Home and Small Office Network Topologies

Article
09/11/2009

Introduction

Home and small office networks can be set up in a variety of configurations. The following factors can affect the ultimate network configuration:

Equipment availability and cost—In many cases, the financial support to connect a set of machines together in a network to share files, printers, and the Internet is limited. Consider the costs of acquiring and installing network adapters, hubs, other network devices such as residential gateways, and cabling.
Internet access availability—The network configuration can also be limited by the available options for connecting to the Internet. While standard modems and dial up access is available to nearly everyone and requires little additional investment, higher bandwidth needs might require a broadband link such as Digital Subscriber Line (DSL) or cable. Depending on the broadband provider, you might be required to use additional equipment such as a cable or DSL modem or a residential gateway.
Configuration simplicity—Most home or small networks are not managed by an information technology (IT) department. The configuration that is eventually chosen must match the resources available to install and maintain it. With the right configuration, anyone can do this.
The environment of the network—Whether the network is being set up in a business or home, environmental factors can affect the choices available. For example, some buildings might have restrictions on installing cabling or requirements to use existing cabling. Other locations might restrict the use of wireless network devices due to electrical shielding or interference.
Security for the Internet connection—The Internet connection, the physical method of connecting one or more of the computers on your internal network, must be protected from Internet attacks. This can be done using a combination of translation and firewall technologies.
Preferences and knowledge of installer—The network configuration is invariably influenced by the knowledge, experience, and personal preferences of the person installing the network components.

In this paper, we will describe some of the ways to connect the computers of the home or small office network together to form an internal network. Then, we will describe how to connect the internal network to the Internet.

The Internal Network

To provide connectivity between all the computers in your home or small office, the computers of the internal network must be either directly or indirectly connected to each other. To connect home or small office computers together, each computer must have a network adapter or device that connects the computer to the network.

Network adapter choices include the following:

Internal network adapters using a Peripheral Component Interconnect (PCI) slot of your computer.
PCMCIA or PC Card network adapters installed in PC Card slots commonly found on laptop or notebook computers.
USB network adapters connected to either a USB port typically found on the back of a computer or a USB port on a USB hub.

An important consideration here is the physical installation of the adapter. With PCI adapters, for example, you must open the computer and insert the adapter in an empty PCI slot. USB attached network adapters may be a better solution when simplicity is a requirement. Laptop computers will likely use PCMCIA or PC Card adapters.

Networking Technologies

You must also choose a type of networking technology, sometimes referred to as the LAN media, which enables your computers to send information to each other. The most common networking technologies used for home networking include:

Ethernet
Phoneline
Wireless

Ethernet

Used in organization networks, Ethernet is widely known, supported, and understood. Ethernet equipment consists of an Ethernet adapter and either coaxial cable (for 10Base2) to serially connect each computer together, or twisted pair cable (for 10BaseT or 100BaseT) to connect each computer to a hub. A hub is required when you are using twisted pair cabling and connecting more than two 10BaseT or 100BaseT computers together.

While Ethernet adapters are generally low cost, the cabling and hub needs add to the complexity and cost.

Figure 1: An Ethernet-based Home or Small Network

Ethernet can operate at speeds of 10 megabits per second (Mbps) or 100 Mbps. To get 100 Mbps, you must use 100 Mbps Ethernet adapters, Category 5 twisted pair cabling, and connect to 100 Mbps port on an Ethernet hub.

Phoneline

Used mostly in home and small office networks, phoneline uses telephone wiring as its medium for communication and operates at speeds up to 10 Mbps. Phoneline equipment consists of a phoneline adapter installed in each computer and standard telephone cables connected to standard phone jacks.

The advantage of phoneline networks is phone jacks are usually found throughout the house and close to areas where computers are used.

Figure 2: A Phoneline-based Home or Small Network

Wireless

Used in both organization and home networks, wireless technology uses radio signals to communicate so there is no cabling required. Wireless solutions are gaining popularity and becoming more affordable. There are many wireless products, however, wireless networks based on the IEEE 802.11 standard are becoming the preferred solution. Organization or large business wireless networks are more likely to be using IEEE 802.11. If your home or small network is also based on IEEE 802.11, you can use the same network adapter to access both work and home or small office networks. IEEE 802.11b can operate at a speed of 11 Mbps. Wireless equipment consists of a wireless adapter installed in each computer.

Figure 3: A Wireless-based Home or Small Network

Mixing Media

While it is ideal to have a single networking technology for all the computers on your home or small office network, it might not be possible due to a mixture of computer types, cabling options, and other factors. When you have more than one media present, you have more than one link or LAN segment that must be bridged together by a common computer that has both types of adapters installed.

For example, if you have three computers connected to an Ethernet hub and two computers connected via phoneline, you have two LAN segments(an Ethernet LAN segment and a phoneline LAN segment. To connect the computers on both LAN segments together, use a computer running Windows XP that has both types of adapters installed and the Network Bridge. The Network Bridge transparently connects the two LAN segments together as if they were the same LAN segment.

Figure 4 shows a home network with three LAN segments. Two computers running Windows XP and the Network Bridge are used to bridge the three LAN segments together.

Figure 4: A Mixed-Media Home or Small Network

Connecting to the Internet

In contrast to the many ways that organizations and large businesses connect to the Internet, the small or home office typically connects to the Internet in the following ways:

Using individual Internet connections for each computer
Using a residential gateway
Using a host computer

Using Individual Internet Connections for Each Computer

One way to connect each individual computer to the Internet is to install an analog modem in each computer and have each computer make its own dial-up connection to the Internet. The disadvantage to this method is that the number of computers that can access the Internet is equal to the number of separate phone lines in your home or small office. If you have only one phone line, only one computer can access the Internet at a time.

