<br><h3> Chapter One </h3> <b>Introduction to Networking</b> <p> <p> <i>Just about any computer</i> you'll use today is on a network. Networked computers are so common it's easy to take them for granted. However, many components and technologies are working together behind the scenes to ensure a networked computer can access resources on the network. <p> In this chapter, I start by identifying the names of many of the physical and logical components of a network. I then introduce the components included in very small networks and show you how additional components are added as a network grows. I conclude with information on some standards organizations that help ensure all of these computers can work together no matter who manufactured them or where they're operating. <p> * <b>Comparing logical and physical networks</b> <p> * <b>Networking home computers</b> <p> * <b>Networking small offices and home offices</b> <p> * <b>Networking large offices</b> <p> * <b>Networking enterprises</b> <p> * <b>Understanding standards organizations <p> <p> Comparing Logical and physical Networks</b> <p> A network is a group of computers and other devices connected together. These connections can be with cables, wireless connections, or both. Networks are discussed in both logical and physical terms. <p> The <i>logical</i> organization of a network identifies the overall design of a network. It differentiates between local area networks (LANs) and wide area networks (WANs). The logical design of the network provides a high-level overview of the entire network and may not show smaller components such as all the switches, routers, and firewalls. By contrast, the <i>physical</i> network infrastructure includes the details of the physical components. The physical components are the devices and cabling that you can touch and feel. <p> This chapter presents concepts on logical network organization. You'll learn about the different types of network designs that you may find in home networks, small offices, larger offices or organizations, and enterprises. <p> Chapter 2 provides an overview of these physical components, and later chapters in the book (such as Chapters 7, 8, and 9) dig deeper into how these devices work. <p> It's important to understand how devices in a logical structure work to fully understand how data moves through a network. Once you understand how the data moves through the network, you are better prepared to maintain it and troubleshoot it when problems occur. <p> <p> <b>Networking home Computers</b> <p> Most home computers are part of a network today. At the very least, home computers have the ability to connect to the Internet, which is a massive network of networks. Figure 1.1 shows a simple networked home computer. <p> In the figure, the computer has access to the Internet through a modem to an Internet service provider (ISP). This could be a cable modem used in a broadband connection or a modem used for dial-up connections. Broadband connections are widely available in urban areas. This includes connections through cable TV systems, fiber-optic lines, and even phone connections such as ISDN and 3G/4G data services. <p> Even if a broadband connection isn't available, home users can connect to the Internet through a phone line, also known as a dial-up system. Dial-up connections are much slower but are used in rural areas where broadband connections are not available. Internet access via satellites is becoming available in more rural areas, providing better connections than dial-up but still not comparable in speed to broadband connections. <p> When home users add additional computers into their home, they typically want to network these computers. Users on the network are then able to share resources. For example, consider Figure 1.2, which shows a typical home network connected to each other and the Internet using both wired and wireless connections. <p> In the figure, the wired user is connected to a wireless router directly with a cable, and another user is connected via a wireless connection. A wireless printer is added that can be shared by any users with access to the wired network. An ISP provides connectivity to the Internet, just as it would for a single user. A single cable modem connects to the ISP, and then the cable modem connects to a wireless router. <p> Without a network, each individual computer would need to connect to the Internet separately, incurring individual access charges. However, the single Internet connection can be shared by adding the wireless router. A great benefit of wireless is that you don't have to install cables to each computer. <p> Most wireless routers include several additional capabilities. For example, it's common for a wireless router used in most home networks to include the following: <p> <b>Wireless access point (WAP)</b> The core purpose of the wireless device is to support connectivity for wireless clients. The WAP provides this connectivity. <p> <b>Routing Capabilities</b> A built-in router will route data from the internal network to the Internet and from Internet data back to the internal network. Chapter 2 provides an overview of routers, and Chapter 9 includes in-depth details on routers. <p> <b>Network address translation (NAT)</b> NAT translates the public IP addresses used on the Internet to private IP addresses on the internal network, and vice versa. If NAT wasn't used, you'd have to purchase or lease public IP addresses for each internal computer. Additionally, each computer would be directly on the Internet and exposed to unnecessary risks. NAT hides the internal computers from Internet attackers. <p> <b>Dynamic Host Configuration protocol (DHCP)</b> DHCP provides clients with IP addresses and other TCP/IP configuration information. The other TCP/IP information includes the address of the DNS server and the address of the router that provides a path