The NT 4.0 ISDN Connection

How to get on the Internet ­fast

The number of Internet users and the complexity of accessible services aregrowing rapidly. With the growth of the Web and its increased functionality,the access speeds of conventional modems aren't meeting user needs. As analternative, many users are turning to Integrated Services Digital Network(ISDN) for faster, more cost-effective Internet access.

To successfully use ISDN to connect NT Server and NT Workstation to theInternet, you need to understand ISDN and you need step-by-step instructions.I'll explain how to use the US Robotics Sportster ISDN 128K adapter (ISDNrequires an adapter instead of a modem), and this information applies to mostISDN adapters that use Remote Access Service (RAS) as a connection mechanism.(For information on available ISDN adapters and more information on ISDN, seeDan Kegel's ISDN page at www.alumni.caltech.edu/~dank/isdn.)

ISDN Primer
ISDN provides a subscriber with three separatedigital channels that are carried over a standard two-wire telephone cable.These channels are 2B+D, which means two 64Kilobits-per-second (Kbps) bearer (B)channels and one 16Kbps data (D) channel. The B channels usually carry userdata, and the D channel ordinarily transmits and receives call setup and controlinformation. Some equipment can bond the two B channels through a protocol suchas Multilink Point-to-Point Protocol (MPPP) to form one 128Kbps channel. (Fordetailed information on ISDN, see Mel Beckman, "ISDN and Windows NT,"January 1996, and John Enck, "ISDN to the Rescue (But Who Will RescueYou?)," May 1996.)

Before you call your local phone company to order an ISDN line, you mustobtain the required line- configuration information from your adapter'smanufacturer. (Call the manufacturer or check the adapter's users manual.) Inmost places, an ISDN line takes longer to install than a standard telephoneline--one to two weeks is common.

You also need to contact your Internet Service Provider (ISP) to find outthe ISDN access phone number, your login and password, the authentication type(i.e., Challenge Handshake Authentication Protocol--CHAP--or PasswordAuthentication Protocol--PAP), and your Domain Name System (DNS) server's TCP/IPaddress. (Your ISP can assign you a different TCP/IP address each time you logon; otherwise, you need to ask for a preassigned TCP/IP address.)

After you install the ISDN line, you need some information from your localtelephone company. You need the telephone number and Service Profile Identifier(SPID) numbers for each B channel. If your line has only one telephone number,you have only one SPID.

Installation and Configuration
The hardware installation isstraightforward. Make sure you know which I/O addresses are available for youradapter card. You can use NT Diagnostics to view the I/O addresses in use.

The Sportster ISDN 128K adapter comes from the factory ready to use asoftware-configurable I/O address. For NT, you need to change this setting andmanually select an I/O address by adding one or two jumpers to the adapter.Select an I/O address not in use--300, 320, or 340--and put your system backtogether. Now you're ready to configure the software.

RAS Installation: The first step is to install RAS. Make sure youconfigure TCP/IP as the protocol RAS will use to dial out. RAS won't let youcomplete the installation until you select a device. For the time being, set RASfor a modem because you haven't installed the ISDN card drivers. If you don'thave a modem, skip autodetection and tell RAS you have a generic modem on COM1.

ISDN Card Driver Installation: You install the drivers for the ISDNcard just as you do a network board. Select Control Panel, Networks, Adapters,and Add to see a list of network adapters. Place your driver disk in your floppydrive, and click Have Disk and OK. After you install the drivers, you enter theadapter's configuration information. The I/O address must match theadapter settings. Then select an available interrupt. NT Diagnostics can showyou which interrupts are in use.

Next, you need to provide the ISDN line information. Select the appropriateISDN switch type and the number of terminals (one terminal for each ISDNtelephone number). Then, enter the ISDN phone numbers and their associated SPIDnumbers. After selecting OK, you'll see the RAS configuration screen. Click Add,and select one of the newly created ISDN devices, as you see in Screen 1.(Repeat this step if you have two ISDN phone numbers.) Then, keep clicking OKuntil a prompt asks you to reboot the server; select Reboot Now.

After the server reboots, you can use the Line Monitor tool that comes withthe Sportster to check the status of the adapter. If the L1, L2, and L3 lightsare green, the adapter is working properly. If L1 is red, NT isn't recognizingthe ISDN adapter. If L2 is red, the ISDN line is either not plugged in to theadapter or not functioning. If L3 is red, the phone numbers and SPIDs in theadapter setup don't match the telephone company's configuration.

RAS Configuration: The next step is to configure RAS to dial yourISP. Select Dial-Up Networking, and create a new Phonebook entry. Enter a namefor this entry, and select the Next button.

