Categories
Networking Tutorials

Types of Computer Network Explained in Easy Language

This tutorial explains the different types of computer network such as LAN, MAN, WAN, PAN, CAN, GAN, Internet, internet, Intranet, Extranet, VPN, Client/Server, Workgroup and HomeGroup in detail. Learn the different types of computer network including their definitions and characteristics in easy language.

What is a computer network?

A computer network is a group of two or more computers connected with each other for sharing resources and information. A simple computer network can be built only from two computers while a complex computer network can be built from several thousand computers.

Types of computer network

A computer network can be categorized based on geographical location and characteristic. Based on geographical location, computer networks are outlined below.

LAN (Local Area Network)

A LAN is a computer network which spans over a small geographical area such as home, building, office, etc. In LAN, computers are placed relatively close. Since computers are located within small distance, they do not need special devices and cables to connect with each other.

computer network type lan

MAN (Metropolitan area networks)



A MAN is a computer network which connects two or more LAN networks within same city. When due to distance connecting two LANs is not possible, MAN network is used. It is larger than LAN but smaller than WAN. It deploys special devices and cables to connect the LANs.

computer network type man

WAN (Wide Area Network)

WAN is a computer network which spans over a large geographical area such as state, region, country etc. WANs are typically used to connect two or more LANs or MANs which are located relatively very far from each other. To provide connectivity, this network uses special devices, cables and technologies.

computer network type wan

Above categorization (LAN, MAN and WAN) of computer network is purely based on geographical location. It has nothing to do with
the number of computers in each network. For example, if one computer is located in Delhi and other computer is located in Mumbai,
connecting these two computers is the example of WAN networking. Just like this, if a company starts a new branch office with 500 computers and all
these computers are installed within a building, this network will be considered as a LAN network.

There are three more types of computer network based on geographical location but they are rarely used to define the network. In real life you may skip these but if you preparing for job interview or for any networking exam, you should learn these also.

PAN (Pearson Area Network)

Same as LAN network, but it is limited to a specific person or location such as home network. This network is usually setup for sharing resources such as internet and printer within personal computers.

computer network type pan

CAN (Campus Area Network)

Same as MAN network, but it is limited to a university or an academy. This network is usually setup for educational activities such as classroom updates, practices labs, emails, exams, notifications, polls, etc.

computer network type

GAN (Global Area Networks)



Same as WAN network, but it covers unlimited geographical area. For example a company has an office in Delhi and another one Washington D.C.,
connecting these two offices will be considered as a GAN network. In other words, GAN is a computer network which connects two or more WANs. This network is increasingly gaining popularity as many companies are expending their working area beyond their native countries.

computer network type gan

So far, we have discussed the types of computer based on geographical location. In following section we will understand the types of computer network based
on characteristic.

Internet

This is the largest computer network ever created by mankind. It interconnects thousands of millions of computing devices including PCs, Laptops, Workstations, Server, Smartphones, tablets, TVs, Webcams, Environmental devices, Automobiles, Security cameras and many mores. According to a report published in January 2018, there were 2150 million end systems connected with the Internet. To connect these devices, a lot of technologies and infrastructure are used. Internet is open for everyone. Anyone can connect with it. Since anyone can connect with it, it is also considered as the most insecure network.

computer network type internet

internet

The internet sounds similar to Internet but it is different. The word Internet starts with capital I, while the word
internet begins with small i. Any group of network which is connected with external network through a gateway such as BGP is considered as internet. Usually this type of network is setup to provide the connectivity between two companies.

Intranet

Intranet is a computer network which is controlled and administered by a single entity such as company or organization. In Intranet, external users are not allowed to connect. Usually in this network, proper authorization is required to access any resources. Further each access is monitored and logged to ensure that only authorized users get access.

Extranet

An Extranet is an extended Intranet where external users are allowed to access a small portion of network. Normally this access is filtered and secured by several security implementations on both hardware and software levels.

VPN (Virtual Private Network)

VPN is the cost effective solution to utilize the goodies of Internet. Companies which can’t afford their own infrastructure for connectivity can use VPN. VPN provides a secure connection over the Internet. For example a company has two offices; one in Delhi and other in Mumbai. Now suppose, company can’t afford a dedicate line to connect these two offices. In this case company can use VPN to connect both offices. VPN creates a secure line over the Internet and uses it for data transmission.

computer network type vpn

Client/Server Network

In this network, a dedicate computer known as server provides sharing resources. All other computers know as clients are used to access the shared resources. This type of network is commonly used in company environment. It provides great security features but requires special hardware and software to setup.

computer network type server client

Workgroup Network

In this network, all computers are equal. Any computer can provide and access shared resources. This type of network is usually used in small office or home network.
It is easy to setup and does not require any special hardware and software. The downside of this network is that it provides very less security.

computer network type workgroup

That’s all for this tutorial. For any suggestion, feedback or comment about this tutorial, please mail me. I really love to listen from you. If you like this tutorial, please share it with friends.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

How Email Works Step by Step Explained

This tutorial explains how email works step by step in detail with examples including essential components of mail system such as UA, MSA, MTA, MDA and AA. Learn fundamentals and basic concepts of mail system along with how email travels from source to destination.

Essential components of mail system

In order to learn how email system works or how email travels from source to destination, we have to understand following essential components.

Email Client or Mail User Agent (UA)

An email client or user agent is a software or program which is used to compose and read the email. At sender side, it is used to compose and send the email. At receiver side, it is used to read and reply the received email. MS Outlook, MacOS Mail, /bin/mail, Alpine and Gmail are some examples of email client.

Mail Submission Agent (MSA)

MSA takes mail from user agent and deliver them to a mail transfer agent. MSA was developed later in email system. It was invented to reduce some burden from MTA.

