SLO # 5: Network Communication and Protocols�5.1 Introduction to Computer Networks �Adapted by: Younus Bashir

Define a computer network;�Cognitive level: Knowledge�

Student Learning outcome # 5.1.1

Networks

A computer network is an interconnection between two or more computers and/or other network devices so that they can communicate with each other to share network resources (both hardware and software).

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OR

A network is a collection of computers or other devices called nodes that communicate with each other on a shared network medium.

Applications of Communication & Computer Network

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Computer systems and peripherals are connected to form a network. They provide numerous advantages:

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• Resource sharing such as printers and storage devices
• Exchange of information by means of e-Mails and FTP
• Information sharing by using Web or Internet
• Interaction with other users using dynamic web pages
• IP phones
• Video conferences
• Parallel computing
• Instant messaging

Recalling..

1- What could be the benefits of using networks in offices?

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Differentiate among different types of networks depending upon coverage area and use: �a. nano network �b. Body Area Network (BAN) �c. Personal Area Network (PAN) �d. Near-me-Area Network (NAN) �e. Local Area Network (LAN) �f. Wide Area Network (WAN) �g. Metropolitan Area Network (MAN) �h. Internet Area Network (IAN) �i. Interplanetary Internet (IPN);�Cognitive level: Understanding�

Student Learning outcome # 5.1.2

1. Nano network

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Nano-network is a communication network at the Nano-scale between Nano-devices. Nano-devices face certain challenges in functionalities, because of limitations in their processing capabilities and power management. Hence, these devices are expected to perform simple tasks, which require different and novel approaches.

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By the arrival of Internet of Things (IoT) the use of the Internet has transformed, where various types of objects, sensors and devices can interact making our future networks connect nearly everything from traditional network devices to people.

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b. Body Area Network (BAN)

A Body Area Network (BAN) is a short-range wireless network comprised of devices positioned in, on, and around the body. It provides data communication over short distances, limited to ranges of just a few meters. Figure 1 below illustrates the basic concept.

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This new, inherently personal type of network uses wearable and implanted electronic circuits. It implements highly useful functions and capabilities in convenient, *unobtrusive configurations that operate at very low power and deliver superlative security.

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* unobtrusive to describe something that doesn't attract much attention

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c. Personal Area Network (PAN)

The smallest and most basic type of network, a PAN is made up of a wireless modem, a computer or two, phones, printers, tablets, etc., and revolves around one person in one building. These types of networks are typically found in small offices or residences, and are managed by one person or organization from a single device.

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This type of network provides great flexibility. For example,

it allows you to:

• Send a document to the printer in the office upstairs while you are sitting on the couch with your laptop.
• Upload a photo from your cell phone to your desktop computer.
• Watch movies from an online streaming service to your TV.

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d. Near-me-Area Network (NAN)

A near-me area network (NAN) is a logical communication network that focuses on communication among wireless devices in close proximity.

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Unlike local area networks (LANs), in which the devices are in the same network segment and share the same broadcast domain, the devices in a NAN can belong to different proprietary network infrastructures (for example, different mobile carriers).

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So, even though two devices are geographically close, the communication path between them might, in fact, traverse a long distance, going from a LAN, through the Internet, and to another LAN. NAN applications focus on two-way communications among people within a certain proximity to each other, but don't generally concern themselves with those people’s exact locations.

d. Near-me-Area Network (NAN)

A near-me area network (NAN) is a logical communication network that focuses on communication among wireless devices in close proximity.

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Unlike local area networks (LANs), in which the devices are in the same network segment and share the same broadcast domain, the devices in a NAN can belong to different proprietary network infrastructures (for example, different mobile carriers).

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So, even though two devices are geographically close, the communication path between them might, in fact, traverse a long distance, going from a LAN, through the Internet, and to another LAN. NAN applications focus on two-way communications among people within a certain proximity to each other, but don't generally concern themselves with those people’s exact locations.

Carol just lost her son in the street, so she sends out his picture, which is stored in her mobile device, to passers-by to see if they can find him.

