ISDN access

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

ISDN access

To enhance your network connection speed, you can use an Integrated Services Digital Network (ISDN) line. Whereas standard phone lines typically transmit at up to 56 kilobits per second (Kbps), ISDN lines can transmit at speeds of 64 or 128 Kbps.

An ISDN line must be installed by the phone company at both the server and at the remote site. ISDN also requires that you install an ISDN adapter on the server and your computer. Costs for ISDN equipment and lines may be higher than standard modems and phone lines. However, the speed of communication reduces the duration of the connection, possibly saving toll charges.

An ISDN line comes with two B channels that transmit data at 64 Kbps, and one D channel for signaling that transmits data at 16 Kbps. You can configure each B channel to operate as a port. With some ISDN drivers, you can aggregate the channels. This means you can statically assign a higher bandwidth by configuring both B channels to act as a single port. With this configuration, line speed increases to 128 Kbps. For information about configuring a connection to use ISDN, see Make a dial-up connection by using an ISDN line or Configure ISDN settings.

The Multilink feature performs channel aggregation for ISDN. Multilink combines multiple physical links into a logical bundle. This aggregate link increases the bandwidth of a connection. In addition, you can allocate multiple links dynamically, which means ISDN lines are used only as they are required. This eliminates excess bandwidth, representing a significant efficiency advantage to users. You can configure the conditions under which extra lines are dialed, and underused lines are disconnected, through Network Connections settings. For more information, see Configuring multiple device dialing.