If implemented, MSA sits between user agent and mail transfer agent. It secures connection between UA and MTA by implementing encryption and authentication. Besides this, it can perform a lot more tasks based on its configuration such as rewriting mail header and performing security checks.

Mail Delivery Agent (MDA)



MDA takes mail from MTA and deliver them to the message store. MDA does opposite of MSA. Just like MSA, it was also invented to reduce the burden from MTA. Since MDA deliver emails to local system, it is also known as LDA (local delivery agent). Same as MSA, several additional functionalities such as virus scanning and spam mail filtering can be configured in MDA.

MSA and MDA are the part of MTA. Whether they will be used or not depend several factors such as volume of emails and security requirement. But if they are configured in MTA, we have to configure the user agent to communication with them instead of MTA.

msa mta mda

Mail Transport agent (MTA)

MTA is the backbone of email system. It takes email from UA or MSA, understand recipient’s address and deliver it to its destination. MTA uses Simple Mail Transport Protocol (SMTP) for its operation.

Essential MTA operations are listed below.

Outgoing mail operation

  • Receive outgoing mail from UA and MSA
  • Understand recipient’s addresses
  • If require, rewrite addresses
  • Perform a DNS MX lookup to resolve the recipient’s address
  • If recipient is directly accessible, forward mail to MDA
  • If recipient is not directly accessible, forward mail to next responsible MTA

Incoming mail operation

  • Receive incoming mail from other MTA
  • Understand recipient’s addresses
  • If recipient belongs to it, perform virus scan and forward mail to MDA
  • If recipient does not belong to it, forward mail to next responsible MTA

Message stores

Message store is the location of recipient’s server or computer where messages are delivered by MDA. Depending on the setting, messages can be stored in several formats such mbox and Maildir.

The mbox format

In this format, all messages are stored in a single file. To separate messages from each other, a special form line is used.

The Maildir format

In this format, each message is stored in a separate file. This method is more convenient but it creates a lot of files.

Maildir or mbox format is convenient, if volume of mail is small. These methods are usually used in small office network or home network. In large network more advance method such as database is used to store the messages.

Access Agent (AA)



Access agent takes messages from message store and delivers them to email client or user agent in local device such as PC, laptop, tablet, smartphone, etc. Two protocols known as POP3 and IMAP are used by access agent to retrieve mail from message store.

POP3

POP3 is a one way protocol. It can only download messages in email client from message store. It does not tell message box what users do with downloaded messages. Since message store does not know what users do with downloaded messages, it keeps locally stored messages as they are or simply delete them once they are downloaded.

IMAP

IMAP is a two way protocol. Besides downloading messages from message store, it also updates message store about the action which user performs with downloaded messages. Since message store knows the action which user takes on downloaded messages, it automatically performs that action on locally stored messages to keep the exact copy of messages at both locations.

This protocol uses advance techniques to download messages in email client from message store. It only downloads the header of mail. It downloads contents and attachments of mail only when user reads the mail.

Difference between POP3 and IMAP

A user uses his laptop and smartphone to check mail. He downloaded all emails from message store in laptop. After downloading, he filtered and deleted unnecessary emails. If user is using POP3, he has to perform same filtration in message store and in smartphone again to keep the exact copy of emails in all locations. But if he is using IMAP, there is no need to repeat the same actions again in message store and in smartphone. IMAP will automatically sync user’s action across all devices.

Following figure shows IMAP and POP3 settings in Gmail.

imap and pop example

How email works

A user wants to send an email to several recipients, so he accesses an email client program and adds recipients in To, CC and BCC fields. He composes the email and click Send button.

Based on configuration, email client sends email to either MSA or MTA for further processing. If MSA is configured, email will be forwarded to it. If MSA is not configured, email will be forwarded to MTA directly.

If MSA is configured and mail is received, it rewrites the header and performs several essential checks based on its configuration. Once all defined checks are done, it forwards mail to MTA.

If MSA is not configured and mail is directly received, MTA performs all MSA’s tasks and checks the recipient’s addresses. If recipients are more than one, it makes a separate copy of email from original email for each recipient.

MTA performs a DNS lookup to figure out the recipient’s address. If recipient address is resolved, MTA packs email in envelop and forwards it to the MTA which is authorized to receive recipient’s mail.

At recipient’s MTA, if MDA is configured, received email will be forwarded to it. Based on configuration, MDA performs several security checks such as virus scanning and spam filtering. If MDA is not configured, MTA will perform all MDA’s tasks. Once pre-delivery checks are done, email is forwarded to message store.

Email remains in message store until it is downloaded by email client program. Once email is downloaded it will be available in inbox of recipient.

how email works step by step example

Parts of email

An email contains three separate parts; envelope, header and body.

Envelope

An email is wrapped in an envelope by first MTA. First MTA puts all necessary information such as delivery address, return address and failure address in envelope. Other MTAs use this information to forward or deliver the mail. An envelope determines where the email will be delivered or to whom it will be returned if it can’t be delivered.

Envelopes are internally used by MTAs to exchange mail between them. An envelope wrapped by first MTA is unwrapped by last MTA. An end user never sends and receives envelope with mail. Envelopes are invisible to users.

Header

Header keeps record of all information about email such as from which address it was sent, the date and time when it was sent, by which MTA it was received and forwarded and when it was delivered at destination. Email clients usually hide header from user while displaying email contents.

Body

Body contains the message text and attachments. Originally mail was developed for text messages. Over the time, it became so popular that a new standard known as MIME was developed to support several other formatting and encoding features.

