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Components of IS (Information System)
Data
Information
Hardware
Software
Telecommunication/Networks
People/Peopleware
Data
raw facts
Information
processed data
Hardware
tangible part
Software
intangible part (ex. OS)
Telecommunication/Networks
internet/ARPANET
People/Peopleware
end users/programmers
DATA COMMUNICATION
the exchange of data between two devices via some forms of transmission medium such as a wire cable
COMPONENTS OF DATA COMMUNICATION
Message
Sender
Receiver
Transmission medium
Protocol
Message
It is the information to be communicated. Popular forms of information include text, pictures, audio, video etc.
Sender
It is the device which sends the data messages. It can be a computer, workstation, telephone handset etc.
Receiver
It is the device which receives the data messages. It can be a computer, workstation, telephone handset etc.
Transmission medium
It is the physical path by which a message travels from sender to receiver. Some examples include twisted-pair wire, coaxial cable, radio waves etc.
Protocol
It is a set of rules that governs the data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating.
SMTP (Simple Mail Transfer Protocol)
used for sending and receiving email messages over networks. It's the standard for email communication between clients and servers, defining their interaction.
HTTP (Hypertext Transfer Protocol)
used for transferring web pages and other resources on the World Wide Web. It defines how web clients (such as web browsers) request resources from web servers and how servers respond to those requests.
HTTPS (Hypertext Transfer Protocol Secure)
a secure version of HTTP, which adds a layer of encryption to protect data transmitted between a web client and a web server.
TCP/IP (Transmission Control Protocol/Internet Protocol)
a crucial internet protocol suite. It guides data packet handling, transmission, and routing among devices. TCP ensures reliable data transfer, and IP manages addressing and routing.
DATA REPRESENTATION
Text
Number
Images
Audio
Text
represented as a bit pattern, a sequence of bits.
Number
represented by bit patterns. However, a code such as ASCII is not used to represent numbers; the number is directly converted to a binary number to simplify mathematical operations.
Images
represented by bit patterns. In its simplest form, an image 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. Audio is by nature different from text, numbers, or images.
DATA FLOW
Simplex
Half-Duplex
Full-Duplex
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 full-duplex mode, signals going in one direction share the capacity of the link: with signals going in the other.
TYPES OF SIGNAL
Digital Signal
Analog Signal
Digital Signal
can have only a limited number of defined values. Although each value can be any number, it is as simple as 1 and 0.
Analog Signal
continuous and passes through or includes an infinite number of continuous values along its path. The curve representing the analog signal passes through an infinite number of points.
TYPES OF TRANSMISSION MEDIA
Guided Media
Unguided Media
Guided Media
It is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.
TYPES OF GUIDED MEDIA
Twisted Pair Cable
Coaxial Cable
Optical Fiber Cable
Twisted Pair Cable
It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media.
TYPES OF TWISTED PAIR CABLE
Unshielded Twisted Pair (UTP)
Shielded Twisted Pair (STP)
Unshielded Twisted Pair (UTP)
This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications.
Shielded Twisted Pair (STP)
This type of cable consists of a special jacket to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.
Coaxial Cable
It has an outer plastic covering containing 2 parallel conductors each having a separate insulated protection cover. It transmits information in two modes: Baseband mode (dedicated cable bandwidth) and Broadband mode (cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables.
Optical Fiber Cable
It uses the concept of reflection of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for transmission of large volumes of data.
Unguided Media
It is also referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals.
TYPES OF UNGUIDED MEDIA
Radio Waves
Microwaves
Infrared
Radio Waves
These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range: 3KHz (Kilohertz) – 1GHz (Gigahertz). AM and FM radios and cordless phones use it for transmission.
Microwaves
It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz – 300GHz (Gigahertz). These are majorly used for mobile phone communication and television distribution.
Infrared
Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. Frequency Range: 300GHz (Gigahertz) – 400THz (Terahertz). It is used in TV remotes, wireless mouse, keyboard, printer, etc.
NETWORK DEVICES
Repeater
Hub
Bridge
Switch
Router
Repeater
It operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. An important point to be noted about repeaters is that they do not amplify the signal. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength. It is a 2 port device.
Hub
It is basically a multiport repeater. It connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. It cannot filter data, so data packets are sent to all connected devices. In other words, the collision domain of all hosts connected through Hub 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
It operates at the data link layer. It is a repeater, which adds on the functionality of filtering content by reading the MAC addresses of 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
It 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. It is a data link layer device. It can perform error checking before forwarding data, that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only. In other words, it divides the collision domain of hosts, but the broadcast domain remains the same.
Router
It is a device like a switch that routes data packets based on their IP addresses. It is mainly a Network Layer device. It normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. It divide broadcast domains of hosts connected through it.
COMPUTER NETWORK TOPOLOGY
Point to Point Topology
Mesh Topology
Star Topology
Bus Topology
Ring Topology
Tree Topology
Hybrid 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. It provides high bandwidth.
