Microsoft Windows Networking Essentials

Chapter 1

Introduction to Networking

Just about any computer 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.

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.

• Comparing logical and physical networks
• Networking home computers
• Networking small offices and home offices
• Networking large offices
• Networking enterprises
• Understanding standards organizations

Comparing Logical and Physical Networks

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.

The logical 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 physical network infrastructure includes the details of the physical components. The physical components are the devices and cabling that you can touch and feel.

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.

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.

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.

Networking Home Computers

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.

Figure 1-1: Home computer with access to Internet

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.

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.

Enable the Local Firewall

When a computer connects directly to the Internet through an ISP (without going through an internal router or wireless access point), it is at significant risk. The computer has a public IP address and is accessible from any other computer on the Internet, anywhere in the world. Attackers often prowl the Internet looking for unprotected computers. Enabling the software firewall on this computer provides a layer of protection.

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.

Figure 1-2: Typical home network

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.

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.

Some ISPs provide a router instead of a cable modem. A wireless router can connect to a router just as easily as it can connect to a cable modem.

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:

Wireless Access Point (WAP) The core purpose of the wireless device is to support connectivity for wireless clients. The WAP provides this connectivity.

Routing Capabilities 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.

Network Address Translation (NAT) 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.

Chapter 9 covers routers and NAT in more depth.

Dynamic Host Configuration Protocol (DHCP) 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 default gateway.

Chapter 5 covers DHCP and IP addressing schemes.

Firewall A WAP will provide basic firewall capabilities. This blocks unwanted traffic from the Internet, providing a layer of protection for internal clients.

Chapter 11 covers more advanced configurations of the firewall. Chapter 12 includes important wireless security concepts.

Networking Small Offices and Home Offices

Small offices and home offices (SOHOs) 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.

Figure 1-3: SOHO network

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.

SOHOs typically have up to 10 workers but may have as many as 100.

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.

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.

The WAP used in a SOHO can be the same as the WAP used in the home network.

Secure Wireless Networks

It's very important to lock down wireless networks with the best security available. The primary method of security for wireless networks is WPA2 (or 802.11i), which is discussed in greater depth in Chapter 12. If the network is not locked down, an attacker can use a simple laptop with a wireless NIC while driving by in a car to compromise it. This "war driving" technique allows an attacker to tap into the network and access the network's resources if the network isn't secured. Historically, wireless networks were notoriously insecure. However, technologies available today make it possible to provide sufficient security for most wireless networks.

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.

Understanding Local Area Networks

The home network shown earlier (in Figure 1-2) and the SOHO (shown in Figure 1-3) are both considered local area networks. A LAN is a...