Upgrading and Repairing Networks (5th Edition)

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

The Point-to-Point Protocol and the Serial Line Internet Protocol 229

The Serial Line Internet Protocol (SLIP) 230

The Point-to-Point Protocol (PPP) 231

Configuring a Windows XP Professional Client for Dial-Up 236

When Dial-Up Isn't Fast Enough 238

If you operate a large corporate network, you might be tempted to skip this chapter. After all, you probably have one or more routers/firewalls and other devices connecting your corporate network to the Internet using a large dedicated data pipe, such as a T1, a T3, an ATM (Asynchronous Transfer Mode), a Frame Relay, or a MPLS (Multi Protocol Label Switching) and/or a SONET connection. However, if you have workers on the move, or employees who work from home, one of the cheapest options available is dial-up. It might be your only option at times. By using a dial-up modem you can connect to the Internet and begin to work immediately using pre-existing copper telephone lines. Obviously, if you can use one of the various flavors of broadband connection, which are discussed in following chapters, that's the preferred method. But despite the rapid adoption of broadband at home and on the road (hotels and so forth), DSL and cable Internet providers still don't have nearly the user base of traditional dial-ups. So why are dial-up connections still important in a corporate setting? Keep in mind the following:

• As with any new technology, you should always have a backup solution in place in case of failure. Eliminating a single point of failure in your design saves you time and gets the network and/or systems back online faster. What happens if your primary network connection fails? You can use backup solutions to satisfy your business need for the day or two it takes to fix your higher bandwidth connection.

• You might need to support mobile employees staying overnight at a hotel that only provides dial-up access.

• You might have to support ROBO or SOHO-based users. Many corporate network users utilize resources from home offices. Will any of them still require dial-up to gain access to your network's resources?

• For non-corporate users, there will come a time when you indeed need a broadband connection. You don't want to spend hours downloading a few files from the Internet. At this point in time, however, a simple dial-up connection might satisfy your needs.

Tip

You might need to remotely administer your systems and network infrastructure out of band (OOB). You can do so by connecting a dial-up line to just about any device that supports it and then configure it with authentication. When the main network does go down, you can still access your devices via the dial-up network. This is a common configuration on most networks today.

Just as you can use Virtual Private Networks (VPNs), which are discussed in Chapter 46, "Virtual Private Networks (VPNs) and Tunneling," to create a secure path through the Internet, you can create VPNs using dial-up techniques and then use a server to process incoming connections. Until the telecoms and Internet service providers have finished wiring their networks for unlimited broadband connections, you might have no choice other than dial-up access.

For these reasons (and more), you should read this chapter to understand just how dial-up protocols, such as PPP, work because there is a good chance that you will be using PPP in the future for encapsulation of your dial-up lines, T1s, and other network systems.

Note

This chapter covers the basics of establishing a typical dial-up connection to the Internet. However, remember that in the case of a dial-up connection, the payload in your network packets is sent out on the Internet, where it is possible for someone to intercept your data. If you are dialing into the Internet instead of a server at your business, read Chapter 47, "Encryption Technology," so that you can use the latest techniques to keep others from viewing your data.

Tip

By using dial-up, you can connect to an Internet Service Provider (ISP) for Internet access and then you can build a VPN tunnel to the corporate network via a Client VPN device set to terminate your connection and authorize you for access to resources. You can also use any connection to the Internet, but in most cases you will find that you will be using dial-up over traditional copper-based telephone cabling.