1.2 Networks Components and 1.3.docx

**1.2 Network Components** 1.2.1 Host Roles If you want to be a part of a global online community, your computer, tablet, or smart phone must first be connected to a network. That network must be connected to the internet. This topic discusses the parts of a network. See if you recognize these com...

**1.2 Network Components** 1.2.1 Host Roles If you want to be a part of a global online community, your computer, tablet, or smart phone must first be connected to a network. That network must be connected to the internet. This topic discusses the parts of a network. See if you recognize these components in your own home or school network! All computers that are connected to a network and participate directly in network communication are classified as hosts. Hosts can be called end devices. Some hosts are also called clients. However, the term hosts specifically refer to devices on the network that are assigned a number for communication purposes. This number identifies the host within a particular network. This number is called the Internet Protocol (IP) address. An IP address identifies the host and the network to which the host is attached. Servers are computers with software that allow 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 many different clients. As mentioned before, clients are a type of host. Clients have software for requesting and displaying the information obtained from the server, as shown in the figure. 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 an audio stream. The table lists three common types of server software.  1.2.2 Peer-to-Peer Client and server software usually run on separate computers, but it is also possible for one computer to be used for 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. In the figure, the print sharing PC has a Universal Serial Bus (USB) connection to the printer and a network connection, using a network interface card (NIC), to the file sharing PC. 1.2.3 End Devices The network devices that people are most familiar with are end devices. To distinguish one end device from another, each end device on a network has an address. When an end device initiates communication, it uses the address of the destination end device to specify where to deliver the message. An end device is either the source or destination of a message transmitted over the network. Click Play in the figure to see an animation of data flowing through a network. 1.2.4 Intermediary Devices Intermediary devices connect the individual end devices to the network. They 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.  Incomplete 1.2.5 Network Media Communication transmits across a network on media. The media provides the channel over which the message travels from source to destination. Modern networks primarily use three types of media to interconnect devices, as shown in the figure: - **Metal wires within cables** - Data is encoded into electrical impulses. - **Glass or plastic fibers within cables (fiber-optic cable)** - Data is encoded into pulses of light. - **Wireless transmission** - Data is encoded via modulation of specific frequencies of electromagnetic waves.  **1.3 Network Representations and Topologies** Incomplete 1.3.1 Network Representations Network architects and administrators must be able to show what their networks will look like. They need to be able to easily see which components connect to other components, where they will be located, and how they will be connected. Diagrams of networks often use symbols, like those shown in the figure, to represent the different devices and connections that make up a network. A diagram provides an easy way to understand how devices connect in a large network. 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 to describe how each of these devices and media connect to each other: - **Network Interface Card (NIC)** - A NIC physically connects the end device to the network. - **Physical Port** - A connector or outlet on a networking device where the media connects to an end device or another networking device. - **Interface** - Specialized ports on a networking device that connect to individual networks. Because routers connect networks, the ports on a router are referred to as network interfaces. **Note:** The terms port and interface are often used interchangeably. Incomplete 1.3.2 Topology Diagrams Topology diagrams are mandatory documentation 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 and logical. **Physical Topology Diagrams** Physical topology diagrams illustrate the physical location of intermediary devices and cable installation, as shown in the figure. You can see that the rooms in which these devices are located are labeled in this physical topology.  **Logical Topology Diagrams** Logical topology diagrams illustrate devices, ports, and the addressing scheme of the network, as shown in the figure. You can see which end devices are connected to which intermediary devices and what media is being used. 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 word "Cisco" to your search phrase, you will find many topologies using icons that are similar to what you have seen in these figures.