to the Internet. The router address is also known as the <i>default gateway</i>. <p> <b>Firewall</b> A WAP will provide basic firewall capabilities. This blocks unwanted traffic from the Internet, providing a layer of protection for internal clients. <p> <p> <b>Networking Small Offices and Home Offices</b> <p> <i>Small offices and home offices (SOHOs)</i> are very similar to the sophisticated home network. They are both considered LANs. SOHOs have access to the Internet and can have either wireless clients, wired clients, or both. Figure 1.3 shows the configuration of sample SOHO network. <p> The primary difference is that a SOHO will typically have a server to provide additional capabilities for the office. For example, the server can be used as a file server to store files used within the business. <p> Although most offices will have a server, it's not necessary. Important files could be stored on a primary user's computer and shared to other users from there if needed. However, if important files are stored on multiple computers, it becomes harder to back up these files. <p> Additionally, a business may have a wireless multifunction printer that can print, scan, and fax documents to meet the needs of the business. It's not necessary to have a wireless printer. However, these are becoming more popular in SOHOs because they are easier to share between the network users. <p> The WAP used in a SOHO can be the same as the WAP used in the home network. <p> Similarly, the WAP used in the SOHO will provide many of the same capabilities to the office as a WAP provides for a home network. This includes routing, NAT, DHCP, and a firewall. <p> <p> <b>Understanding Local Area Networks</b> <p> The home network shown earlier (in Figure 1.2) and the SOHO (shown in Figure 1.3) are both considered <i>local area networks</i>. A LAN is a group of computers and/or other devices that are connected in a single physical location (such as a home, office, or corporate building). LANs can be much bigger than the networks shown so far. As you go through the book, you'll see how many different devices are used within the LAN. <p> LANs have fast network connectivity between the different devices in the LAN. Common speeds of wired LANs today are 100 Mbps or 1000 Mbps (also called 1 Gbps) and 54 Mbps or 300 Mbps for wireless. <p> A LAN is an internal network. Most LANs will have connectivity to the Internet through a router or firewall, but the LAN itself is internal. Traffic back and forth through a firewall to the Internet is filtered for security purposes. However, traffic within the LAN itself is usually not filtered. The internal network is considered a high trust area, so any traffic on the network is allowed. <p> <p> <b>Comparing Workgroups and Domains</b> <p> A SOHO will typically include from one to ten workers and will usually be configured as a <i>workgroup</i>. A workgroup is a group of networked computers that share a common workgroup name. The default name of a Microsoft workgroup is simply <i>Workgroup</i>, and all computers in the workgroup will share the same workgroup name. User accounts are located on each individual computer. <p> Consider Figure 1.4, which shows an office with four users. Each of the users has their own computer, and an additional server is available to them. For Sally to log onto her computer, she needs a computer account on her computer. However, this account won't work on Bob's, Alice's, or Joe's computers. If Sally needs to log onto any other computer in the workgroup, she must have a separate account on that computer. <p> In this scenario, there are five separate user databases—one on the server and one on each of the four computers. Similarly, each user would need to remember five usernames and five passwords to log onto each of the five computers. <p> However, most users in a SOHO will typically log onto only one computer in the network and will need only one user account. If users had to remember five usernames and five passwords, they would probably break a cardinal rule of security. They would probably start writing down the usernames and passwords. <p> When offices get larger than 10 computers or whenever offices need to have more centralized user and computer management, they move into a <i>domain</i> configuration. You can add a server and promote it to a domain controller or promote an existing server to a domain controller. <p> In Microsoft domains, the domain controller hosts Active Directory Domain Services (AD DS). AD DS includes objects such as user and computer accounts. Each user would have one user account in the domain, and each computer would have one computer account. <p> Figure 1.5 shows a SOHO configured as a domain. It has eight users with nine computers connected to the LAN. The server has been promoted to a domain controller and is hosting Active Directory. Instead of requiring users to memorize passwords for each computer, each user has a single account hosted on the domain controller. <p> This supports <i>single sign-on (SSO)</i> where a user needs to sign on only once. All access to domain resources for the user is granted using this single account. Additionally, this one account is used to log onto almost any computer in the domain. <p> By default, domain users are authorized to log onto any computer in the domain except for domain controllers. Administrators are granted the right to log onto domain controllers. However, it is possible to restrict users from logging onto other computers within the domain if necessary. <p> Even though the server has been promoted to a domain controller, it can still perform other functions on the network. For example, a domain controller can still host files as a file server. <p> <p> <b>Exploring the Benefits of Domains and Domain Controllers</b> <p> Promoting a server to a domain controller provides several benefits beyond single