MIME (Multipurpose Internet Mail Extensions) allows us to format and encode email text with more advance formatting technique such as HTML. Since MIME uses its own methods for formatting and encoding the mail text and attachment, email client doesn’t need to be running on same platform or using same operating system. Nearly all modern email clients support and use MIME standards.

That’s all for this tutorial. If you have any feedback, suggestion or comment about this tutorial, please mail me. If you like this tutorial, please share it friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Types of User account in Computer Network Explained

This tutorial explains user account types in computer network. Learn different types of user accounts such as system account, regular user account, guest user account, super user account, group account, local user account, remote user account, network user account and anonymous user account in detail.

Every user who uses the system should have an individual user account. Having a separate user account allows user to store his files securely and customize his user interface.

Types of user accounts

Regardless which operating system we use, it uses user accounts to authenticate, trace, log and monitor its services. When we install an operating system, it automatically creates some essential user accounts which allow us to access it just after the installation. During the installation, usually it creates four types of user account; system account, super user account, regular user account and guest user account.

System accounts

These accounts are used by different services running in operating system to access the system resources. Operating system uses these accounts to check whether a particular service which is requesting for system resources is allowed to access those resources or not. Usually services create necessary accounts on their own when they are installed. After installation, services use these accounts to access necessary resources. Unless you are a system or network administrator, you never need to know about these accounts.

Super user account



This user account has the highest privilege in operating system. In Windows, this user account is known as Administrator account. In Linux it is known as root account. Operating system allows this user account to perform all privileged tasks such as changing system files, installing new software, removing existing software, starting services, stopping services, creating new user accounts and deleting existing user accounts.

Regular user account

This user account has moderate privilege. This user account is not allowed to make any change in system files and properties. Operating system allows this user account to perform only the tasks that it is authorized to do such as creating files and folders, running applications, customizing environmental variables, etc.

Guest user account

This user account has the lowest privilege. It can’t make any change in any system files or properties. Usually this account is used to access the system for temporary tasks such as suffering internet, watching movies, playing games etc. In Windows, this account is automatically created during the installation. In Linux, if require, we have to create this account manually after the installation.

User account vs Group account

User account is an individual identity of a user while group account is the collective identity of all users those belong to a specific group. Grouping helps system administrators in managing system effectively. For example, in a company all the users of the development department may belong to a group called developers. Once group is created, administrator can create and configure several security rules and applications to ensure that only the users from developers group access the development department’s resources such as SQL server, Language API, source code compiler, etc.

user account vs group account

Group accounts are only used to manage the user accounts which are alike or require access to a particular resource. Unlike user account, group account does not have login capability. A user may belong to an individual group or multiple groups.

Local user account vs Network User account



User name and password of local user accounts are stored in local machine. Local user accounts are bound with physical machine. As discussed earlier, every operating system creates some user accounts during the installation. By default all these accounts are considered as local user accounts.

local user

User name and password of network user accounts are stored in a central machine usually known as server. Unlike local user accounts, network user accounts are not bound with any particular system. Based on configuration, a network user can login in a specific machine or any machine of network.

network user

Local user account and network user account both are used to access a fully featured operating system.

Remote service account

User name and password of these accounts are stored in remote machine. These accounts are used to remotely access a specific service or an application running in remote system. FTP accounts, email accounts, website accounts are some examples of the remote service accounts.

remote user

Anonymous user accounts

This account does not require a password to login. This account has the lowest privilege among all available accounts. Usually this account type is used to share data publicly through a service which normally requires login access.

anonymous user account

For example, a user account is required to download anything from FTP server. If an administrator wants to allow anyone to download the data stored in a particular folder at FTP server, he can configure an anonymous account and set its default location to this folder. Once anonymous account is enabled, users will be able to download all files and folders stored in this folder.

That’s all for this tutorial. If you have any suggestion or feedback about this tutorial, let me know. If you like this tutorial, please don’t forget to share it.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Network Topologies Explained with Examples

This tutorial explains network topologies (Bus, Star, Ring, Mesh, Point-to-point, Point-to-multipoint, and Hybrid) in detail with their advantages and disadvantages.

Network topology is the layout of a network. It consists of two parts; physical and logical. The physical part describes the physical layout of a network while the logical part describes how the data flows in that network. Both, physical and logical parts are also known as the physical topology and the logical topology.

Physical part (topology) + Logical part (topology) = Network topology

difference between logical topology and physical topology

Types of network topology

The popular types of network topology are; Bus, Star, Hybrid, Ring, Mesh, point-to-point, and point-to-multipoint. Let’s understand each of these types in detail.



Bus topology

In this topology, all computers connect through a single continuous coaxial cable. This cable is known as the backbone cable.
Both ends of the backbone cable are terminated through the terminators. To connect a computer to the backbone cable, a drop cable is used.
To connect the drop cable to the computer and backbone cable, the BNC plug and BNC T connector are used respectively.

The following image shows the bus topology.

bus topology

When a computer transmits data in this topology, all computers see that data over the wire, but only that computer accepts the data to which it is addressed. It is just like an announcement that is heard by all but answered only by the person to whom the announcement is made.

For example, if in the above network, PC-A sends data to the PC-C then all computers of the network receive this data but only the PC-C accepts it. The following image shows this process.

data transfer in bus topology

If PC-C replies, only the PC-A accepts the return data. The following image shows this process.

logical layout of bus topology

The following table lists the advantages and disadvantages of the bus topology.

Advantages Disadvantages
It is very simple to install. It is very difficult to troubleshoot.
It uses less cable than other topologies. It provides slow data transfer speed.
It is relatively inexpensive. A single fault can bring the entire network down.

This topology is no longer used. But there was a time when this topology used to be the first choice among the network administrators. The concept that this topology uses to transmit the data is also used in the other topologies.

