The Internet

The Internet is a worldwide collection of interconnected networks (internetworks or internet for short). The figure shows one way to view the Internet as a collection of interconnected LANs and WANs. Some of the LAN examples are connected to each other through a WAN connection. WANs are then connected to each other. The red WAN connection lines represent all the varieties of ways we connect networks. WANs can connect through copper wires, fiber optic cables, and wireless transmissions (not shown).
The Internet is not owned by any individual or group. Ensuring effective communication across this diverse infrastructure requires the application of consistent and commonly recognized technologies and standards as well as the cooperation of many network administration agencies. There are organizations that have been developed for the purpose of helping to maintain structure and standardization of Internet protocols and processes. These organizations include the Internet Engineering Task Force (IETF), Internet Corporation for Assigned Names and Numbers (ICANN), and the Internet Architecture Board (IAB), plus many others.
Note: The term internet (with a lower case “i") is used to describe multiple networks interconnected. When referring to the global system of interconnected computer networks or the World Wide Web, the term Internet (with a capital “I”) is used.

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Wide Area Networks

WANs are a network infrastructure that spans a wide geographical area. WANs are typically managed by service providers (SP) or Internet Service Providers (ISP).
Specific features of WANs include:

• WANs interconnect LANs over wide geographical areas such as between cities, states, provinces, countries, or continents.

• WANs are usually administered by multiple service providers.

• WANs typically provide slower speed links between LANs.

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Local Area Networks

LANs are a network infrastructure that spans a small geographical area. Specific features of LANs include:

• LANs interconnect end devices in a limited area such as a home, school, office building, or campus.

• A LAN is usually administered by a single organization or individual. The administrative control that governs the security and access control policies are enforced on the network level.

• LANs provide high speed bandwidth to internal end devices and intermediary devices.

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Types of Networks

Network infrastructures can vary greatly in terms of:

• Size of the area covered

• Number of users connected

• Number and types of services available

• Area of responsibility

The figure illustrates the two most common types of network infrastructures:

• Local Area Network (LAN) - A network infrastructure that provides access to users and end devices in a small geographical area, which is typically an enterprise, home, or small business network owned and managed by an individual or IT department.

• Wide Area Network (WAN) - A network infrastructure that provides access to other networks over a wide geographical area, which is typically owned and managed by a telecommunications service provider.

Other types of networks include:

• Metropolitan Area Network (MAN) - A network infrastructure that spans a physical area larger than a LAN but smaller than a WAN (e.g., a city). MANs are typically operated by a single entity such as a large organization.

• Wireless LAN (WLAN) - Similar to a LAN but wirelessly interconnects users and end points in a small geographical area.

• Storage Area Network (SAN) - A network infrastructure designed to support file servers and provide data storage, retrieval, and replication.

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Topology Diagrams

Topology diagrams are mandatory for anyone working with a network. They provide a visual map of how the network is connected.
There are two types of topology diagrams:

• Physical topology diagrams - Identify the physical location of intermediary devices and cable installation.  
  

• Logical topology diagrams - Identify devices, ports, and addressing scheme.
  

The topologies shown in the physical and logical diagrams are appropriate for your level of understanding at this point in the course. Search the Internet for “network topology diagrams” to see some more complex examples. If you add the “Cisco” to your search phrase, you will find many topologies using similar icons to what you have seen in this chapter.

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Network Representations

Diagrams of networks often use symbols, like those shown in Figure 1, to represent the different devices and connections that make up a network. A diagram provides an easy way to understand how devices in a large network are connected. This type of “picture” of a network is known as a topology diagram. The ability to recognize the logical representations of the physical networking components is critical to being able to visualize the organization and operation of a network.
In addition to these representations, specialized terminology is used when discussing how each of these devices and media connect to each other. Important terms to remember are:

• Network Interface Card - A NIC, or LAN adapter, provides the physical connection to the network at the PC or other end device. The media that are connecting the PC to the networking device, plug directly into the NIC (Figure 2).

