CS004 - MODULE 1 Fundamentals of Computer Network and Data Communication

Components of IS (Information System) (6)

1. Data

2. Information

3. Hardware

4. Software

5. Telecommunication/Networks

6. People/Peopleware

Data communications

are the exchange of data between two devices via some forms of transmission medium such as a wire cable.

1. Message
2. Sender
3. Receiver
4. Transmission Medium
5. Protocol

**COMPONENTS OF DATA COMMUNICATION (5)**

Data

Raw facts

Information

processed data

Hardware

tangible part

Software

intangible part (ex. OS) - binary (0 & 1)

Telecommunication/Networks

internet/ARPANET

**People/Peopleware**

end users/programmers

Message

The _____ is the information (data) to be communicated.

Sender

sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on.

Receiver

receives the message. It can be a computer, workstation, telephone handset, television, and so on.

Transmission medium

physical path by which a message travels from sender to receiver.

Protocol

set of rules that govern data communications.

1. SMTP
2. HTTP
3. HTTPS
4. TCP/IP

DIFFERENT KINDS OF PROTOCOL

SMTP (Simple Mail Transfer Protocol)

a protocol for sending and receiving emails over networks. It's the standard for email communication between clients and servers, defining their interaction.

HTTP (Hypertext Transfer Protocol)

web protocol for fetching web pages and resources. It guides how browsers request content from servers and how servers provide responses. It's the basis of web data communication.

HTTPS (Hypertext Transfer Protocol Secure)

a web protocol for sharing web pages and resources. It guides how browsers request and servers deliver content, forming the basis of web communication.

**TCP/IP** *(Transmission Control Protocol/Internet Protocol)*

a crucial internet protocol suite. It guides data packet handling, transmission, and routing among devices. ____ ensures reliable data transfer, and IP manages addressing and routing.

1. Text
2. Number
3. Images
4. Audio

DATA REPRESENTATION (4)

Text

In data communications, ____ is represented as a bit pattern, a sequence of bits (Os orIs).

Number

____ are also represented by bit patterns. However, a code such as ASCII is not used to represent ____ ; the ____ is directly converted to a binary number to simplify mathematical operations.

Images

____ are also represented by bit patterns. In its simplest form, an ___ is composed of a matrix of pixels (picture elements), where each pixel is a small dot. The size of the pixel depends on the resolution.

Audio

____ refers to the recording or broadcasting of sound or music. ____ is by nature different from text, numbers, or images.

1. Simplex
2. Half-Duplex
3. Full-Duplex

DATA FLOW (3)

Simplex

the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive. 

Half-Duplex

each station can both transmit and receive, but not at the same time :When one device is sending, the other can only receive, and vice versa.

Full-Duplex

is like a two-way street with traffic flowing in both directions at the same time. In ____ mode, signals going in one direction share the capacity of the link: with signals going in the other.

1. Digital Signal
2. Analog Signal

TYPES OF SIGNAL

\
**Digital Signal**

\- have only a limited number of defined values. Although each value can be any number, it is simple as 1 and 0. Well-suited for modern electronic devices and communication systems, includes technologies like digital phones, computers, and the internet.

**Analog Signal**

\- a continuous representation of information, where data is conveyed through varying voltage levels or continuously changing physical properties such as amplitude, frequency, or phase. They are used in older forms of communication, like traditional telephony and radio broadcasting.

1. GUIDED MEDIA
2. UNGUIDED MEDIA

TYPES OF TRANSMISSION MEDIA

1. Twisted Pair Cable
2. Coaxial Cable
3. Optical Fiber Cable

GUIDED MEDIA CABLES (3)

* Unshielded Twisted Pair (UTP)
* Shielded Twisted Pair (STP)

TWISTED PAIR CABLE (2)

**Guided Media**

referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links. 

**Twisted Pair Cable**

used for transmitting data in telecommunications and computer networks.

Unshielded Twisted Pair (UTP)

widely used for Ethernet networking and telephone connections in homes and offices.

Shielded Twisted Pair (STP)

used in environments with higher levels of interference, such as industrial settings or areas with a lot of electronic equipment.

Coaxial Cable

carry signals over longer distances with less signal degradation compared to other cable types.

Optical Fiber Cable

high-speed transmission medium used for transmitting data using light signals.

Unguided Media

\
referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals. 

**Radio Waves**

 long wavelengths, used in radio broadcasting, television transmission, and various wireless technologies like Wi-Fi, Bluetooth, and cellular networks.

Microwaves

shorter wavelengths than radio waves, utilized in microwave ovens for heating food, and crucial for satellite communication, point-to-point wireless links, and radar systems.

Infrared

shorter wavelengths than microwaves and invisible to the human eye, used in remote controls, short-range wireless communication, and data transmission between devices like smartphones, laptops, and other peripherals.

1. Radio Waves
2. Microwaves
3. Infrared

UNGUIDED MEDIA (3)

1. Repeater
2. Hub
3. Bridge
4. Switch
5. Router

NETWORK DEVICES (5)

Repeater

\
A ___ operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted to extend the length to which the signal can be transmitted over the same network. An important point to be noted about ___ is that they not only amplify the signal but also regenerate it. When the signal becomes weak, they copy it bit by bit and regenerate it at its star topology connectors connecting following the original strength. It is a 2-port device.