Star topology



In this topology, all computers connect to a centralized networking device.
Usually, a networking switch or a Hub (in earlier days) is used as the centralized device.
Each computer in the network uses its own separate twisted pair cable to connect to the switch. Twisted pair cable uses RJ-45 connectors on both ends.

The following image shows an example of the star topology.

star topology

To transmit data, the star topology uses the same concept which the bus topology uses. It means,
if you build a network using the star topology, then that network will use the bus topology to transmit the data.

The following table lists the advantages and disadvantages of the star topology.

Advantages Disadvantages
It is easy to install. It uses more cables than other topologies.
Relocating of computers is easier than other topologies. If the centralized device fails, it brings the entire network down.
Since each computer uses its own separate cable, a fault in cable does affect other computers of the network. The total installation cost is higher than the other topologies.
Troubleshooting is relatively easy. Use the twisted pair cable which is prone to break.
It provides higher data transfer speed. Too many cables make the network messy.

In modern computer networks, the star topology is the king. Nearly all new network installations, including small home and office networks, use some form of the star topology.

Hybrid Topology

This topology is a mix of two or more topologies. For example, there are two networks; one is built from the star topology and another is built from the bus topology. If we connect both networks to build a single large network, the topology of the new network will be known as the hybrid topology.

You are not restricted to the bus and star topologies. You can combine any topology with another topology. In modern network implementations, the hybrid topology is mostly used to mix the wired network with the wireless network.

The following image shows an example of the hybrid network topology.

hybrid topology

Unlike a wired network, a wireless network does not use cables to connect computers. A wireless network uses radio spectrum to transmit data.

Ring topology

In this topology, all computers connect in a circle. Each computer directly connects to two other computers in the network. Data moves down a one-way path from one computer to another. When data signals pass from one computer to the next, each computer regenerates the signals. Since the signals are regenerated on each passing computer, the quality of the signals remains constant throughout the ring.

The following image shows a typical ring topology.

ring topology

The following table lists the advantages and disadvantages of the ring topology.

Advantages Disadvantages
It does not uses terminators. It uses more cables.
It is relatively easy to troubleshoot. It is too expensive.
Since data flows only in one direction, there is no collision in the network. A single break in the cable can bring the entire network down.

Like the bus topology, this topology is also no longer used in modern networks. This topology was originally developed by IBM to overcome the existing drawbacks of the bus topology.

Mesh Topology

In this topology, multiple paths exist between end devices. Based on paths, a mesh topology can be divided into two types; fully meshed and partially meshed. If a direct path exists from each end device to every other end devices in the network, it’s a fully meshed topology. If multiple paths exist between the end devices in the network, it’s a partially meshed topology.

To know how many connections require to make a network fully meshed, we can use the following formula.

Required connections = n * (n-1)/2

Here, n is the number of end devices or locations.

For example, to make a fully meshed network of 4 end devices, we need 4*(4-1)/2 = 6 connections.

We can also use this formula to figure out whether a network is fully meshed or partially meshed. If the number of connections in a network is less than the total required number of the connections then the network is considered as the partially meshed network. For example, a network of 4 end devices has less than 6 connections, then it will be considered as the partially meshed network.

The following image shows an example of both types.

mesh topology

Mesh topology is commonly used in the WAN network for backup purposes. This topology is not used in the LAN network implementations.

Point-to-multipoint topology

In this topology, an end device connects directly to multiple end devices in the network. Just like mesh topology, this topology is also used in the WAN network to connect multiple remote sites/locations/offices with a central site/location/office.

The following image shows an example of the point-to-multipoint topology.

point to multipoint topology

Partially meshed topology and the point-to-multipoint topology are the same except the number of connections. In partially meshed topology number of connections are higher the point-to-multipoint topology.

Point-to-point topology

This is the simplest form of network topology. In this topology, two end devices directly connect with each other. The following image shows a few examples of this topology.

point to point topology

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

How Analog and Digital Signals Work

This tutorial explains the functionality of analog signaling and digital signaling. Learn how analog and digital signals work and how they transmit information.

To transmit information, two types of signals are used; analog and digital. Both types of signals not only have different properties but also function differently. In the below section, we will understand both types of signals in detail.

Analog signaling

This is the classic method of signaling. In this method, signals move like waves. The sending device converts data into waves and loads those waves on the media. The receiving device picks up those waves from the media and converts them back into the data.

example of analog signaling

An analog signal has four essential properties; amplitude, frequency, wavelength, and phase. The following image shows an example of these properties.

properties of analog signals

Amplitude

Amplitude measures the signals’ strength. At any point, in the given time, the amplitude is the height of the wave.



In our example:-

  • At 0 seconds, the amplitude is 0 volts.
  • At 0.25 seconds, the amplitude is +5 volts.
  • At 0.5 seconds, the amplitude is 0 volts.
  • At 0.75 seconds, the amplitude is -5 volts.
  • At 1 second, the amplitude is 0 volts.

Frequency

Frequency measures the number of cycles in a given time. In a given time, a frequency is the number of times that a wave cycles from its starting point through its highest amplitude and its lowest amplitude and back to its starting point. To express the frequency, unit Hz (Hertz) is used.

Hz = number of cycles per second

In our example, in one second, the wave completes one cycle (starting point – highest amplitude -lowest amplitude – starting point) so the frequency is 1Hz.



Few more examples:-

5Hz = 5 cycles in a second
30Hz = 30 cycles in a second
1 KHz = 1,000 cycles per second
1 MHz = 1,000,000 cycles per second

Wavelength

Wavelength is the distance between corresponding points of a wave’s cycles. It is expressed in meters or feet. It is inversely proportional to the frequency.

