Microsoft KB Archive/174033

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XFOR: Performance Tuning a 16Mbps Token Ring Network for a PROFS Connector

Article ID: 174033

Article Last Modified on 10/28/2006


  • Microsoft Exchange Server 5.5 Standard Edition

This article was previously published under Q174033


It is possible for Microsoft Exchange Administrators to improve performance of the Microsoft Exchange PROFS connector over the Microsoft SNA Server connection. The following information may be helpful in reaching that goal.


The following actions improve the performance of the PROFS connector over SNA:

  1. Maximizing the SNA Basic Transmission Unit (BTU) size.

    On a 16Mbps SNA Token-Ring network, the maximum SNA BTU size is 16393. To support this configuration the Token Ring Driver must be able to handle this packet size. In the Control Panel, click the Network icon, click the Adapters tab, and configure the Token Ring driver. If the maximum size is not configurable, consult your card vendor for the maximum packet size permitted. For maximum performance, select a reasonable packet size above 1K byte on a token ring network.
  2. Update BTU in the 802.2 setup profile.

    In the SNA, select a BTU size that is smaller than the packet size. A reasonable BTU size ranges between 1929 and 16393 bytes (16K+9). This parameter must be less than or equal to the VTAM MAXDATA size. The RSCS PARM Buffer Size can be configured to control the RU size of the mail session. Configure the RSCS PARM B parameter to support RU size larger than 3K. This can be accomplished using an updated version of WINRUI32.DLL supplied by Microsoft or in the latest Microsoft SNA Server Service Pack.
  3. Configuring the Host side:

    The VTAM MAXDATA parameter should be configured to take advantage of the token-ring high bandwidth. It must match the BTU size specified in the SNA Server mentioned above.
  4. For information about Maximizing the IND$FILE 3270 Host file Transfer Throughput, please see the following article in the Microsoft Knowledge Base:

    125881 Maximizing IND$FILE 3270 Host File Transfer Throughput

Additional query words: linakge sna profs 802.5

Keywords: kbhowto kbinterop KB174033