Microsoft KB Archive/95630

= Windows for Workgroups and NetBEUI Protocol =

Article ID: 95630

Article Last Modified on 11/14/2003

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APPLIES TO


 * Microsoft Windows for Workgroups 3.1
 * Microsoft Windows for Workgroups 3.11
 * Microsoft Windows for Workgroups Connection 1.0

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This article was previously published under Q95630



1.00 3.10 3.11

WINDOWS

kbnetwork



SUMMARY
Microsoft Windows for Workgroups is a peer-to-peer networking operating system. Every network operating system must provide a way to organize the data that is to be sent and received over the network. The primary way Windows for Workgroups accomplishes this is through the NetBEUI protocol.

NOTE: In addition to NetBEUI, Windows for Workgroups version 3.11 has a routable protocol that you can use with routers.



MORE INFORMATION
Some protocols are aided by a transport. A transport handles the organization of application messages, leaving the protocol to handle only data. NetBEUI (NetBIOS Extended User Interface) is a protocol that manages the packaging of both data and application messages.

NetBEUI and the Sliding Window Algorithm
NetBEUI, developed by IBM in 1985, is a windowing protocol. It uses an adaptive sliding window algorithm, enabling it to determine how to balance the load between sending and receiving data based on the size of the network.

For example, when a workstation sends information over the network, an acknowledgment is sent back telling the workstation the data reached its destination. By utilizing adaptive windowing provided by NetBEUI, the workstation can send additional information before it receives an acknowledgment. With NetBEUI, it is possible to send more data overall and increase throughput. This must be done on a controlled level so no data is lost.

NetBEUI and Data Loss
NetBEUI controls data loss in two ways:


 * By limiting the amount of data a receiver can store before it sends an acknowledgment. This is called the &quot;receive window.&quot;
 * By limiting the amount of data that can be sent by the sending workstation before it must send an acknowledgment. This is referred to as a &quot;send window.&quot;

To increase network throughput, the send window is sized greater than or equal to the receive window. Having a larger send window increases the chance of losing data. The lost data causes the sender to resend the data and could potentially slow down the network. NetBEUI adjusts these parameters dynamically so that the network load is optimized for the size of the network.

Reliable Connection-Oriented vs. Unreliable Connectionless-Oriented
The sliding window algorithm provides increased performance for a type of network traffic called &quot;reliable connection-oriented,&quot; or session meaning that data is sent to a specific address on the network and it must be acknowledged.

The other kind of traffic, &quot;unreliable connectionless-oriented&quot; or datagram, does not require an acknowledgment. It is not sent to an individual address. A datagram is broadcast to either a group of workstations on the network (multicast address), or to everyone on the network that understands the data (broadcast address). The benefit of using a datagram is that it provides the ability to communicate with a workstation without knowing its exact address. It can be used as a precursor to the reliable connection-oriented method of exchanging data.

NetBEUI and Routing
NetBEUI is not a routable protocol. A routable protocol has the ability to communicate with servers on networks in different cities, or on different networks within the same city via routers or bridges. NetBEUI can be routable only if it is on a Token Ring network. It can accomplish this due to built-in Token Ring source routing. Not as sophisticated as conventional routing, Token Ring source routing does not include the ability to control the path that the data takes to other networks. NetBEUI is optimized for the local area network environment.

NetBEUI in Microsoft LAN Manager and Windows for Workgroups
If you load NetBEUI services from MS-DOS in Windows for Workgroups, the functionality is the same as with LAN Manager.

In each implementation of the NetBEUI protocol, the services are achieved through NetBIOS services provided to the presentation layer of the OSI model, they all provide windowing services to optimize throughput, and they all implement their session layer services via DLC CCB2 and CCB3 protocols. They are functionally equivalent.

Loading NetBEUI at MS-DOS (before Windows)
NetBEUI is limited by static resources when loaded at the MS-DOS level. Two examples of resources are the number of network connections that can be made and the number of drives that can be shared. These network resources are controlled by the SESSIONS= entry in the PROTOCOL.INI file. If the line reads SESSIONS=6, no more than six connections can be established.

Within windows, there are two settings which also must be pre- allocated. They are NETHEAPSIZE=, for both standard and enhanced mode, and NETDMASIZE= for enhanced mode only. These settings are in the SYSTEM.INI file. The NETHEAPSIZE= setting controls the buffers windows sets up in conventional memory for transferring data over the network. Increasing this value decreases available conventional memory in MS- DOS sessions. The NETDMASIZE= setting specifies the direct memory access buffer size for NetBIOS transport software.

Loading NetBEUI from Windows
Loading NetBEUI from Windows is also referred to as loading the protected mode protocol. VNB.386 is the virtual device driver that is responsible for providing NetBEUI services in enhanced mode. VNB.386 allocates resources dynamically, so the static settings discussed above are ignored. This means that if you have six network connections, and you want a seventh it is possible even though your SESSIONS= entry is set to 6.

One additional advantage is memory. VNB.386 starts with Windows, and, as a result, does not use conventional memory; it loads into protected mode. This means more memory at the MS-DOS command prompt in Windows.

Additional query words: WC 1.00 3.10 3.11

Keywords: KB95630

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