• Physical Port - A connector or outlet on a networking device where the media is connected to an end device or another networking device.

• Interface - Specialized ports on a networking device that connect to individual networks. Because routers are used to interconnect networks, the ports on a router are referred to as network interfaces.

Note: Often, the terms port and interface are used interchangeably.

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Network Media

Communication across a network is carried on a medium. The medium provides the channel over which the message travels from source to destination.
Modern networks primarily use three types of media to interconnect devices and to provide the pathway over which data can be transmitted. As shown in Figure 1, these media are:

• Metallic wires within cables - data is encoded into electrical impulses

• Glass or plastic fibers (fiber optic cable) - data is encoded as pulses of light

• Wireless transmission - data is encoded using wavelengths from the electromagnetic spectrum

Different types of network media have different features and benefits. Not all network media have the same characteristics, nor are they all appropriate for the same purpose.
Figure 2 displays criteria to consider when choosing network media.

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Intermediary Network Devices

Intermediary devices connect the individual end devices to the network and can connect multiple individual networks to form an internetwork. These intermediary devices provide connectivity and ensure that data flows across the network.
Intermediary devices use the destination end device address, in conjunction with information about the network interconnections, to determine the path that messages should take through the network. Examples of the more common intermediary devices and a list of functions are shown in the figure.

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End Devices

The network devices that people are most familiar with are called end devices. Some examples of end devices are shown in Figure 1.
An end device is either the source or destination of a message transmitted over the network, as shown in the animation in Figure 2. To distinguish one end device from another, each end device on a network is identified by an address. When an end device initiates communication, it uses the address of the destination end device to specify where the message should be sent.

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Overview of Network Components

The path that a message takes from source to destination can be as simple as a single cable connecting one computer to another, or as complex as a collection of networks that literally spans the globe. This network infrastructure provides the stable and reliable channel over which these communications occur.
The network infrastructure contains three categories of network components:

• Devices

• Media

• Services

Click each button in the figure to highlight the corresponding network components.
Devices and media are the physical elements, or hardware, of the network. Hardware is often the visible components of the network platform such as a laptop, PC, switch, router, wireless access point, or the cabling used to connect the devices.
Services include many of the common network applications people use every day, like email hosting services and web hosting services. Processes provide the functionality that directs and moves the messages through the network. Processes are less obvious to us but are critical to the operation of networks.

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Peer-to-Peer

Client and server software usually runs on separate computers, but it is also possible for one computer to carry out both roles at the same time. In small businesses and homes, many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network.
The advantages and disadvantages of peer-to-peer networking are shown in the figure.

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Clients and Servers

All computers connected to a network that participate directly in network communication are classified as hosts. Hosts are also called end devices.
Servers are computers with software that enable them to provide information, like email or web pages, to other end devices on the network. Each service requires separate server software. For example, a server requires web server software in order to provide web services to the network. A computer with server software can provide services simultaneously to one or many clients. Additionally, a single computer can run multiple types of server software. In a home or small business, it may be necessary for one computer to act as a file server, a web server, and an email server.
Clients are computers with software installed that enable them to request and display the information obtained from the server. An example of client software is a web browser, like Chrome or FireFox. A single computer can also run multiple types of client software. For example, a user can check email and view a web page while instant messaging and listening to Internet radio.

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Networks of Many Sizes

Networks come in all sizes. They can range from simple networks consisting of two computers to networks connecting millions of devices. Click the images in the figure to read about networks of different sizes.
Simple networks installed in homes enable sharing of resources, such as printers, documents, pictures and music between a few local computers.
Home office networks and small office networks are often set up by individuals that work from a home or a remote office and need to connect to a corporate network or other centralized resources. Additionally, many self-employed entrepreneurs use home office and small office networks to advertise and sell products, order supplies and communicate with customers.
In businesses and large organizations, networks can be used on an even broader scale to provide consolidation, storage, and access to information on network servers. Networks also allow for rapid communication such as email, instant messaging, and collaboration among employees. In addition to internal benefits, many organizations use their networks to provide products and services to customers through their connection to the Internet.
The Internet is the largest network in existence. In fact, the term Internet means a ‘network of networks’. The Internet is literally a collection of interconnected private and public networks, such as those described above.