sign-on. These include the following: <p> <b>Simplified Management</b> Managing accounts in a domain is done with a group of centralized tools. For example, Active Directory Users and Computers is used to perform common administration tasks for all the users and computers in the domain. Additionally, user and computer accounts are organized in organizational units within the domain. <p> <b>Group Policy</b> Group Policy is used in a domain to configure, control, and manage users and computers. For example, Group Policy can be used to configure password-protected screen savers for all computers in the domain. An administrator can configure the setting one time in Group Policy, and the setting is configured on all the computers in the domain. It doesn't matter if the organization has 20 users or 20,000 users; the setting is configured once, and Group Policy does the rest. Thousands of settings can be configured through Group Policy. <p> <b>Built-in Redundancy and Fault Tolerance</b> If you have at least two domain controllers, the domain data is automatically replicated to each domain controller. If an account is added on one domain controller, it's copied to the other. If a user changes a password, the change is copied. This ensures you always have a redundant copy of Active Directory providing fault tolerance. In other words, if one domain controller develops a fault or fails, the domain can tolerate the fault. The other domain controller will carry the load. <p> Microsoft domains require a Domain Name System (DNS) server. DNS is used primarily to resolve computer names to IP addresses, but it's also used to locate domain controllers within a domain. If you don't have DNS or DNS fails, Active Directory fails. <p> <p> <b>Networking Large Offices</b> <p> Large offices include more people, more end user computers, and more users. Although you can network thousands of people in a single LAN, you do have to take additional steps to improve the performance of the LAN. The primary difference is that you subdivide groups of computers into different <i>subnets</i>. <p> Figure 1.6 shows a diagram for a larger office. Notice that the office includes multiple subnets and each subnet is separated by a router. The computers are separated on the different subnets so that each subnet has less traffic. Notice that subnet A has only servers while other subnets have users. Placing the servers on separate subnets is common in larger networks. <p> Traffic on a network is similar to traffic on roads and highways. When there are fewer cars, traffic runs smoother. When there are more cars, traffic becomes congested, and the potential for collisions increases. You can improve traffic flow by adding more roads and highways, providing multiple paths to common destinations, and widening commonly used roads. <p> Similarly, more computers on a network results in more network traffic and more congestion. You can improve performance by adding subnets to control and limit traffic in different areas. <p> Just as cars can have collisions on a road, data packets sent on a network can collide, resulting in collisions. When two computers on the same subnet send data at the same time, the data collides and is unreadable. Both computers must then send the data again. They both wait a random amount of time and send the data again. If the network is very busy, the data can collide again when it's resent. <p> Of course, every time data has to be resent, it makes the network that much busier since there is more traffic. More traffic results in more collisions, and more collisions results in even more traffic. If the network isn't optimized, the network performance can slow to a crawl. This is similar to rush-hour traffic in a city where it may take you an hour to get somewhere that normally takes only 10 minutes. <p> <p> <b>Networking Enterprises</b> <p> There is no formal definition of an enterprise, but it generally implies an organization with multiple locations. Occasionally, documentation defines an enterprise as an organization with more than 250 users to differentiate it from a large office, while other documentation defines it as more than 5,000 users. <p> From an IT professional's perspective, the biggest difference between a large office and an enterprise is the number of IT professionals supporting the network. Some offices with as many as 50 users are supported by only one or two administrators. These administrators do a little of everything. <p> In contrast, an enterprise may have dozens of IT professionals, with many of them having specialized knowledge. Some may be experts on email systems such as Microsoft Exchange. Others may be experts on database systems such as Microsoft SQL Server. End user help-desk professionals are experts on Windows 7 and other desktop operating systems and provide direct support to the users. <p> Another significant difference with enterprises is the method used to connect the different locations. Instead of just a single LAN in a single location, the organization is connected using different WAN technologies. WANs can be used to connect large offices to large offices. WANs can also connect smaller branch offices to the larger main offices. <p> Last, many workers are mobile. For example, salespeople are often traveling to meet customers. These mobile workers still need access to resources on the main network. Remote access technologies allow mobile workers to connect to the main network from remote locations. <p> <i>(Continues...)</i> <p> <p> <!-- copyright notice --> <br></pre> <blockquote><hr noshade size='1'><font size='-2'> Excerpted from <b>Microsoft Windows Networking Essentials</b> by <b>Darril Gibson</b> Copyright © 2011 by John Wiley & Sons, Ltd. Excerpted by permission of John Wiley & Sons. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.<br>Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.