Higher frequency = shorter wavelength
Lower frequency = longer wavelength

For example, if a wave is transmitted on the 1 MHz frequency, it creates a wavelength of 300 meters while if the same wave is transmitted on the 2 MHz frequency, it creates a wavelength of 150 meters.

Phase

A phase is the progress of a wave in relationship to a fixed point and time. A phase is measured in degrees. By using different phases, multiple waves of identical amplitudes and frequencies can be transmitted on the same media.

For example, to transmit two separate waves of the same amplitude, one wave can be started at its lowest amplitude at the same time the second wave can be started at its highest amplitude. Since both waves have a 180 degrees phase difference, they both can carry different signals.

analog signal phase

Digital signaling

This is the modern method of signaling. In this method, signals are transmitted in binary form as pulses. In binary form, information is stored by using two types of bit; on bit and off bit.

To transmit both types of bits, two types of pluses are used in digital signaling; a pulse of positive voltage and a pulse of zero voltage. Both pulses are represented as on bit (1) and off bit (0) respectively.

To transmit a binary bit, an individual pulse is used. In other words, every pulse in digital signals represents a signal binary bit.

The following image shows an example of digital signaling.

digital signals

Differences between analog signaling and digital signaling

Analog signaling uses infinite and continuous waves to transmit the information. These waves are represented as sine waves. As sine waves have infinite variations, analog signals are more prone to distortion and noise. Human voices and natural sounds are examples of analog signals.

Digital signaling uses pluses to transmit information. These pluses are represented as square waves. A pulse either carries a positive voltage or no voltage at all. Since there are no infinite variations, digital signals are less prone to distortion and noise. Data storage devices such as hard disks and optical drives are examples of digital signaling.

That’s all for this tutorial. In the next part of this article, we will understand how analog signals and digital signals are converted into each other. If you like this tutorial, please don’t forget to share it with friends.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Multiplexing and Demultiplexing Explained with Types

This tutorial explains the types of multiplexing and demultiplexing in detail. Learn what the multiplexing is and how it works in computer networks.

Multiplexing is a process that allows multiple signals to travel simultaneously over a single communication channel or path. Multiplexing in computer networks increases the amount of data that can be transmitted in a given time-span over a given bandwidth.

Multiplexing divides a given path logically into several short paths and then uses each path to transmit the data of an individual node. The following image shows an example of this concept.

example of multiplexing

In multiplexing, two devices are mainly used; a multiplexer and a demultiplexer. Both devices work on both ends of the path. A multiplexer works on the transmitting side and a demultiplexer works on the receiving side.

A multiplexer merges signals of all nodes and loads them on the medium/path. When these signals arrive at the demultiplexer, the demultiplexer separates all the signals and passes them to their respective nodes.

There are several types of multiplexing, depending on the technique used to merge signals. Some common and most widely used techniques are explained below.

Time Division Multiplexing (TDM)



In this technique, time intervals are used to merge signals.
The multiplexer creates time-slots equal to the number of sending nodes and then assigns a separate time-slot to each node.
Each node can send data only in its designated time-slot. If a node has no data to send, it sends nothing in its time-slot.
If a node has more data to send, it must have to wait till the next time-slot.

Let’s take a simple example. Suppose four nodes (A, B, C, and D) are connected to a network over a single channel. The multiplexer creates four time-slots (1, 2, 3, and 4) and assigns a time-slot to each node; time-slot 1 to node A, time-slot 2 to node B, time-slot 3 to node C, and time-slot 4 to node D.

The following image shows this example.

Time Division Multiplexing

This technique is not more efficient because it reserves a time-slot for each participant node,
regardless of whether a participant node has any data to send or not. A node that rarely sends data can waste too much bandwidth by keeping
its specified time-slot empty in each data cycle.

Statistical Multiplexing (SM)



Statistical multiplexing works similar to TDM. It also divides a data cycle into time-slots and assigns a separate time-slot to each node.
After assigning time-slots, it actively monitors the transmission. If a node does not have any data to send, it assigns the time-slot of
that node to the next node.

Statistical Multiplexing

This technique is more efficient than the TDM because it utilizes each time-slot.

Frequency Division Multiplexing (FDM)

This multiplexing technique is used in analog communication. This technique works in two steps. In the first step, it divides the communication channel into sub-channels and assigns a separate sub-channel to each node.

In the second step, it modulates the frequency of the carrier wave of each node. A carrier wave is a simple analog wave that does not contain any data. A node uses a carrier wave to transmit digital signals over an analog channel.

To know more about the carrier wave and how it is used in analog transmission, you can check this tutorial.

Data Modulation in Computer Networks

Changing the frequency of the carrier wave does not affect the transmitted data. By changing the frequency of the carrier wave, this technique can transmit multiple waves simultaneously over a single path.

The following image shows an example of this technique.

Frequency Division Multiplexing

This technology is mainly used by telephone companies to provide internet facilities through existing telephone lines. A human can hear signals of frequency 300–3400 Hz. Telephone companies implement FDM to subdivide telephone lines and send data signals in frequencies greater than 3400 Hz. Since a human cannot hear frequencies above 3400 Hz, data transmission above this frequency does not affect voice communication over the telephone.

Wavelength Division Multiplexing (WDM)

This technology is used in fiber-optic connections to carry multiple light signals simultaneously over a single fiber-optic cable. This technology can work over any type of fiber-optic cable.

Fiber-optic cable uses a light beam to transmit data. WDM divides this light beam into up to 40 different light beams of different wavelengths or colors and then assigns a separate light beam to each node. Since each beam uses a different wavelength or color, it does not overlap or blend with the other beams.

The following image shows an example of WDM.