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Networks Support the Way We Communicate

The globalization of the Internet has ushered in new forms of communication that empower individuals to create information that can be accessed by a global audience.
Some forms of communication include:

• Texting – Texting enables instant real-time communication between two or more people.

• Social Media – Social media consists of interactive websites where people and communities create and share user-generated content with friends, family, peers, and the world.

• Collaboration Tools - Without the constraints of location or time zone, collaboration tools allow individuals to communicate with each other, often across real-time interactive video. The broad distribution of data networks means that people in remote locations can contribute on an equal basis with people in the heart of large population centers.

• Blogs - Blogs, which is an abbreviation of the word “weblogs”, are web pages that are easy to update and edit. Unlike commercial websites, blogs give anyone a means to communicate their thoughts to a global audience without technical knowledge of web design.

• Wikis - Wikis are web pages that groups of people can edit and view together. Whereas a blog is more of an individual, personal journal, a wiki is a group creation. As such, it may be subject to more extensive review and editing. Many businesses use wikis as their internal collaboration tool.

• Podcasting - Podcasting allows people to deliver their audio recordings to a wide audience. The audio file is placed on a website (or blog or wiki) where others can download it and play the recording on their computers, laptops, and other mobile devices.

• Peer-to-Peer (P2P) File Sharing – Peer-to-Peer file sharing allows people to share files with each other without having to store and download them from a central server. The user joins the P2P network by simply installing the P2P software. P2P file sharing has not been embraced by everyone. Many people are concerned about violating the laws of copyrighted materials.

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No Boundaries

Advancements in networking technologies are perhaps the most significant changes in the world today. They are helping to create a world in which national borders, geographic distances, and physical limitations become less relevant presenting ever-diminishing obstacles.
The Internet has changed the manner in which social, commercial, political, and personal interactions occur. The immediate nature of communications over the Internet encourages the creation of global communities. Global communities allow for social interaction that is independent of location or time zone. The creation of online communities for the exchange of ideas and information has the potential to increase productivity opportunities across the globe.
Cisco refers to this as the human network. The human network centers on the impact of the Internet and networks on people and businesses.
How has the human network affected you?

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Class Activity - Draw Your Concept of the Internet

 

Welcome to a new component of our Networking Academy curriculum: Modeling Activities! You will find them at the beginning and end of each chapter.
Some activities can be completed individually (at home or in class), and some will require group or learning-community interaction. Your instructor will be facilitating so that you can obtain the most from these introductory activities.
These activities will help you enhance your understanding by providing an opportunity to visualize some of the abstract concepts that you will be learning in this course. Be creative and enjoy these activities!
Here is your first modeling activity:
Draw Your Concept of the Internet
Draw and label a map of the Internet as you interpret it now. Include your home or school/university location and its respective cabling, equipment, devices, etc. Some items you may wish to include:

• Devices/Equipment

• Media (cabling)

• Link Addresses or Names

• Sources & Destinations

• Internet Service Providers

Upon completion, save your work in a hard-copy format, as it will be used for future reference at the end of this chapter. If it is an electronic document, save it to a server location provided by your instructor. Be prepared to share and explain your work in class.

