JSI Tip 6511. Windows 2000 Asynchronous Transfer Mode Frequently Asked Questions.

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Microsoft Knowledge Base article Q282179 contains:


This article contains answers to frequently asked questions (FAQs) about Asynchronous Transfer Mode (ATM) in Windows 2000.

As of January 2003, Microsoft supports the following three methods for ATM in Windows 2000:
  • Well-known address (WKA)
  • Well-known virtual circuit (WKVC)
  • Integrated Local Management Interface (ILMI)
As of January 2003, manual configuration or hard coding the LAN Emulation Server (LES) or LAN Emulation Configuration Server (LECS) is not supported.


Background Information

In Microsoft Windows NT 4.0, third-party vendors wrote their own ATM drivers. Fore Systems wrote a driver that made it possible for users to connect to LECS without using WKA, WKVC, or ILMI.

In Windows 2000 there were many changes and enhancements made in the Network Driver Interface Specification 5 (NDIS5), Winsock, and Telephony API (TAPI). ILMI is the recommended solution if you have to use a non-well-known address in Windows 2000 .

ILMI is used if there is more than one LECS, or for security reasons. ILMI is the recommended method where security is an issue. When you use ILMI, you are not required to also use WKA. You can use ILMI to discover an LECS by using either a WKA or non-WKA address, but when you use a non-WKA for LECS, you must use ILMI.

Frequently Asked Questions

  1. Question: How does Windows 2000 select the ELAN (Emulated Local Area Network) to join? When I installed ATM, it automatically joined 1 of my 16 ELANs. How does it decide?

    Answer: If you are using ILMI on the switch, this is done automatically. The recommended implementation when you use a well-known address is to use ILMI with LECS on the ATM switch, and to use port filtering for security reasons. You can also configure Port # 1 on your switch specifically to use ELAN 2. This is configured on the switch.

    You can also give the ELAN name in the driver:
    1. Right-click My Network Places, and then click Properties.
    2. Right-click ATM LAN Emulation, click Properties, and then click Add to manually add an ELAN name.
    The LANE client in Windows 2000 chooses an ELAN by using the following process:
    1. Connect to LECS:
      Query the switch by using ILMI to look for a switch-specified LECS address. If one is found, connect to the switch-specified LECS address. If the connection is successful, go to step b. Otherwise, connect to LECS at the well-known LECS ATM address. If the connection is successful, go to step b. Otherwise, open a permanent virtual circuit (PVC) (VPI=0, VCI=17), and then go to step b.
    2. Get configuration:
      The client sends a CONFIGURE_REQUEST on the connection to the LECS. This configure request contains basic default information, but also includes the network adapter's Media Access Control (MAC) address. The configure request also contains an ELAN NAME if one was specified in the LANE configuration graphical user interface (GUI).

      The LECS uses the configure request data to do a "best match" to a particular ELAN. Most LECS servers are set up to match on an ELAN name, and if an ELAN name is not specified, there is a default ELAN that is chosen.

      The LECS sends back a CONFIGURE_RESPONSE to the client. The most important information in this response is the ATM address of the LAN Emulation Server (LES). When the client receives the response, the client closes the connection to the LECS.
    3. Connect to the LES, and then join the ELAN:

      The client connects to the ATM address of the LES. It sends a JOIN request to the LES and receives back a JOIN response. The client sends an ARP request for the MAC broadcast address (all Fs) to discover the BUS address. The client is now ready to use the ELAN.
    This process provides for a simple default setup of LAN emulation but also makes it possible for overrides to cause different behavior. The ILMI LECS address query provides an override on the network side that causes a specific LECS address. The LECS matching algorithms make it possible for overrides of ELAN assignment of clients.
  2. Question: Is there a way to automate the assignment of an ELAN on a server? For example, for unattended or "ghost" installations of servers such as by using the Symantec Norton Ghost program?

    Answer: There is no support in Windows 2000 to modify the ELAN NAME configuration in an unattended installation. There is a way at the LECS server to cause a Windows 2000-based computer to join a specific ELAN. To do this, add entries to the LECS server configuration file that maps the Windows 2000-based computer's ATM network adapter MAC address to an ELAN NAME. Without any configuration on the Windows 2000-based computer, it will join the correct ELAN.
  3. Question: How do you tell what Broadcast and Unknown Server (BUS), or LES you are currently using? The Windows NT 4.0 Fore Info Center used to provide this functionality. Is there an equivalent tool in Windows 2000?

    Answer: Use the Atmlane.exe program in the Resource Kit to find the LANE emulation configuration with the requested information.

    Note MARS and ARP server information have nothing to do with ATM LAN emulation.
  4. Question: How can you see your Network Service Access Point (NSAP) in Windows 2000?

    Answer: Use the Atmlane.exe program. Use the atmadm -a command to see the address.
  5. Question: How do you monitor the ATM statistics in Windows 2000? Signal errors, statistics, utilization, or other statistics. The Windows NT 4.0 Fore Info Center used to provide this functionality.

    Answer: Atmadm and Atmlane are the two utilities that can provide information. Some of the detailed information that is provided by the FORE Info Center is not available. Use the atmadm -s command for the statistics. Type atmadm /? at the command line, and then press ENTER for more information.
  6. Question: Who provides support for the FORE ATM drivers that are supplied on the Windows 2000 CD-ROM?

    Answer: There has been some confusion about who wrote the drivers that are included with Windows 2000. Microsoft now provides a generic ATM Driver/Interface. Third-party vendors only have to provide a miniport driver for their adapter. The specific network adapter drivers such as Forehe.sys and Pca200e.sys are provided and indirectly supported by FORE. Microsoft is the first level of support for all the components that are included with Windows 2000. The ATM protocol components (LANE, TCP/IP over ATM, UNI signaling, ATM Winsock, PPP over ATM) are fully supported and maintained by Microsoft. Microsoft supports the ATM drivers that are included with Windows 2000. Note that Microsoft does support the drivers that are included with Windows 2000. Third-party vendors typically release updated drivers and tools for their products.

    For more information about the ATM drivers that are included with Windows 2000, visit the following Microsoft Web site:


  7. Question: Does use of LECS create a possible single point of failure?

    Answer: Because you can have more then one LECS, using LECS should not create a single point of failure.
The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

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