  • Protocol
  • Receiver

Sender

• Also referred to as a transmitter.
• It is a computer/device that sends the message (data or information) from source to destination within a communication network.
• The can be a computer, workstation, cell phone, or camera.
• It converts the electrical signal into a suitable form for transmission over the network.

Message

• Message refers to the data or information that is to be transmitted.
• Data can be in the form of text, audio, video, or any combination of these.

Medium

• The path through which the message travels from source to destination.
• It can be wired, such as telephone cable, coaxial cable, and fibre optics.
• It can be wireless such as Bluetooth, Wi-Fi, microwave, radio wave, and satellite.

Receiver

• A receiver is the device which the transmitted message is sent to.
• Can be a computer, workstation, telephone handset or television set.
• Receives data from the transmission medium but may need to convert and adapt data into appropriate form.

Protocol

• Set of rules that govern data communications and represents an agreement between communicating devices.
• Without a protocol, two devices may be connected but unable to communicate effectively.

Modes of Network Communication

• Refer to the methods or ways information is transmitted from one place to another.
• Different types of communication modes:
  • Simplex
  • Half-duplex
  • Full-duplex
  • Synchronous
  • Asynchronous

Simplex Mode

• Communication takes place in only one direction.
• This mode is unidirectional.
• Communication can only take place in one direction as the receiver cannot send data back.
• Examples include data being sent to an electronic notice board in train stations and airports, radio and television broadcasts.

Half-Duplex Mode

• Communication takes place in both directions, but not at the same time.
• The signal can only be sent or received at any one time.
• A common example is the use of walkie-talkies where each person must indicate when they have finished speaking.
• Also used in transaction-oriented systems, e.g., communication between a computer and credit card machine.

Full-Duplex Mode

• Communication takes place in both directions simultaneously.
• Sender and receiver can both send and receive data simultaneously.
• This mode is the fastest bi-directional form of communication.
• A common example includes the telephone network

Asynchronous Transmission

• The time interval between two characters is variable and not fixed.
• Devices can exchange information at their own rate, slow or fast.
• Start and Stop bits are a feature and are used in asynchronous transmission, providing timing for the connection between sender and receiver.
• The start bit tells the receiver that a character is coming, and the stop bit signals the end of the transmission.
• This transmission type is ideal for slow-speed communication when gaps may occur, such as in keyboard data transmission

Synchronous Transmission

• The time interval between two characters is always the same with this method.
• Communication devices are synchronized, continuously sending characters to remain synchronixzed, even if there is no data.
• A special "idle" character is sent when there is no data for transmission.
• There is no need for start and stop bits, instead data is sent as one long bit stream or block of data.
• Relies on count of bits and reconstructs the sent information in bytes.
• Accuracy depends on receiver keeping an accurate count of the bits as they come in
• Synchronous transmission is faster than being asynchronous.
• Used for data transmission between devices in network communications links.

Communication Devices

• Refers to a device used in telecommunication systems for transmitting data from one location to another.
• Commonly used communication devices:
  • Hub
  • Switch
  • Router
  • Gateway

Hub

• It is a connectivity device used in LAN, connecting multiple LAN devices on one network.
• Allows multiple devices to as a single network.
• Hubs are non-intelligent devices and sends output to all network devices.
• Hubs have multiple input/output (I/O) ports - input in one port results in output in all other ports except the initial one where input was given.

Switch

• A networking device that performs the same job as a hub but considered more intelligent.
• Gathers information about the data packet and forwards it only to the intended node, such as a computer.
• A data packet is a basic unit of communication sent over a computer network, which is broken into smaller data upon transmission and reassembled upon reaching its destination.

Router

• A communication device which connects two or more networks
• Routers receive data packets, look for the remote computer address, and forwards it to a computer closer to the remote computer.
• They forward data packets by selecting the best path based on network traffic.
• Many routers may be involved in transmitting data packets from one location to another.

Gateway

• A device used to connect a network to another network that uses different protocols.
• Used to link different kinds of networks, such as networks of IBM mainframe computers and networks of PCs needing a gateway.
• Gateways change the format of the data packets to conform to the application program of the remote computer.
• Gateways do not affect or alter the message content itself

Network Architecture

• Design of a communication system.
• Includes hardware devices (routers and switches), cabling, network topology, and connections.
• Computer networks consist of server computers and client computers.

Server Computer

• A computer on the network that shares resources for use with others.
• Shares resources like information, software, printer, plotter, Internet connection, hard disk, etc.

Client Computer

• A computer on the network that accesses resources shared by other computers.

Network Architectures

• There are two commonly used types of network architectures:
  • Client/Server Network
  • Peer-to-Peer Network

Client/Server Networks

• Each computer acts as either server or client.
• Each server computer operates on the network which is a dedicated server.
• Servers are not used as client computers and client computers do not act as servers
• The servers are optimized to deliver quick access to shared network resources,
• Includes one or more computers dedicated to acting as servers.
• Ensures adequate security so that data cannot be accessed by unauthorized users.
• Centralizes control of data. and assigns responsibility to one group.

