Microsoft KB Archive/95140

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Last reviewed: May 1, 1997

Article ID: Q95140 3.10 WINDOWS kbnetwork kb3rdparty kbfile kbappnote The information in this article applies to:


 * Microsoft Windows for Workgroups version 3.1

The Microsoft Product Support Services (PSS) Application Note titled &quot;WG0673: Novell NetWare Not Supported with ArcNet Adapter Cards&quot; explains why you cannot connect to a Novell NetWare server from your Microsoft Windows for Workgroups 3.10 workstation if you have an ArcNet network adapter card (also known as a network interface card, or NIC).

This information does not apply to later versions of Windows for Workgroups.

You can obtain this Application Note from the following sources:


 * Microsoft's World Wide Web Site on the Internet
 * The Internet (Microsoft anonymous ftp server)
 * Microsoft Download Service (MSDL)
 * Microsoft FastTips Technical Library
 * Microsoft Product Support Services

For complete information, see the &quot;To Obtain This Application Note&quot; section at the end of this article.

THE TEXT OF WG0673
Microsoft Product Support Services Application Note (Text File) WG0673: NOVELL(R) NETWARE(R) NOT SUPPORTED WITH ARCNET(R) ADAPTER CARDS Revision Date: 01/93 No Disk Included The following information applies to Microsoft Windows for Workgroups 3.1.
 * INFORMATION PROVIDED IN THIS DOCUMENT AND ANY SOFTWARE THAT MAY   |
 * ACCOMPANY THIS DOCUMENT (collectively referred to as an           |
 * Application Note) IS PROVIDED &quot;AS IS&quot; WITHOUT WARRANTY OF ANY     |
 * KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO   |
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A    |
 * PARTICULAR PURPOSE. The user assumes the entire risk as to the    |
 * accuracy and the use of this Application Note. This Application   |
 * Note may be copied and distributed subject to the following       |
 * conditions: 1) All text must be copied without modification and   |
 * all pages must be included; 2) If software is included, all files |
 * on the disk(s) must be copied without modification [the MS-DOS(R) |
 * utility DISKCOPY is appropriate for this purpose]; 3) All         |
 * components of this Application Note must be distributed together; |
 * and 4) This Application Note may not be distributed for profit.   |
 * Copyright 1993 Microsoft Corporation. All Rights Reserved.        |
 * Microsoft and MS-DOS are registered trademarks and Windows        |
 * is a trademark of Microsoft Corporation.                          |
 * 3Com is a registered trademark of 3Com Corporation.               |
 * ArcNet is a registered trademark of Datapoint Corporation.        |
 * NetWare and Novell are registered trademarks of Novell, Inc.      |
 * NetWare and Novell are registered trademarks of Novell, Inc.      |

INTRODUCTION
This application note discusses why you cannot connect to a Novell NetWare server from your Microsoft Windows for Workgroups workstation if you have an ArcNet network adapter card (also known as a network interface card, or NIC).

For your reference, a glossary of network-related terms is located at the end of this document.

SUPPORTED PROTOCOLS AND NOVELL CONNECTIVITY
Windows for Workgroups primarily supports two network protocols: NetBEUI (the protocol that Windows for Workgroups uses), and MSIPX, an NDIS-compliant IPX protocol stack supplied by Microsoft that allows Windows for Workgroups to communicate with Novell NetWare servers. With NetBEUI and MSIPX loaded concurrently, you can connect to NetBEUI- compliant servers and Novell NetWare servers from the same Windows for Workgroups workstation. If you are using an ArcNet network adapter card, however, this configuration does not work.

If you have an ArcNet card and you try to connect to a NetWare server from your Windows for Workgroups workstation, you will receive the following error message:

The network Novell NetWare cannot be added because Windows for Workgroups does not support this network with your ArcNet adapter. This error is caused by an incompatibility between the NetWare ArcNet MAC driver and the Windows for Workgroups ArcNet MAC driver. This incompatibility involves the packet fragmentation scheme Novell NetWare uses to transmit ArcNet data packets.

NetBEUI Encapsulated Ethernet Packets
NetBEUI, which conforms to the NDIS standard, supports Ethernet and token ring header formats, but not the ArcNet header format. NetBEUI therefore needs a special way to handle data packets it sends or receives across the ArcNet media. ArcNet provides a MAC driver that supports the NetBEUI protocol. When a Windows for Workgroups server sends data across the ArcNet media, NetBEUI attaches an Ethernet-type header to the data. The ArcNet MAC driver recognizes this header type, but before the data can travel on the ArcNet media, it needs to be packaged with an ArcNet header. The ArcNet MAC driver performs this function and sends the data packet across the media as an ArcNet packet. On the receiving end, the reverse process occurs: the ArcNet MAC driver receives the ArcNet data packet, replaces the ArcNet header with an Ethernet-type header, and passes it to NetBEUI. NetBEUI recognizes the packet and successfully passes it to the Windows for Workgroups client workstation.