Screen 2 shows the Server screen, which provides three options: If you areconnecting directly to the Internet, select the first option. To send yourpassword as plain text, if that's the only method available or if you're notsure whether your ISP supports encrypted passwords, select the second option. Ifyour ISP requires a terminal login or a preassigned address, select the thirdoption.

Select Next, and enter your ISP's ISDN dial-up access phone number. SelectNext to continue. If you selected the third option from the server screen (yourISP requires a terminal login or a preassigned address), you need to enter an IPaddress. If your ISP assigns a dynamic address, leave the IP address at 0.0.0.0,as in Screen 3. If your ISP gave you an address to use, enter it here. Next youneed to provide your ISP's DNS server address. Then select Next and Finish.

Now you need to edit the Dial-Up Networking Phonebook entry you justcreated. Select More, and then select Edit entry and modem properties.On the Basic tab on the Dial using field, select an ISDN line. (To useboth B channels bonded for a 128Kbps MPPP connection, set this field to MultipleLines.)

On the Server tab are two options: Enable software compression andEnable PPP LCP Extension. Make sure these options are not selected fornow. Also on the Server tab under TCP/IP settings, make sure Use defaultgateway on remote network is checked. (For information about defaultgateways, see Mark Minasi, "Unlock Your Gateway to the Internet," June1996, and "Gateways Revisited," page 47.)

On the Script tab, select None if your ISP doesn't require a terminallogin. If your ISP requires a terminal login, select Pop up a terminalwindow. You can automate your login later by choosing the third option onthe server screen to run a script. Save your Phonebook entry changes.

Now you can try to connect to your ISP. Select Dial. A prompt willask you to enter your login and password. Enter the name and password that yourISP gave you. If the remote system you are logging on to is not an NT system,leave the field for the domain name blank. After you click OK, the connectionprocess will begin. If the login was unsuccessful, you may need to click Enablethe PPP LCP Extensions in the Phonebook Server TCP/IP properties.

After you successfully connect to your ISP, you can run your favoriteInternet application. Be prepared for a shocking increase in speed if you'vebeen using a modem. Even one ISDN B channel can more than double the throughputof a 28.8Kbps modem.

Use NT as an IP Router
After you successfully connect NT to yourISP and access the Internet, you can configure NT as an Internet router. Thiscapability is useful if you have workstations connected to your NT system andyou want to let them access the Internet. (For more information about IProuters, see Mark Minasi, "NT Workstations Using an IP Router," May1996.)

An ISP can require that you connect in various ways. One popular method isto give you a randomly assigned IP address when your NT system calls in and toprovide addresses for your workstations. Suppose you have 14 workstationsconnected to your NT server. Your ISP might provide the addresses 204.57.116.65through 204.57.116.78 with a subnet mask of 255.255.255.240.

To connect in this manner, you have to configure TCP/IP on your server'snetwork card using one of these 14 assigned addresses, for example,204.57.116.65. Make sure you assign the correct subnet mask (255.255.255.240),and don't assign a default gateway. You also need to select Enable IPForwarding on the Routing tab under Control Panel, Network, TCP/IPProperties and configure any other information, such as DNS servers (for moreinformation about DNS, see Spyros Sakellariadis, "Configuring andAdministering DNS," August 1996, and "Integrating and AdministeringDNS," September 1996) and domain name, from your ISP.

Now you need to add a new Registry entry. Run Registry Editor (regedt32.exe), and go tohkey_local_machinesystemcurrentcontrolsetservicesrasarpparameters. SelectAdd Value from the Edit menu to create a new value. EnterDisableOtherSrcPackets as the name of the value, and select a Data Type ofdword. After selecting OK, enter 0 for the string value. Now the workstationpackets will contain the correct source address after crossing the RASconnection from the NT machine.

Configure your workstations as if NT Server were a dedicated router. Youneed to use the addresses and subnet mask from your ISP to configure TCP/IP oneach workstation. Each workstation must have a unique TCP/IP address. Configurethe DNS servers and domain name the same way you did for NT Server. However,this time, instead of leaving the default gateway blank, enter the TCP/IPaddress you configured on NT Server (204.57.116.65 in this example). For moreinformation on configuring IP routers, see Ed Tittel and Mary Madden, "EasyAccess to the Internet," July 1996.

Beware of Traffic Jams
As long as the server remains connectedto the Internet, all your workstations will be able to access the Internet. Keepin mind though, that when several of your workstations access the Internet atthe same time, the speed of the connection can drastically decrease.