Hub

\
A ___ is a basically multi-port repeater. A --- connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. ___ cannot filter data, so data packets are sent to all connected devices.  In other words, the collision domain of all hosts connected through ___ remains one.  Also, they do not have the intelligence to find out the best path for data packets which leads to inefficiencies and wastage.

Bridge

\
A ___ operates at the data link layer. A ___ is a repeater, which adds on the functionality of filtering content by reading the MAC addresses of the source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device.

Switch

\
A ____ is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance. A ____ is a data link layer device. The ____ can perform error checking before forwarding data, which makes it very efficient as it does not forward packets that have errors and forward good packets selectively to the correct port only.  In other words, the ____ divides the collision domain of hosts, but the broadcast domain remains the same.

Router

A ___ is a device like a switch that routes data packets based on their IP addresses. The ___ is mainly a Network Layer device. ___ normally connect LANs and WANs and have a dynamically updating routing table based on which they make decisions on routing the data packets. The ___ divides the broadcast domains of hosts connected through it.

1. Point to Point Topology
2. **Mesh Topology**
3. Star Topology
4. **Bus Topology**
5. Tree Topology
6. Hybrid Topology

COMPUTER NETWORK TOPOLOGY

Point to Point Topology

\
works on the functionality of the sender and receiver. It is the simplest communication between two nodes, in which one is the sender and the other one is the receiver. ____ provides high bandwidth.

**Mesh Topology**

every device is connected to another device via a particular channel. This design creates a redundant and highly reliable network structure. Information can take multiple paths to reach its destination, enhancing fault tolerance and minimizing disruptions. While offering robustness, ____ topology can require more cables and configuration complexity compared to other network layouts.

Star Topology

all the devices are connected to a single hub through a cable. This hub is the central node and all other nodes are connected to the central node. The hub can be passive in nature i.e., not an intelligent hub such as broadcasting devices, at the same time the hub can be intelligent known as an active hub. Active hubs have repeaters in them. Coaxial cables or RJ-45 cables are used to connect the computers. 

**Bus Topology**

a network type in which every computer and network device is connected to a single cable. It is bi-directional. It is a multi-point connection and a non-robust topology because if the backbone fails the topology crashes.

**Ring Topology**

it forms a ring connecting devices with exactly two neighboring devices. A number of repeaters are used for ____ topology with a large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.

Tree Topology

the variation of the Star topology. This topology has a hierarchical flow of data. It features a hierarchical structure resembling a tree, with multiple star-configured networks connected to a central bus backbone. This design allows for the expansion of the network by adding more star-configured networks, while maintaining a central point for control and management.

Hybrid Topology

the combination of all the various types of topologies we have studied above. ____ Topology is used when the nodes are free to take any form. It means these can be individuals such as Ring or Star topology or can be a combination of various types of topologies seen above. Each individual topology uses the protocol that has been discussed earlier.

1. PAN
2. LAN
3. WAN
4. MAN
5. CAN

TYPES OF NETWORK

**PAN** -  A *Personal Area Network (PAN)*

\
is a small-scale network that connects devices within a limited range, typically within a person's personal workspace or immediate vicinity. 

**LAN** - A *Local Area Network (LAN)*

s a network of connected devices within a small area like a building or home. It's used to share resources like printers, files, and internet connections locally.

**WAN** - A *Wide Area Network (WAN)*

connects large geographic areas, linking multiple LANs together. The internet is a prime example, uniting global computers and networks.

**MAN** - A *Metropolitan Area Network (MAN)*

is bigger than a LAN but smaller than a WAN, connecting multiple LANs within a city. It offers fast connectivity for organizations with multiple city locations.

**CAN** - A *Campus Area Network (CAN)*

spans a university or corporate campus. It's bigger than a LAN but smaller than a MAN, enabling effective communication and resource sharing within the campus.

**OSI MODEL**

OSI stands for *Open Systems Interconnection*.

It was developed by ISO – ‘International Organization for Standardization‘, in 1984. It is a 7-layer architecture with each layer having specific functionality to perform. All these 7 layers work collaboratively to transmit the data from one person to another across the globe.

Layer 1 - Physical Layer

The lowest layer of the OSI reference model is the ____ layer. It is responsible for the actual physical connection between the devices. The ____ layer contains information in the form of bits. It is responsible for transmitting individual bits from one node to the next. When receiving data, this layer will get the signal received and convert it into 0s and 1s and send them to the Data Link layer, which will put the frame back together.

Layer 2 - Data Link Layer (DLL)

The____ layer is responsible for the node-to-node delivery of the message. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. When a packet arrives in a network, it is the responsibility of the ____ to transmit it to the Host using its MAC address.

Layer 3 - Network Layer

The ____ layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender & receiver’s IP addresses are placed in the header by the ____ layer.