Recalling..

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1- Where we can use the following networks specifically:

1. Nano networks.
2. Body area networks
3. Personal Area networks
4. Near-me area networks

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�e. Local Area Network (LAN)

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 LANs connect groups of computers and low-voltage devices together across short distances (within a building or between a group of two or three buildings in close proximity to each other) to share information and resources. Enterprises typically manage and maintain LANs.

Using routers, LANs can connect to wide area networks

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LANs are typically used for single sites where people need to share resources among themselves but not with the rest of the outside world. Think of an office building where everybody should be able to access files on a central server or be able to print a document to one or more central printers.

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e. Local Area Network (LAN)

e. Local Area Network (LAN)

g. Metropolitan Area Network (MAN)

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A metropolitan area network, or MAN, consists of a computer network across an entire city, college campus or small region. A MAN is larger than a LAN, which is typically limited to a single building or site. Depending on the configuration, this type of network can cover an area from several miles to tens of miles.

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A MAN is often used to connect several LANs together to form a bigger network. When this type of network is specifically designed for a college campus, it is sometimes referred to as a campus area network, or CAN.

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f. Wide Area Network (WAN) �

Slightly more complex than a LAN, a WAN connects computers together across longer physical distances. This allows computers and low-voltage devices to be remotely connected to each other over one large network to communicate even when they’re miles apart.

The Internet is the most basic example of a WAN, connecting all computers together around the world. Because of a WAN’s vast reach, it is typically owned and maintained by multiple administrators or the public.

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f. Wide Area Network (WAN)

Recalling..

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2- Where we can use the following networks specifically:

1. LAN.
2. MAN
3. WAN

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h. Internet Area Network (IAN)

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An Internet area network (IAN) is a concept for a communications network that connects voice and data endpoints within a cloud environment over IP, replacing an existing local area network (LAN), wide area network (WAN) or the public switched telephone network (PSTN).

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Unlike a LAN and WAN, the IAN eliminates a geographic profile for the network entirely because the applications and communications services have become virtualized. Endpoints need only be connected over a broadband connection to the Internet.

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Examples: Emails

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�i. Interplanetary Internet (IPN);

Interplanetary Internet that will connect us to probes and human space travelers, and allow more information to be sent back to Earth.

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The interplanetary Internet is a conceived computer network in space, consisting of a set of network nodes that can communicate with each other.

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If we ever want to find out more about other planets, we will need a better communication system for future space missions.

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How will we communicate with these distant travelers? Scientists, engineers and programmers are already working to develop an interplanetary Internet�

The way the Internet allows us to visit foreign lands without leaving our desks.

Recalling..

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3- Where we can use the following networks specifically:

1. IAN.
2. Interplanetary Area network

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Describe basic network components, i.e. sender, message, medium, protocol, receiver;�Cognitive level: Understanding�

Student Learning outcome # 5.1.3

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Basic Network Communication components

Data communication is the process of transferring information from one point to another in a networking environment. Network communication consists of five basic components, as shown

• Sender
• Message
• Medium
• Protocol
• Receiver

Basic Network Communication components

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1-Sender

Sender, also called transmitter is a computer/device that sends the message (data or information) from source to destination in a communication network. It may be a computer, workstation, cell phone or camera. The sender device converts the electrical signal into a form that is suitable for transmission over the communication network.

Basic Network Communication components

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2- Message

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

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3- Medium

Medium is the path through which message travels from source to destination. Medium can be wired, for example telephone cable, coaxial cable and fiber optics. It can also be wireless for example bluetooth, Wi-Fi, microwave, radio wave and satellite.

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Basic Network Communication components

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4- Receiver

Receiver is the device which receives transmitted message. It can be a computer, workstation telephone handset or television set. The data received from transmission medium may not be in proper form to be accepted to the receiver and it must be converted to appropriate form before it is received.

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5- Protocol

A protocol is a set of rules that governs data communications. It represents an agreement between the communicating devices. Without a protocol, two devices are connected but may not communicating with each other.