Novell IPX Packet Fragmentation
The maximum packet size for an ArcNet data packet is 507 bytes of data following the header. The NetWare protocol requires a minimum data packet size of 576 bytes, enabling reads and writes of 512 bytes of data with 64 bytes of header information. Because of the difference in size between ArcNet and Novell data packets, Novell defined a scheme to transmit several consecutive ArcNet data packets in such a way that they could be reconstructed at the receiver into one data packet. This is referred to as packet fragmentation.

When a NetWare server sends data across the ArcNet media, the Novell IPX protocol, which supports the ArcNet header format, fragments the data and attaches a standard ArcNet header to each fragment. The Novell ArcNet MAC driver then transmits these data packets over the ArcNet media. When the packets are received at the Windows for Workgroups client workstation, the Microsoft ArcNet MAC driver converts the packet headers from ArcNet to Ethernet and passes them to the MSIPX protocol stack. MSIPX doesn't use a packet fragmentation scheme for Ethernet-type headers; therefore it assumes each packet with a separate header is complete. Because this isn't the case, the Windows for Workgroups client workstation can't interpret data sent by a Novell NetWare server over the ArcNet media.

ARCNET NETWORK INTERFACE CARDS: MANUFACTURERS AND SUPPORT
There are currently two major manufacturers of ArcNet network cards: Thomas Conrad (TC), and Standard Microsystems Corporation (SMC). Both cards support the Novell NetWare IPX protocol and the LAN Manager NetBEUI protocol. They support NetBEUI by using encapsulated Ethernet, as described previously.

Standard Microsystems Corporation (SMC)
SMC cards are supported by Novell. (The PC130, PC220, and PS110 boards are documented in the &quot;Novell Standard Microsystems ArcNet Supplement.&quot;)

The SMC ArcNet driver for NetWare ships with NetWare as the RX-Net driver. The SMC ArcNet driver for LAN Manager was written by DWB Associates and is now maintained directly by Microsoft.

Thomas Conrad (TC)
The TC ArcNet MAC drivers were written and are maintained by TC.

GLOSSARY
header: A block of bytes preceding the data that identifies the type of data requesting transport across the network.

media access control (MAC) driver: MAC drivers, also known as network- adapter-card drivers, communicate directly with the network adapter card. The MAC driver moves incoming data from the network adapter card to the protocol stack and vice versa.

Network Device Interface Specification (NDIS): This specification, jointly developed by Microsoft and 3Com(R) in 1989, standardizes how the MAC driver communicates bidirectionally with the protocol stack. Prior to implementation of the NDIS standard, manufacturers of network adapter cards had to provide the protocol stack and the MAC driver functionality in one piece of software (called a monolithic stack). The NDIS standard enables network adapter card vendors to simply provide NDIS-conformant MAC drivers that are compatible with all NDIS- conformant protocol stacks.

protocol stack: The protocol stack implements the set of procedural rules, or protocols, used to communicate across the network.

This Application Note can be found in the Software/Data Library by searching on the word WG0673, the Q number of this article, or S13993. WG0673 was archived using the PKWARE file-compression utility.

TO OBTAIN THIS APPLICATION NOTE
You can find by.SEA, a self-extracting file, on the following services:

  Microsoft's World Wide Web Site on the Internet On the www.microsoft.com home page, click the Support icon. Click Knowledge Base, and select the product. Enter kbfile by.SEA, and click GO! Open the article, and click the button to download the file.   Internet (anonymous FTP) ftp ftp.microsoft.com Change to the Softlib/Mslfiles folder. Get by.SEA   Microsoft Download Service (MSDL) Dial (425) 936-6735 to connect to MSDL Download by.SEA 

For additional information about downloading, please see the following article in the Microsoft Knowledge Base: ARTICLE-ID: Q119591 TITLE    : How to Obtain Microsoft Support Files from Online Services You can have this Application Note mailed or faxed to you from the automated Microsoft FastTips Technical Library, which you can call 24 hours a day, 7 days a week at (800) 936-4200. NOTE: The FastTips Technical Library is available only to customers within the U.S. and Canada. If you are unable to access the source(s) listed above, you can have this Application Note mailed or faxed to you by calling Microsoft Product Support Services Monday through Friday, 6:00 A.M. to 6:00 P.M. Pacific time at (425) 936-4200. If you are outside the United States, contact the Microsoft subsidiary for your area.
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