Typical external DSL or cable modem devices have an Ethernet port that you can use to connect it to an Ethernet hub. If you also connect your internal network computers to the same hub, then each computer can send and receive information directly to and from the Internet. This configuration is shown in Figure 5.

Figure 5: Using Individual Internet Connections for Each Computer

The advantage to this configuration is that it does not require one computer to be on all the time to access the Internet. Each computer can individually access the Internet without any intervening equipment. Note that this configuration will only work if your broadband provider issues you multiple IP addresses, one for each computer on your network. If your broadband provider does not issue you enough addresses, then you must use a residential gateway.

The disadvantages of setting up your network using this network configuration are the following:

Security against Internet attacks must be maintained on each computer in your network. The computers running Windows XP should enable Internet Connection Firewall (ICF) (for Windows XP or Windows XP with Service Pack 1) on their Internet connection, Windows Firewall (for Windows XP with Service Pack 2), or a third-party firewall product. For computers running earlier versions of Windows, using another firewall is recommended.
If ICF, Windows Firewall, or another firewall is not enabled on each Internet connection, by default, files and folders that are shared can be seen on the Internet. To prevent shared files and folders from being seen on the Internet, disable file and print sharing on the Internet Protocol (TCP/IP).
If you are using ICF, Windows Firewall, or another firewall on each Internet connection, it might block file and printer sharing and the use of Universal Plug and Play devices between each computer in your internal network.

In both of the above cases in which file and printer sharing is disabled, to enable file and print sharing between computers in the local network, add the NWLink IPX/SPX NetBIOS Compatible Transport Protocol to your Internet connection or enable the File and Printer Sharing exception for Windows Firewall.

Using a Residential Gateway

A residential gateway is a hardware device that connects the home or small office network to the Internet. Similar to Windows XP Internet Connection Sharing (ICS), the residential gateway provides translation and allows you to share a DSL or cable modem Internet connection with all of the computers in your internal network. The residential gateway sits between your DSL or cable modem and internal network. Alternately, the DSL or cable modem might be integrated into the residential gateway. Figure 6 shows a residential gateway.

Figure 6: Using a Residential Gateway

Residential gateways are also known as Internet gateways or broadband routers.

The advantages of using a residential gateway are the following:

The residential gateway appears to the Internet as the only computer on the Internet, hiding the computers in your internal network.
The residential gateway shares one Internet connection with all the computers in your network.
One of your computers does not have to be on to provide Internet connectivity.
You can utilize Universal Plug and Play in your home or small office.

The disadvantage of using a residential gateway is the additional cost of the residential gateway hardware.

Using a Host Computer

A host computer is a computer running Windows XP that is connected to both the Internet and the internal network. The host computer acts as a gateway, providing connectivity between Internet and internal network hosts, and a firewall, providing protection from Internet attacks for the host computer and internal network computers.

Figure 7 shows an example of using a host computer when the internal network is using a single Ethernet LAN segment.

Figure 7: Using a Host Computer

You can also use a host computer when the internal network is using phoneline, wireless, or a mixture of media.

The host computer is running Windows XP with the following features:

Internet connection sharing (ICS) is enabled on the Internet connection.
With ICS, the Internet connection is shared with all the other computers on the internal network. The host computer acts as a router, forwarding traffic between internal network and Internet hosts. Additionally, ICS protects internal network computers by discarding all traffic from the Internet that was not requested by an internal network computer. This prevents Internet attacks against internal network computers.
Internet Connection Firewall (ICF) is enabled on the Internet interface or Windows Firewall is enabled.

While ICS protects internal network computers from Internet attacks, it does not protect the host computer. By enabling ICF on the Internet interface or enabling Windows Firewall (for all interfaces), Windows XP discards any traffic from the Internet that was not requested by the host computer. This helps protect the host computer from Internet attacks.

The advantages of using Windows XP on a host computer are:

Sharing one Internet connection with all the computers on your network can reduce the cost of connecting to the Internet and allows all the computers on your internal network to be online at the same time.
The host computer appears to the Internet as the only computer on the Internet, hiding the computers in your internal network.
The host computer with ICS and either ICF or Windows Firewall provides a level of security for your host computer and internal network computers.
If your internal network has different types of LAN media, you can use the Network Bridge feature of Windows XP to automatically configure transparent bridging of the separate LAN segments.
You can utilize Universal Plug and Play in your home or small office. With Universal Plug and Play you can control your Internet connection from any computer running Windows XP, Windows Millennium Edition, Windows 98 Second Edition, or Windows 98 in your internal network.
Enabling ICF or Windows Firewall effectively disables file and print sharing on the Internet connection of the host computer. Therefore, private files stored on the host computer cannot be seen from the Internet. However, you can enable the File and Printer Sharing exception for Windows Firewall so that you can still use file and print sharing on your internal network.
An additional device such as a residential gateway is not needed. You can use an existing computer on your internal network to act as the host computer.

The disadvantages of using the host computer are the following:

The host computer must be on for the internal network computers to access the Internet.
The host computer must have two network adapters installed(one to connect to the Internet and one to connect to the internal network.

If you are not required to use a residential gateway by your Internet service provider, connecting your internal network to the Internet using a host computer running Windows XP with ICS and either ICF or Windows Firewall provides a level of protection from Internet attacks and full connectivity between your internal network computers.