Wavelength Division Multiplexing

There are two popular types of WDM; DWDM and CWDM.

Dense Wavelength Division Multiplexing (DWDM)

DWDM uses more wavelengths for signaling than the original form of WDM. Because of this, a signal fiber cable can carry between 80 to 160 channels. This technology uses costly transceivers equipment. Due to cost, usually, this technology is only used on high-bandwidth or long-distance WAN links.

Coarse Wavelength Division Multiplexing (CWDM)

CWDM was developed in an effort to lower the cost of the transceiver equipment. This technology uses cheaper transceivers equipment. In this technology, channels are spaced more widely and signals are not amplified. Because of these, the effective distance of CWDM is less than the original from WDM. Through CWDM, a signal fiber cable can carry between 8 to 16 channels.

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Data Modulation in Computer Networks

This tutorial explains data modulation in computer networks. Learn what the data modulation is and how it works in computer networks.

Data modulation is a process that converts analog signals into digital signals and digital signals into analog signals. Computers store and process data in digital format. Data modulation allows computers to store and process analog signals.

Let’s take a simple example. When you record and play an audio clip, the following happens.

You use a microphone to record the audio clip. The microphone sends your voice to the computer. Since the human voice consists of analog signals, the computer converts the received voice into digital signals before processing and storing them onto the hard disk.

When the recorded clip is played, the computer reads digital signals from the hard disk and converts them into analog signals before sending them to the speaker.

The following image shows this process.

data modulation with in computer

Modulators and demodulators are devices or chips or components that convert analog signals into digital signals and digital signals into analog signals, respectively.

Data modulation is not only used within the computer, but it is also used outside the computer. It allows computers to send digital signals on a media that can only carry analog signals. It converts signals in such a way that they become suitable for transport on a communication path that is not designed to carry such signals.

For example, telephone lines are designed to carry analog signals. Through data modulation, the same telephone lines can also be used to provide the Internet facility. To provide the Internet facility through telephone lines, a device known as the modem is used. A modem can act as both a modulator and a demodulator.



A modem connects a computer to the ISP network via a telephone line. It modulates digital signals into analog signals at the transmitting end, then demodulates analog signals into digital signals at the receiving end.

data modulation example in computer networks

How does the data modulation work?

To convert digital signals into analog signals, a simple analog wave, known as the carrier wave, is combined into digital signals. A carrier wave does not contain any information or data. In simple words, it’s only a messenger that transfers information between two nodes.

An analog wave has four properties; amplitude, frequency, wavelength, and phase. From these, amplitude and frequency are used to blend digital signals. To load digital signals on the analog wave, the modulator modifies either amplitude or frequency in a pre-defined way.

To understand the properties of analog and digital signals in detail, you can check the tutorial.

How analog and digital signals work

After modification, the modulator loads the blended wave on the media. When the blended wave reaches its destination, the demodulator separates the data from the blended wave by using the same pre-defined way. After separation, the data is sent on its destination in the digital format and the carrier wave is discarded.

The following image shows an example of this process.

how does data modulation work

AM / FM Radio



A radio uses radio waves to receive the transmission from broadcasting stations. Radio waves can carry only analog signals. To transmit digital signals on radio waves, radio stations also use data modulation.

As mentioned above, digital signals can be mixed in the carrier wave either by modifying the amplitude or by modifying the frequency of the carrier wave. Based on the modified property, a radio station can be categorized into two types; AM radio station and FM radio station.

To broadcast the digital signals: –

An AM (Amplitude Modulation) radio station modifies the amplitude of the carrier wave.

An FM (Frequency Modulation) radio station modifies the frequency of the carrier wave.

Radio stations may also modify the phase (third property) of the carrier wave to broadcast multiple signals.

Digitizing analog signals

To convert analog signals into digital signals, an ADC (Analog to Digital Converter) is used. An ADC is an integrated electronic circuit. It takes input analog signals and converts them in digital (binary) signals.

adc convertor

An ADC converts the output data into a series of digital values by approximating the signals with fixed precision. In each cycle of the analog signal, an ADC measures all falling and rising of signals and converts them into digital values.

To understand how an ADC converts analog signals into digital signals, think about a staircase and a ramp. A ramp is analog because it has an infinite number of heights. To construct a parallel staircase, a constructor uses sample heights of the ramp. The more samples the constructor takes, the more accurate the staircase will be.

data modulation example

The process of measuring height and width of steps work similarly to the process of digitizing analog signals.

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social channel.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Differences between Baseband and Broadband Explained

This tutorial explains the differences between the baseband and broadband transmissions in detail. Learn what the baseband and broadband transmissions are and how they differ from each other.

Both baseband and broadband describe how data is transmitted between two nodes. Baseband technology transmits a single data signal/stream/channel at a time while broadband technology transmits multiple data signals/streams/channels simultaneously at the same time.

The following image shows an example of both technologies.

differences between baseband and broadband

To understand the basic differences between both technologies, consider the baseband as a railway track and the broadband as a highway. Like, at a time, only one train can go on a railway track, in the baseband transmission only one data signal can be transmitted at a time.

Unlike a railway track on a highway, multiple vehicles can go simultaneously. For example, on a 3 lanes highway, 3 vehicles can go at the same time. Same as a highway, in the broadband transmission, multiple data signals can be transmitted at the same time.

examples of baseband and broadband

Technical differences between the baseband and broadband transmissions



Baseband technology uses digital signals in data transmission. It sends binary values directly as pulses of different voltage levels. Digital signals can be regenerated using repeaters in order to travel longer distances before weakening and becoming unusable because of attenuation.

Baseband supports bidirectional communication. It means, this technology can send and receive data simultaneously. To support bidirectional communication, this technology uses two separate electric circuits together; one for sending and another for receiving.