Peer-to-Peer Networks

• Each computer is capable of acting as a client, server or both at the same time.
• Computers on the network are refereed to as 'peers'.
• Peer computer can share files and printers with other computer, while also accessing their resources from the other computers simultaneuously.
• Peer-to-peer networks are often small, typically ranging between two and ten computers.
• Larger peer-to-peer networks can be difficult to manage, with many network administrators in control

Types of Networks

• There are three common types of networks based on the physical size:
  • Local Area Networks (LAN)
  • Wide Area Networks (WAN)
  • Metropolitan Area Network (MAN)
  • Virtual Private Network (VPN)

Local Area Networks

• Spans a limited physical area, confined to a single building or group of nearby buildings.
• Facilitates the sharing of applications, printers, group scheduling, e-mail, project tracking and other tasks

Characteristics of LAN

 - small physical area
 - high-speed wired/wireless connections between computers
 - reliable network
 - communication errors are very rare
 - limited number of computers

Wide Area Networks

• Spans a large physical area, connecting several sites of an organization across cities, countries and continents.
• Referred to as long-haul networks because of the distances involved.
• Often made of two or more LANs connected together to form a single WAN.

Characteristics of WAN

 - large physical area to be worldwide
 - connection speeds that are slow compared to LAN
 - connects computers through public networks, leased lines or satellites
 - connects multiple LANs
 - communication errors due to complexity

Metropolitan Area Networks

• Spans several buildings or a large campus to entire cities.
• Used by many organizations.
• Connects local networks with high-speed communication lines.

Characteristics of MAN

 - larger than a LAN and smaller than a WAN
 - covers an area of between 5 to 50 km in diameter
 - transmits data using fiber optic cable or microwave transmission
 - provides high-speed communication
 - used by telephone companies, Internet Service Providers and cable TV companies

Virtual Private Networks

• Provides remote access to indivudals and offices to their organization's networks.
• Provides communication by using public telecommunication such as the Internet.
• Allows employees to connect their desktops as if they were physically at the office.

Characteristics of VPN

 - uses Internet data transmission, such as Internet to connect computers
 - provides secure remote access
 - enables file sharing, video conferencing and similar network services
 - delivers data communications over long distances

Wireless Networks

• Networks use wireless communication technology to transmit network data between devices.
• Can operate over short distanes (within a building) or vast geographical areas (cellular networks)

Examples Of Wireless Networks

 - Wi-Fi (Wireless Fidelity): wireless networking technology for LAN usage that enables devices to connect to network and the Internet over wireless
 - Bluetooth: short rang, close proximity wireless for audio streaming, sharing files, connecting devices
 - Cellular Networks: provide connectivity over over large geographical areas via cells with base cellular towers that transmit wireless and data to mobile devices
 - Satellite Networks - Uses orbiting satellites to relay wireless and network connectivity with satellite usage to provide for and connect Internet, Tv and GPS navigation.

Advantages of Wireless Networks

 - connect to network resources from any connectivity
 - easier and cheaper to install
 - expands and connect to accommodated devices and users is easy
 - connect to network and share date between devices is easy
 - network data can be transmitted and shared easier without more cables
 - remote worker connectivity access to networks

Advantages of Wireless Networks

 - networks can get network interference from other devices which impact connectivity speeds
 - security risks from unauthorised network sharing
 - limited range, and requires signal and networking boosters
 - may get slower with network demand
 - signal reliability concerns

Network Topologies

• The arrangement of network nodes (any devices which are part of network) and connections between them.
• Four popular modern network topologies:
  • Bus
  • Star
  • Ring
  • Mesh

Bus Topology

• Bus network connects each node to the network along a single piece of cable, called a bus.

Features Bus Topology

 - Suitable for a small network
 - Easy to connect a computer
 - Requires less cable to implement
 - Terminator is installed at each end of the cable to prevent signals from reflecting back onto the bus and cause errors.

Limitations of Bus Topology

 - the single cable is damaged or broken at any point, the entire network can go down
 - difficult to identify problem
 - not suitable for larger networks

Star Topology

In a star network topology, each network node is connected to a central device called a hub. Large networks can require many hubs and hubs can be connected to each other to create a single large network.

Features of Star Topology

 - suitable for small networks
 - wiring is easier
 - faults easy to detect

Limitations Of Star Topology

• hub failure crashes all network
  • implement expnsive with complex wired set-ups

Ring Topology

• A topology made as wired loops

Feaures of Ring Topology

   - eas ier wiring
   - data runs to one network

Limitations Of Ring Topology

   - stops all connected devices
   -slower network speeds

Mesh Topology

• most secure topology with each network connection connecting with all network devices

Features Mesh Topology

    - more reliable since all network sources are back-up
     - manage lots of traffic

Limitations Mesh Topology

• expensive since connecting each network will devices is complicated and intensive
  • setting-up is difficult