Eicon Networks DIVA LAN ISDN Using the corporate connection, NetBIOS name resolution, Timeouts

Chapter Eight: Connecting to a Corporate Network Using the corporate connection 107

Using the corporate connection

The DIVA LAN ISDN Modem automatically dials out and establishes the ISDN link to your corporate network as required. You simply launch the applications you use to do your work, such as a web browser or e-mail program, and you are automatically connected.

You can also establish your connections manually, dialing and hanging up connections as you see fit. See page 45 for details.

How long will the line stay connected?

By default, the DIVA LAN ISDN Modem will stay connected until the line has been idle for two minutes. To adjust this setting, see “The Cost Control page” on page 59.

Support for Microsoft Network Neighborhood

If you are connecting to an Microsoft NT network, see “Spoofing NetBIOS services” on page 68 for information on supporting Network Neighborhood functions.

NetBIOS name resolution

If you use Microsoft networking, then you will need to be able to resolve NetBIOS names to IP addresses. If you allow the Microsoft WINS client to use DNS as a method of resolving names (Windows NT), then it could result in persistent ISDN calls being generated. In general, it is recommended that you make entries in the LMHOSTS file of each computer connected to the DIVA LAN ISDN Modem to resolve NetBIOS names. Consult the Microsoft documentation for your operating system for more information on how to do this.

Timeouts

To save communications charges, the DIVA LAN ISDN Modem will drop the ISDN line when it is idle. Although this may not cause problems for most applications, it can cause difficulties for the corporate server you are connected to. If the server implements TCP keep alives, then the server will hang up your TCP/IP session if the ISDN line is down when the keep alives are sent. Thus, when the DIVA LAN ISDN Modem reconnects (i.e., the client sends more data), the session will have been aborted.

Dynamic IP addressing

If the corporate network uses dynamic IP address assignment, it is possible that each time the DIVA LAN ISDN Modem connects it will be given a different IP address. This can cause problems for some session-based applications when the DIVA LAN ISDN Modem drops the ISDN link due to inactivity. When the link is re-established, the server has given the DIVA LAN ISDN Modem a new IP address. When the application attempts to continue using the previous session, it is refused because of the address change.

Although applications may not themselves timeout when the DIVA LAN ISDN Modem drops the line due to inactivity, the IP stack on the corporate server you are connected to may.