Microsoft KB Archive/175903

= ARI Bit Mismatch =

Article ID: 175903

Article Last Modified on 6/29/2004

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APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1
 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft LAN Manager 2.2c
 * Microsoft Windows for Workgroups 3.11
 * Microsoft Windows 95
 * Microsoft Network Client 3.1

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This article was previously published under Q175903



SUMMARY
If you see in a network trace an error "ARI bits mismatch", you will also see retransmissions of frames issued by higher level protocols like TCP/IP. In this case, network bandwidth is wasted on retransmissions.

The above error will only be seen on a Token Ring network.



CAUSE
The problem described above is caused by your hardware. The following are probable causes of your problem:


 * Insufficient receive buffers on your Token Ring network adapter card.
 * Slow data transfer rates to the PC bus.
 * Available memory in your system (RAM).

Usually the first item listed is the problem, but the second and third should be considered also.



MORE INFORMATION
The Address Recognized Indicator (ARI) bits mismatch error indicates frames that have the ARI bit set, but the Frame Copied Indicator (FCI) bit is not set.

The ARI bit is set by a ring station when it detects a frame addressed to it, but has insufficient buffer to copy the frame because of congestion in the ring station's Frame Copy pipeline.

The following 3 items make up the Frame Copy pipeline:


 * On-Board receive buffers on the network adapter. The more on-board receive buffers an adapter has, the more frames can be buffered and congestion errors are less likely to occur. Check your Token Ring adapter's specifications and determine the amount of on-board memory available for frame buffering.
 * Data bus transfer rate.

How quickly data can be moved from the network adapter to host memory depends on the bus interface of your adapter. To keep up with incoming frame traffic, your network adapter should always fit your personal computer's bus architecture.

Using a 16-bit or 32-bit bus and adapter is highly recommended for devices that must handle a large number of incoming frames. Another factor in moving data between card and the host memory is how the data is copied into memory. The two basic methods are DMA and shared memory. In general, shared memory is preferred.
 * Host receive buffers (RAM).

The amount of buffer available in a host affect how quickly data is moved off the adapter. Insufficient buffer in the host can cause a backlog in the adapter's on-board buffer.



RESOLUTION
To resolve this problem, perform the following steps:


 * 1) Increase the onboard receive buffers of your Token Ring network adapter card.
 * 2) Use a different network adapter card (with more onboard memory that fits your bus architecture).
 * 3) Increase the physical memory of your host.

Keywords: kbinterop kbprb KB175903

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