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Exploring the Network

We now stand at a critical turning point in the use of technology to extend and empower our ability to communicate. The globalization of the Internet has succeeded faster than anyone could have imagined. The manner in which social, commercial, political and personal interactions occur is rapidly changing to keep up with the evolution of this global network. In the next stage of our development, innovators will use the Internet as a starting point for their efforts, creating new products and services specifically designed to take advantage of the network capabilities. As developers push the limits of what is possible, the capabilities of the interconnected networks that form the Internet will play an increasing role in the success of these projects.
This chapter introduces the platform of data networks upon which our social and business relationships increasingly depend. The material lays the groundwork for exploring the services, technologies, and issues encountered by network professionals as they design, build, and maintain the modern network.

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How Packet Tracer Helps Master Concepts

 

Educational Games
Packet Tracer Multi-User games enable you or a team to compete with other students to see who can accurately complete a series of networking tasks the fastest. It is an excellent way to practice the skills you are learning in Packet Tracer activities and hands-on labs.
Cisco Aspire is a single-player, standalone strategic simulation game. Players test their networking skills by completing contracts in a virtual city. The Networking Academy Edition is specifically designed to help you prepare for the CCENT certification exam. It also incorporates business and communication skills ICT employers seek in job candidates. Click here to learn more about Cisco Aspire Networking Academy Edition.
Performance-Based Assessments
The Networking Academy performance-based assessments have you do Packet Tracer activities like you have been doing all along, only now integrated with an online assessment engine that will automatically score your results and provide you with immediate feedback. This feedback helps you to more accurately identify the knowledge and skills you have mastered and where you need more practice. There are also questions on chapter quizzes and exams that use Packet Tracer activities to give you additional feedback on your progress.

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Practice Leads to Mastery

In a typical lesson, after learning about a topic for the first time, you will check your understanding with some interactive media items. If there are new commands to learn, you will practice them with the Syntax Checker before using the commands to configure or troubleshoot a network in Packet Tracer, the Networking Academy network simulation tool. Next, you will do practice activities on real equipment in your classroom or accessed remotely over the internet.
Packet Tracer can also provide additional practice any time by creating your own activities or you may want to competitively test your skills with classmates in multi-user games. Packet Tracer skills assessments and skills integration labs give you rich feedback on the skills you are able to demonstrate and are great practice for chapter, checkpoint, and final exams.

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How We Teach

E-doing is a design philosophy that applies the principle that people learn best by doing. The curriculum includes embedded, highly interactive e-doing activities to help stimulate learning, increase knowledge retention, and make the whole learning experience much richer – and that makes understanding the content much easier.

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More Than Just Information

The NetSpace learning environment is an important part of the overall course experience for students and instructors in the Networking Academy. These online course materials include course text and related interactive media, Packet Tracer simulation activities, real equipment labs, remote access labs, and many different types of quizzes. All of these materials provide important feedback to help you assess your progress throughout the course.
The material in this course encompasses a broad range of technologies that facilitate how people work, live, play, and learn by communicating with voice, video, and other data. Networking and the internet affect people differently in different parts of the world. Although we have worked with instructors from around the world to create these materials, it is important that you work with your instructor and fellow students to make the material in this course applicable to your local situation.

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A Global Community

When you participate in the Networking Academy, you are joining a global community linked by common goals and technologies. Schools, colleges, universities, and other entities in over 160 countries participate in the program. 
a video about how Cisco Networking Academy is changing the world.
Look for the Cisco Networking Academy official site on Facebook© and LinkedIn©. The Facebook site is where you can meet and engage with other Networking Academy students from around the world. The Cisco Networking Academy LinkedIn site connects you with job postings, and you can see how others are effectively communicating their skills.

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Welcome

Welcome to the CCNA Introduction to Networks course. The goal of this course is to introduce you to fundamental networking concepts and technologies. These online course materials will assist you in developing the skills necessary to plan and implement small networks across a range of applications. The specific skills covered in each chapter are described at the start of each chapter.
You can use your smart phone, tablet, laptop, or desktop to access your course, participate in discussions with your instructor, view your grades, read or review text, and practice using interactive media. However, some media are complex and must be viewed on a PC, as well as Packet Tracer activities, quizzes, and exams.

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