Layer 4 - Transport Layer

The ____ layer provides services to the application layer and takes services from the network layer. The data in the ____ layer is referred to as Segments. It is responsible for the End to End Delivery of the complete message. The ____ layer also provides the acknowledgment of the successful data transmission and re-transmits the data if an error is found.

Layer 5 - Session Layer

This layer is responsible for the establishment of connection, maintenance of sessions, and authentication, and also ensures security.

Layer 6 - Presentation Layer

The ____ layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network.

Layer 7 - Application Layer

At the very top of the OSI Reference Model stack of layers, we find the ____ layer which is implemented by the network applications. These applications produce the data, which has to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user.

Voice network

 a network that transmits only telephone signals (essentially xtinct)

Data network

 a network that transmits voice and computer data (replacing voice networks).

Data communications

the transfer of digital or analog data using digital or analog signals

Telecommunications

the study of telephones and the systems that transmit telephone signals (becoming simply data communications) 

Network management

the design, installation, and support of a network, including its hardware and software

Network cloud

 a network (local or remote) that contains software, applications, and/or data.

Microcomputer-to-local area network

• Highly common throughout business and academic environments, and now homes Typically a medium- to high-speed connection

• Computer (device) requires a NIC (network interface card)

• NIC connects to a hub-like device (switch)

Microcomputer-to-Internet

• Popular with home users and small businesses

• For some, a dial-up modem is used to connect user’s microcomputer to an Internet service provider

• Technologies such as DSL and cable modems are quickly replacing dial-up modems

Local area network-to-local area network

• Found in systems that have two or more LANs and a need for them to intercommunicate

• A bridge-like device (such as a switch) is typically used to interconnect LANs 

• Switch can filter frames

Personal area network-to-workstation

• Interconnects wireless devices such as PDAs, laptops and notebooks, and music playback devices

• Used over short distances such as a few meters

Local area network-to-metropolitan area network

• Used to interconnect companies (usually their local area networks) to networks that encompass a city

• High-speed networks with redundant circuits

• Metro Ethernet is latest form of metropolitan LAN

Local area network-to-wide area network

• One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network)

• A router is the typical device that performs LAN to WAN connections

• Routers are more complex devices than switches

Wide area network-to-wide area network 

• High-speed routers and switches are used to connect one wide area network to another

• Thousands of wide area networks across North America, many interconnected via these routers and switches

Sensor-to-local area network

• Not all local area networks deal with microcomputer workstations

• Often found in industrial and laboratory environments

• Assembly lines and robotic controls depend heavily on sensor-based local area networks

Satellite and microwave

• Typically long distance wireless connections

• Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services

• Typically expensive services but many companies offer competitive services and rates 

• Newer shorter-distance services such as WiMa

Cell phones

• Constantly expanding market across the U.S. and world

• Third generation services available in many areas and under many types of plans with fourth generation services starting to appear

• Latest generation includes higher speed data transfers (100s to 1000s of kilobits per second) 

Computer terminal / microcomputer-to-mainframe

• Predominant form in the 1960s and 1970s

• Still used in many types of businesses for data entry and data retrieval

• Few dumb terminals left today – most are microcomputers with terminal emulation card, a web browser and web interface, Telnet software, or a thin client 

NETWORK ARCHITECTURES

• A reference model that describes the layers of hardware and software necessary to transmit data between two points or for multiple devices / applications to interoperate

• Reference models are necessary to increase likelihood that different components from different manufacturers will converse

• Two models to learn: TCP/IP protocol suite and OSI model

THE TCP/IP PROTOCOL SUITE

• Application layer

• Where the application using the network resides

• Common network applications include web browsing, e-mail, file transfers, and remote logins

Transport layer

Performs a series of miscellaneous functions (at the end-points of the connection) necessary for presenting the data package properly to the sender or receiver

Network (Internet or internetwork or IP) layer

• Responsible for creating, maintaining and ending network connections

• Transfers data packet from node to node (e.g. router to router) within network

Network access (data link) layer

Responsible for taking the data and transforming it into a frame with header, control and address information, and error detection code, then transmitting it between the workstation and the network

Physical layer

• Handles the transmission of bits over a communications channel

• Includes voltage levels, connectors, media choice, modulation techniques

OSI MODEL

In 1984, the International Organization for Standardization (ISO) developed the Open Systems Interconnection (OSI) Reference Model to describe how information is transferred from one networking component to another, from the point when a user enters information using a keyboard and mouse to when that information is converted to electrical or light signals transferred along a piece of wire (or radio waves transferred through the air). 

• Defines the process for connecting two layers together, promoting interoperability between vendors.

• Separates complex functions into simpler components.

• Allows vendors to compartmentalize their design efforts to fit a modular design, which eases implementation and simplifies troubleshooting.

• Provides a teaching tool to help network administrators and students alike understand the communication process used between network components. 

LAYERS OF OSI MODELS

Layer 7, the application layer,

provides an interface for the end user operating a device connected to a network. This layer is what the user sees, in terms of loading an application (such as Web browser or e-mail); that is, this application layer is the data the user views while using these applications. 

Examples of application layer functionality include:

• Support for file transfers

• Ability to print on a network

• Electronic mail • Electronic messaging

• Browsing the World Wide Web