Sharing Bandwidth

Unfortunately, dial-up connections are rather slow and are generally unsuitable for connections that must transmit large amounts of data. One way of improving dial-up connection speed is to combine the available bandwidth of multiple communications lines into a single logical channel using a Windows XP feature known as multilink. To take advantage of Windows XP Professional's multilink support, the computer must have multiple modems and phone lines. In addition, the dial-up server that is to be called must also support multilink. Once connected, Windows XP can send and receive data over all available communication lines. This allows, for example, a computer with two 56k modems to potentially double its transmission speeds.

The following procedure outlines the steps involved in setting up a multilink session using multiple modems.

1. Click on Start and then right-click on My Network Places. The Network Connections folder appears.
2. Right-click on a dial-up connection and select Properties. The connection's Properties dialog appears.
3. Select the General property sheet.
4. In the Connect using section, select the modems to be used in establishing the multilink connection.
5. Select All devices call the same number.
6. Select the Options property sheet.
7. Select one of the following options from the Multiple devices section located at the bottom of the property sheet:
   • Dial only first available device
   • Dial all devices
   • Dial devices only as needed
8. Click on OK.

Setting Up a Windows XP Professional Dial-Up Server

In addition to providing a client dial-up connection to a dial-up server, Windows XP Professional has the ability to act as a dial-up server by supporting a single incoming dial-up connection. While not generally appropriate for the corporate computing environment, this capability may be of interest to smaller companies or individuals with home networks.

The following procedure outlines the steps involved in setting up a computer running Windows XP Professional to act as a dial-up server.

1. Click on Start/All Programs/Accessories/Communications and then New Connection Wizard. The New Connection Wizard starts.
2. Click on Next.
3. Select Set up an advanced connection and click on Next.
4. Select Accept incoming connections and click on Next.
5. Select the modem that is to be monitored for incoming calls and click on Next.
6. The wizard displays two options that deal with virtual private connections. Neither are relevant to this procedure. Select either option and click on Next.
7. The wizard displays a list of local user accounts. Select the users who are to be permitted to establish dial-up sessions with the computer. Optionally, select an individual account, click on Properties, and then select the Callback property sheet to specify any of the following Callback options:
   • Do not allow callback
   • Allow the caller to set the callback number
   • Always use the following callback number
     Configuring a callback option adds additional security to dial-up sessions by requiring the caller either to specify their phone number or to connect from a predetermined phone number. Click on Next.
8. The wizard displays a list of network software that will be used to create and manage dial-up connections. Select TCP/IP and click on Properties. The Incoming TCP/IP Properties dialog appears.
9. Select Allow caller to access my local area network to allow Windows XP Professional to act as a gateway connection to the rest of the network, or clear this option to limit the dial-up connection's access to the resources located on the Windows XP Professional computer. Select Assign TCP/ IP addresses automatically using DHCP to allow the network DHCP server to assign the dial-up client's TCP/IP connection settings. Alternatively, select Specify TCP/IP addresses to specify a range of IP addresses that Windows XP Professional is authorized to assign. To provide the dial-up client computer with the ability to specify its own TCP/IP settings, select Allow calling computer to specify its own IP address. Click on OK.
10. Click on Next.
11. The New Connection Wizard displays a summary of the information that it has gathered. Click on Finish to complete the setup of the dial-up server connection.

An icon representing the incoming dial-up connection now appears in the Network Connections folder. Windows XP Professional automatically answers any calls received on its assigned modem and allows authorized users to establish a dial-up session.