Mesh Topology
each device is connected to every other device on the network through a dedicated point-to-point link. When we say dedicated it means that the link only carries data for the two connected devices only. Let's say we have n devices in the network then each device must be connected with (n-1) devices of the network.
Star Topology
each device in the network is connected to a central device called a hub. Unlike Mesh topology, this topology doesn’t allow direct communication between devices, a device must have to communicate through a hub. If one device wants to send data to other device, it has to first send the data to hub and then the hub transmit that data to the designated device.
Bus Topology
there is a main cable and all the devices are connected to this main cable through drop lines. There is a device called tap that connects the drop line to the main cable. Since all the data is transmitted over the main cable, there is a limit of drop lines and the distance a main cable can have.
Ring Topology
each device is connected with the two devices on either side of it. There are two dedicated point to point links a device has with the devices on either side of it. This structure forms a ring thus it is known as ring topology. If a device wants to send data to another device then it sends the data in one direction, each device in this topology has a repeater, if the received data is intended for other device then repeater forwards this data until the intended device receives it.
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
a type of network topology that uses two or more differing network topologies. These topologies can include a mix of bus topology, mesh topology, ring topology, star topology, and tree topology. The choice to use a hybrid topology over a standard topology depends on the needs of a business, school, or the users. The number of computers, their location, and desired network performance are all factors in the decision.
TYPES OF NETWORK
Computer network
PAN
LAN
MAN
CAN
Data network
Data communications
Telecommunications
Network management
Network cloud
Computer network
an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas.
PAN
a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices.
LAN
a network that is small in geographic size spanning a room, floor, building, or campus.
WAN
a large network that encompasses parts of states, multiple states, countries, and the world.
MAN
a network that serves an area of 1 to 30 miles, approximately the size of a typical city.
CAN
a network that spans multiple buildings on a business or school campus.
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.
COMMUNICATIONS NETWORKS - BASIC LAYOUTS
Microcomputer-to-local area network
Microcomputer-to-Internet
Local area network-to-local area network
Personal area network-to-workstation
Local area network-to-metropolitan area network
Local area network-to-wide area network
Wide area network-to-wide area network
Sensor-to-local area network
Satellite and microwave
Cell phones
Computer terminal / microcomputer-to-mainframe
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
Transport layer
Network (Internet or internetwork or IP) layer
Network access (data link) layer
Physical layer
Application layer (TCP/IP)
- Where the application using the network resides
- Common network applications include web browsing, e-mail, file transfers, and remote logins
Transport layer (TCP/IP)
- 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 (TCP/IP)
- 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 (TCP/IP)
- 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 (TCP/IP)
- 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
- 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).
LAYERS OF OSI MODEL
Layer 7 - THE APPLICATION LAYER
Layer 6 - THE PRESENTATION LAYER
Layer 5 - THE SESSION LAYER
Layer 4 - THE TRANSPORT LAYER
Layer 3 - THE NETWORK LAYER
Layer 2 - THE DATA LINK LAYER
Layer 1 - THE PHYSICAL LAYER
Layer 7 - THE APPLICATION LAYER (OSI)
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.
Layer 6 - THE PRESENTATION LAYER (OSI)
responsible for how an application formats the data to be sent out onto the network. The presentation layer basically allows an application to read (or understand) the message.
Layer 5 - THE SESSION LAYER (OSI)
provides various services, including tracking the number of bytes that each end of the session has acknowledged receiving from the other end of the session. This session layer allows applications functioning on devices to establish, manage, and terminate a dialog through a network.
Layer 4 - THE TRANSPORT LAYER (OSI)
offers end-to-end communication between end devices through a network. Depending on the application, the transport layer either offers reliable, connection-oriented or connectionless, best-effort communications.
Layer 3 - THE NETWORK LAYER (OSI)
provides an end-to-end logical addressing system so that a packet of data can be routed across several layer 2 networks (Ethernet, Token Ring, Frame Relay, etc.). Network layer addresses can also be referred to as logical addresses.
Layer 2 - THE DATA LINK LAYER (OSI)
provides node-to-node data transfer—a link between two directly connected nodes. It detects and possibly corrects errors that may occur in the physical layer. It, among other things, defines the protocol to establish and terminate a connection between two physically connected devices. It also defines the protocol for flow control between them.
Layer 1 - THE PHYSICAL LAYER (OSI)
defines connector and interface specifications, as well as the medium (cable) requirements. Electrical, mechanical, functional, and procedural specifications are provided for sending a bit stream on a computer network.
NETWORK INTERFACE CARDS
connect a device to the network. Ethernet NICs are used for a wired connection, whereas WLAN (Wireless Local Area Network) NICs are used for wireless. An end-user device may include one or both types of NICs. A network printer, for example, may only have an Ethernet NIC, and therefore, must connect to the network using an Ethernet cable. Other devices, such as tablets and smartphones, might only contain a WLAN NIC and must use a wireless connection.
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