The following image shows an example of this.

baseband communication

Although baseband transmits only a single data stream at a time, it is possible to transmit signals of multiple nodes simultaneously. This is done by combining all the signals into a single data stream. To combine the signals of multiple nodes, a technology known as multiplexing is used. Baseband supports the Time Division Multiplexing (TDM).

To learn the types of multiplexing and how the multiplexing is done, you can check this tutorial.

Multiplexing and Demultiplexing Explained with Types

Baseband technology is mainly used in Ethernet networks to exchange data between nodes. This technology can be used on all three popular cable media types of Ethernet; coaxial, twisted-pair, fiber-optic.

Broadband transmission



Broadband technology uses analog signals in data transmission. This technology uses a special analog wave known as the carrier wave. A carrier wave does not contain any data but contains all properties of the analog signal. This technology mixes data/digital signal/binary values into the carrier wave and sends the carrier wave across the channel/medium.

To transmit data of multiple nodes simultaneously, this technology supports the Frequency Division Multiplexing. FDM (Frequency Division Multiplexing) divides the channel (medium or path) into several sub-channels and assigns a sub-channel to each node. Each sub-channel can carry a separate carrier wave.

The following image shows an example of this process.

analog multiplexing

Analog signals can be regenerated using amplifiers in order to travel longer distances.

Broadband supports only unidirectional communication. It means, nodes connected at both ends of a medium can send or receive data but can’t perform both actions simultaneously. Only one action is allowed at a time.

For example, two nodes A and B are connected through a cable that uses broadband technology to transmit signals. When node A transmits signals, node B receives the transmitted signals and when node B transmits signals, node A receives the transmitted signals.

The following image shows this example.

broadband transmission

Broadband is typically used in an environment that transmits audio, video, and data simultaneously. For example, Cable TV Networks, Radio stations, and Telephone companies. Usually radio waves, coaxial, fiber-optic cables are used for broadband transmission.

Key differences between baseband and broadband transmissions
Baseband transmission Broadband transmission
Transmit digital signals Transmit analog signals
To boost signal strength, use repeaters To boost signal strength, use amplifiers
Can transmit only a single data stream at a time Can transmit multiple signal waves at a time
Support bidirectional communication simultaneously Support unidirectional communication only
Support TDM based multiplexing Support FDM based multiplexing
Use coaxial, twisted-pair, and fiber-optic cables Use radio waves, coaxial cables, and fiber optic cables
Mainly used in Ethernet LAN networks Mainly used in cable and telephone networks

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Differences between Throughput and Bandwidth Explained

This tutorial explains the differences between the throughput and bandwidth in detail. Learn what the throughput and bandwidth are and how they differ from each other.

Both throughput and bandwidth describe transmission speeds. Bandwidth describes the information-carrying capacity of a medium, while throughput describes the actual use of that capacity.

To understand the basic difference between throughput and bandwidth, think about a highway. If 24 cars can go through on a highway in a second, then the bandwidth of that highway is 24 cars per second.

But, in practice, this never happens. Cars can’t be driven in bumper-to-bumper mode. The actual number of cars that can go through depends on several conditions such as weather, road condition, and lights. If under given conditions only 20 cars can go through in a second, then the throughput of that highway is 20 cars per second.

The following image shows this example.

throughput and bandwidth

Let’s take one more example.



File size: 46 megabits

Ethernet overhead (the total of extra information which each data packet contains such as header and trailer): 10 megabits.

The total amount of data to be transferred: 56 megabits (46 megabits + 10 megabits)

Bandwidth (Maximum data transfer speed): 56 Mbps

Amount of data lost due to errors and acknowledgments: 28 Mbps

Throughput: 56 Mbps – 28 Mbps = 28 Mbps

The time it takes to transfer the entire file: 56 megabits/28 Mbps = 2 seconds

Throughput always remains lower than the bandwidth. Because of this, provides usually advertises connection speed in up to form such as; up to 100 Mbps, up to 1 Gbps, etc.

Next time, when you subscribe for a new Internet connection, subscribe for a connection that offers a higher bandwidth than your requirement. For example, if you require 1Gbps bandwidth, subscribe for a connection that offers a bandwidth rate of 1.25 Gbps or higher.

Measuring throughput and bandwidth

Computer networks use two types of signals; analog and digital for data transmission. The throughput and bandwidth of digital signals are measured in the bit rate. A bit rate is the number of bits transmitted per second, such as 1000 bits per second or 1Kbps.

The following table lists the common bits rate of digital signals used in computer networks.

Bits Rate Description
1bps 1 bit per second
1Kbps 1000 bits per second
1Mbps 1,000,000 bits per second
1Gbps 1,000,000,000 bits per second
1Tbps 1,000,000,000,000 bits per second

The throughput and bandwidth of analog signals are measured in the baud rate. A baud rate is the number of symbols transmitted per second. A symbol is a voltage, frequency, pulse, or phase change in the analog transmission.

Calculating bandwidth of analog signals



The bandwidth of analog signals is computed by subtracting the lower frequency from the higher one. For example, if a cable can carry frequencies from 300 Hz to 3300 Hz, then the bandwidth of that cable is 3000 Hz (3300 – 300).

Let’s take one more example, a human can hear a signal of frequency range 300 to 3000. So the bandwidth of a human voice is 2700 Hz (3000 – 300).

Frequency range Used by
535 kHz to 1605 kHz AM Radio stations
88 to 108 MHz FM Radio stations
108 to 174 MHz VHF Cable stations
174 to 216 MHz VHF television stations
216 to 470 MHz UHF Cable stations
470 to 890 MHz UHF television stations
230MHz to 3 THz Radar

A higher frequency represents a larger bandwidth. A larger bandwidth provides faster transmission.