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Discuss the role of the four data communication devices, i.e. hub, switch, router and gateway;�Cognitive level: Understanding�

Student Learning outcome # 5.1.4

Data communication Devices

A device that is used in telecommunication systems for transmission data from one location to another location is known as communication device.

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Commonly used communication devices can be classified into

hub, switches, routers and gateways.

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Data communication Devices

1- Switch

A switch or network switch (also known as hub) is a small hardware like a box, that filters and forwards packets between LAN segments.

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A switch inspects data packets as they are received, determines the source and destination device of packet and forwards them appropriately.

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It has small level of intelligence, in that it can open a message, check the IP address and direct the message packets to destination.

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Switch

A packet is a basic unit of communication over a computer network.

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When data is transmitted, it is broken down into packets which reassembled to the original form once they reach the destination.

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Switches allow computers to communicate directly with one another in a smooth and efficient manner.

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It operates on the data link layer (Layer 2)

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Data communication Devices

2- Hub

A hub, also called a network hub, is a common connection point for devices in a network.

Hubs are devices commonly used to connect segments of a LAN.

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The hub contains multiple ports, there is no intelligence or circuitry in it. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

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Switch VS HUB

Data communication Devices

3- Router

A router is a communication device which is used to connect two or more networks. Today, most of the networks are connected to internet. When the computer is sending data to another computer on the internet, router receives the data packets, looks for the remote computer address and forwards the data packets by selecting the best path-way based on network traffic. Many routers take part in transmitting the data packets from one location to another.

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Data communication Devices

4- Gateway

It is device that is used to connect a network to another network that uses different protocols. If we have to link different kinds of networks, such as a network of IBM mainframe computers and a network of PCs, we might have to use a gateway. Gateways change the format of the data packets but not the contents of the message, the format of the data packets but not the contents of the message, to make it confirm to the application program of the remote computer.

Differentiate between guided and unguided media and their types, i.e. �a. guided media (telephone cable, twisted pair cable, coaxial cable and fibre optic cable) ��b. unguided media (microwave transmission and satellite communication);�Cognitive level: Understanding�

Student Learning outcome # 5.1.5

Communication Media

In network communication system, communication media are the links that provide paths for communicating devices. Communication media is used to transmit data from one network device(also called a node) to another.

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There are two main categories of communication media

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• Guided Communication Media
• Unguided Communication Media

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Telephone

Cable

Satellite

Communication Media

(a) Guided Communication Media

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• It is also called physical or bounded communication media.
• Guided media, which are those that provide a conduit from one device to another.
• A signal travelling along any of these media is directed and contained by the physical limits of the medium. 
• It uses cables that guide the data signals along a specific path.
• The following are some important guided media.

(i) Telephone cable

(ii) Twisted pair cable

(iii) Coaxial cable

(iv) Fibre optic cable

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Communication Media

(a) Guided Communication Media

• Telephone cable
• Standard telephone cable is widely used as communication lines. Telephone lines are particularly useful to the user of data communication because the complex network of lines that has already been established allows data to be transmitted to any location in the world.

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• The disadvantage of telephone line is that transmission speed is very slow. Therefore, its use of data communication is slowly declining.

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Communication Media

(a) Guided Communication Media

(ii) Twisted pair cable

• Twisted pair cables are twisted together in pairs.
• A twisted pair consists of two conductors(normally copper), each with its own plastic insulation, twisted together.
• This cable is the most commonly used and is cheaper than others. It is lightweight, cheap, can be installed easily, and they support many different types of network
• Cables with a shield are called shield twisted pair(STP) and without shields are called Unshielded twisted pair.

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Communication Media

(a) Guided Communication Media

(ii) Twisted pair cable

Advantages:

• Installation is easy
• Flexible
• Cheap
• It has high speed capacity,
• 100 meter limit

Disadvantages:

• Bandwidth is low when compared with Coaxial Cable.
• Difficult to manufacture
• Eliminates crosstalk

Applications

• Local Area Network, such as 10Base-T and 100Base-T.
• In telephone lines to provide voice and data channels

Communication Media

(a) Guided Communication Media

(iii) Coaxial cable

• Coaxial is called by this name because it contains two conductors that are parallel to each other.
• Copper is used in this as centre conductor.
• It is surrounded by PVC installation, a sheath.
• Outer metallic wrapping is used as a shield against noise and as the second conductor which completes the circuit.
• The outermost part is the plastic cover which protects the whole cable.
• It is mainly used for long distance transmission.

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Communication Media

(a) Guided Communication Media

(iii) Coaxial cable

Advantages:

• Bandwidth is high, without distortion.
• Used in long distance telephone lines.
• Transmits digital signals at a very high rate of 10Mbps.
• Much higher noise immunity
• Coaxial cable can have been led under the ocean.

Disadvantages:

• Single cable failure can fail the entire network.
• Difficult to install and expensive when compared with twisted pair.

Applications

• Cable TV networks also use coaxial cables.
•  Analog telephone networks
• In traditional Ethernet LANs

Communication Media

(a) Guided Communication Media

(iv) Fibre optic cable

• It is new technology that is replacing the conventional cable in communication systems.
• A fibre-optic cable is made of glass or plastic and transmits signals in the form of light.
• Fibre optic is smooth hair-thin strands of transparent material that transmits light waves at high speed.
• Optical fibres use reflection to guide light through a channel.

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Communication Media

(a) Guided Communication Media

(iii) Fibre optics

Advantages:

• Higher bandwidth
• Immunity to electromagnetic interference
• Resistance to corrosive materials
• Light weight
• Greater immunity to noise and distortion.

Disadvantages:

• Installation and maintenance
• Unidirectional light propagation
• High Cost

Applications

• Often found in backbone networks because its wide bandwidth is cost-effective.
• Some cable TV companies use a combination of optical fibre and coaxial cable.
• Local-area Networks such as 100Base-FX network and 1000Base-X.

Communication Media

(a) Unguided Communication Media

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• It is also called unbounded communication media.
• In this type of communication media transmission takes place through open air.
• Unguided medium transport electromagnetic waves without using a physical conductor.
• They are not guided through any specific path.
• Signals are normally broadcast through free space and thus are available to anyone who has a device capable of receiving them.
• The following are important unguided media.

(i) Microwave transmission.

(ii) Communication Satellites.

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Communication Media

(a) Unguided Communication Media

• Microwave transmission.
• Microwave transmission signals travel through open space much like radio signals.
• Microwave systems transmit information with transmitters which are normally installed on high buildings, mountains tops o high towers.
• Long distance microwave channels consist of a series of rely stations(boosters) spaced approximately 30 miles apart.
• Two stations must be within sight of one another.
• Electromagnetic waves having frequencies between 1 and 300 GHz are called micro waves. Micro waves are unidirectional.

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Communication Media

(a) Guided Communication Media

(iii) Microwave stations

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Advantages:

• Used for long distance telephone communication
• Carries 1000's of voice channels at the same time

Disadvantages:

• It is very costly
• Line of sight is needed.

Applications

• They are used in cellular phones, satellite networks and wireless LANs.
• They are very useful when unicast(one-to-one) communication is needed

Communication Media

(a) Unguided Communication Media

(ii) Communication Satellites

• Satellite is a rely station positioned approximately 22,000 to 36000 miles above the earth.
• It orbits around the earth with exactly the same speed as rotation speed of earth.
• Earth stations beam signals to satellite, the satellite amplifies and re transmits the signals to another earth station.
• The satellites are launched either by rockets or space shuttles carry them.

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Communication Media

(a) Guided Communication Media

(iii) Satellites

Advantages:

• Ideal for long distance communication
• Transmission allows large amount of data to be sent long distance at rapid speeds.

Disadvantages:

• Satellite manufacturing and launching is very expensive
• Transmission highly depends on whether conditions, it can go down in bad weather

Compare three modes of data transmission, i.e. simplex, half-duplex and full-duplex;�Cognitive level: Understanding�

Student Learning outcome # 5.1.6

Data transmission Modes

Transmission mode means transferring of data between two devices. It is also known as communication mode.

There are three types of transmission mode:-

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

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Data transmission Modes

1. Simplex Mode

In Simplex mode, 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.

The simplex mode can use the entire capacity of the channel to send data in one direction e.g data being sent to an electronic notice board found in train stations.

Examples:

• Keyboard and traditional monitors.
• Radio and television broad casting.

Data transmission Modes

2) Half-duplex mode

In half-duplex modes, the communication takes place in both the directions but not at the same time.

When one device is sending, the other can only receive, and vice versa.

The half-duplex mode is used in cases where there is no need for communication in both direction at the same time.

The entire capacity of the channel can be utilized for each direction.

Examples:

• Walkie-talkies.
• Transaction oriented systems.

Data transmission Modes

3) Full-duplex mode

• In full-duplex mode, both stations can transmit and receive simultaneously. In full-duplex mode, signals going in one direction share the capacity of the link with signals going in other direction. For example two or more computers connected to a network device such as switch.
• Full-duplex mode is used when communication in both direction is required all the time. 

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Examples:

• Telephone network.

Differentiate between two types of transmission, i.e. serial and parallel;�Cognitive level: Understanding�

Student Learning outcome # 5.1.7

Difference Between Serial and Parallel Transmission

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There are two methods are used for transferring data between computers which are given below: Serial Transmission, and Parallel Transmission.

Serial Transmission:�In Serial Transmission, data-bit flows from one computer to another computer in bi-direction. In this transmission one bit flows at one clock pulse. In Serial Transmission, 8 bits are transferred at a time having a start and stop bit.

Serial Transmission has two subclasses synchronous and asynchronous.

Advantages

• It is cost-effective
• It is appropriate for long-distance communication.
• More reliable

Disadvantage

• Data transmission rate is low.
• Throughput relies on the bit rate.

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Parallel Transmission:�In Parallel Transmission, many bits are flow together simultaneously from one computer to another computer. Parallel Transmission is faster than serial transmission to transmit the bits. Parallel transmission is used for short distance.

Advantages

• Transmits data at a higher speed.
• Suits better for short-distance communication.
• Set of bits are transferred simultaneously.

Disadvantage

• It is a costly transmission system.
• In order to transmit the data over long ranges, the thickness of the wire has to be increased to diminish signal degradation.
• There are multiple communication channels required.

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Differentiate between synchronous and asynchronous transmission of data;�Cognitive level: Understanding�

Student Learning outcome # 5.1.8

Asynchronous Transmission and synchronous transmission

Asynchronous and synchronous transmission are the two different methods which are used for transmitting characters between components within a computer or from computer to other devices such as printer, modem etc.

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Synchronous Transmission

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• In this method two communicating devices are synchronized and they continue to send characters in order to remain synchronized, even if there is no data to be transmitted.
• A special “idle” character is sent when there is no data for transmission.
• It sends data as one long bit stream or block of data and each bit is send one after the other.
• The receiver reconstructs the sent information in bytes.
• Receiving device acquires the data until a special ending character is identified.
• In synchronous transmission, there is no gap present between data.

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Synchronous Transmission

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• It provides real-time communication between connected devices. Chat Rooms, Video Conferencing, telephonic conversations.
• The voice-band, broad-band channels and devices in network communication links are usually used in the synchronous transmission modes as it provides a faster speed up to 1200 bps.

Asynchronous Transmission

• The computer devices can exchange information at their own rate, slow or fast.
• It transmits the data in a continuous stream of bytes.
• In general, the size of a character sent is 8 bits to which a parity bit is added, i.e. a start and a stop bit
• These bits provides timing (synchronization) for the connection between the sender and the receiver.
• The start bit tells the receiver that a character is coming and stop bit indicates that the transmission of character has ended.
• This type of transmission is ideal for slow-speed communication when gaps may occur during transmission.

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Asynchronous Transmission

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• Example of asynchronous transmission is keyboard.
• It is simple, fast, economical and does not require a 2-way communication. Letters, emails, forums, televisions and radios are some of the examples of Asynchronous Transmission.

Analyze the both images.

What did you find?

Compare the types of network topologies, (i.e. star, ring, bus, mesh and tree) with the help of diagrams;�Cognitive level: Understanding�

Student Learning outcome # 5.1.9

Network Topologies

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The arrangement of network nodes and connections between them is called the network’s topology. A node represents any device on the network.

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Topology is simply a map of the layout of nodes and connections in the network.

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These following topologies are very popular, namely

1. Star topology
2. Ring topology
3. Bus topology
4. Mesh topology
5. Tree topology

Network Topologies

1. Star topology

In star 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.

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Features of star topology

• It is suitable for both small and large networks.
• Easy to install and wire.
• Easy to detect and remove faults.
• Failure of cable does not stop functioning of the entire network.

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Network Topologies

1. Star topology

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Limitations

• Failure of the hub causes the entire network to go down.
• Expensive topology to implement.
• Lengthy cable with a hub is required to install star topology

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Network Topologies

b) Ring topology

Ring topology is shaped just like a ring. It is made up of an unbroken circle of network nodes.

In a ring network, packets of data travel from one device to the next until they reach their destination.

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Features of ring topology

• Each node is directly connected to the ring.
• Easy to install and wire.
• Data on the network flows in one direction.
• Not costly to implement.

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Network Topologies

b) Ring topology

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Limitations

• If the ring is broken at any point, the entire network stops functioning.
• Slower than other network topologies.
• Adding or deleting the computers disturbs the network activity.
• Adding or deleting the computers disturbs the network activity.

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Network Topologies

c) Bus topology

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

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Features of bus topology

• Suitable for a small network.
• Easy to connect a computer or a peripheral device to the network.
• 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.

• Terminator is a device that is attached to

ground.

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Network Topologies

c) Bus topology

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Limitations

• Cables fails then whole network fails.
• Difficult to identify the problem if the entire network goes down.
• Not suitable for large network, cable has limited length
• If network traffic is heavy or nodes are more the performance of the network decreases.
• It is slower than the ring topology.

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Network Topologies

d) Mesh topology

It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. 

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Features of Mesh topology

• Most reliable network topology.
• Can manage high traffic.
• Fault is diagnosed easily.
• Each connection can carry its own data load.

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Network Topologies

d) Mesh topology

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Limitations

• Installation and configuration is difficult.
• Cabling cost is more.
• Bulk wiring is required.
• Data can be routed around failed computers or busy ones.

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Network Topologies

e) Tree topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

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Features of Mesh topology

• Expansion of nodes is possible and easy.
• Easily managed and maintained.
• Error detection is easily done.
• Ideal if workstations are located in groups.
• Used in Wide Area Network.

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Network Topologies

e) Tree topology

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Limitations

• Heavily cabled.
• Costly.
• If more nodes are added maintenance is difficult.
• Central hub fails, network fails.

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Network Topologies

f) Hybrid topology

It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).

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THANK YOU

Resources

Computer Science grade 11�National Book Foundation

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Communication Modes

�https://www.geeksforgeeks.org/transmission-modes-computer-networks/

Resources

Computer Science grade 11�National Book Foundation

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Types of network�https://www.belden.com/blog/smart-building/network-types

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https://study.com/academy/lesson/types-of-networks-lan-wan-wlan-man-san-pan-epn-vpn.html

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Internet area network

https://www.youtube.com/watch?v=5F8q4-exucw

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Communication media

https://www.studytonight.com/computer-networks/bounded-transmission-media

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Resources

Serial VS Parallel

https://techdifferences.com/difference-between-serial-and-parallel-transmission.html

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https://www.geeksforgeeks.org/difference-between-serial-and-parallel-transmission/

Network Topologies

https://www.studytonight.com/computer-networks/network-topology-types

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