Common factors that affect bandwidth and throughput

Transmitting device
A transmitting device converts data into signals and load signals on the medium. A slow transmitting device can lower the throughput rate. For example, suppose, a cable of 100Mbps bandwidth is connected with a NIC that can transmit data at the rate of 10Mbps. In this case, even the bandwidth of the cable is 100Mbbps, the bandwidth of transmission will be 10 Mbps and the actual data transmission rate (throughput) will be even less.

Distance
Signals lose strength as they travel on a medium. Because of this, the throughput of a medium decreases as the distance increases. Amplifiers (for analog signals) and repeaters (for digital signals) are used to increase signals’ strength.

Environment
When signals travel through a medium, their environment affects them. For example, EMI (electro-magnetic-interface) fields and cross-talk affect digital signals, noise and attenuation affect analog signals, and weather and obstacles affect radio waves.

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Basic Functions of a Computer Explained

This tutorial explains the basic functions, operations, and characteristics of a computer. Learn the four major functions of a computer through diagrams and examples.

Taking data and instructions from a user, processing the data as per instructions, and displaying or storing the processed data, are the four major functions of a computer. These functions are also known as the input function, process function, output function, and storage function, respectively.

The following diagram shows an example of these functions.

function of a computer

To provide these functions, a computer uses its components or devices. Usually, components of a computer are designed to perform only one of these four functions. But, some specialized components or devices are designed to perform two, three or all four functions. For example, a hard disk can perform three functions: input (when files are read), storage (when files are saved), and output (when files are written).

Components or devices of a computer, based on the function in which they are used, can be classified into four major types: the input devices, output devices, storage devices, and processing devices. For example, if a component processes the given instructions, the component is known as the processing device. Or if a device displays the processed data, the device is known as the output device.

Input function and devices



A computer is a data processing machine. It does nothing until a user (or a script or a program) provides the data that needs to be processed and the instructions that tell it how to process the data.

Any standard device or component that a user uses to instruct a computer is known as the standard input device. In other words, a computer uses its standard input devices or components to get instructions from a user.

The most common input devices are the keyboard and mouse. Almost all modern computers have these devices. Other common input devices are scanners, microphones, USB drives, and webcams.

Input data and instruction can also be generated from a non-standard input device such as the hard disk and CD/DVD. For example, a batch file in the Windows system may instruct the CPU to execute a program or a script at a particular time.

Installation disks are another good example of non-standard input devices. Usually, they contain a script or an executable program that automatically starts the installation process as soon as the disk is read.

Process function and devices

Once the data and instructions are received by the input function, the computer starts the processing function. In this function, a computer processes the received data according to the instructions.

To process the input data according to the instructions, the computer uses the CPU. A CPU is the main processing component of a computer. It processes user instructions, executes scripts and programs, and runs commands of the OS that provide a platform for installing and using application software.

Other important processing components are auxiliary processors. Auxiliary processors are also known as onboard processors. Auxiliary processors are used in devices to enhance their functionalities. You can think of an auxiliary processor as the private CPU of a device.

Only components or devices that provide the complex functionality such as Graphics cards, I/O devices, and network interface cards use auxiliary processors. For example, if a user draws an image, the auxiliary processor on the graphics card performs all calculations that require in drawing the image on the display device.

The following image shows a sample of both a CPU and an auxiliary processor.

cpu and auxiliary

The following table lists the main differences between a CPU and an auxiliary processor.

CPU Auxiliary processor
A CPU is a compulsory component. Without it, a computer does not work. An auxiliary processor is an optional component.
A CPU is an individual component. It is installed separately in the system. An auxiliary processor is an integrated part of a device. It can’t be installed separately.
A CPU is designed to perform all types of tasks. An auxiliary processor is designed to perform only a specific type of task.

Output function and devices



After processing the input data, the CPU, auxiliary processor, or the process function sends the processed data to the output function or to the default or configured output device. By default, computers use monitors as the default output device.

Aside from monitor, a variety of output devices are also available. Each output device presents the processed data in a different form, for example, a monitor, a printer, and a speaker displays, prints, and plays the processed data, respectively.

A user, based on his requirement, can connect and use two, three or more output devices to the computer. For example, after viewing the processed data, a user can send it to the printer for printing.

Storage function and devices

Storing data and information is the fourth major function of a computer. This function allows us to save the processed data for later use. To store data and information, a computer uses two types of storage components: temporary and permanent.

Temporary storage components are used to store data temporarily. Data stored in a temporary storage component is erased when the system is shutdown. RAM is a compulsory temporary storage component. A computer uses the ram to store the running applications and their data.

Permanent storage components are used to store data permanently. Data stored in a permanent storage component is not erased when the system is shutdown. The hard disk is the most common permanent storage component. Usually, all computers have at least one hard disk to store data. Other common permanent storage components or devices are external drives, USB drives, and CD/DVD.

The following image shows an example of both types of storage components.

ram and hard disk

Storage devices are also used in the input and output functions, allowing data to be saved (output function) and then accessed again later (input function).

Examples

The following table lists a few sample actions along with the name of devices and functions that are used when they are performed.

Action Device Function
A user running a text-editor program types the letter Z on the keyboard. The keyboard sends a code representing the letter Z to the CPU. Keyboard Input
The CPU processes the code and determines what letter was typed. Then the CPU sends instructions to the monitor to display the letter Z. CPU Process
The monitor displays the letter Z. Monitor Output
The user clicks the save button. The mouse sends a code representing the click. Mouse Input
The CPU processes the code and determines what action was clicked. CPU Process
The CPU saves the file on the disk. Hard disk Storage

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo